Variational Quantum Operator Simulation

TL;DR

This paper introduces VQOS, a variational method to implement quantum time evolution operators with shallower circuits, enhancing the practicality of near-term quantum computers for simulations.

Contribution

VQOS provides a new variational approach to realize time evolution operators without Trotterization, resulting in significantly shallower quantum circuits.

Findings

VQOS successfully implements time evolution operators in shallower circuits.

Numerical simulations show VQOS circuits are up to 5 times shallower than Trotterization.

VQOS enhances the feasibility of quantum simulations on near-term hardware.

Abstract

Implementing time-evolution operators in shallow quantum circuits is important for quantum simulations. The standard method of Trotterization requires a large number of gates to achieve practical accuracy. Variational Quantum Simulation (VQS) is an algorithm that calculates the time evolution of a quantum state and can be executed with shallower circuits than Trotterization. However, the operator obtained by VQS evolves only a fixed initial state and is not the time evolution operator itself. In this paper, we propose Variational Quantum Operator Simulation (VQOS), a method to realize time evolution operators in shallow quantum circuits. This method is based on the variational principle for operators and does not require the implementation of the desired Trotter decomposition of the time evolution operator. We performed numerical simulations of the VQOS algorithm and successfully implemented the time evolution operator for closed systems in a quantum circuit that is up to 5 times shallower than the Trotterization. By providing a more practical way to implement time evolution operators, VQOS increases the applicability of near-term quantum computers.