Toward graviton detection via photon-graviton quantum state conversion

TL;DR

This paper develops a quantum field theoretic approach to photon-graviton conversion in magnetic fields, revealing enhanced conversion probabilities and the potential to detect quantum gravitational effects through entanglement signatures.

Contribution

It introduces a quantum framework for photon-graviton conversion, showing how quantum states evolve and how entanglement can be generated or swapped, providing new insights for graviton detection.

Findings

Conversion probability can be significantly enhanced.

Conversion can swap and generate entanglement between sectors.

Detection of nonclassical correlations could evidence quantum gravity.

Abstract

A magnetic field enables the interconversion of photons and gravitons, yet the process is usually analysed only at the level of classical wave equations. We revisit photon-graviton conversion in a quantum field theoretic framework, allowing us to track the evolution of arbitrary quantum states. Treating the photons as squeezed coherent states and the gravitons as the squeezed vacuum expected for primordial gravitational waves, we derive analytic expressions for the conversion probability and show that it can be significantly enhanced compared to the conventional estimate. We further demonstrate that the conversion both swaps preexisting entanglement and generates genuinely new entanglement between the electromagnetic and gravitational sectors, which is impossible in any classical description. Detecting such nonclassical correlations would constitute compelling evidence for the quantization of gravity and offers a novel pathway toward graviton detection.