Feynman's Clock for open quantum systems

TL;DR

This paper extends Feynman's Clock construction to open quantum systems, allowing the simulation of system-environment interactions and stochastic trajectories via non-Hermitian Hamiltonians.

Contribution

It introduces a novel formalism that encodes open quantum system evolution as ground states of non-Hermitian Hamiltonians, enabling new simulation methods.

Findings

Ground states of non-Hermitian Hamiltonians yield stochastic trajectories.

The method can simulate system-environment interactions like heat baths or measurements.

A numerical example demonstrates spontaneous emission in a two-level atom.

Abstract

We show that Feynman's Clock construction, in which the time-evolution of a closed quantum system is encoded as a ground state problem, can be extended to open quantum systems. In our formalism, the ground states of an ensemble of non-Hermitian Feynman Clock Hamiltonians yield stochastic trajectories, which unravel the evolution of a Lindblad master equation. In this way, one can use Feynman's Clock not only to simulate the evolution of a quantum system, but also it's interaction with an environment such as a heat bath or measuring apparatus. A simple numerical example of a two-level atom undergoing spontaneous emission is presented and analyzed.