Monday December 9

Chair : Jason Twamley

09:00– 09:45 Tracey Northrup, Prof, University of Innsbruck, Austria
Co-Trapping An Ion And A Nanoparticle In A Two-Frequency Paul Trap

09:45– 10:10 A Kani Mohamed, Dr, Assit Prof, University of Hyderabad, India
Rotational Schrödinger’s Cat

10:10– 10:35 Ajmeri Amreen (Shushmi) Chowdhury, Ms, University of Strathclyde, UK
Higher Order Weak Values For Paths In Nested Mach-Zender Interferometers

10:35– 10:55 Coffee

10:55– 11:40 Andrea Morello, Prof, University of New South Wales, Sydney, Australia
Schroedinger Cats With High-Spin Nuclei: Quantum Information, Quantum Foundations, And Spin-Mechanics Entanglement

11:40– 12:05 Kiyotaka Aikawa, Prof, University of Tokyo, Japan
Towards 3D ground-state cooling of a microparticle

12:05– 13:40 Lunch

13:40– 16:00 Afternoon Discussions and Posters

16:00– 16:45 Ivette Fuentes Guridi, Prof, University of Southampton and Fellow of Keble College University of Oxford , UK
Exploring The Unification Of Quantum Theory And General Relativity With A Bose-Einstein Condensate

16:45– 17:10 Anna Pachol, Assoc Prof, University of South-Eastern Norway, Norway
Exploring Models Of Quantum Phase Spaces Via Noncommutative Geometry And Modifications To Uncertainty Principles

17:10– 17:35 Chenyue Gu, Ms, Quantum Innovation Centre(Q.InC), Agency for Science, Technology and Research(A*STAR); National University of Singapore(NUS)
Coherent Optical Levitation For Quantum Sensing

17:35– 18:00 Collins Okon Edet, Mr., Institute of Engineering Mathematics, Universiti Malaysia, Malaysia
Irreversibility In A Cavity Magnomechanical System

18:00– 18:25 Daisuke Miki, Mr., Kyushu University, Japan
Testing Quantum Nature Of Gravity In Optomechanical Systems Under Causal Estimation

18:25– Reception and Poster Session


 

Tuesday December 10

Chair :James Millen

09:00– 09:45 Markus Aspelmeyer, Prof, University of Vienna, Austria
TBA

09:45– 10:10 Davide Candoli, Mr, ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels, Barcelona, Spain
Theory Of Levitated Cavity Optomechanics In The Presence Of Laser Phase And Intensity Noise

10:10– 10:35 Dennis Uitenbroek, Mr, Leiden Institute of Physics / Leiden University, The Netherlands
Cryogenic Magnetic Levitation For Future Gravity Experiments Using Small Source Masses

10:35– 10:55 Coffee

10:55– 11:40 Kazuhiro Yamamoto, Prof, Kyushu University, Japan
A Perspective Of Optomechanical Approach For Testing Quantumness Of Gravity

11:40– 12:05 Germain Tobar, Mr, Stockholm University, Sweden
Detecting Single Gravitons With Quantum-Controlled Resonant Mass Detectors

12:05– 13:40 Lunch

13:40– 16:00 Afternoon Discussions and Posters

16:00– 16:45 Andrew Geraci, Prof, Northwestern University, USA
Optical Trapping And Cooling Of High-Aspect-Ratio Dielectric Objects For Precision Sensing And Fundamental Physics

16:45– 17:10 Jayadev Vijayan, Dr., University of Manchester, UK
Cavity Quantum Optomechanics With Multiple Levitated Nanoparticles

17:10– 17:55 Anupam Mazumdar, Prof, Van Swinderen Institute, University of Groningen, The Netherlands
20 Years Program To Test The Quantum Nature Of Gravity In A Laboratory

17:55– 18:20 Maria Fuwa, Dr. Advanced Industrial Science and Technology (AIST)
Ferromagnetic Levitation Of Yttrium Iron Garnet Spheres For Macroscopic Quantum Mechanics

18:20– 18:45 Marit O. E. Steiner, Ms, Institute of Theoretical Physics, Ulm University, Germany
Pentacene-Doped Naphthalene For Levitated Optomechanics

19:00– Evening Meal at OIST

09:45– 10:10 Martijn Janse, Mr. Leiden University, The Netherlands
Characterisation Of A Levitated Sub-Milligram Ferromagnetic Cube In A Planar Alternating-Current Magnetic Paul Trap

10:10– 10:35 Melissa Kleine, Ms, LOMA, CNRS, Université de Bordeaux, France
Boosting Optomechanical Performances Of A Levitated Particle Through Wavefront Shaping

10:35– 10:55 Coffee

10:55– 11:40 Nadine Meyer, Prof, NanoPhotonics Systems Laboratory, ETH Zurich, Switzerland
Vacuum Levitation And Motion Control On Chip

11:40– 12:25 Mika Sillanpää, Prof, Department of Applied Physics, Aalto University, Finland
Quantum Backaction And Entanglement With Mechanical Oscillators

12:25– 12:50 N Sneha, Ms., National Institute of Science Education and Research Bhubaneswar, India
Emergence Of Classicality From Quantum Foundations: Testing The Schrodinger-Newton Equation

12:50– 14:00 Lunch

14:00– 19:00 Excursion

19:00– Evening Meal

Thursday December 12

Chair :Kiyotaka Aikawa

09:00– 09:45 Markus Arndt, Prof, University of Vienna, Faculty of Physics, QNP Group, Austria
From Organic Kittens Towards Metallica Cats

09:45– 10:10 Qian Ling Kee, Ms, A*STAR Quantum Innovation Centre(Q.InC), Institute for Materials Research and Engineering(IMRE), Agency for Science, Technology and Research(A*STAR), Singapore
Modelling Of Recirculating Multipass Alkali Cell For Ultrahigh Sensitivity Atomic Magnetometry

10:10– 10:35 Qiongyuan Wu, Dr, Research Associate, King's College London, UK
Squeezing In A Non-Linear Potential: A Psesuit For Non-Classical Quantum States

10:35– 10:55 Coffee

10:55– 11:40 James Millen, A/Prof Kings College London, UK
Rotational Optomechanics

11:40– 12:05 Ray-Kuang Lee, Prof, National Tsing Hua University, Taiwan
Experimental Realization Of Optical Cat States With Photon-Added Squeezed States

12:05– 13:40 Lunch

13:40– 16:00 Afternoon Discussions and Posters

16:00– 16:45 Benjamin Stickler, Prof, Ulm University, Germany
Non-Reciprocal Interactions And Entanglement Between Optically Levitated Nanoparticles

16:45– 17:10 Rémi Claessen, Mr, University of Vienna, Austria
Remote Sensing Of A Levitated Superconductor With A Flux-Tunable Microwave Cavity

17:10– 17:35 Ruvi Lecamwasam, Dr, A*STAR Quantum Innovation Centre (Q.InC), Institute for Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore
How To Leverage Lie Algebras In Quantum Optomechanics

17:35– Evening Meal at OIST

Friday December 13

Chair : Nadine Meyer

09:00– 09:45 Yiwen Chu, Prof, ETH Zürich, Switzerland
Quantum States Of Massive Mechanical Objects

09:45– 10:10 Shilu Tian, Dr. Okinawa Institute of Science and Technology, Japan
Macroscopic Quantum Superpositions With Magneto-Mechanics

10:10– 10:35 Tommaso Trognacara, Mr., Università degli Studi di Milano, Italy
Generation And Protection Of Schroedinger Cat States Of Mechanical Oscillators Interacting With A Non-Markovian Environment

10:35– 10:55 Coffee

10:55– 11:40 Andrea Vinante, Senior Researcher, CNR-Institute of Photonics and Nanotechnologies, Trento, Italy
Levitated Ferromagnets In Superconducting Traps

11:40– 12:05 Ulysse Reglade, Dr, Alice & Bob, ENS Paris
Quantum Control Of A Cat-Qubit With Bit-Flip Times Exceeding Ten Seconds

12:05– 13:40 Lunch

13:40– 15:35 Afternoon Discussions and Posters

15:35– 16:00 Xi Yu, Mr, University of New South Wales, Sydney, Australia
Creation And Manipulation Of Schrodinger Cat States Of A Nuclear Spin Qudit In Silicon

16:00– 16:45 John Teufel, Dr, Applied Physics Division of NIST, at Boulder, USA
TBA

16:45– 17:10 Xianfeng Chen, Dr. Agency for Science, Technology and Research (A*STAR), Singapore
Diamagnetically Levitated Cavity Optomechanics With Low Eddy Current Materials

17:10– 17:55 Gavin W Morley, Prof, Warwick University, Physics Department, UK
Levitating Nanodiamonds Towards A Test Of The Quantum Nature Of Gravity

18:30– Evening Meal at OIST

All Talk Titles and Abstracts (alphabetical first name)

Rotational Schrödinger Cat

A Kani Mohamed, Dr, Assit Prof, University of Hyderabad, India

Quantum rotation of levitated particles has recently attracted significant research interest [1]. Over the past few years, significant control over particle rotation has been achieved, and librational motion has been cooled to the quantum ground state [2]. Here, we introduce a scheme to engineer a novel rotational Schrödinger cat, which refers to the superposition of an object's angular oscillations or libration. This is accomplished by utilizing the intrinsic magnetocrystalline anisotropy of a levitated magnetic nanoparticle possessing magnons [3].

When an anisotropic magnetic particle is levitated in the presence of a uniform static magnetic field, the magnetocrystalline anisotropy traps the orientation of the crystal and induces nonlinear magnon-rotational coupling. As a result, driving the magnon with a bichromatic microwave field enables an efficient generation of a rotational cat state, which under high vacuum conditions can persists for several minutes. Our approach provides a robust and novel platform for exploring quantum superposition of rotation which has potential applications in testing collapse models and gravitational effects on rotating quantum objects.

Co-authors: A. Kani, M. Hatifi, and J. Twamley

[1] B. A. Stickler, K. Hornberger, and M. S. Kim, "Quantum rotations of nanoparticles," Nat. Rev. Phys. 3, 589 (2021).
[2] F. van der Laan et al., "Sub-Kelvin Feedback Cooling and Heating Dynamics of an Optically Levitated Librator,” Phys. Rev. Lett. 127, 123605 (2021).
[3] A. Gurevich and G. Melkov, Magnetization Oscillations and Waves (CRC Press, 2020).

