# Speakers

### Veronica Ahufinger, Autonomous University of Barcelona, Spain

**Spatial adiabatic passage: light, sound and matter waves (Slides)**

We review our recent work in spatial adiabatic passage (SAP) processes [1] for light, sound and matter waves.

We show the experimental implementation of SAP for light in a system of three evanescent-coupled silicon oxide total internal reflection waveguides [2] and we demonstrate its use as high- and low-pass spectral filter taking advantage of the fact that the coupling strength depends on the wavelength [3]. Due to its robustness against technological variations and its low cost, this SAP spectral filter presents an alternative to interference-based and absorbance-based filters.

The application of SAP processes to sound waves propagating in sonic crystals with linear defects [4] is also reported. By modifying the geometry of the linear defects along the propagation direction we design a coherent multifrequency adiabatic splitter, a phase difference analyzer and a coherent multi frequency adiabatic coupler.

In the context of matter waves in few coupled potential wells or waveguides, we investigate SAP processes focusing onto the possibilities of coherent control that they offer. For instance, we discuss how SAP of matter waves in a triple well potential can be used to prepare vibrational states on demand and to perform quantum tomography of the initial population of vibrational states [5]. Also a velocity filter for matter waves has been proposed for SAP of matter waves in coupled waveguides [6]. In addition, SAP processes in two dimensional systems are addressed leading to a robust mechanism for coherent splitting of matter waves for atomic interferometry [7], to the generation of angular momentum carrying states for single atoms [8] and to the detection of geometrical phases.

[1] R. Menchon-Enrich, A. Benseny, V. Ahufinger, A. D. Greentree, Th. Busch and J. Mompart, arXiv:1602.06658, submitted to Reports on Progress in Physics (2016).

[2] R. Menchon-Enrich, A. Llobera, V. J. Cadarso, J. Mompart and V. Ahufinger, IEEE Photonics Technology Letters **24**, 536 (2012).

[3] R. Menchon-Enrich, A. Llobera, J. Vila-Planas, V. J. Cadarso, J. Mompart and V. Ahufinger, Light: Science & Applications **2**, e90; doi:10.1038/lsa.2013.46 (2013).

[4] R. Menchon-Enrich, J. Mompart and V. Ahufinger, Phys. Rev. B **89**, 094304 (2014).

[5] Yu. Loiko, V. Ahufinger, R. Corbalán, G. Birkl and J. Mompart, Phys. Rev. A **83**, 033629 (2011).

[6] Yu. Loiko, V. Ahufinger, R. Menchon-Enrich, G. Birkl, and J. Mompart, Eur. Phys. J. D **68**, 147 (2014).

[7] R. Menchon-Enrich, S. McEndoo, Th. Busch, V. Ahuﬁnger, and J. Mompart, Phys. Rev. A. **89**, 053611 (2014).

[8] R. Menchon-Enrich, S. McEndoo, J. Mompart, V. Ahuﬁnger, and Th. Busch, Phys. Rev. A **89**, 013626 (2014).

### Nicolay Vitanov, Sofia University, Bulgaria

#### A quantum optics perspective to spatial adiabatic passage

In this talk I will review the activities in my group related to the applications of quantum-optical techniques beyond quantum physics. These include adiabatic and composite techniques in waveguides, polarization optics and light frequency conversion, including recent experimental demonstrations. I will describe some other intriguing results in quantum optics that may have applications in spatial adiabatic passage and classical optics.

### Valentin Nesterenko, Joint Institute for Nuclear Research, Dubna, Russia

#### Spatial adiabatic passage and Josephson effect for Bose-Einstein condensate in a double-well trap (Slides)

The controlled spatial adiabatic passage (SAP) of the Bose-Einstein condensate (BEC) in multi-well traps can be designed within various scenarios [1], e.g. by using the Stimulated Raman Adiabatic Passage in a triple-well trap [2] and Landau-Zener (Rosen-Zener) schemes in a double-well trap [3]. The nonlinear effect of the interaction between BEC atoms makes SAP of BEC especially interesting. Depending on the trap configuration, the interaction can both destroy [2] and favor [3] the passage.

In this talk we focus on SAP aspect which was not yet properly inspected : the analogy between SAP and dc Josephson effect in BEC [4,5]. As a relevant example, the transport of the repulsive BEC in a double-well trap is analyzed [5] within the 3D time-dependent Gross-Pitaevskii equation. The population transfer is driven by a time-dependent shift of the barrier separating the left and right wells. The evolution of the relevant characteristics (currents, phase differences, chemical potentials) is inspected. It is shown that the repulsive interaction substantially supports SAP leading to a wider interval of the barrier velocity. As a result, SAP in the interacting BEC can be three orders of magnitude faster than in the ideal BEC. It is shown that SAP can be treated as the dc Josephson effect. The dual origin of the critical barrier velocity (break of the adiabatic following and dc/ac transition) is discussed. Following the calculations, the robustness of the SAP (dc Josephson) crucially depends on the interaction and profile of the barrier velocity.

