Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2601.20553 · Physical review. D/Physical review. D.

Gravitational wave detection via photon-graviton scattering and quantum interference

K. Hari, S. Shankaranarayanan

gr-qchep-thphysics.opticsquant-phSubmitted Jan 28, 2026• Announced Jan 29, 2026• 0 citations• Revised Oct 29, 2026 (v2)
v1 · Jan 28, 2026v2 · Oct 29, 2026
arXivHTMLPDF

Abstract

We present a fully quantum field-theoretic framework for gravitational wave (GW) detection, describing the interaction as inelastic photon-graviton scattering. We demonstrate that for \textit{a coherent graviton state}, this microscopic model explicitly reproduces the standard classical geometric-optics time delay, providing a rigorous consistency test of the correspondence limit. We propose a detection scheme based on Hong-Ou-Mandel interference, where the GW-induced spectral shifts render entangled photon pairs distinguishable. This encodes the gravitational signal into the modulation of photon coincidence rates --- a quantum observable robust against laser intensity noise. Furthermore, we show that non-classical graviton states, such as squeezed states, induce unique decoherence signatures, establishing theoretical bounds on gravitational decoherence and defining the operational limits for probing the quantum nature of gravity.

Comments
21 pages, 11 figures, expanded discussion on Fisher Information, SNR and detection aspects, refs added, accepted for publication in Phys. Rev. D

Related papers

State-Selective Signatures of Quantum and Classical Gravitational Environments

Partha Nandi, Sankarshan Sahu, Bibhas Ranjan Majhi +1 more

A unified framework is developed for determining whether a gravitational-wave (GW) background behaves as a classical field or as a genuinely quantum environment. Unified here means that both descriptions originate from the same tidal coupling derived from geodesic deviation, which yields an identical quadratic interaction Hamiltonian for the detector; the only distinction lies in whether the GW degrees of freedom are modeled as classical phase-randomized coherent states or as quantized graviton modes. Within this common framework, the reduced dynamics of a quantum harmonic oscillator exhibit a sharp structural contrast: a quantized graviton bath preserves coherence within the lowest phonon-number manifold, forming a protected sector at leading order, whereas a classical stochastic GW field inevitably induces decoherence even inside this subspace. This difference provides an operational criterion for diagnosing the classical or quantum nature of gravitational waves using mesoscopic optomechanical systems. Our results establish decoherence structure - not merely its magnitude - as a sensitive probe of gravitational quantumness and delineate the experimental regimes under which such tests may become feasible.

gr-qcCross-listedarXiv:2603.05731•Mar 9, 2026

Revealing the Quantum Signature of Gravity via Gravitational Waves

Partha Nandi

Can propagating gravitational waves serve as operational probes of the quantum nature of gravity? We address this question by developing a unified theoretical framework that combines spacetime geometry, quantum information, and gravitational-wave physics. Starting from the geodesic deviation equation in linearized General Relativity, we derive the effective detector Hamiltonian directly from spacetime geometry and construct the complete quantum dynamics for detector subsystems interacting with both classical and quantized propagating gravitational-wave fields. This unified formulation enables a direct comparison between classical and quantum descriptions of gravitational radiation within the same physical framework. We demonstrate that classical gravitational-wave backgrounds can induce mixedness in the detector state but cannot generate genuine quantum correlations between the detector subsystems. In contrast, quantized gravitational waves coherently mediate gravity-induced entanglement, quantum coherence, quantum memory, and nonclassical correlations, providing clear operational signatures of the quantum nature of propagating gravitational radiation. We further discuss how mesoscopic quantum mechanical oscillators offer a promising route towards experimentally probing these effects. Our results establish a geometric and quantum-information-based framework for exploring quantum gravity through propagating gravitational waves.

