2026/08/04 by Thomas Mieling, Andreas Wolfgang Schell, David Edward Bruschi
Physics and Astronomy · #quant-ph #gr-qc
10 pages, 4 figures
arxiv created 2026/08/04 · arxiv updated 2026/08/05
The gravitational frequency shift of light is well understood in the theory of classical electromagnetism. Nevertheless, its description in quantum theory is not yet fully developed. Recent work pointed out inconsistencies in previously developed models aimed at describing gravitational redshift as an effective multi-mode mixer (MMM) acting on modes of light, however, a complete solution of the issues was not obtained. Here, we identify the root cause of the MMM model's inconsistency and provide two complementary approaches to correct it: a "natural" one from a field-theoretic perspective, and another adapted to the language of quantum mechanics of finite-dimensional systems. We show that the second approach allows for modeling of the redshift in a multi-mode transmission setup as a quantum channel that can be characterized using standard quantum information-theoretic techniques when restricting the input states to Gaussian states of light.