Finally the peculiarities of SAP and Josephson dynamics in the synthetic spin-orbit BEC are discussed.

[1] E. Torrontegui et al, Adv. At. Mol. Opt. Phys. 62, 117 (2013).

[2] V.O. Nesterenko, A.N. Novikov, F.F. de Souza Cruz, and E.L. Lapolli, Laser Phys. 19, 616 (2009).

[3] V.O. Nesterenko, A.N. Novikov, A.Y. Cherny, F.F. de Souza Cruz, and E. Suraud, J. Phys. B: At. Mol. Opt. Phys. 42, 235303 (2009).

[4] S. Giovanazzi, A. Smerzi, and S. Fantoni, Phys. Rev. Lett. 84 4521 (2000).

[5] V.O. Nesterenko, A.N. Novikov, and E. Suraud, Laser Phys. 24, 125501 (2014).

### Andrew Greentree, RMIT University, Melbourne, Australia

#### STIRAP in space: spatial adiabatic passage in engineered systems for transport and gates (Slides)

### Xi Chen, Shanghai University, China

#### Fast and robust quantum state control by shortcuts to adiabaticity

Precise and fast quantum control is a fundamentally demanding in many areas of modern science ranging from quantum information processing to high-precision measurements. The ultimate goal is to prepare a desired state as fast as possible with sufficient high-fidelity allowed by available resources and the experimental constraints. Therefore, several techniques, sharing the concept of shortcuts to adiabaticity, have been put forward to accelerate the slow adiabatic passage, that is, to achieve adiabatic-like results but within shorter time. In this talk, I will first review the shortcut methods, including counter-diabatic driving (or quantum transitionless algorithm), and the difficulty to implement in the experiment. Particularly, I apply the counter-diabatic driving along with a unitary transformation to achieve the fast and robust quantum state control in a three-level system by modifying the Raman pulses. The experimental demonstration with atom assembles is also discussed, showing the robustness against control parameter variation. I also like to say that the shortcut can be further optimized by using inverse engineering combing with the optimal control theory. Finally, the talk will end up with the comparison among different shortcuts protocols with various applications in atom, molecular, optical physics, and even quantum information processing.

References

[1] M. Berry, J. Phys. A: Math. Theor. 42, 365303 (2009).

[2] X. Chen, L. Lizuain, A. Ruschhaupt, D. G. Odelin, and J. G. Muga, Phys. Rev. Lett. 105, 123003 (2010).

[3] S. Ibanez, S., X. Chen, E. Torrontegui, J. G. Muga, and A. Ruschhaupt, Phys. Rev. Lett. 109, 100403 (2012).

[4] Y.-X. Du, Z.-T. Liang, Y.-C. Li, X.-X. Yue, Q.-X. Lv, W. Huang, X. Chen, H. Yan, S.-L. Zhu, 1601.06058.

[5] Y.-C. Li and X. Chen, in preparation.

### Adolfo del Campo, University of Massachusetts Boston, US

#### Shortcuts to adiabaticity for matter-waves (Slides)

Shortcuts to adiabaticity (STA) have the potential to revolutionize quantum technologies by tailoring the far-from-equilibrium dynamics of quantum systems to reproduce aspects of adiabatic protocols without the requirement of slow driving.

STA use counterdiabatic driving fields to speed up the dynamics of matter-waves in processes such as expansions [1] and transport [2] of matter waves or the loading of an optical lattice [3].

Here we present the first experimental realization of counterdiabatic driving in a continuous variable system, implementing a shortcut to the adiabatic transport of a trapped ion, in which nonadiabatic transitions are suppressed during all stages of the process [4]. We shall also report alternative techniques to tailor the dynamics of matter waves in bent waveguides, aimed at suppressing curvature-induced effects [5].

We shall close discussing the use of STA in finite-time thermodynamics of thermal machines [6,7] and show that many-particle effects can be used to enhance the performance of heat engines and achieve quantum supremacy [8].

References:

[1] A. del Campo, Phys. Rev. Lett. 111, 100502 (2013)

[2] S. Deffner, C. Jarzynski, A. del Campo, Phys. Rev. X 4, 021013 (2014)

[3] S. Masuda, K. Nakamura, A.del Campo, Phys. Rev. Lett. 113, 063003 (2014)

[4] Shuoming An, Dingshun Lv, A. del Campo, Kihwan Kim, arXiv:1601.05551

[5] A. del Campo, M. G. Boshier, A. Saxena, Sci. Rep. 4, 5274 (2014)

[6] A. del Campo, J. Goold, M. Paternostro, Sci. Rep. 4, 6208 (2014)

[7] M. Beau, J. Jaramillo, A. del Campo, Entropy 18, 168 (2016)

[8] J. Jaramillo, M. Beau, A. del Campo, arXiv:1510.04633

### Shintaro Taie, Kyoto University, Japan

#### Spatial Adiabatic Passage of Ultracold Atoms in an Optical Lieb Lattice

Ultracold atomic systems have made great success in investigating few and many- body physics, owing to their highly controllable system parameters. Dynamical control of the parameters can access both sudden and adiabatic limit, which realizes various initialization, manipulation and detection techniques.

