Quantum repeaters based on concatenated bosonic and discrete-variable quantum codes

TL;DR

This paper introduces a quantum repeater architecture that combines continuous-variable GKP codes with discrete-variable codes in a concatenated structure, improving long-distance quantum communication efficiency.

Contribution

It presents a novel hybrid quantum repeater design using concatenated bosonic and discrete-variable codes, enhancing error correction and reducing resource costs.

Findings

Error correction on two levels improves performance.

Analog information from GKP codes enhances second-level correction.

Long-distance communication feasible with minimal optical modes.

Abstract

We propose an architecture of quantum-error-correction-based quantum repeaters that combines techniques used in discrete- and continuous-variable quantum information. Specifically, we propose to encode the transmitted qubits in a concatenated code consisting of two levels. On the first level we use a continuous-variable GKP code encoding the qubit in a single bosonic mode. On the second level we use a small discrete-variable code. Such an architecture has two important features. Firstly, errors on each of the two levels are corrected in repeaters of two different types. This enables for achieving performance needed in practical scenarios with a reduced cost with respect to an architecture for which all repeaters are the same. Secondly, the use of continuous-variable GKP code on the lower level generates additional analog information which enhances the error-correcting capabilities of the second-level code such that long-distance communication becomes possible with encodings consisting of only four or seven optical modes.