Passive environment-assisted quantum communication with GKP states

TL;DR

This paper demonstrates that using GKP states for both the system and environment can enable perfect quantum information transmission through a beam splitter at low transmissivities, enhancing bosonic pure-loss channels.

Contribution

It introduces a method to achieve perfect quantum communication at low transmissivities by employing ideal GKP states for environment assistance, with explicit constructions suitable for experimental realization.

Findings

Perfect transmission achievable at low transmissivities with GKP states

Experimental feasibility demonstrated at the few-photon level

Passive environment control enhances quantum channel performance

Abstract

Bosonic pure-loss channel, which represents the process of photons decaying into a vacuum environment, has zero quantum capacity when the channel's transmissivity is less than 50%. Modeled as a beam splitter interaction between the system and its environment, the performance of bosonic pure-loss channel can be enhanced by controlling the environment state. We show that by choosing the ideal Gottesman-Kitaev-Preskill (GKP) states for the system and its environment, perfect transmission of quantum information through a beam splitter is achievable at arbitrarily low transmissivities. Our explicit constructions allow for experimental demonstration of the improved performance of a quantum channel through passive environment assistance, which is potentially useful for quantum transduction where the environment state can be naturally controlled. In practice, it is crucial to consider finite-energy constraints, and high-fidelity quantum communication through a beam splitter remains achievable with GKP states at the few-photon level.