Higher Order Weak Values For Paths In Nested Mach-Zender Interferometers

Ajmeri Amreen (Shushmi) Chowdhury, Ms, University of Strathclyde, UK

We consider weak values in the Feynman propagator framework, to gain a broader understanding of their interpretation in terms of path integrals. In particular, we examine the phenomenon of seemingly discontinuous paths that particles take in nested Mach-Zender interferometer experiments. We extend on existing path integral approaches for weak values by deriving expressions to model a sequence of weak measurements, and study the probe shifts across the different branches of a weak value interferometer. We apply this to scrutinise two scenarios of interest, one which treats photons as measurement apparatus via their spatial projection operators, and the second treating mirrors as probes.

Chowdhury, Shushmi, and Jörg B. Götte. "Higher order weak values for paths in nested Mach-Zender interferometers." arXiv preprint arXiv:2407.06989 (2024).

Schroedinger Cats With High-Spin Nuclei: Quantum Information, Quantum Foundations, And Spin-Mechanics Entanglement

Andrea Morello, Prof, University of New South Wales, Sydney, Australia

I will present recent experiments, and exciting new directions, for the use of high-spin nuclei in silicon for quantum information, quantum foundations, and spin-mechanics entanglement. Nuclear spins in silicon are among the most coherent quantum objects to be found in the solid state. They have infinite relaxation time, and second-scale coherence time. By using the I=7/2, 8-dimensional nucleus of antimony, we have prepared a nuclear Schroedinger cat within a functional nanoelectronic device [1]. This will allow us to adapt to atomic-scale objects the cat-based quantum error correction codes that are very popular in superconducting system, and exploit the extreme bias of the noise. We then used this and other nonclassical states to perform a curious experiment, where the quanutmness of the state is certified by monitoring its uniform precession, in seeming contradiction with Ehrenfest's theorem [2]. High-spin nuclei possess a quadrupole moment that couples them to electric fields and lattice strain [3]. I will discuss plans to entangle a single nuclear spin with a MHz-range mechanical oscillator, and perspectives to scale up the mass of the oscillator to test gravitational collapse models.

[1] X. Yu et al., arXiv:2405.15494
[2] A. Vaartjes et al., arXiv:2410.07641
[3] S. Asaad et al., Nature 579, 205 (2020)

Levitated Ferromagnets In Superconducting Traps

Andrea Vinante, Senior Researcher, CNR-Institute of Photonics and Nanotechnologies, Trento, Italy

We levitate microferromagnetic particles in superconducting traps at low temperature, and detect their motion using SQUIDs. We aim at achieving extreme isolation from the environment, enabling force, torque and magnetic field sensing with very high resolution. At the same time, this platform may open a way towards testing the macroscopic limits of quantum mechanics. I will summarize recent results, and discuss future prospects

Optical Trapping And Cooling Of High-Aspect-Ratio Dielectric Objects For Precision Sensing And Fundamental Physics

Andrew Geraci, Prof, Northwestern University, USA

Optically levitated particles in high vacuum achieve excellent environmental decoupling making them ultrasensitive detectors of forces or accelerations. While many levitated optomechanics experiments employ spherical particles, for some applications non-spherical geometries offer advantages. For example, rod-shaped or dumbbell shaped particles have been demonstrated for torque and rotation sensing and plate-like and disc-like particles with a high aspect ratio offer the possibility of a high mass-frequency product and low photon recoil heating, making them well suited for detection of high-frequency accelerations. I will discuss recent work on trapping and cooling high-aspect ratio dielectric particles and our progress towards achieving optimal detection of their motion to improve the sensitivity, cooling, and quantum control in these systems. Finally, I will place these results into context of the levitated sensor detector (LSD) experiment being constructed which intends to search for high-frequency gravitational waves

Exploring Models Of Quantum Phase Spaces Via Noncommutative Geometry And Modifications To Uncertainty Principles

Anna Pachol, Assoc Prof, University of South-Eastern Norway, Norway

To reconcile the principles of quantum mechanics and general relativity we must challenge the foundational concepts of classical space-time. When quantum and gravitational interactions are equally strong, the known structure of space-time should be modified (quantized) and this may affect the quantum mechanical phase space as well. Noncommutative geometry (NCG) can be considered as a mathematical framework for the description of such quantum space-times leading to new types of relations between quantum position and momenta operators, and therefore introducing modifications/corrections to the quantum mechanical phase space commutation relations. This leads to the modifications arising in the (Heisenberg) Uncertainty Principle (UP), introducing its generalisations. Such modifications are often investigated in the search for the new effects that could be tested or provide new bounds on model parameters when compared against the existing experimental data.

In my talk I will consider the quantum space-time models and noncommutative generalizations of phase space as a natural framework for the modified UPs. I will discuss properties of such models and give some examples of how modifications in the quantum mechanical phase space may impact physical systems and density of states.

20 Years Program To Test The Quantum Nature Of Gravity In A Laboratory

Anupam Mazumdar, Prof, Van Swinderen Institute, University of Groningen, The Netherlands

I will discuss the steps we must take to witness the quantum nature of gravity in a dedicated laboratory. I will introduce the idea of quantum gravity-induced entanglement of masses (QGEM) protocol, which will test the quantum nature of gravity via Newtonian potential. We must create a macroscopic quantum spatial superposition of 10-100 microns with masses around 10^{-14} -10^{-15} Kg objects. I will discuss how to create such a superposition in a diamagnetically levitated setup (current carrying chip-based technology) within the Stern-Gerlach setup; I will discuss why such an experimental setup is the best way to develop large spatial superposition and how it requires extreme precision over every aspect of the experiment, from levitation to controlling the current, its gradient and many subtle aspects of material properties, such as dangling bonds and the rotation of the nanocrystal in a levitating setup. Furthermore, I will discuss how to create a new R&D for experimenting with nearly 1 Hz in a dedicated underground facility such as the one in the future Einstein Telescope to mitigate seismic, gravity gradient and relative acceleration noise.

* Spin Entanglement Witness for Quantum Gravity,'' Phys. Rev. Lett. 119 (2017) no.24, 240401, doi:10.1103/PhysRevLett.119.240401 [arXiv:1707.06050 [quant-ph]].
* Relative acceleration noise mitigation for nanocrystal matter-wave interferometry: Applications to entangling masses via quantum gravity, Phys. Rev. Res. 3 (2021) no.2, 023178, doi:10.1103/PhysRevResearch.3.023178 [arXiv:2007.15029 [gr-qc]].
* Micrometer-size spatial superpositions for the QGEM protocol via screening and trapping, Phys. Rev. Res. 6 (2024) no.1, 1, doi:10.1103/PhysRevResearch.6.013199 [arXiv:2307.15743 [quant-ph]].

Non-Reciprocal Interactions And Entanglement Between Optically Levitated Nanoparticles

Benjamin Stickler, Prof, Ulm University, Germany

Optically levitating dielectric nanoparticles in ultra-high vacuum, where their motion can be cooled into the deep quantum regime, provides a promising platform for force and torque sensing and for high-mass tests of quantum physics. In this talk I will discuss recent results on the coupled dynamics of co-levitated nanoparticles interacting via optical binding and via electrostatic forces. I will show how non-reciprocal interactions [1,2] and mechanical entanglement [3,4] between two particles can be generated and observed by controlling the light fields suspending them.

[1] Rieser, Ciampini, Rudolph, Kiesel, Hornberger, Stickler, Aspelmeyer, and Delić, Science 377, 987 (2022)
[2] Reisenbauer, Rudolph, Egyed, Hornberger, Zasedatelev, Abuzarli, Stickler, and Delić, Nat. Phys. 20, 1629 (2024)
[3] Rudolph, Delić, Aspelmeyer, Hornberger, and Stickler, Phys. Rev. Lett. 129, 193602 (2022)
[4] Rudolph, Delić, Hornberger, and Stickler, arXiv:2306.11893 (2023)

Coherent Optical Levitation For Quantum Sensing

Chenyue Gu, Ms, Quantum Innovation Centre(Q.InC), Agency for Science, Technology and Research(A*STAR); National University of Singapore(NUS)

Optomechanical systems are fundamentally limited by thermal noise from the environment. In the emerging field of levitodynamics, systems are suspended using optical or electromagnetic means. The resulting isolation means that the quantum ground state could be attained at room temperature using only feedback-cooling. This could allow for macroscopic state generation, for investigations into the fundamental nature of quantum mechanics and gravity. However, existing methods such as optical tweezers are limited to objects of at most micrometer size. Furthermore the optical field interacts incoherently with the system, resulting in decoherence. We will report progress towards achieving levitation of a milligram mirror, using the radiation pressure force of reflected photons. This coherent levitation provides a pathway towards mass regimes unattainable with existing methods, and unlocks precision optical quantum control.

Our system consists of a tripod arrangement of vertical Fabry-Perot cavities [1]. Photons reflecting from the upper mirror impart a vertical force which opposes gravity. To generate sufficient force for levitation, an intra-cavity power of several kilowatts is required, resulting extreme optical power densities. In this regime, novel photothermal effects arise. We will discuss our experimental studies of these effects, how these can be accurately modelled [4], and even engineered to achieve stability [5]. We will report our observations of the nonlinear dynamics of the system, which differ from standard optomechanical systems [2,3]. Finally, we will discuss preliminary work in achieving ultra-light, highly-reflective mirrors for levitation, and new proposals of different experimental configurations, such as diamagnetic assistance and a self-stabilising meta-surface.

Co-authors:Chenyue Gu, Vincent Han Leong Lau, Biveen Shajilal, Sherry Lee Koon Yap, Zhaogang Dong, Syed Assad, Ruvi Lecamwasam, and Ping Koy Lam

[1] Guccione, G., Hosseini, M., Adlong, S., Johnsson, M. T., Hope, J., Buchler, B. C., & Lam, P. K. (2013). Scattering-free optical levitation of a cavity mirror. Physical Review Letters, 111(18), 183001.
[2] Ma, J., Qin, J., Campbell, G. T., Guccione, G., Lecamwasam, R., Buchler, B. C., & Lam, P. K. (2020). Observation of nonlinear dynamics in an optical levitation system. Communications Physics, 3(1), 1-10.
[3] Lecamwasam, R., Graham, A., Ma, J., Sripathy, K., Guccione, G., Qin, J., ... & Lam, P. K. (2020). Dynamics and stability of an optically levitated mirror. Physical Review A, 101(5), 053857.
[4] Gu, C., Qin, J., Guccione, G., Ma, J., Lecamwasam, R., & Lam, P. K. (2023). Modeling photothermal effects in high power optical resonators used for coherent levitation. New Journal of Physics, 25(12), 123051.
[5] Qin, J., Guccione, G., Ma, J., Gu, C., Lecamwasam, R., Buchler, B. C., & Lam, P. K. (2022). Cancellation of photothermally induced instability in an optical resonator. Optica, 9(8), 924-932.

