# Reconstructing the ideal results of a perturbed analog quantum simulator

## TL;DR

This paper introduces a method to reconstruct ideal quantum simulation results from perturbed systems by leveraging statistical knowledge of environmental effects, enabling more reliable simulations despite noise.

## Contribution

The paper presents a novel approach to recover ideal correlators from noisy quantum simulators using statistical assumptions and additional measurements, without extra quantum overhead.

## Key findings

- Reconstruction of ideal correlators is possible under certain statistical assumptions.
- Verification of assumptions can be done experimentally with additional measurements.
- Method enables noise-resilient quantum simulations without extra quantum resources.

## Abstract

Well-controlled quantum systems can potentially be used as quantum simulators. However, a quantum simulator is inevitably perturbed by coupling to additional degrees of freedom. This constitutes a major roadblock to useful quantum simulations. So far there are only limited means to understand the effect of perturbation on the results of quantum simulation. Here, we present a method which, in certain circumstances, allows for the reconstruction of the ideal result from measurements on a perturbed quantum simulator. We consider extracting the value of the correlator $\langle\hat{O}^i(t) \hat{O}^j(0)\rangle$ from the simulated system, where $\hat{O}^i$ are the operators which couple the system to its environment. The ideal correlator can be straightforwardly reconstructed by using statistical knowledge of the environment, if any $n$-time correlator of operators $\hat{O}^i$ of the ideal system can be written as products of two-time correlators. We give an approach to verify the validity of this assumption experimentally by additional measurements on the perturbed quantum simulator. The proposed method can allow for reliable quantum simulations with systems subjected to environmental noise without adding an overhead to the quantum system.