Gravitational-Wave Distinguishability as an Information-Theoretic Mechanism for Decoherence

Brahim Lamine

Brahim Lamine, R. Hervé, Astrid Lambrecht +1 more

Eran Sinbar

We propose that gravitational-wave distinguishability provides a universal, information-theoretic mechanism for decoherence in quantum superpositions involving massive systems. When alternative quantum histories imprint distinguishable gravitational radiation states into spacetime, which-branch information exists in principle even in the absence of measurement. This suppresses interference purely through unitary entanglement with the gravitational field. Unlike collapse models, this framework relies only on standard quantum mechanics and the information-carrying capacity of gravitational radiation. We argue heuristically that the Planck mass emerges as an information-theoretic crossover scale beyond which gravitationally induced decoherence becomes unavoidable. To clarify the conceptual content, we introduce a Schrödinger’s-cat–type thought experiment in which one branch of a quantum superposition produces colliding black holes and gravitational waves, while the other does not. In this limit case, spacetime itself functions as an irreversible which-branch environment. The analysis positions gravity not as a modifier of quantum mechanics, but as a universal information channel contributing to the quantum–classical transition.

K. Hari, S. Shankaranarayanan

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.

Yuanxin Li

Fateme Shojaei Arani, M. Bagheri Harouni, Brahim Lamine +1 more

Abstract Based on optical medium analogy, we establish a formalism to describe the interaction between an electromagnetic (EM) system with gravitational waves (GWs) background. After a full discussion on the classical treatment of the EM-GW interaction and finding the EM field mode-functions in the presence of the magneto-dielectric media caused by GWs, the governing quantum interaction Hamiltonian is obtained. Investigation of the optical quadrature variance as well as the visibility of a laser field interacting with the multi-mode squeezed primordial gravitational waves imply that the inflationary primordial gravitational waves (PGWs) act as a decoherence mechanism that destroy EM coherency after a characteristic time scale, τ c , which depends on the inflationary parameters (β, β s , r), or equivalently, the fractional energy density of PGWs, Ω gw,0. The decoherency mechanism overcomes the coherent effects, such as revivals of optical squeezing, thus leaving their confirmation out of reach. Influenced by the continuum of the squeezed PGWs, the laser field suffers a line-width broadening by γ = τ c − 1 . The most peculiar property of the EM spectrum is the apparition of side bands at ω ∼ ω 0 ± 1.39 τ c − 1 Hz, stemming from the squeezed nature of PGWs. The laser phase noise induced by the squeezed PGWs grows with time squarely, Δ ϕ = t / τ c 2 , that can most possibly be sensed within a finite flight time.