Irreversibility In A Cavity Magnomechanical System

Collins Okon Edet, Mr., Institute of Engineering Mathematics, Universiti Malaysia, Malaysia

We present the irreversibility generated by a stationary cavity magnomechanical system. In this system, the magnons are coupled to the cavity photon mode via magnetic dipole interaction and to the phonon mode via magnetostrictive force (optomechanical-like). We employ the quantum phase-space formulation to evaluate the steady-state entropy production rate and associated quantum correlation in the system. We find that the behaviour of the entropy flow between the cavity photon mode and the phonon mode is determined by the magnon-photon coupling and the cavity photon dissipation rate. Interestingly, the entropy production rate can increase/decrease depending on the strength of the magnon-photon coupling and the detuning parameters. We further show that the amount of correlations between the magnon and phonon modes is linked to the irreversibility generated in the system for small magnon-photon coupling. Our results demonstrate the possibility of exploring irreversibility in driven magnon-based hybrid quantum systems and open a promising route for quantum thermal applications.

Co-authors: Muhammad Asjad, Denys Dutykh, Norshamsuri Ali, and Obinna Abah

Testing Quantum Nature Of Gravity In Optomechanical Systems Under Causal Estimation

Daisuke Miki, Mr., Kyushu University, Japan

Verifying quantum entanglement due to gravity is one of the critical milestones in quantum gravity. The effects of quantum gravity have yet to be experimentally verified, and several theories have even been proposed that treat gravity classically. However, gravity-induced entanglement may prove that gravity obeys quantum mechanics because entanglement is a quantum nonlocal correlation that cannot occur by classical evolution. Hence, detecting gravity-induced entanglement implies that the gravitational interaction is represented as a quantum operator. Further, Some papers discussed that gravity-induced entanglement can be a verification of quantized dynamical degrees of freedom in gravitational field theory.

In this presentation, we discuss the quantum effects of gravity in optomechanical systems under quantum control. We demonstrate that the two mechanical mirrors are entangled through gravitational interaction conditional on the measurement results. However, semiclassical gravity also causes correlations because the measurement process changes the classical gravitational effects. To distinguish the quantum and classical signatures of gravity, we introduce two methods: the time delay in measurement and the non-stationary measurement. We can show that we distinguish gravity signatures using these measurements for a single optomechanical device. We also discuss the distinguishability of gravitational signature for two optomechanical devices.

Theory Of Levitated Cavity Optomechanics In The Presence Of Laser Phase And Intensity Noise

Davide Candoli, Mr, ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels, Barcelona, Spain

Levitated nanoparticles [1] are emerging as highly promising systems for observing large quantum superposition states with massive objects. Significant milestones include the achievement of quantum ground-state cooling of a particle’s motion [2–7] and the development of realistic protocols for the coherent delocalization of a particle’s wavefunction [8, 9]. A major challenge in this pursuit is the various types of decoherence that affect nanoparticle dynamics. For this reason, it is crucial to identify and understand the sources of noise relevant to state-of-the-art experiments. Coherent light scattering into an optical cavity [10, 11] has been instrumental in approaching the quantum regime. This technique allowed ground-state cooling of the particle’s center-of-mass motion in one and two dimensions [2, 6, 7] and has the potential to achieve it for the rotational degrees of freedom too [12]. To further improve cooling performance in coherent scattering setups, one needs to model sources of noise beyond the primary mechanism of laser photon recoil. In particular, secondary effects such as phase and intensity noise of the laser can affect significantly the purity of the particle’s state.

In our work, we derive a quantum theory of the translational and librational dynamics of a particle levitated in a cavity, explicitly incorporating the effects of laser phase and intensity noise. We go beyond the white-noise approximation and treat both noises as stochastic processes with finite correlation times. Through the evolution of the cavity mode, phase noise is converted to intensity noise leading to additional heating of the particle’s motion. Specifically, for parameter configurations of experimental interest we estimated a phase noise contribution to the number of librational phonons up to the 70 % of the total occupation number. By defining quantitative bounds on the laser noise rates required for cooling the particle’s motion to a specific temperature, our work offers a guideline to improve coherent scattering experiments limited by these types of noise.

Co-authors:Davide Candoli, Andreu Riera-Campeny, Oriol Romero-Isart, Carlos Gonzalez-Ballestero

[1] C. Gonzalez-Ballestero, M. Aspelmeyer, L. Novotny, R. Quidant, and O. Romero-Isart, Science 374, eabg3027 (2021).
[2] U. Delić, M. Reisenbauer, K. Dare, D. Grass, V. Vuletić, N. Kiesel, and M. Aspelmeyer, Science 367, 892 (2020).
[3] L. Magrini, P. Rosenzweig, C. Bach, A. Deutschmann-Olek, S. G. Hofer, S. Hong, N. Kiesel, A. Kugi, and M. Aspelmeyer, Nature 595, 373 (2021).
[4] F. Tebbenjohanns, M. Mattana, M. Rossi, M. Frimmer, and L. Novotny, Nature 595, 378 (2021).
[5] M. Kamba, R. Shimizu, and K. Aikawa, Opt. Express 30, 26716 (2022).
[6] A. Ranfagni, K. Børkje, F. Marino, and F. Marin, Phys. Rev. Res. 4, 033051 (2022).
[7] J. Piotrowski, D. Windey, J. Vijayan, C. Gonzalez-Ballestero, A. de los Ríos Sommer, N. Meyer, R. Quidant, O. Romero-Isart, R. Reimann, and L. Novotny, Nat. Phys. (2023).
[8] M. Roda-Llordes, A. Riera-Campeny, D. Candoli, P. T. Grochowski, and O. Romero-Isart, Phys. Rev. Lett. 132, 023601 (2024).
[9] L. Neumeier, M. A. Ciampini, O. Romero-Isart, M. Aspelmeyer, and N. Kiesel, PNAS 121, e2306953121 (2024).
[10] U. Delić, M. Reisenbauer, D. Grass, N. Kiesel, V. Vuletić, and M. Aspelmeyer, Phys. Rev. Lett. 122, 123602 (2019).
[11] C. Gonzalez-Ballestero, P. Maurer, D. Windey, L. Novotny, R. Reimann, and O. Romero-Isart, Phys. Rev. A 100, 013805 (2019).
[12] H. Rudolph, J. Schäfer, B. A. Stickler, and K. Hornberger, Phys. Rev. A 103, 043514 (2021).

Cryogenic Magnetic Levitation For Future Gravity Experiments Using Small Source Masses

Dennis Uitenbroek, Mr, Leiden Institute of Physics / Leiden University, The Netherlands

Meissner levitation provides a platform for extremely isolated systems and can be used to measure small-scale gravity. Gravitational interaction is fundamentally weak and becomes prominent only at macroscopic scales, which lets open the question how gravity manifests itself in the microscopic regime where quantum effects dominate and quantum coherent effects of gravity possibly become apparent. In our group we have recently measured gravitational coupling between a levitated sub-millimeter scale ferromagnetic particle (mass of 0.43 mg) inside a type-I superconducting trap and kilogram source masses, placed approximately half a meter away. The source masses are placed on a rotating wheel that can resonantly drive the test mass. Our results extend gravity measurements to low gravitational forces of 10 attonewton and underline the importance of levitated mechanical sensors for measuring gravity.

All six mechanical degrees of freedom of the levitated magnet are detectable using a Superconducting QUantum Interference Device (SQUID). Some of the modes are measured to have a mode temperature below 1K with quality factors of 10^7. This is only possible with an extensive vibration isolation system inside and outside the dilution refrigerator. This experiment is currently world leading in detecting gravity with the smallest source mass. Westphal et al. is currently leading in measuring gravity between two small masses (90 mg), with a signal around 20 femtonewton. We aim to develop a smaller source mass, which allows for measurements of gravitational attraction between two objects of 1 to 10 milligram. This results in a gravitational force of the order of 1 attonewton and would be the smallest gravitational signal ever detected.

Levitating Nanodiamonds Towards A Test Of The Quantum Nature Of Gravity

Gavin W Morley, Prof, Warwick University, Physics Department, UK

We diamagnetically levitate individual nanodiamonds in vacuum, towards tests of fundamental physics. We aim to use a spin superposition of a nitrogen-vacancy (NV) centre to put the diamond into a superposition of being in two places at once, using an inhomogeneous magnetic field [1,2]. This is the first step of a much more ambitious experiment to test if gravitational effects can be in a quantum superposition: can gravity entangle things [3]? The NV centres in the nanodiamonds we have developed for this have the longest spin coherence times and the longest longitudinal spin relaxation times which is required for us to make a macroscopic spatial superposition, and will also be useful for quantum sensing [4,5].

[1] M Scala et al, Physical Review Letters 111, 180403 (2013)
[2] BD Wood, S Bose & GW Morley, Physical Review A 105, 012824 (2022)
[3] S Bose et al, Physical Review Letters 119, 240401 (2017)
[4] BD Wood et al, Physical Review B 105, 205401 (2022)
[5] JE March et al, Physical Review Applied 20, 044045 (2023)

Detecting Single Gravitons With Quantum-Controlled Resonant Mass Detectors

Germain Tobar, Mr, Stockholm University, Sweden

The quantization of gravity is widely believed to result in gravitons - particles of discrete energy that form gravitational waves. But their detection has so far been considered impossible. Here we show that signatures of single gravitons can be observed in laboratory experiments. We show that stimulated and spontaneous single graviton processes can become relevant for massive quantum acoustic resonators and that stimulated absorption can be resolved through optomechanical read-out of single phonons of a multi-mode resonant mass detector. We analyse the feasibility of observing a signal from the inspiral, merger and post-merger phase of a compact binary inspiral. Our results show that single graviton signatures are within reach of experiments. In analogy to the discovery of the photoelectric effect for photons, such signatures can provide the first experimental evidence of the quantization of gravity.

