Fermionic Simulators for Enhanced Scalability of Variational Quantum Simulation

TL;DR

This paper demonstrates that fermionic quantum simulators, enabled by recent advances in atomic manipulation, outperform qubit-based simulators in resource efficiency and scalability for simulating strongly correlated fermionic systems.

Contribution

The study provides a comprehensive comparison showing fermionic simulators are more resource-efficient and scalable than qubit-based ones for variational ground-state emulation of fermionic systems.

Findings

Fermionic simulators require fewer resources for quantum evolution.

They show less sensitivity to initial circuit parameters.

Performance advantage increases with system size and interaction strength.

Abstract

Near-term quantum simulators are mostly based on qubit-based architectures. However, their imperfect nature significantly limits their practical application. The situation is even worse for simulating fermionic systems, which underlie most of material science and chemistry, as one has to adopt fermion-to-qubit encodings which create significant additional resource overhead and trainability issues. Thanks to recent advances in trapping and manipulation of neutral atoms in optical tweezers, digital fermionic quantum simulators are becoming viable. A key question is whether these emerging fermionic simulators can outperform qubit-based simulators for characterizing strongly correlated electronic systems. Here, we perform a comprehensive comparison of resource efficiency between qubit and fermionic simulators for variational ground-state emulation of fermionic systems in both condensed matter systems and quantum chemistry problems. We show that the fermionic simulators indeed outperform their qubit counterparts with respect to resources for quantum evolution (circuit depth), as well as classical optimization (number of required parameters and iterations). In addition, they show less sensitivity to the random initialization of the circuit. The relative advantage of fermionic simulators becomes even more pronounced as interaction becomes stronger, or tunneling is allowed in more than one dimension, as well as for spinful fermions. Importantly, this improvement is scalable, i.e., the performance gap between fermionic and qubit simulators only grows for bigger system sizes.