Southwest Quantum Information and Technology

Reliability of simulation on NISQ-era devices

Presenting Author: Karthik Chinni, University of New Mexico CQuIC
Contributing Author(s): Manuel Munoz, Pablo Poggi, Ivan Deutsch

The goal of NISQ-era quantum processors is to outperform classical computers on targeted tasks, such as quantum simulation, with moderately sized devices that are well controlled, but lack full fault-tolerant error correction. Here, we consider two different types of errors that could affect the reliability of NISQ devices: a background perturbation that leads to quantum chaos and Trotterization of the unitary dynamical map. In the first case, we consider simulation of the LMG model, which is integrable in the mean-field limit, but becomes chaotic in the presence of a background time-dependent perturbation. Here, we show that the quantities that depend on the global structure of the phase space, such as critical point estimates of the quantum phase transition, are robust to the presence of this perturbation while other aspects of the system such as the mean magnetization that depend on the local trajectories are fragile and cannot be reliably extracted from the simulator. Next, we analyze the effects of Trotterization on the simulation of p-spin models and identify the existence of “dynamical instability regions” in the Trotterized unitary map that are absent in the time evolution operator of the ideal p-spin model. We show that, even in the absence of chaos, Trotter errors proliferate in these dynamical instability regions, as the effective Hamiltonian associated with the Trotterized unitary becomes very different from the target p-spin Hamiltonian.

Read this article online: https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.3.033145

(Session 3 : Thursday from 3:10pm-3:30pm)