Co-authors:G. Tobar, S.K. Manikandan, T. Beitel, Michael E. Tobar, I. Pikovski

[1] G. Tobar, S. K. Manikandan, T. Beitel, and I. Pikovski, Nature Communications 15 7229
[2] G. Tobar, Igor Pikovski ,Michael E. Tobar, arXiv:2406.16898 (2024)
[4] F. Dyson, International journal of modern physics. A, Particles and fields, gravitation, cosmology 28, 1330041 (2013)
[5] T. Rothman and S. Boughn, Foundations of Physics 36, 1801 (2006)

Exploring The Unification Of Quantum Theory And General Relativity With A Bose-Einstein Condensate

Ivette Fuentes Guridi, Prof, University of Southampton and Fellow of Keble College University of Oxford , UK

The unification of quantum theory and general relativity remains one of the most important open issues in fundamental physics. A main problem is that we are missing experimental input at scales where quantum and relativistic effects coexist. Developing instruments sensitive at these scales might also help answer other big questions, such as the nature of dark energy and dark matter. In this talk I will show how Bose-Einstein condensates (BECs) could be used to search for clues. A single BEC in a superposition of two locations could test if gravity induces the collapse of the wavefunction. Current experiments involve solids such as mirrors and glass nanobeads. In BECs atoms are not bounded as in solids, producing a variety of quantum states that might present advantages. I will also present a proposal to use Bose-Einstein condensates to access new spacetime scales directly. Applications include detecting gravitational waves at high frequencies, miniaturize devices to measure gravitational fields and gradients and set further constrains on dark energy/matter models.

Rotational Optomechanics

James Millen, A/Prof Kings College London, UK

In the last few years, it has become possible to cool levitated nanoparticles to the ground-state of an optical potential, opening the possibility of performing quantum experiments with solid objects made out of billions of atoms. In this talk, I will outline why understanding and manipulating the rotation of levitated nanoparticles is key to this endeavour. I will introduce research from my group on controlling the motion and rotation of silicon nano-cylinders. and how they can be used for quantum and classical sensing applications. I will also introduce some novel detection and feedback control technology developed in the group, for tracking and controlling multiple levitated objects simultaneously.

Cavity Quantum Optomechanics With Multiple Levitated Nanoparticles

Jayadev Vijayan, Dr., University of Manchester, UK

Levitated optomechanics has established itself as a promising platform to explore macroscopic quantum science and building high fidelity mechanical sensors, thanks to recent advances such as quantum control of mechanical motion and tunable interactions between multiple nanoparticles levitated in vacuum.

I will first describe our results on using cavity optomechanics to achieve quantum ground-state cooling of multiple translational as well as librational degrees of freedom of an optically levitated nanoparticle [1]. Second, I will briefly discuss scalable optical techniques to trap and feedback-cool multiple nanoparticles simultaneously [2]. In the final part, I will describe how we combine cavity optomechanics with multi-particle trapping to create a unique experimental platform for many-body quantum optomechanics. By coupling light scattered by each nanoparticle into a single cavity mode, we demonstrate the ability to passively cool and engineer long-range interactions between multiple nanoparticles [3], paving the way towards generating entanglement and exploring many-body phenomena in levitated optomechanics.

Co-authors:Jayadev Vijayan (University of Manchester), Johannes Piotrowski (ETH Zurich), Lorenzo Dania (ETH Zurich), and Lukas Novotny (ETH Zurich),

[1] Piotrowski et al, Nature Physics 19, 1009-1013 (2023)
[2] Vijayan et al, 18, 49–54 (2023)
[3] Vijayan et al, Nature Physics 20, 859-864 (2024)

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John Teufel, Dr, Applied Physics Division of NIST, at Boulder, USA

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A Perspective Of Optomechanical Approach For Testing Quantumness Of Gravity

Kazuhiro Yamamoto, Prof, Kyushu University, Japan

I will discuss a perspective of the optomechanical approach for testing the quantumness of gravity. We focus on generating gravity-induced entanglement between optomechanical mirrors with feedback control and quantum filters. We investigated the conditions necessary for generating gravity-induced entanglement in an optomechanical approach. We also consider optimizing the optomechanical approach by evaluating the signal-to-noise ratio to detect gravity-induced entanglement. We also discuss milestones to achieve the detection of gravity-induced entanglement. If I have time, I mention the interaction between optomechanics and gravitational waves.

D. Miki, A. Matsumura, K. Yamamoto, PHYSICAL REVIEW D 109, 064090 (2024)
D. Miki, A. Matsumura, K. Yamamoto, PHYSICAL REVIEW D 110, 024057 (2024)
D. Miki, et al. PHYSICAL REVIEW A 107, 032410 (2023)
S. Iso, K. Izumi, N. Matsumoto, A. Matsumura, D. Miki, K. Yamamoto, et al., in preparation

Towards 3D ground-state cooling of a microparticle

Kiyotaka Aikawa, Prof, University of Tokyo, Japan

Cooling the motions of levitated nanoparticles to near the ground state is an important step for observing and manipulating their quantum behaviors. We realize purely optical feedback cooling of a neutral nanoparticle with its motional occupation numbers of (6,6,0.7) in three directions. Given the possibility that each degree of freedom is coupled with each other via various mechanisms, cooling all the translational motions to the ground state might be desirable for future applications. It has been theoretically predicted that the motions of particles with diameters of around 1 micrometer can be observed efficiently in any direction. In this talk, we present a step towards cooling a levitated microparticle.

Ferromagnetic Levitation Of Yttrium Iron Garnet Spheres For Macroscopic Quantum Mechanics

Maria Fuwa, Dr. Advanced Industrial Science and Technology (AIST)

I will report passive magnetic levitation and three-dimensional harmonic trapping of a 0.3-milligram, 0.5-millimeter-diameter yttrium iron garnet sphere at 4 K. The gradient of an external magnetic field is used for vertical trapping, while the finite-size effect of the diamagnetic effect is used for horizontal trapping. The dynamics of the levitated sphere was optically measured to have trapping frequencies of up to around 600 Hz and mechanical Q factors of the order of Q ∼ 10^3 . These results were quantitatively reproduced by three-dimensional finite-element method simulations. These results can provide a system where magnetism, rigid body motions, microwaves, and optics interact.

Pentacene-Doped Naphthalene For Levitated Optomechanics

Marit O. E. Steiner, Ms, Institute of Theoretical Physics, Ulm University, Germany

I will talk about pentacene-doped naphthalene as a material for diamagnetic levitation, offering compelling applications in matter-wave interferometry and nuclear magnetic resonance. Pentacene-doped naphthalene offers remarkable polarizability of its nuclear spin ensemble, achieving polarization rates exceeding 80 % at cryogenic temperatures with polarization lifetimes extending weeks. We design a multi-spin Stern-Gerlach-type interferometry protocol which, thanks to the homogeneous spin distribution and the absence of a preferential nuclear-spin quantization axis, avoids many of the limitations associated with materials hosting electronic spin defects, such as nanodiamonds containing NV centers. We assess the potential of our interferometer to enhance existing bounds on the free parameters of objective collapse models. Beyond matter-wave interferometry, we analyze the prospects for implementing magic angle spinning at frequencies surpassing the current standard in NMR, capitalizing on the exceptional rotational capabilities offered by levitation. Additionally, we outline a novel protocol for measuring spin ensemble polarization via the position of the nanoparticle and conduct an analysis of dominant noise sources, benchmarking the required isolation levels for various applications.

Co-authors:Marit O. E. Steiner, Julen S. Pedernales, Martin B. Plenio

[1] M. Steiner, J. S. Pedernales, and M. B. Plenio, Pentacene-Doped Naphthalene for Levitated Optomechanics, arXiv:2405.13869

From Organic Kittens Towards Metallica Cats

Markus Arndt, Prof, University of Vienna, Faculty of Physics, QNP Group, Austria

When Erwin Schrödinger proposed his monstrous idea of placing a living cat in a superposition of being dead and alive, he invoked entanglement as an essential tool to achieve this feat. And while entanglement is a fundamental aspect of the quantum physics of many-body systems, it turns out not to be necessary for preparing superpositions of distinct states of massive, warm, organic, or inorganic systems. Over the years, we have developed numerous experimental setups capable of demonstrating the delocalization of massive objects across distances many times their own diameter. These range from diffraction experiments with carbonaceous molecules to near-field interferometry with biologically relevant molecules, peptides, and clusters of organic molecules, which can be well described as Schrödinger kittens. I will review these efforts and recent progress in scaling up from “kittens” to “cats” using massive metal nanoparticles, which are already as large as proteins or small viroids. Additionally, I will discuss what is still needed to advance matter-wave research to systems closer to the living world.

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Markus Aspelmeyer, Prof, University of Vienna, Austria

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Characterisation Of A Levitated Sub-Milligram Ferromagnetic Cube In A Planar Alternating-Current Magnetic Paul Trap

Martijn Janse, Mr. Leiden University, The Netherlands

Microscopic levitated objects are a promising platform for inertial sensing, testing gravity at small scales, optomechanics in the quantum regime, and large-mass superpositions. However, existing levitation techniques harnessing optical and electrical fields suffer from noise induced by elevated internal temperatures and charge noise, respectively. Meissner-based magnetic levitation circumvents both sources of decoherence but requires cryogenic environments. In this presentation, we characterise a sub-milligram ferromagnetic cube levitated in an alternating-current planar magnetic Paul trap at room temperature. We show behavior in line with the Mathieu equations and quality factors of up to 2500 for the librational modes. Besides technological sensing applications, this technique sets out a path for megahertz librational modes in the micrometer-sized particle limit and can be extended by implementing superconducting traps in cryogenic environments, allowing for magnetic coupling to superconducting circuits and spin-based quantum systems.

Co-authors: Martijn Janse, Eli van der Bent, Mart Laurman, Robert Smit, Bas Hensen

Boosting Optomechanical Performances Of A Levitated Particle Through Wavefront Shaping

Melissa Kleine, Ms, LOMA, CNRS, Université de Bordeaux, France

Achieving high trap stiffness is essential for stable confinement, particularly in low-pressure environments where reduced damping can otherwise amplify frequency fluctuations and compromise measurement accuracy. We developped an experimental method for optimizing the stiffness of an optical trap in the Rayleigh regime through wavefront shaping, significantly enhancing trap stability and control. This optimization proves especially effective when the dipole approximation fails to accurately describe the system. Our findings reveal that wavefront optimization can reduce both scattering forces along the optical axis and Duffing-type nonlinearities.

Co-authors:Mélissa Kleine, Yacine Amarouchene, Yann Louyer, Stefan Rotter, Mathias Perrin, Nicolas Bachelard

Quantum Backaction And Entanglement With Mechanical Oscillators

Mika Sillanpää, Prof, Department of Applied Physics, Aalto University, Finland

Quantum mechanics sets a limit for the precision of continuous measurement of the position of an oscillator. Mechanical oscillators affected by radiation pressure forces allow to explore such quantum limits in measurement and amplification. An interesting setup for the purpose consists of superconducting microwave cavities coupled to micromechanical vibrating membranes. We show how it is possible to measure an oscillator without quantum back-action of the measurement by constructing one effective oscillator from two physical oscillators. We realize such a quantum mechanics-free subsystem using two micromechanical oscillators, and show the measurements of two collective quadratures while evading the quantum back-action by 8 decibels on both of them, obtaining a total noise within a factor of 2 of the full quantum limit. By perturbing the measurement slightly, such measurements could be used to generate stabilized entanglement between two macroscopic mechanical oscillators. This prepares a canonical entangled state known as the two-mode squeezed state. We carry out this measurement, and verify the existence of entanglement in the steady state by direct access to fluctuations in all the collective motional quadratures.