gr-qcCross-listedarXiv:2609.09931•Sep 10, 2026

Witnessing entanglement between photon and matter due to graviton exchange

Arijit Dutta, Marko Toroš, Sougato Bose +1 more

The paper presents a scheme to detect entanglement arising from the quantum nature of gravity between a spin qubit and photons, using Stokes parameters. One of the crucial tests of the general theory of relativity is the bending of light due to the curvature. Recently, a quantum counterpart of this experiment to test the quantum nature of the gravitational interaction has been proposed, in which the spin-2, massless graviton yields entanglement between matter and a photon sector. Hence, it provides one of the most crucial experimental signatures for testing the quantum nature of gravity in a lab, since only spin-2-induced entanglement can yield the correct deflection of light due to matter. Here, we propose a positive partial-transpose (PPT) witness criterion for witnessing such an entanglement. We scan the entangled states in this context by studying the overlap of the final state, which is proportional to the entanglement phase. We exploit the Stokes observables to measure the photon state and the spins in the matter sector, thereby constructing a witness for the quantum nature of gravity in this setup. To quantify this entanglement, we will couple the photon to a local oscillator, whose phase need to be controlled to probe the orthogonal components of the macroscopic interference in the laser beam. We have shown that for a non-maximally entangled state mediated by the quantum nature of gravity, the witness attains a maximal negativity of $-0.052$. Our findings indicate that this witness effectively detects entanglement within the range $0.71 \leq |γ| < 1$, where $γ$ is the overlap between the two coherent states of the photon, providing a clear signature of quantum correlations.

quant-pharXiv:2604.24496•Apr 28, 2026•0 citations

Quantum State Characterization of Gravitational Waves via Graviton Counting Statistics

Kristian Toccacelo, Thomas Beitel, Ulrik Lund Andersen +1 more

Although gravitational waves are now routinely observed, the detection of individual gravitons has long been regarded as impossible. Recent work, however, has demonstrated that single-graviton detection can be achieved and may be feasible in the near future. Here we show that beyond mere particle detection, these detectors provide access to the quantum state and particle statistics of gravitational waves. We show that graviton detection probabilities enable the discrimination between squeezed, coherent, and thermal radiation. We further demonstrate that the full quantum statistics contained in the second-order correlation function of the passing wave can be directly measured at the detector, independent of the weak gravitational interaction strength. Building on recent quantum-optical techniques, this capability opens the way to full quantum state tomography of Gaussian states. Our results demonstrate that single-graviton detection is not only of foundational significance but also of practical value, allowing for the characterization of quantum statistics and the states of the gravitational radiation field, which remain currently unknown.

quant-pharXiv:2602.09125•Feb 11, 2026

Cavity-QED Transducer of Gravitons

Fateme Shojaei Arani, Brahim Lamine, Jiro Soda

We develop a quantum description of the resonant interaction between electromagnetic (EM) and gravitational waves (GW). We first show that Lorentz invariance together with polarization selection rules forbids any photon-graviton mixing in free space. We demonstrate that confining the EM field within a cavity quantum electrodynamics (cavity-QED) environment breaks translational symmetry and isotropy, leading to non-vanishing mode coupling between EM and gravitational degrees of freedom. Within this framework, we identify multiple photon-graviton scattering channels, including photon up- and down-conversion and photon creation. In the semiclassical limit of the trilinear interaction where GW acts as a classical pump and the EM field is in a vacuum, spontaneous parametric photon amplification and two-mode squeezing occur. When the gravitational field is quantized, however, the back-action and energy exchange between photons and gravitons result in saturation of amplification, in contrast to exponential growth, and the loss of purity in the photonic subsystem. The characteristic timescale scales as $t_{\text{sp}}\sim (g\sqrt{n_g})^{-1}$, where $g$ and $n_g$ refer to the coupling strength and the mean graviton number, demonstrating collective enhancement of the interaction with the graviton occupation number. In the stimulated regime, where one EM mode is initially populated, the effective coupling is further enhanced, analogous to Dicke-type superradiant emission. This work introduces a cavity-based graviton transducer for probing quantum aspects of GWs.

quant-pharXiv:2603.27687•Mar 31, 2026

Fundamental relations between measurement, radiation, and decoherence in gravitational wave laser interferometer detectors

