Analog simulation of noisy quantum circuits
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Abstract
It is well known that simulating quantum circuits with low but nonzero 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. We give explicit expressions for noise that can be represented by Pauli channels, as well as for certain non-Pauli channels. 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 generic Pauli channels into a concatenation of channels involving only one nontrivial Pauli string. Published by the American Physical Society 2025