Decoherence-Free Communication over Multiaccess Quantum Channels

TL;DR

This paper explores conditions under which decoherence-free communication is possible over multiaccess quantum channels, focusing on unitary noise models and extending results to multiple senders and general Kraus operators.

Contribution

It introduces a new criterion based on Schmidt matrix decomposability for decoherence-free codes in two-access channels and extends the approach to more complex multiaccess scenarios.

Findings

Decoherence-free codes exist under certain decomposability conditions for eigensubspaces.

The technique applies to generic random unitary two-access channels.

Results extend to multiple senders and general Kraus operators.

Abstract

In this paper we consider decoherence-free communication over multiple access and $k$-user quantum channels. First, we concentrate on a hermitian unitary noise model $U$ for a two-access bi-unitary channel and show that in this case a decoherence-free code exists if the space of Schmidt matrices of an eigensubspace of $U$ exhibits certain properties of decomposability. Then, we show that our technique is also applicable for generic random unitary two-access channels. Finally, we consider the applicability of the result to the case of a larger number of senders and general Kraus operators.