Belinda Pang, Yanbei Chen

As laser interferometer gravitational wave (GW) detectors become quantum noise dominated, understanding the fundamental limit on measurement sensitivity imposed by quantum uncertainty is crucial to guide the search for further noise reduction. Recent efforts have included applying ideas from quantum information theory to GW detection---specifically the quantum Cramer-Rao bound, which is a minimum bound on error in parameter estimation using a quantum state and is determined by the state's quantum Fisher information (QFI) with respect to the parameter [Helstrom, J. Stat. Phys. 1, 231 (1969)]. Identifying the QFI requires knowing the interaction between the quantum probe and the signal, which was rigorously derived for GW interferometer detectors in Pang and Chen [Phys. Rev. D 98, 124006 (2018)]. In this paper, we calculate the QFI and fundamental quantum limit (FQL) for GW detection, and furthermore we derive explicit reciprocity relations involving the QFI that summarize information exchange between the detector and a surrounding weak quantum GW field. Specifically, we show that the GW power radiation by the detector's quantum fluctuations are proportional to the QFI, and therefore are inversely proportional to its FQL. Similarly, the detector's decoherence rate in a white noise GW bath can be explicitly related to the QFI/FQL. These relations are fundamental and appear generalizable to a broader class of quantum measurement systems.

arXiv:1903.09378•Physical review. D/Physical review. D.•Jun 11, 2019•10 citations
We present a fully quantum field-theoretic framework for gravitational wave (GW) detection, describing the interaction as inelastic photon-graviton scattering. We demonstrate that for \textit{a coherent graviton state}, this microscopic model explicitly reproduces the standard classical geometric-optics time delay, providing a rigorous consistency test of the correspondence limit. We propose a detection scheme based on Hong-Ou-Mandel interference, where the GW-induced spectral shifts render entangled photon pairs distinguishable. This encodes the gravitational signal into the modulation of photon coincidence rates --- a quantum observable robust against laser intensity noise. Furthermore, we show that non-classical graviton states, such as squeezed states, induce unique decoherence signatures, establishing theoretical bounds on gravitational decoherence and defining the operational limits for probing the quantum nature of gravity.
A unified framework is developed for determining whether a gravitational-wave (GW) background behaves as a classical field or as a genuinely quantum environment. Unified here means that both descriptions originate from the same tidal coupling derived from geodesic deviation, which yields an identical quadratic interaction Hamiltonian for the detector; the only distinction lies in whether the GW degrees of freedom are modeled as classical phase-randomized coherent states or as quantized graviton modes. Within this common framework, the reduced dynamics of a quantum harmonic oscillator exhibit a sharp structural contrast: a quantized graviton bath preserves coherence within the lowest phonon-number manifold, forming a protected sector at leading order, whereas a classical stochastic GW field inevitably induces decoherence even inside this subspace. This difference provides an operational criterion for diagnosing the classical or quantum nature of gravitational waves using mesoscopic optomechanical systems. Our results establish decoherence structure - not merely its magnitude - as a sensitive probe of gravitational quantumness and delineate the experimental regimes under which such tests may become feasible.
Can propagating gravitational waves serve as operational probes of the quantum nature of gravity? We address this question by developing a unified theoretical framework that combines spacetime geometry, quantum information, and gravitational-wave physics. Starting from the geodesic deviation equation in linearized General Relativity, we derive the effective detector Hamiltonian directly from spacetime geometry and construct the complete quantum dynamics for detector subsystems interacting with both classical and quantized propagating gravitational-wave fields. This unified formulation enables a direct comparison between classical and quantum descriptions of gravitational radiation within the same physical framework. We demonstrate that classical gravitational-wave backgrounds can induce mixedness in the detector state but cannot generate genuine quantum correlations between the detector subsystems. In contrast, quantized gravitational waves coherently mediate gravity-induced entanglement, quantum coherence, quantum memory, and nonclassical correlations, providing clear operational signatures of the quantum nature of propagating gravitational radiation. We further discuss how mesoscopic quantum mechanical oscillators offer a promising route towards experimentally probing these effects. Our results establish a geometric and quantum-information-based framework for exploring quantum gravity through propagating gravitational waves.
