Southwest Quantum Information and Technology

Robustness and sensitivity to imperfections in the dynamics of general observables within near-term quantum simulators

Presenting Author: Pablo Poggi, University of New Mexico CQuIC
Contributing Author(s): Nathan Lysne, Kevin Kuper, Poul Jessen, Ivan Deutsch

We analyze how robust the output of analog quantum simulators is in the presence of weak perturbations. To this end, we focus on the dynamics of expectation values of general observables under the simulated dynamics and study the error arising from the imperfect operation of the device. We show that the properties of the error depend crucially on the observable considered as output of the simulator. and that even a low-fidelity quantum simulation is still able to reproduce the dynamics of other observables with a small relative error. We define the observable purity, which quantitatively characterizes the magnitude of the support of the observable in Hilbert space, and analytically show that, in general, these imperfect devices are able to reproduce the dynamics of low-purity observables (such as collective operators like the magnetization in a spin system) accurately, while the error in the expectation value of high-purity observables (such as projectors onto pure states) are much larger on average. We demonstrate the universality of these features by experimentally simulating various physical models of interest in a state-of- the-art 16-dimensional quantum simulator, which is universal and fully programmable by optimal control methods. Without assuming any particular error model, we show that the predicted behavior is generic for a highly accurate device where we expect imperfections to be small.

(Session 5 : Saturday from 5:00pm - 7:00pm)