Analog simulation of noisy quantum circuits

TL;DR

This paper introduces a novel simulation method for noisy quantum circuits that reduces variance and accelerates simulations by leveraging a trajectory representation close to identity, improving efficiency significantly.

Contribution

It proposes a new trajectory-based simulation technique for noisy quantum circuits that reduces variance and computational overhead compared to existing methods.

Findings

Simulation speed improved by factors of 10 to 100.

Provides a formula for factorizing multiple-Pauli channels.

Reduces variance in quantum trajectory sampling.

Abstract

It is well-known that simulating quantum circuits with low but non-zero hardware noise is more difficult than without noise. It requires either to perform density matrix simulations (coming with a space overhead) or to sample over "quantum trajectories" where Kraus operators are inserted randomly (coming with a runtime overhead). We propose a simulation technique based on a representation of hardware noise in terms of trajectories generated by operators that remain close to identity at low noise. This representation significantly reduces the variance over the quantum trajectories, speeding up noisy simulations by factors around $10$ to $100$. As a by-product, we provide a formula to factorize multiple-Pauli channels into a concatenation of single Pauli channels.