Here we report the realization of spatial adiabatic passage of atoms loaded into an optical lattice. The Lieb lattice consists of three sublattices (A, B and C sublattice), among which A-B and A-C are coupled by nearest-neighbor tunneling amplitudes. In momentum space, Λ-type three-level systems naturally arise where the tunneling amplitudes and energy offsets on each sublattice play roles of Rabi frequencies and detuning, respectively. By adiabatically changing the tunneling, atoms on the B- sublattice can be transferred to the C-sublattice without no population on the A- sublattice.

This kind of adiabatic technique will be useful to prepare specific many-body states in optical lattices. As an example, we show that loading atoms into a flat energy band in the Lieb lattice is possible with spatial adiabatic passage. In addition, the observation of tunneling phenomena analogous to electromagnetically induced transparency will also be discussed.

### Germano Montemezzani : University of Metz, France

**Spatial adiabatic passage of light in waveguide structures (Slides)**

Light waves passing from an optical waveguide to another via evanescent coupling can present a classical analogy to quantum effects, such as for instance the STImulated Raman Adiabatic Passage (STIRAP) process. Adiabaticity is a key element in these processes and the coupling coefficient between waveguides and/or the detuning of the mode propagation constants in different waveguides should evolve slowly along the propagation direction. If this is verified, very robust structures can be demonstrated because the waves can remain in a same spatially evolving eigenstate of the whole system, in a way nearly independent on the details of the coupling and detuning. This robustness can lead for instance to a largely extended bandwidth of operation and the whole approach can inspire novel integrated optical components. Our recent works in this context use reconfigurable and tunable waveguide structures that are optically induced by an auxiliary illumination of a nonlinear photorefractive crystal. Spatial adiabatic passage of light and potential applications based on longitudinally homogeneous or non-homogeneous waveguides will be discussed.

### Sigmund Kohler, Instituto de Ciencia de Materiales de Madrid, Spain

#### Steady-state adiabatic passage, electron transport, and shot noise (Slides)

We consider an all-electron version of coherent transfer by adiabatic passage (CTAP) in triple quantum dots. A major experimental obstacle for the implementation of a CTAP protocol is the impossibility of directly measuring the non-occupation of the middle dot, because the unavoidable backaction would influence the effect that it should substantiate. It will be shown that an indirect verification is possible by attaching electron source and drain to the triple dot. Then the protocol can be repeated such that a steady state current flows. The noise properties of this current hint on the proper course of the protocol [1].

A question of much practical relevance is whether the Gauss pulses employed in Ref.[1] can be replaced by an AC driving, where the basic driving frequency may be augmented by a second AC field with a different frequency. Such driving has recently been used in an experiment on Landau-Zener interferences in double quantum dots [2]. There the repeated sweeping through an avoided level crossing represents a realization of a Mach-Zehnder interferometer in energy space. We discuss the main aspects of this experiment such as the role of the commensurability of the driving frequencies and the possible extension to triple quantum dots in view of an implementation of a CTAP protocol.

[1] Steady-state coherent transfer by adiabatic passage

J. Huneke, G. Platero, and S. Kohler

Phys. Rev. Lett. 110, 036802 (2013)

[2] Landau-Zener interference at bichromatic driving

F. Forster, M. Mühlbacher, R. Blattmann, D. Schuh, W. Wegscheider,

S. Ludwig, and S. Kohler

Phys. Rev. B 92, 245422 (2015)

### Enrico Prati, Institute for Photonics and Nanotechnologies (IFN-CNR), Italy

### Albert Benseny, OIST Graduate University, Japan

#### SAP beyond STIRAP: interactions, higher dimensions and shortcuts (Slides)

Adiabatic passage of neutral atoms in space allows to consider situations that possess more degrees of freedom than usually found on optical systems. Among these additional degrees of freedom are access to higher dimensionalities, the possibility to create and control finite (angular) momentum states, the presence of interactions in many-particle systems and the ability to add external fields. Here we will discuss all of these and show that they allow to extend the range of quantum states that can be accessed significantly.

While adiabatic techniques allow to obtain high fidelities and are robust against noise and errors, their adiabatic nature is often considered to be an obstacle, as it prevents experimental implementation. For spatial adiabatic passage, however, we will show that a shortcut to adiabaticity exists, which can be experimentally implemented with existing technology.