Telefilters, telemirrors, and causality

TL;DR

This paper introduces quantum optical mode-selective filters and mirrors based on continuous-variable teleportation, analyzing their causality implications and proposing methods to mitigate delays in mode transmission.

Contribution

The paper develops new theoretical models for telefilters and telemirrors using continuous-variable teleportation, addressing causality issues in relativistic quantum optics.

Findings

Telemirrors impose a fundamental time-delay to preserve causality.

Continuous teleportation of temporal components can transmit modes but introduces uncorrelated noise.

Mode discrimination without strict mode selectivity is possible with on-the-run teleportation.

Abstract

We present new theoretical models for quantum optical mode-selective filters and mirrors using continuous-variable teleportation. We call these devices telefilters and telemirrors respectively. Both devices act as the identity channel on a mode of interest from an input multi-mode field while filtering or reflecting all the orthogonal modes. We utilise these models to analyse a causality problem in relativistic quantum optics, specifically the apparently acausal transmission and propagation of temporally delocalised wavepackets through mode-selective mirrors. Firstly, we show how telemirrors - and thus mode-selective operations generally - enact a fundamental time-delay on such wavepackets, which is necessary in order to prevent violations of causality. In an attempt to circumvent this delay, we next consider teleporting the independent temporal components of the input field separately and continuously, that is, performing operations on-the-run. In this scenario, the telemirror transmits the mode of interest as well as orthogonal modes which carry with them uncorrelated noise. In this scenario, the device may be considered mode-discriminating but not mode-selective.