The paper presents a scheme to detect entanglement arising from the quantum nature of gravity between a spin qubit and photons, using Stokes parameters. One of the crucial tests of the general theory of relativity is the bending of light due to the curvature. Recently, a quantum counterpart of this experiment to test the quantum nature of the gravitational interaction has been proposed, in which the spin-2, massless graviton yields entanglement between matter and a photon sector. Hence, it provides one of the most crucial experimental signatures for testing the quantum nature of gravity in a lab, since only spin-2-induced entanglement can yield the correct deflection of light due to matter. Here, we propose a positive partial-transpose (PPT) witness criterion for witnessing such an entanglement. We scan the entangled states in this context by studying the overlap of the final state, which is proportional to the entanglement phase. We exploit the Stokes observables to measure the photon state and the spins in the matter sector, thereby constructing a witness for the quantum nature of gravity in this setup. To quantify this entanglement, we will couple the photon to a local oscillator, whose phase need to be controlled to probe the orthogonal components of the macroscopic interference in the laser beam. We have shown that for a non-maximally entangled state mediated by the quantum nature of gravity, the witness attains a maximal negativity of −0.052-0.052−0.052. Our findings indicate that this witness effectively detects entanglement within the range 0.71≤∣γ∣<10.71 \leq |γ| < 10.71≤∣γ∣<1, where γγγ is the overlap between the two coherent states of the photon, providing a clear signature of quantum correlations.
Although gravitational waves are now routinely observed, the detection of individual gravitons has long been regarded as impossible. Recent work, however, has demonstrated that single-graviton detection can be achieved and may be feasible in the near future. Here we show that beyond mere particle detection, these detectors provide access to the quantum state and particle statistics of gravitational waves. We show that graviton detection probabilities enable the discrimination between squeezed, coherent, and thermal radiation. We further demonstrate that the full quantum statistics contained in the second-order correlation function of the passing wave can be directly measured at the detector, independent of the weak gravitational interaction strength. Building on recent quantum-optical techniques, this capability opens the way to full quantum state tomography of Gaussian states. Our results demonstrate that single-graviton detection is not only of foundational significance but also of practical value, allowing for the characterization of quantum statistics and the states of the gravitational radiation field, which remain currently unknown.
We develop a quantum description of the resonant interaction between electromagnetic (EM) and gravitational waves (GW). We first show that Lorentz invariance together with polarization selection rules forbids any photon-graviton mixing in free space. We demonstrate that confining the EM field within a cavity quantum electrodynamics (cavity-QED) environment breaks translational symmetry and isotropy, leading to non-vanishing mode coupling between EM and gravitational degrees of freedom. Within this framework, we identify multiple photon-graviton scattering channels, including photon up- and down-conversion and photon creation. In the semiclassical limit of the trilinear interaction where GW acts as a classical pump and the EM field is in a vacuum, spontaneous parametric photon amplification and two-mode squeezing occur. When the gravitational field is quantized, however, the back-action and energy exchange between photons and gravitons result in saturation of amplification, in contrast to exponential growth, and the loss of purity in the photonic subsystem. The characteristic timescale scales as tsp∼(gng)−1t_{\text{sp}}\sim (g\sqrt{n_g})^{-1}tsp​∼(gng​​)−1, where ggg and ngn_gng​ refer to the coupling strength and the mean graviton number, demonstrating collective enhancement of the interaction with the graviton occupation number. In the stimulated regime, where one EM mode is initially populated, the effective coupling is further enhanced, analogous to Dicke-type superradiant emission. This work introduces a cavity-based graviton transducer for probing quantum aspects of GWs.
As laser interferometer gravitational wave (GW) detectors become quantum noise dominated, understanding the fundamental limit on measurement sensitivity imposed by quantum uncertainty is crucial to guide the search for further noise reduction. Recent efforts have included applying ideas from quantum information theory to GW detection---specifically the quantum Cramer-Rao bound, which is a minimum bound on error in parameter estimation using a quantum state and is determined by the state's quantum Fisher information (QFI) with respect to the parameter [Helstrom, J. Stat. Phys. 1, 231 (1969)]. Identifying the QFI requires knowing the interaction between the quantum probe and the signal, which was rigorously derived for GW interferometer detectors in Pang and Chen [Phys. Rev. D 98, 124006 (2018)]. In this paper, we calculate the QFI and fundamental quantum limit (FQL) for GW detection, and furthermore we derive explicit reciprocity relations involving the QFI that summarize information exchange between the detector and a surrounding weak quantum GW field. Specifically, we show that the GW power radiation by the detector's quantum fluctuations are proportional to the QFI, and therefore are inversely proportional to its FQL. Similarly, the detector's decoherence rate in a white noise GW bath can be explicitly related to the QFI/FQL. These relations are fundamental and appear generalizable to a broader class of quantum measurement systems.