Some implications of superconducting quantum interference to the application of master equations in engineering quantum technologies

TL;DR

This paper explores how different master equations affect the modeling of superconducting quantum interference devices, highlighting the influence of external flux bias on decoherence and dissipation in quantum systems.

Contribution

It derives and compares master equations at various approximation levels for SQUIDs, revealing the flux bias's role in decoherence and Lindblad dissipation.

Findings

Decoherence depends on approximation level and flux bias.

External flux influences Lindblad terms beyond the Hamiltonian.

Master equations show qualitative and quantitative differences.

Abstract

In this paper we consider the modelling and simulation of open quantum systems from a device engineering perspective. We derive master equations at different levels of approximation for a Superconducting Quantum Interference Device (SQUID) ring coupled to an ohmic bath. We demonstrate that the master equations we consider produce decoherences that are qualitatively and quantitativly dependent on both the level of approximation and the ring's external flux bias. We discuss the issues raised when seeking to obtain Lindbladian dissipation and show, in this case, that the external flux (which may be considered to be a control variable in some applications) is not confined to the Hamiltonian, as often assumed in quantum control, but also appears in the Lindblad terms.