Heralded nonlocal quantum gates for distributed quantum computation in a decoherence-free subspace

TL;DR

This paper introduces a heralded protocol for nonlocal quantum gates that operates on spatially separated qubits, utilizing a decoherence-free subspace to enhance fidelity and robustness against noise, advancing distributed quantum computing.

Contribution

It presents a novel heralded protocol for implementing nonlocal quantum gates with high success probability, leveraging a decoherence-free subspace for noise immunity.

Findings

Success probability approaches unity with high cooperativity

Protocol removes detrimental dissipation effects

Applicable for scalable distributed quantum networks

Abstract

We propose a heralded protocol for implementing nontrivial quantum gates on two stationary qubits coupled to spatially separated cavities. By dynamically controlling the evolution of the composite system, nonlocal two-qubit quantum (e.g., CPHASE and CNOT) gates can be achieved without real excitations of either cavity modes or atoms. The success of our protocol is conditioned on projecting an auxiliary atom onto a postselected state, which simultaneously removes various detrimental effects of dissipation on the gate fidelity. In principle, the success probability of the gate can approach unity as the single-atom cooperativity becomes sufficiently large.Furthermore, we show its application for implementing single- and two-qubit gates within a decoherence-free subspace that is immune to a collective dephasing noise. This faithful, heralded, and nonlocal protocol could, therefore, be useful for distributed quantum computation and scalable quantum networks.