Simulating Open Quantum Systems on Near Term Quantum Computers

Abstract

The simulation of quantum systems is poised to be one of the first and most impactful applications of quantum computers. This thesis focuses on such simulation with a particular emphasis on simulating open quantum systems, i.e. systems which can exchange energy, particles, information, or more with their surroundings. Chapter 1 introduces the fundamentals of quantum computing and quantum information. In chapter 2 we review the basics of quantum dynamics, and open quantum systems. Chapter 3 explores errors in actual quantum computers and discusses techniques to optimize results when running on currently available quantum hardware. Chapter 4 comes from the paper “Simulation of Thermal Relaxation in Spin Chemistry Systems on a Quantum Computer Using Inherent Qubit Decoherence”[1] in which we show how to use qubit decoherence to our advantage to simulate an open spin chemistry system undergoing thermal relaxation on IBM’s quantum computers. Chapter 5 originates from the paper “Driven-dissipative quantum mechanics on a lattice: Simulating a fermionic reservoir on a quantum computer ”[2] where we show how to simulate the dynamics of a driven dissipative Hubbard model on IBM’s quantum computers without reset gates. Chapter 6 is derived from the paper “Demonstrating robust simulation of driven-dissipative problems on near-term quantum computers”[3]. This paper extends the work presented in chapter 5 with the introduction of selective reset gates - allowing us to simulate Trotterized time evolution further than had previously been achieved on any digital quantum computer. We also calculate the current through the system and prepare the thermal state of atomic limit of the same model. Finally, chapter 7 contains concluding remarks.