Co-authors: Laure Mercier de Lépinay, Caspar F. Ockeloen-Korppi, Matthew J. Woolley, Mika A. Sillanpää

Emergence Of Classicality From Quantum Foundations: Testing The Schrodinger-Newton Equation

N Sneha, Ms., National Institute of Science Education and Research Bhubaneswar, India

The macro-objectification problem addresses the role of quantum mechanics in the classical world. The Schrödinger-Newton (SN) equation, derived in the Newtonian limit, assumes quantum matter and classical gravity[1]. Papers such as "Testing Gravitational Self-Interaction via Matter-Wave Interferometry[2]" and "Emergence of Classicality in Stern-Gerlach Experiment via Self-Gravity[3]" by SK Sahoo, et al., propose tests to validate the SN equation and its significance in the emergence of classicality. These studies distinguish the effects of the SN equation from environmental decoherence, an alternative approach to the macro-objectification problem. Superposition and entanglement are fundamental aspects of quantum mechanics. We now aim to further investigate the effect of the SN equation on superposition and entanglement separately. We investigate the evolution of the interference term in a double-slit experiment involving a single massive particle. The initial wavefunction, defined as a superposition (in the position basis) of two Gaussians corresponding to the slits, is evolved using the Crank-Nicolson method. For low mass, the SN evolution aligns with the free Schrödinger evolution over large timescales, as expected. We deal with Schrodinger Cat states for higher masses ($10^{10}$ u), and the interference term under SN evolution significantly deviates from the free Schrödinger case over short timescales. The SN potential helps maintain coherence but localizes the wavefunction to such a great extent that the outcome initially agrees with the classical expectation but causes attraction of the two peaks at late times. We interpret interference as a measure of coherence. We explore the interplay between the broadening effect of the free Schrödinger term and the shrinking effect due to self-gravity (SN potential) by observing the evolution of a single Gaussian in the initial superposition. Additionally, we consider how gravitational decoherence can help to explain the observation of classical results for massive objects. The geometric phase, a robust property and a measure of entanglement are proposed to be examined under the SN equation. We show that the geometric phase accumulated by a single particle in an Aharanov-Bohm setup remains unchanged under SN evolution compared to the free Schrödinger case. We are currently studying the effect of the SN equation on the geometric phase of two entangled particles in a Mach-Zehnder setup. Carrying out the proposed experiments will unravel the nature of gravity and its role in the emergence of classicality.

Co-authors:N Sneha, Prof. Radhika Vathsan, Dr. Sourav K Sahoo, Mr. Dharmaraj

[1]: Bahrami, M., Großardt, A., Donadi, S. \& Bassi, A. The Schrodinger Newton equation and its foundations. New Journal of Physics (Nov. 2014).
[2]: Sahoo, S. K., Dash, A., Vathsan, R. \& Qureshi, T. Testing gravitational self-interaction via matter-wave interferometry. Phys. Rev. A 106, 012215 (1 July 2022).
[3]:S. K. Sahoo, R. Vathsan, T. Qureshi, Emergence of Classicality in Stern–Gerlach Experiment via Self-Gravity. ANNALEN DER PHYSIK 2023, 535, 2200627.

Vacuum Levitation And Motion Control On Chip

Nadine Meyer, Prof, NanoPhotonics Systems Laboratory, ETH Zurich, Switzerland

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Quantum Computing With Dissipative Cat Qubits

Nicolas Didier, Dr, Head of Device Theory Team Lead at Alice & Bob, Paris, France

The massive hardware overhead required to implement quantum error correction remains a big roadblock towards the realization of a fault-tolerant, universal quantum computer. Bosonic codes are a promising approach to decrease significantly the number of physical qubits per logical qubit by implementing a first layer of error correction at the physical level. In particular, dissipative cat qubits suppress bit-flip errors exponentially over orders of magnitude, such that in principle only phase-flip errors need an active error correction. Combining the strong noise bias of dissipative cat qubits with the efficiency of LDPC codes, we estimate a 200-fold reduction in physical qubits to run Shor's algorithm compared to the surface code. In this talk, I will present our work to engineer and increase the peculiar kind of dissipation, known as two-photon dissipation, allowing to suppress exponentially the bit-flips of cat qubits. I will also present our results realizing quantum gates on cat qubits that leverage the two-photon dissipation in order to preserve the exponential suppression of bit-flips during the gate, a key requirement for the repetition code correcting for phase-flip errors.

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Oriol Romero-Isart, Prof, ICFO Barcelona, Spain

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Modelling Of Recirculating Multipass Alkali Cell For Ultrahigh Sensitivity Atomic Magnetometry

Qian Ling Kee, Ms, A*STAR Quantum Innovation Centre(Q.InC), Institute for Materials Research and Engineering(IMRE), Agency for Science, Technology and Research(A*STAR), Singapore

Multipass cells are widely used in atomic magnetometry as they reduce spin projection noise by increasing the interaction volume of the probe beam with the atomic vapour. We develop an analytical form of the diffusion component of spin noise time-correlation function and the spin noise frequency spectrum in an astigmatic Gaussian probe beam in multipass cells. Furthermore, we introduce a novel recirculating multipass cell design for atomic magnetometry with high active-to-cell volume ratio, and derive an analytical model to predict the distribution of beam spots on the cell mirrors. Finally, we demonstrate that this recirculating multipass cell design offers a slower decay of the spin noise correlation function compared to conventional cylindrical multipass cells.

Co-authors: Qian Ling Kee, Lingyi Zhao, Ruvi Lecamwasam, Xinan Liang, Biveen Shajilal, Joel K Jose, Yao Chen, Ping Koy Lam, and Tao Wang

Squeezing In A Non-Linear Potential: A Psesuit For Non-Classical Quantum States

Qiongyuan Wu, Dr, Research Associate, King's College London, UK

Optically levitated nanoparticle experiments are great candidates for testing fundamental physics due to their excellent control over the system and great separation from the environment. Nowadays, the centre-of-motion (COM) of the levitated nanoparticle can be cooled down to its ground state, paving the way for potential quantum applications. Current limitations of this platform are 1) the size of the ground state and 2) that the system mainly follows a Gaussian process, such that it is difficult to demonstrate macroscopic quantumness and the dynamics is efficiently simulatable. We demonstrated the squeezing protocol [1] and the classical non-Gaussian state generation protocol [2], with the hope that a combination of both techniques can guide us to the generation of non-classical quantum states in the levitating nanoparticle experiments.

Co-authors:Rafael Muffato, Diana A. Chisholm, Tiberius Georgescu, Jack Homans, Hendrik Ulbricht, Matteo Carlesso, Mauro Paternostro

[1]. Qiongyuan Wu, Diana Chisholm, et al. Mar. 2024. “Squeezing below the ground state of motion of a continuously monitored levitating nanoparticle”. Wu et al 2024 Quantum Sci. Technol.
[2]. Rafael Muffato, [. . .], Qiongyuan Wu, et al. Jan. 2024. “Generation of classical non-Gaussian distributions by squeezing a thermal state into non-linear motion of levitated optomechanics”. arXiv:2401.04066.

Experimental Realization Of Optical Cat States With Photon-Added Squeezed States

Ray-Kuang Lee, Prof, National Tsing Hua University, Taiwan

Here, we report the first experimental realization of optical cat states by adding a photon to a squeezed vacuum state; so far only photon-subtraction protocols have been realized. Photon addition gives us the advantage of using heralded signal photons as experimental triggers, and we can generate cat states at rates exceeding 2.3 x 10^5 counts per second. Moreover, our recent progress will be demonstrated in applying a machine-learning (ML) enhanced quantum state tomography (QST) on Wigner currents, Bayesian estimation, and quantumness measure for optical cat states.

Remote Sensing Of A Levitated Superconductor With A Flux-Tunable Microwave Cavity

Remi Claessen, Mr, University of Vienna, Austria

In our approach towards quantum mechanical control of macroscopic objects, we levitate superconducting microspheres with a mass of 6 µg in a magnetic trap, enabling mass-independent levitation with ultralow dissipation [1]. In a recent evolution of the experiment, we have inductively coupled the mechanical motion of the levitating microsphere to a resonant superconducting quantum circuit [2], thereby demonstrating a tunable electromechanical interaction. This allows us to define a quantitative path towards ground-state cooling and quantum control of levitated particles with Planck-scale masses at millikelvin environment temperatures. This contribution will discuss the prospects and challenges of the envisioned approach, along with the current status of our experiment and readout system.

Co-authors:R. Claessen, P. Schmidt, G. Higgins, J. Hofer, J, Hansen, M, Zemlicka, M Trupke, M. Aspelmeyer

[1] J. Hofer et al., High-Q Magnetic Levitation and Control of Superconducting Microspheres at Millikelvin Temperatures, Phys. Rev. Lett. 131, 043603 (2023)
[2] P. Schmidt, R. Claessen, et al., Remote sensing of a levitated superconductor with a flux-tunable microwave cavity, Phys. Rev. Appl. (accepted), 2024

How To Leverage Lie Algebras In Quantum Optomechanics

Ruvi Lecamwasam, Dr, A*STAR Quantum Innovation Centre (Q.InC), Institute for Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore

Lie algebras arise from the natural structure of quantum mechanics. In this talk I will discuss what a Lie algebra is, and how you can use them in quantum sensing and optomechanics. I’ll discuss recent work showing how Lie algebras can provide linear parameterisations of nonlinear quantum dynamics, greatly simplifying calculations in metrology [1]. I’ll then introduce a Mathematica package called OperatorAlgebra, which can automatically perform many Lie algebra calculations that would otherwise be pages of tedious algebra [2]. Finally I’ll discuss upcoming work using perturbation theory to obtain an analytical solution for nonlinear optomechanics. This solution is the first to consider the full nonlinear optomechanical Hamiltonian, and also includes the effects of damping. We’ll discuss how this can be used to analyse quantum effects in regimes accessible to experiment.

