Overhead for simulating a non-local channel with local channels by quasiprobability sampling

TL;DR

This paper introduces a framework for simulating non-local quantum channels with local channels using quasiprobability sampling, aiming to reduce resource costs on early quantum devices.

Contribution

It defines the channel robustness of non-locality and provides an explicit decomposition upper bound for two-qubit unitaries, generalizing previous work.

Findings

Defined channel robustness of non-locality.

Provided an explicit decomposition upper bound for two-qubit unitaries.

Developed a resource reduction framework for first-generation quantum devices.

Abstract

As the hardware technology for quantum computing advances, its possible applications are actively searched and developed. However, such applications still suffer from the noise on quantum devices, in particular when using two-qubit gates whose fidelity is relatively low. One way to overcome this difficulty is to substitute such non-local operations by local ones. Such substitution can be performed by decomposing a non-local channel into a linear combination of local channels and simulating the original channel with a quasiprobability-based method. In this work, we first define a quantity that we call channel robustness of non-locality, which quantifies the cost for the decomposition. While this quantity is challenging to calculate for a general non-local channel, we give an upper bound for a general two-qubit unitary channel by providing an explicit decomposition. The decomposition is obtained by generalizing our previous work whose application has been restricted to a certain form of two-qubit unitary. This work develops a framework for a resource reduction suitable for first-generation quantum devices.