Large-Scale Quantum Simulation and Error Mitigation of Integrable Spin Chains

We are now at the beginning of the era of utility-scale quantum computers, where we have quantum devices with a large number of qubits, allowing us to run circuits that are becoming more and more challenging to simulate classically. Integrable models, being exactly solvable, provide useful benchmarks for quantum simulation algorithms running on quantum hardware, as we have an exact reference value for observables at our disposal. In particular, these models can be used to measure the strength of (or lack of) biases exhibited by different error mitigation methods. We report on our large-scale quantum simulations of integrable models on IBM devices, where Qedma's error mitigation technique QESEM plays a crucial role in protecting the conserved charges against decay due to hardware noise. We also present our latest results on quantum many-body scars, which are another example of the breaking of the Eigenstate Thermalization Hypothesis (ETH). This demonstrates that today's hardware, combined with state-of-the-art error mitigation techniques, is becoming useful for exploring quantum many-body non-equilibrium phenomena.