QSense OIST Mini-Symposium Talk 7: "An Experiment for Evidencing Entanglement via Gravity: Its Motivation, Challenges and Related Sensing Opportunities"


Monday, February 15, 2021 - 17:00


Zoom (link is distributed to registered participants)


Speaker: Prof Sougato Bose, Department of Physics and Astronomy, University College London

An Experiment for Evidencing Entanglement via Gravity: Its Motivation, Challenges and Related Sensing Opportunities
(QSense OIST Mini Symposium Talk 7)​

A lack of empirical evidence has lead some researchers to doubt whether gravity is a quantum entity. This is often accompanied by the doubt that sufficiently large masses themselves will not obey the quantum superposition principle beyond a certain scale. We show how mechanisms to engineer ever larger superpositions of ever larger masses eventually gives rise to a domain in which the masses involved become sufficiently large to gravitationally affect each other. In this domain, I will present a feasible idea for a test of the quantum nature of gravity based on the principle that two objects cannot be entangled without a quantum mediator. I will show that despite the weakness of gravity, the phase evolution induced by the gravitational interaction of two micron size test masses in adjacent matter-wave interferometers can detectably entangle them even when they are placed far apart enough to keep Casimir-Polder forces at bay. A prescription for witnessing this entanglement, which certifies gravity as a quantum coherent mediator, is also provided and can be measured through simple spin correlations. Further, I clarify the assumptions underpinning the above proposal such as our reasonable definition of "classicality", as well as the crucial aspect of the locality of physical interactions. We note a few ways to address two principal practical challenges: Screening EM forces and Inertial noise reduction. I will also describe how unprecedented compact sensors for classical gravity (including meter scale sensors for low frequency gravitational waves) will also arise on the way to the above grand goal.

OIST Mini-Symposium for Quantum Sensors of Magnetic and Inertial Forces

This mini-symposium is hosted by the Quantum Machines Unit in the Okinawa Institute of Science and Technology Graduate University, and will take place from Feb 1, 2021 - March 5, 2021. To get the precise schedule and zoom invitation please register below. Attendance is open to any student/faculty member from any of the institutions associated with the speakers.


Quantum systems are extremely fragile, sensitive to noise and fluctuations by their environments. This, in turn, makes them excellent sensors for a variety of forces and fields. In this mini-symposium we focus on the development of novel quantum sensors which are aimed at the precision sensing of inertial forces such as acceleration or gravity, and magnetic forces.

Such sensors - accelerometers/gravimeters or magnetometers, have a widespread application in industry such as sensing underground water movements using gravimeters, through to magnetic brain imaging using magnetoencephelography. Each week we hear from three international experts on these topics in hour-long seminars and discussions.

For more information, visit the QSense website.

Website URL

Sponsor or Contact: 
Quantum Machines Unit (Jason Twamley)
All-OIST Category: 

Subscribe to the OIST Calendar: Right-click to download, then open in your calendar application.