Abstract
Quantum simulation on emerging quantum hardware is a topic of intense interest. While many studies focus on computing ground-state properties or simulating unitary dynamics of closed systems, open quantum systems are an interesting target of study owing to their ubiquity and rich physical behavior. However, their nonunitary dynamics are also not natural to simulate on digital quantum devices. Here, we report algorithms for the digital quantum simulation of the dynamics of open quantum systems governed by a Lindblad equation using adaptations of the quantum imaginary–time evolution algorithm. We demonstrate the algorithms on IBM Quantum’s hardware with simulations of the spontaneous emission of a two-level system and the dissipative transverse field Ising model. Our work advances efforts to simulate the dynamics of open quantum systems on quantum hardware.
- Received 7 June 2021
- Accepted 11 January 2022
DOI:https://doi.org/10.1103/PRXQuantum.3.010320
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Using quantum computers to simulate other quantum systems, known as quantum simulation, is one of the most promising applications of near-term quantum computers. Many different methods have been proposed to simulate isolated quantum systems; however, when a system is in contact with another larger, uncontrolled environment (an open quantum system), these methods need to be adapted to include the effects of the environment. In this paper, methods are developed for simulating a quantum system weakly interacting with an environment on near-term quantum hardware.
Two new algorithms are proposed to simulate the dynamics of open quantum systems, using adaptations of the quantum imaginary–time evolution algorithm used to find low-energy states of quantum systems. The first algorithm doubles the number of qubits to capture the effects of the environment acting on the system, whereas the second algorithm is able to simulate on open quantum system without the use of any ancilla qubits. Instead, the dynamics can be simulated on the original system with a classical overhead and increased number of measurement circuits.
Open quantum systems are ubiquitous in quantum science and engineering. The algorithms developed in this paper can be applied to non-Markovian systems, open fermionic systems, quantum thermodynamics, and open systems in condensed matter physics.