Co-authors:Ruvi Lecamwasam, Tatiana Iakovleva, Bojko Bakalov, Jason Twamley

[1] Ruvi Lecamwasam, Tatiana Iakovleva, & Jason Twamley (2023), Quantum metrology with linear Lie algebra parameterisations arXiv:2311.12446.
[2] Joseph J Hope & Ruvi Lecamwasam (2024), OperatorAlgebra github.com/ruvilecamwasam/operatoralgebra

Macroscopic Quantum Superpositions With Magneto-Mechanics

Shilu Tian, Dr. Okinawa Institute of Science and Technology, Japan

In this talk, we propose two methods to produce ultra-large spatial superposition of massive objects where the spatial separation between the individual states: ∆x, is much larger than their zero point motion xzpm, (χ ≡ ∆x/xzpm~10^6). In the first method, we consider the levitation of an insulating ferromagnetic micro particle and we use nearby superconducting circuits that produce quantum magnetic forces to create a spatial superposition and find we can achieve extremely high χ which is independent of the size. In the second method we propose the magnetic levitation of an entire superconducting quantum circuits. The superconducting circuits can be levitated and driven inductively. We consider superconducting circuits on spatial scales of 100-300 microns and show under what conditions they can be levitated and compute, both analytically and numerically (via Comsol), their motional trap frequencies. By driving these circuits inductively we can achieve extremely large values for χ ∼ 10^6.

Co-authors: S. Raman Nair, G.K. Brennen, S. Bose and J. Twamley.

Generation And Protection Of Schroedinger Cat States Of Mechanical Oscillators Interacting With A Non-Markovian Environment

Tommaso Trognacara, Mr., Università degli Studi di Milano, Italy

Quantum mechanics allows a system to exist in multiple states at one time or in a quantum superposition. This property can be exploited in a wide range of physical systems and in particular in optomechanical systems. In optomechanics, the mechanical degrees of freedom can nontrivially interact with confined modes of the electromagnetic field, leading to the emergence of quantum superpositions of massive objects. Apart from their fundamental interest, such superpositions would constitute a powerful resource for the implementation of novel quantum technologies, with applications ranging from continuous-variable quantum information processing to quantum sensing and quantum communication. Despite a wide range of potential application, achieving quantum superposition in controllable mechanical degrees of freedom remains a significant challenge. Recent progress in the field has led to successful experimental realizations [cite Quantum squeezing in a nonlinear mechanical oscillator]. However, the unavoidable interaction with the environment causes such bosonic motional superpositions to be short lived. This short lifetime is a significant barrier towards their use in quantum technologies. Normally, the key to achieve longer-lived superpositions relies on enhancing the quality of the experimental setup with a quieter environment. In this work we adopt a different solution where we develop a time dependent drive which act only on the bosonic system which reduces the effects of the surrounding environment. We derive time dependent controls to not only generate a motional macroscopic quantum superposition in an optomechanical system but also to protect this generated superposition from the effects of a non-Markovian environment. We show, both numerically and analytically, that the quantumness of the state can be preserved for extremely long durations.

Co-authors: Tommaso Trognacara, Anil Kumar, Kani Mohamed, Jason Twamley

Co-Trapping An Ion And A Nanoparticle In A Two-Frequency Paul Trap

Tracey Northrup, Prof, University of Innsbruck, Austria

Coupling a spin qubit to a mechanical system provides a route to prepare the mechanical system's motion in nonclassical states, such as a Fock state or an entangled state. While such quantum states have already been realized with superconducting qubits coupled to clamped mechanical oscillators, here we are interested in achieving an analogous coupling between a spin and a levitated oscillator, namely, between an atomic ion and a silica nanoparticle in a linear Paul trap. Levitated systems offer extreme isolation from the environment and the possibility to dynamically adjust the oscillator's confining potential, providing a path for the generation of macroscopic quantum superpositions.

I will present recent steps in this direction: First, we have adapted techniques originally developed for trapped atomic ions, including detection via self-interference and sympathetic cooling, for the domain of nanoparticles [1,2]. Second, we have confined a nanoparticle oscillator in ultra-high vacuum and obtained quality factors above 10^10, evidence of its extreme isolation from its environment [3]. Finally, we have trapped a calcium ion and a nanoparticle together in a linear Paul trap, taking advantage of a dual-frequency trapping scheme [4].

[1] L. Dania, K. Heidegger, D. S. Bykov, G. Cerchiari, G. Arenada, T. E. Northup, Phys. Rev. Lett. 129, 013601 (2022)
[2] D. S. Bykov, L. Dania, F. Goschin, T. E. Northup, Optica 10, 438 (2023)
[3] L. Dania, D. S. Bykov, F. Goschin, M. Teller, A. Kassid, T. E. Northup, Phys. Rev. Lett. 132, 133602 (2024)
[4] D. Bykov, L. Dania, F. Goschin, T. E. Northup, arXiv:2403.02034 (2024)

Quantum Control Of A Cat-Qubit With Bit-Flip Times Exceeding Ten Seconds

Ulysse Reglade, Dr, Alice & Bob, ENS Paris

Quantum bits (qubits) are prone to several types of errors due to uncontrolled interactions with their environment. Common strategies to correct these errors are based on architectures of qubits involving daunting hardware overheads. A hopeful path forward is to build qubits that are inherently protected against certain types of errors, so that the overhead required to correct remaining ones is significantly reduced. However, the foreseen benefit rests on a severe condition: quantum manipulations of the qubit must not break the protection that has been so carefully engineered. A recent qubit - the cat-qubit - is encoded in the manifold of metastable states of a quantum dynamical system, thereby acquiring continuous and autonomous protection against bit-flips. Here, in a superconducting circuit experiment, we implement a cat-qubit with bit-flip times exceeding 10 seconds. This is a four order of magnitude improvement over previous cat-qubit implementations. We prepare and image quantum superposition states, and measure phase-flip times above 490 nanoseconds. Most importantly, we control the phase of these quantum superpositions without breaking bit-flip protection. This experiment demonstrates the compatibility of quantum control and inherent bit-flip protection at an unprecedented level, showing the viability of these dynamical qubits for future quantum technologies.

Co-authors: Ulysse Réglade, Adrien Bocquet, Ronan Gautier, Joachim Cohen, Antoine Marquet, Emanuele Albertinale, Natalia Pankratova, Mattis Hallén, Felix Rautschke, Lev-Arcady Sellem, Pierre Rouchon, Alain Sarlette, Mazyar Mirrahimi, Philippe Campagne-Ibarcq, Raphaël Lescanne, Sébastien Jezouin, Zaki Leghtas

Creation And Manipulation Of Schrodinger Cat States Of A Nuclear Spin Qudit In Silicon

Xi Yu, Mr, University of New South Wales, Sydney, Australia

High-dimensional quantum systems are a valuable resource for quantum information processing. They can be used to encode error-correctable logical qubits, for instance in continuous-variable states of oscillators such as microwave cavities or the motional modes of trapped ions. Powerful encodings include ‘Schrödinger cat' states, superpositions of widely displaced coherent states. Recent proposals suggest encoding logical qubits in high-spin atomic nuclei, which can host hardware-efficient versions of continuous-variable codes on a finite-dimensional system. Here we demonstrate the creation and manipulation of Schrödinger cat states using the spin-7/2 nucleus of a single antimony atom, embedded in a silicon nano-electronic device. We use a coherent multi-frequency control scheme to produce spin rotations that preserve the SU(2) symmetry of the 8-level qudit. These SU(2)-covariant rotations (CR) constitute logical Pauli operations for logical qubits encoded in the Schrödinger cat states. Together with the set of ‘virtual-SNAP’ gates, which impart an arbitrary phase on each qudit level, the CR are used to generate the cat state (see the pulse sequence in figure a). After the generation protocol, We measure an equal superposition of the two spin-coherent states with opposite magnetization (figure b) and the Wigner function of the cat states (figure d) exhibits parity oscillations with a contrast up to 0.982(5) (figure c), and state fidelities up to 0.913(2). Furthermore, a strong orientation-dependent lifetime of the spin-7/2 cat state is observed, with T2* values of 15.0(6) ms for parallel and 49(2) ms for perpendicular orientations. These findings hold promise for encoding logical qubits into perpendicular cat states, leveraging inherent biases in physical noise affecting nuclear spins. These results demonstrate high-fidelity preparation and logical control of nonclassical resource states and underscore the feasibility of quantum error correction on a single atomic site within a semiconductor platform.

Diamagnetically Levitated Cavity Optomechanics With Low Eddy Current Materials

Xianfeng Chen, Dr. Agency for Science, Technology and Research (A*STAR), Singapore

Cavity optomechanics is widely used in applications ranging from precision sensing to tests of fundamental physics [1]. The ultimate limit to an optomechanical system’s performance is fundamentally determined by the energy dissipation rate, and many different methods have been proposed to minimize this. Among those, levitation that provides an ideal isolation of objects from their environment is emerging as a promising platform for ultra-low loss optomechanical systems [2]. This is exemplified by the motional quantum ground state cooling of an optically levitated particle [3], and an electrically levitated resonator with ultra-high mechanical quality factor exceeding 1010 [4]. However, these levitation schemes can only levitate nanometer-sized particles and require continuous energy supply that limits their wide applications.

Here, we study a low loss optomechanical system based on diamagnetic levitation, which is the only passive method that can levitate macroscopic objects at zero energy consumption. Due to its strong diamagnetic property, pyrolytic graphite with mass beyond milligram can easily be levitated above permanent magnets at room temperature. At high vacuum, the dominant source of dissipation is caused by eddy currents, induced as the conducting graphite moves through the magnetic field of the magnets [5]. To suppress the eddy currents, we disperse micro graphite particles in an insulating polymer and demonstrate a low-dissipation resonator with a mechanical Q factor beyond 105. To study the optomechanical interaction, we build a Fabry–Pérot cavity composed of a fixed mirror, and a levitated resonator whose surface is engineered with a high reflectivity coating. The high-finesse cavity allows us to read out the motion of the levitated resonator with extremely high precision and facilitates a radiation pressure force interaction with the levitated object. Through this optomechanical interaction, our low loss levitated optomechanical system with macroscopic mass has strong coupling to weak external forces, thus is of interest for precision sensing applications like accelerometers and gravimeters.

