Abstract
Understanding gravity in the framework of quantum mechanics is one of the great challenges in modern physics. However, the lack of empirical evidence has lead to a debate on whether gravity is a quantum entity. Despite varied proposed probes for quantum gravity, it is fair to say that there are no feasible ideas yet to test its quantum coherent behavior directly in a laboratory experiment. Here, we introduce an idea for such a test based on the principle that two objects cannot be entangled without a quantum mediator. We 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. We provide a prescription for witnessing this entanglement, which certifies gravity as a quantum coherent mediator, through simple spin correlation measurements.
- Received 6 September 2017
DOI:https://doi.org/10.1103/PhysRevLett.119.240401
© 2017 American Physical Society
Physics Subject Headings (PhySH)
Synopsis
A Test of Gravity’s Quantum Side
Published 13 December 2017
Two proposals describe how to test whether gravity is inherently quantum by measuring the entanglement between two masses.
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