arXiv subjects

Andreas Wolfgang Schell

Publications and source records attributed to Andreas Wolfgang Schell.

6 recordsLinked to original sources

arXiv2026

Gravitational redshift of broadband relativistic quantum photons

Gravitational redshift is a key prediction of general relativity that has been experimentally verified. Nevertheless, its existence in the context of relativistic and quantum physics has not yet been established. We employ linearized quantum gravity to study the effects of quantum coherence on gravitational redshift of broadband photons that interact with a planet via graviton exchange. We find that gravitational redshift, as predicted by general relativity, occurs when the initial photonic state contains no quantum coherence between orthogonal photonic modes, such as position states. If quantum coherence is initially present, different photonic modes overlap, a genuine quantum correction occurs solely for single-photon states. Our work not only explains gravitational redshift as the interaction of gravitons and photons in flat spacetime, but also shows that deviations from the theory occur already at low energies when quantum interference of photonic states is important.

gr-qc↗

arXiv2026

Gravitational redshift as a quantum channel: modeling the effects of gravitational redshift in quantum optics

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 the gravitational redshift as an effective multi-mode mixer (MMM) acting on modes of light, but so far a complete solution of these 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.

quant-ph↗

arXiv2026

Limits to the validity of gravitational redshift as a quantum-optical multimode mixer

We analyze the domain of validity of a quantum optical model that describes the effects of gravitational redshift on the quantum state of photons that propagate in curved spacetime. This model assumes that the modes defining the initial state of the photon are mixed with an auxiliary environment mode via an effective multimode mixer. We find that the model, as proposed, is consistent only to first order for small redshift, where the range of validity is conditional not only to the gravitational parameters, but also to those that define the photonic modes. We identify the problem and provide a partial solution in terms of a necessary condition on the transformation matrix representing the process, which requires the use of a number of auxiliary modes that is at least equal to the number of modes that define the photonic state. We conclude by discussing implications for theoretical quantum optics and photonics in curved spacetime, as well as for the development of quantum technologies.

quant-ph↗

arXiv2025

Bounding the rotating wave approximation for coupled harmonic oscillators

In this work we study the validity of the rotating wave approximation of an ideal system composed of two harmonic oscillators evolving with a quadratic Hamiltonian and arbitrarily strong interaction. We prove its validity for arbitrary states by bounding the error introduced. We then restrict ourselves to the dynamics of Gaussian states and are able to fully quantify the deviation of arbitrary pure Gaussian states that evolve through different dynamics from a common quantum state. We show that this distance is fully determined by the first and second moments of the statistical distribution of the number of excitations created from the vacuum during an appropriate effective time-evolution. We use these results to completely control the dynamics for this class of states, therefore providing a toolbox to be used in quantum optics and quantum information. Applications and potential physical implementations are also discussed.

quant-ph↗

arXiv2023

Introduction to gravitational redshift of quantum photons propagating in curved spacetime

Gravitational redshift is discussed in the context of quantum photons propagating in curved spacetime. A brief introduction to modelling realistic photons is first presented and the effect of gravity on the spectrum computed for photons largely confined along the direction of propagation. It is then shown that redshift-induced transformations on photon operators with sharp momenta are not unitary, while a unitary transformation can be constructed for realistic photons with finite bandwidth. The unitary transformation obtained is then characterized as a multimode mixing operation, which is a generalized rotation of the Hilbert-space basis. Finally, applications of these results are discussed with focus on performance of quantum communication protocols, exploitation of the effects for quantum metrology and sensing, as well as potential for tests of fundamental science.

quant-ph↗

arXiv2023

Quantum memories for fundamental science in space

Investigating and verifying the connections between the foundations of quantum mechanics and general relativity will require extremely sensitive quantum experiments. To provide ultimate insight into this fascinating area of physics, the realization of dedicated experiments in space will sooner or later become a necessity. Quantum technologies, and among them quantum memories in particular, are providing novel approaches to reach conclusive experimental results due to their advanced state of development backed by decades of progress. Storing quantum states for prolonged time will make it possible to study Bell tests on astronomical baselines, to increase measurement precision for investigations of gravitational effects on quantum systems, or enable distributed networks of quantum sensors and clocks. We here promote the case of exploiting quantum memories for fundamental physics in space, and discuss both distinct experiments as well as potential quantum memory platforms and their performance.

quant-ph↗