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Nuclear Physics B

Testing quantum gravity with cold atoms: A quantum-information method

Abdelâali Boudjemâa, Asma Tahar Taiba

Published Sep 23, 2026• 0 citations
Publisher

Abstract

We investigate the interface between quantum mechanics and gravity employing techniques from quantum information theory. The focus is primarily on investigating the gravitationally mediated entanglement (measured here by the concurrence) between two probe qubits created by two-level atoms with a reservoir consisting of thermally equilibrated homogeneous three-dimensional Bose-Einstein condensates. Our results demonstrate that below a certain temperature, the gravitational contribution to the qubit-reservoir interaction may strongly modify their coherence and entanglement dynamics even at large interqubit distance. By analyzing multi-parameter estimation techniques such as the quantum Fisher information, and quantum signal-to-noise ratio as a metric for certifying quantum effects and sensing performance, we show that the spatial separation between qubits and gravitational interaction may enhance estimation efficiency, providing a high-precision quantum gravity sensor.

DOI
10.1016/j.nuclphysb.2026.117669

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We investigate the interface between quantum mechanics and gravity employing techniques from quantum information theory. The focus is primarily on investigating the gravitationally mediated entanglement (measured here by the concurrence) between two probe qubits created by two-level atoms with a reservoir consisting of thermally equilibrated homogeneous three-dimensional Bose-Einstein condensates. Our results demonstrate that below a certain temperature, the gravitational contribution to the qubit-reservoir interaction may strongly modify their coherence and entanglement dynamics even at large interqubit distance. By analyzing multi-parameter estimation techniques such as the quantum Fisher information, and quantum signal-to-noise ratio as a metric for certifying quantum effects and sensing performance, we show that the spatial separation between qubits and gravitational interaction may enhance estimation efficiency, providing a high-precision quantum gravity sensor.
Abstract We explore the possibility of testing the quantum nature of the gravitational field with an ensemble of ultra-cold atoms. The use of many microscopic particles may circumvent some of the experimental obstacles encountered in recent proposals involving a pair of particles with mesoscopic mass. We employ multi-parameter estimation techniques, including the quantum and classical Fisher information to provide a criteria for the observability of the quantum effects, and compare to other recently proposed schemes. Crucially, we find that by preparing the appropriate initial state, interactions mediated via a quantum-valued gravitational field provide a signature that is distinct from classical gravitational interactions. We find that a definitive demonstration of the quantum gravitational interaction is not possible with current experimental capabilities, due to uncertainty in the residual electromagnetic interactions between the atoms. However, it may be possible with significant improvements to current experimental techniques.
We suggest a test of a central prediction of perturbatively quantized general relativity: the coherent communication of quantum information between massive objects through gravity. To do this, we introduce the concept of interactive quantum information sensing, a protocol tailored to the verification of dynamical entanglement generation between a pair of systems. Concretely, we propose to monitor the periodic wavefunction collapse and revival in an atomic interferometer which is gravitationally coupled to a mechanical oscillator. We prove a theorem which shows that, under the assumption of time-translation invariance, this collapse and revival is possible if and only if the gravitational interaction forms an entangling channel. Remarkably, as this approach improves at moderate temperatures and relies primarily upon atomic coherence, our numerical estimates indicate feasibility with current devices.
Detecting gravity mediated entanglement can provide evidence that the gravitational field obeys quantum mechanics. We report the result of a simulation of the phenomenon using a photonic platform. The simulation tests the idea of probing the quantum nature of a variable by using it to mediate entanglement, and yields theoretical and experimental insights. We employed three methods to test the presence of entanglement: Bell test, entanglement witness and quantum state tomography. We also simulate the alternative scenario predicted by gravitational collapse models or due to imperfections in the experimental setup and use quantum state tomography to certify the absence of entanglement. Two main lessons arise from the simulation: 1) which--path information must be first encoded and subsequently coherently erased from the gravitational field, 2) performing a Bell test leads to stronger conclusions, certifying the existence of gravity mediated nonlocality.
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A promising route to testing quantum gravity in the laboratory is to look for gravitationally induced entanglement (GIE) between two or more quantum matter systems. To date, proposed tests have primarily focused on microsolid platforms prepared in highly nonclassical states, such as N00N states or strongly squeezed states. Here, we instead consider measuring GIE in atom interferometry as evidence of quantum gravity. We propose placing two atom interferometers next to each other in parallel and looking for correlations in the atom-number statistics at their output ports. Importantly, GIE is possible without challenging macroscopic superposition states, such as N00N or Schrödinger-cat states. Instead, GIE can arise using coherent, near-classical atomic states, substantially reducing the experimental complexity. Observing the effect in this regime would require the total mass of the atom interferometers to be near the Planck mass scale. However, we show that state-of-the-art quantum squeezing techniques in cold-atom systems can significantly lower this mass requirement, and outline realistic pathways by which the necessary mass scales could be achieved in the near future, placing laboratory tests of GIE with atom interferometers within reach.
The effect of noise induced by gravitons on a Bose-Einstein condensate has been explored in Sen and Gangopadhyay [Probing the quantum nature of gravity using a Bose-Einstein condensate, ]. In the previous paper, we investigated the effects of graviton while detecting a gravitational wave using a Bose-Einstein condensate. In this work, we shall explicitly calculate the decoherence due to the noise of gravitons for maximally entangled momentum states of the Bose-Einstein condensate. This decoherence happens due to bremsstrahlung from the Bose-Einstein condensates due to the effect of the noise induced by gravitons. It is observed that the maximally entangled state becomes entangled with the graviton state and it decays over time as a result of this gravitational bremsstrahlung. This new entangled state is termed as a Bose-Einstein supercondensate. Using this property of the Bose-Einstein condensate in a quantum gravity background, we propose an experimental test via the use of atom lasers (generated from the condensate) which would, in principle, help to detect gravitons in future generations of very advanced ultracold temperature experiments.