[1] Aspelmeyer, M., Kippenberg, T. J., & Marquardt, F. (2014). Cavity optomechanics. Reviews of Modern Physics, 86(4), 1391.
[2] Gonzalez-Ballestero, C., Aspelmeyer, M., Novotny, L., Quidant, R., & Romero-Isart, O. (2021). Levitodynamics: Levitation and control of microscopic objects in vacuum. Science, 374(6564), eabg3027.
[3] Delić, U., Reisenbauer, M., Dare, K., Grass, D., Vuletić, V., Kiesel, N., & Aspelmeyer, M. (2020). Cooling of a levitated nanoparticle to the motional quantum ground state. Science, 367(6480), 892-895.
[4] Dania, L., Bykov, D. S., Goschin, F., Teller, M., & Northup, T. E. (2024). Ultra-high quality factor of a levitated nanomechanical oscillator. Physical review letters.
[5] Chen, X., Ammu, S. K., Masania, K., Steeneken, P. G., & Alijani, F. (2022). Diamagnetic Composites for High‐Q Levitating Resonators. Advanced Science, 9(32), 2203619.

Quantum States Of Massive Mechanical Objects

Yiwen Chu, Prof, ETH Zürich, Switzerland

One of the first model systems we encounter in quantum mechanics class is a mass on a spring. However, in practice, it is not easy to observe a massive mechanical object exhibiting the quantum properties of a harmonic oscillator, such as zero-point fluctuations, energy quantization, or quantum superpositions. Nevertheless, in recent years, it has become possible to control and the measure the quantum states of the motion of macroscopic mechanical objects. I will present our recent experiments on creating “Schrödinger cat” states in a bulk acoustic wave resonator by coupling it to a superconducting circuit, and how we can observe the quantum ground state of a several hundred microgram mechanical mode using light. I will also discuss the applications of these systems in quantum information, quantum sensing, and explorations of fundamental physics.

Co-authors: Marius Bild, Matteo Fadel, Yu Yang, Uwe von Luepke, Phillip Martin, Alessandro Bruno

Posters

1 Coupled Dynamics Of Non-Rotating Absorbing Particles Levitated In A Photophoretic Trap

Presenting Author: Anita Pahi, Ms, Indian institute of Science Education and Research Kolkata, India

We study the dynamics of non-rotating carbon micro clusters trapped in air with photophoretic force using a loosely focused Gaussian beam. We observe that the clusters show irregular thermal fluctuations with amplitudes higher than typical Brownian fluctuations in the beam propagation direction (z-direction) while stably confined in the plane perpendicular to it. We have shown both experimentally and numerically that the autocorrelation function along x has a two-step relaxation, which is indicative of a coupled motion arising due to the particle's asymmetric shape and a tilted harmonic potential.

Anita Pahi, Kirty Ranjan Sahoo, Biswajit Das, Shuvojit Paul and Ayan Banerjee

2 Exploring Hybrid Levitated Optomechanics With Molecules For Precision Measurements

Presenting Author: Bart Schellenberg, Mr, University of Groningen, The Netherlands

We are currently exploring the use of trapped nanoparticles with molecules using a hybrid trap as a new means of experimental control. Cold atoms or molecules can be used to sympathetically cool a trapped nanoparticle through collisional interactions [1]. By trapping a charged nanosphere with molecular ions, the strong Coulomb coupling even allows for direct interactions despite an orders of magnitude mass difference [2]. The rotational and vibrational degrees of freedom of polar molecules in such a system presents a new channel for probing the nanosphere’s properties, with potentially excellent sensitivity to the its shape and mass [3].

[1] Hopper et al., New J. Phys. 26 013015 (2024)
[2] Bykov et al., arXiv:2403.02034 (2024)
[3] Schellenberg et al., Appl. Phys. Lett. 123 114102 (2023)

3 Quantum Fluctuation Forces Between Optically Trapped Nanospheres

Presenting Author: Clemens Jakubec, Mr, University of Vienna, Austria

We present an analysis of the quantum fluctuation forces between two dielectric nanospheres trapped via optical tweezers. We develop a full quantum description of the radiative forces between the two nanospheres using an open quantum system master equation approach. Considering their mutual interaction mediated via the classical trapping field and the quantum fluctuations of the electromagnetic field, an analysis of the three separate contributions to the total potential – the Casimir-Polder potential, the classical trap potential and the optical binding potential – is presented. The total potential is subsequently studied as a function of various parameters, such as the tweezer field intensity and phase, demonstrating that, for appropriate sets of parameters, there exists a mutual bound state of the two nanospheres which can be ~200 K deep. Furthermore, we utilize the master equation approach to study the decoherence and dissipation of the quantized centre of mass of the nanospheres, focusing in particular on the interplay between fluctuation fields and the external drive. Our results are pertinent to ongoing experiments with trapped nanospheres in the macroscopic quantum regime and for exploring quantum thermodynamic phenomena.

Co-authors: Uroš Delić, Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna
Markus Aspelmeyer, Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna
Pablo Solano, Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción
Kanu Sinha, Wyant College of Optical Sciences and Department of Physics, University of Arizona

4 How To Make N-Partite Quantum Interactions Tractable

Presenting Author: Derek Abbott, Prof, University of Adelaide, Australia

We use an N-qubit setting that uses an Einstein-Podolsky-Rosen (EPR) type experiment, as the underlying physical setup. In the EPR setting the quantum system reduces itself to the corresponding classical case when the shared quantum state reaches zero entanglement. We find the relations for the probability distribution for N-qubit GHZ and W-type states, subject to general measurement directions. As a specific example, we solve the quantum Prisoners’ Dilemma game for the general case of N >= 2. By dispensing with the standard unitary transformations on state vectors in Hilbert space and using instead rotors and multivectors, based on Clifford’s geometric algebra (GA), we show how the N-qubit case becomes tractable. The new mathematical approach presented here has wide implications in the areas of quantum information and quantum complexity, as it opens up a powerful way to tractably analyze N-partite qubit interactions.

5 Schrodinger Cat Paradox With A Entangling Past

Presenting Author: Ekta Rupareliya, Ms, Indian Institute Of Technology Delhi, India

The quantum system is observed yet defining the properties of the quantum system has proven itself to be the Pandora of secrets. Implication of the quantum world would open up various possibilities of understanding of time and space and the complexity of the entire universe and the nature of the universe.

The paradoxes and the interpretation in the quantum physics is always been a mysterious yet and inrailing experimental techniques whether they are the wigner's friend , Entanglement, Copenhagen interpretation, decoherence, many world , bohemian theory, QBism , retrocausality , collapse theory ,bell test, local friendliness,. The AGI would would be able to solve the problems and would be a paradigm shift . My interpretation of the solution of the problem would be named as super pretentious as Scientist have already observed wave particle duality and how the electrons from the electron beam changes its form depending on the observer which have to pretend or make a mind that this would be the reality this is also observed in one of the experiments by Dr. Masaru Emoto how the molecules of water are affected by our thoughts ,words ,feeling. Another approach always problem can also be proved from the existence of ether which we can also proved to be a linking block between the two identical particles and can prove this smoky action at the distance . If experimentally proven it can also be explained by symmetries of the universe how the human body visually resemblance with the universe which is province by the astrophysics. This observation can also give rise to the paradox or the theory of existence of something a signal or a stimuli which accelerate the smoky action at a distance. This time space paradox and the multidimensional universe at the atomic scale. The various approaches given above can only be scientifically proven after the intervention or invention of superior technology and techniques which can approach the universe and the existence of multidimensional reality or the existence of the multiple universe. If given proof of the existence of the theory it would be revolutionize the quantum theory and define the various parameters of the Quantum mechanics. I want to work in an quantum experimental laboratory in the near future and learn various approaches which I can use to prove this theory.

6 State Preparation Of Multi-Mode Grid States From Multi-Mode Gaussian States And Stabilizer Measurements

Presenting Author: Ha Nguyen, Mr, INRIA Centre de Recherche de Paris, France

Quantum error correction (QEC) will be essential to achieve large-scale quantum computations. Bosonic error correcting codes have recently emerged as hardware-efficient schemes to protect quantum information by taking advantage of their mathematical description involving continuous variables, that is, spaces of infinite dimension. This adds an additional degree of freedom which is not available in more standard qubit architectures.

Recent advances in quantum engineering have enabled realizations of bosonic qubits with good quality such as long-live cat qubits [1], preparation of autonomous quantum error correction of logical states in the mode of a superconducting cavity [2], and propagating light [3]. In particular, the Gottesman-Kitaev-Preskill (GKP) codes have led to the first experimental demonstration of quantum error correction beyond break-even [4]. GKP codes have extraordinary properties that are resilient to noise channels that can be approximated by random displacement errors. However, it comes at a cost of extremely challenging state preparation. Moreover, to correct larger displacements, multi-mode GKP codes are required. Optimizing state preparation of multi-mode GKP states is therefore essential for GKP-QEC to work in practice.

We present a new method of preparing a general multi-mode GKP (grid) state, where we first prepare an appropriate multi-mode Gaussian state (ansatz) and then project it to the GKP code space by stabilizer measurements. The method is based on a subtle choice of the generator matrix of the GKP lattice state. The advantage of starting with an ansatz is twofold. First, the ansatz can be designed such that it is favorable to realize experimentally. Second, we can do optimization on ansatz’s parameters to minimize the noise due to imperfections or approximations such as finite squeezing. In contrast, the standard approach limits the freedom of state preparation when the stabilizer measurements are fixed at the beginning. Furthermore, our method could serve as a valuable theoretical tool for analyzing existing procedures used in the preparation of GKP states in photonics and superconducting architectures, including methods that do not necessitate explicit stabilizer measurements. This is also useful for studying GKP-type state conversion protocols with Gaussian transformations.

[1] U. Réglade et al. “Quantum control of a cat qubit with bit-flip times exceeding ten seconds”. In: Nature 629.8013 (2024).
[2] Dany Lachance-Quirion et al. “Autonomous Quantum Error Correction of Gottesman-Kitaev-Preskill States”. In: Phys. Rev. Lett. 132. 150607.
[3] Shunya Konno et al. “Logical states for fault-tolerant quantum computation with propagating light”. In: Science 383.6680 (2024).
[4] V. V. Sivak et al. “Real-time quantum error correction beyond break-even”. In: Nature 616.7955 (2023).

7 Towards A Test Of Quantum Gravity Using Superfluid Helium

Presenting Author: Joseph Aziz, Mr, Royal Holloway, University of London, UK

Witnessing gravitationally induced entanglement (GIE) is considered to be the most promising avenue for obtaining the first experimental evidence that the gravitational field is a quantum field. GIE experiments have been proposed in a number of different systems; spin controlled micro-diamonds, cold atoms, opto-mechanical systems etc. Here we analyse the possibility of using the Josephson effect to entangle super fluid helium via gravity.

