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Gravitationally Induced Entanglement between Two Massive Particles is Sufficient Evidence of Quantum Effects in Gravity

C. Marletto and V. Vedral
Phys. Rev. Lett. 119, 240402 – Published 13 December 2017
Physics logo See Synopsis: A Test of Gravity’s Quantum Side
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Abstract

All existing quantum-gravity proposals are extremely hard to test in practice. Quantum effects in the gravitational field are exceptionally small, unlike those in the electromagnetic field. The fundamental reason is that the gravitational coupling constant is about 43 orders of magnitude smaller than the fine structure constant, which governs light-matter interactions. For example, detecting gravitons—the hypothetical quanta of the gravitational field predicted by certain quantum-gravity proposals—is deemed to be practically impossible. Here we adopt a radically different, quantum-information-theoretic approach to testing quantum gravity. We propose witnessing quantumlike features in the gravitational field, by probing it with two masses each in a superposition of two locations. First, we prove that any system (e.g., a field) mediating entanglement between two quantum systems must be quantum. This argument is general and does not rely on any specific dynamics. Then, we propose an experiment to detect the entanglement generated between two masses via gravitational interaction. By our argument, the degree of entanglement between the masses is a witness of the field quantization. This experiment does not require any quantum control over gravity. It is also closer to realization than detecting gravitons or detecting quantum gravitational vacuum fluctuations.

  • Figure
  • Received 6 September 2017

DOI:https://doi.org/10.1103/PhysRevLett.119.240402

© 2017 American Physical Society

Physics Subject Headings (PhySH)

General PhysicsQuantum Information, Science & TechnologyGravitation, Cosmology & Astrophysics

Synopsis

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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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Authors & Affiliations

C. Marletto1 and V. Vedral1,2

  • 1Clarendon Laboratory, Department of Physics, University of Oxford, England
  • 2Centre for Quantum Technologies, National University of Singapore, Block S15, 3 Science Drive 2, Singapore

See Also

Spin Entanglement Witness for Quantum Gravity

Sougato Bose, Anupam Mazumdar, Gavin W. Morley, Hendrik Ulbricht, Marko Toroš, Mauro Paternostro, Andrew A. Geraci, Peter F. Barker, M. S. Kim, and Gerard Milburn
Phys. Rev. Lett. 119, 240401 (2017)

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Issue

Vol. 119, Iss. 24 — 15 December 2017

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