Simulation of open quantum systems via low-depth convex unitary evolutions

TL;DR

This paper introduces a hybrid quantum-classical method for simulating open quantum systems, specifically random-unitary channels, using low-depth convex unitary evolutions that are more feasible on NISQ devices.

Contribution

It presents a novel approach that avoids deep ancilla circuits by decomposing open system dynamics into convex unitary evolutions, enabling efficient simulation on near-term quantum hardware.

Findings

Successfully simulated open quantum systems with dozens of qubits.

Demonstrated efficient sampling of convex unitary evolutions.

Reduced noise costs compared to traditional methods.

Abstract

Simulating physical systems on quantum devices is one of the most promising applications of quantum technology. Current quantum approaches to simulating open quantum systems are still practically challenging on NISQ-era devices, because they typically require ancilla qubits and extensive controlled sequences. In this work, we propose a hybrid quantum-classical approach for simulating a class of open system dynamics called random-unitary channels. These channels naturally decompose into a series of convex unitary evolutions, which can then be efficiently sampled and run as independent circuits. The method does not require deep ancilla frameworks and thus can be implemented with lower noise costs. We implement simulations of open quantum systems up to dozens of qubits and with large channel ranks.