Co-author: Richard Howl

8 Towards The Investigation Of The Collision Between Ultracold Atoms And A Levitated Nanoparticle

Presenting Author: Rahul Mohanty, Mr, Tata Institute Of Fundamental Research, Mumbai, India

Collision between ultracold atoms and a nanoparticle is an interesting area of research, as it can reveal the transition from the classical to the quantum regime. Experimentally it has not yet been achieved due to the distinct experimental conditions required for each trap. Ultracold atoms require a magneto-optical trap within an ultra-high vacuum (10^(-8)mbar-10^(-11)mbar), whereas trapping nanoparticles is more feasible at medium vacuum (up to 1mbar) because of damping provided by surrounding gas molecules. These processes occur at different pressure regimes, making it experimentally challenging to achieve simultaneously. Recently, Silica nano-particles are trapped at a pressure of 2 ×10^(-9)mbar [1] paving the way for studies requiring Ultra High Vacuum conditions. Even lower pressures can be achieved by selecting an appropriate initial loading mechanism for the nanoparticles.

We are developing a method to launch and trap a single nanoparticle using a cantilever driven by a piezo [2] .This approach will help us to launch a single nanoparticle even with a smaller sized piezo. Using this as an initial loading method for silica nanoparticles, we are aiming to trap both a nanoparticle and ultracold atoms under the same pressure conditions. This will enable us to study collisions between the two.

We will present our experimental setup designed to trap both species and a launching method for nanoparticles using a cantilever driven by a piezo.

[1] D. Grass, J. Fesel, S. G. Hofer, N. Kiesel and M. Aspelmeyer, "Hollow-core fiber loading of nanoparticles into ultra-high vacuum," Applied Physics Letters, vol. 124, no. 14, pp. 143501-4, 2024.
[2] A. Khodaee, K. Dare, A. Johnson, U. Delić and M. Aspelmeyer, "Dry launching of silica nanoparticles in vacuum," AIP Advances, vol. 12, no. 12, pp. 125023-4, 2022.

9 Optimization Of Static Potentials For Large Delocalization And Non-Gaussian Quantum Dynamics Of Levitated Nanoparticles Under Decoherence

Presenting Author: Silvia Casulleras, Msc. Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, Institute for Theoretical Physics, University of Innsbruck, Austria

Levitated nanoparticles provide a versatile and isolated platform for exploring fundamental quantum phenomena at macroscopic scales. In this work, we present an optimization method tailored to identify optimal static potentials for producing largely delocalized and non-Gaussian quantum states of levitated nanoparticles. Our method incorporates the effects of position-dependent noise originating from the fluctuations of the potential. To reduce the computational cost associated with the multiscale simulation of the system, we define key figures of merit—coherence length and coherent cubicity—characterizing delocalization and quantum non-Gaussianity, respectively. As a proof of principle, we apply this optimization framework to a class of quartic potentials, revealing that the ideal potential configuration is sensitive to both the type and intensity of system noise. The performance of the optimized potentials is validated through full quantum dynamics simulations.

Co-authors: Piotr T. Grochowski and Oriol Romero-Isart

10 Towards Gravitational Wave Sensing With Hbar Devices

Presenting Author: Simon Storz, Dr. ETH Zurich, Switzerland

In High Overtone Bulk Acoustic Wave Resonators (hBARs), quantum information is stored in the collective motion of the atoms in a crystal. These quantum systems are considered macroscopic and are therefore interesting candidates for coupling to gravitational forces. Specifically, hBAR devices could, in principle, detect gravitational waves in the MHz to GHz regime. We discuss initial attempts to characterize the potential effect of such gravitational waves on our hBAR devices through thermometry measurements, and the prospects for future studies.

With: Simon Storz, Andraz Omahen, Marius Bild, Matteo Fadel, Yiwen Chu

11 Microscopic Spin-Lattice Dynamics For Enhanced Quantum Sensing

Presenting Author: Xueqi Ni, National University of Singapore, Singapore

The dynamics of a levitated nanoparticle is intriguing for enhanced quantum sensing. In this work, we present a theoretical model of the dynamics of a levitated ferromagnetic needle. We model the needle as a one-dimensional spin chain with additional lattice degrees of freedom. Our results show that the atoms constituting the lattice precesses collectively like a macrospin under static magnetic fields. Additionally, we analyze fluctuations in the precession angle due to spin-lattice relaxation, which appear as white noise, leading to a T^{-3/2} scaling in magnetic field sensitivity. We also explore the spin-lattice dynamics under a rotating magnetic field, revealing that the lattice can acquire an additional geometric phase. Our findings not only deepen the understanding of how levitated needle dynamics can benefit sensing but also connect to other research possibilities, such as realizing macroscopic superposition states and exploring weak interactions.

Xueqi Ni, Zhixing Zou, Ruvi Lecamwasam, Tao Wang, Jiangbin Gong

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Attendees

1 A Kani Mohamed, Dr Assistant Professor, University of Hyderabad, India

2 Ajmeri Amreen (Shushmi) Chowdhury, University of Strathclyde, UK

3 Alexander Hodges, Mr, OIST, Japan

4 Andrea Morello, Prof, University of New South Wales, Sydney, Australia

5 Andrea Vinante, Senior Researcher, CNR-Institute of Photonics and Nanotechnologies, Trento, Italy

6 Andrew Geraci, Prof, Northwestern University, USA

7 Andrii Yakymenko, Mr, OIST, Japan

8 Anil Kumar, Dr, OIST, Japan

9 Anita Pahi, Ms, Indian institute of Science Education and Research Kolkata, India

10 Anna Pachol, University of South-Eastern Norway

11 Anshuman Nayak, Mr, OIST, Japan

12 Anupam Mazumdar, Prof, Van Swinderen Institute, University of Groningen, The Netherlands

13 Bart Schellenberg, Mr. Van Swinderen Institute, University of Groningen, The Netherlands and Nikhef, Amsterdam, The Netherlands

14 Benjamin Stickler, Prof Ulm University, Germany

15 Bilyana Tomova, Dr, OIST, Japan

16 Chenyue Gu, Ms 1. Quantum Innovation Centre (Q.InC), Agency for Science, Technology and Research (A*STAR); 2. National University of Singapore (NUS)

17 Christophe Pin, Dr, OIST, Japan

18 Clemens Jakubec, Mr, University of Vienna, Austria

19 Collins Okon Edet, Mr. Institute of Engineering Mathematics, Universiti Malaysia, Malaysia

20 Daehee Kim, Mr, OIST, Japan

21 Daisuke Miki, Mr., Kyushu University, Japan

22 Davide Candoli, M. Sc. ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain

23 Dennis Uitenbroek, Mr, Leiden Institute of Physics / Leiden University, The Netherlands

24 Derek Abbott, Prof, University of Adelaide, Australia

25 Ekta Rupareliya, Ms, Indian Institute Of Technology Delhi, India

26 Gavin W Morley, Prof, Warwick University, Physics Department, UK

27 Germain Tobar, Mr, Stockholm University, Sweden

28 Ivette Fuentes Guridi, Prof, University of Southampton and Fellow of Keble College University of Oxford , UK

29 James Millen, Assoc Prof King's College London, UK

30 Jason Twamley, Prof, OIST, Japan

31 Jayadev Vijayan, Dr. University of Manchester, UK

32 Jinjin Dr, Dr, OIST, Japan

33 John Teufel, Dr, Applied Physics Division of NIST, at Boulder, USA

34 Joseph Aziz, Mr. Royal Holloway University of London, UK

35 Juan Bernate, Mr, OIST, Japan

36 Kazuhiro Yamamoto, Prof, Kyushu University, Japan

37 Ketevan Sikharulidze, Ms, OIST, Japan

38 Kiyotaka Aikawa, Prof, University of Tokyo, Japan

39 Maria Fuwa, Dr. National Institute of Advanced Industrial Science and Technology (AIST), Japan

40 Marit O. E. Steiner Institute of Theoretical Physics, Ulm University, Germany

41 Markus Arndt, Prof, University of Vienna, Faculty of Physics, QNP Group, Austria

42 Markus Aspelmeyer, Prof, University of Vienna, Austria

43 Martijn Janse, Mr. Leiden University, The Netherlands

44 Matthew Edmonds, Mr, Swansea University, UK

45 Melissa Kleine, LOMA, CNRS, Université de Bordeaux, France

46 Mika Sillanpää, Prof, Department of Applied Physics, Aalto University, Finland

47 Mojtaba Moshkani, Dr., OIST, Japan

48 N Sneha, Ms. National Institute of Science Education and Research Bhubaneswar, India

49 Nadine Meyer, Prof, NanoPhotonics Systems Laboratory, ETH Zurich, Switzerland

50 Nicolas Didier, Dr, Head of Device Theory Team Lead at Alice & Bob, Paris, France

51 Oriel Romero-Isart, Prof, ICFO Barcelona, Spain

52 Qian Ling Kee, Ms, A*STAR Quantum Innovation Centre (Q.InC), Institute for Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore

53 Qiongyuan Wu, Dr. Research Associate, King's College London, UK

54 Rahul Mohanty, Mr, Tata Institute Of Fundamental Research, Mumbai, India

55 Ray-Kuang Lee,Prof, National Tsing Hua University, Taiwan

56 Remi Claessen, Mr, University of Vienna, Austria

57 Ruvi Lecamwasam, Dr A*STAR Quantum Innovation Centre (Q.InC), Institute for Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore

58 Sergio Ernesto Aguilar Gutierrez, Dr, OIST, Japan

59 Shilu Tian, Dr., Okinawa Institute of Science and Technology, Japan

60 Silvia Casulleras, MSc.Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, Institute for Theoretical Physics, University of Innsbruck, Austria

61 Simon Storz, Dr. ETH Zurich, Switzerland

62 Steven Marz, Mr, OIST, Japan

63 Steven Sagona Stophel, Dr, OIST, Japan

64 Tatiana Oakovleva, Ms, OIST, Japan

65 Tommaso Trognacara, Mr., Università degli Studi di Milano, Italy

66 Tracey Northrup, Prof, University of Innsbruck, Austria

67 Ulysse Reglade, Dr, Alice & Bob , ENS Paris

68 William Munro, Prof, OIST, Japan

69 Xi Yu, Mr, University of New South Wales, Sydney, Australia

70 Xianfeng Chen, Dr. Agency for Science, Technology and Research (A*STAR), Singapore

71 Xueqi Ni, National University of Singapore, Singapore

72 Yuimaru Kubu, Dr, OIST, Japan

73 Yuliya Osika, Ms, OIST, Japan

74 Zhibo Niu, University of Science and Technology of China, China