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Open quantum systems, effective Hamiltonians, and device characterization

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journal contribution
posted on 08.11.2017, 15:35 by Vincent Dwyer, Stephen N.A. Duffus, Mark Everitt
High fidelity models, which are able to both support accurate device characterization and correctly account for environmental effects, are crucial to the engineering of scalable quantum technologies. As it ensures positivity of the density matrix, one preferred model of open systems describes the dynamics with a master equation in Lindblad form. In practice, Linblad operators are rarely derived from first principles, and often a particular form of annihilator is assumed. This results in dynamical models that miss those additional terms which must generally be added for the master equation to assume the Lindblad form, together with the other concomitant terms that must be assimilated into an effective Hamiltonian to produce the correct free evolution. In first principles derivations, such additional terms are often canceled (or countered), frequently in a somewhat ad hoc manner, leading to a number of competing models. Whilst the implications of this paper are quite general, to illustrate the point we focus here on an example anharmonic system; specifically that of a superconducting quantum interference device (SQUID) coupled to an Ohmic bath. The resulting master equation implies that the environment has a significant impact on the system’s energy; we discuss the prospect of keeping or canceling this impact and note that, for the SQUID, monitoring the magnetic susceptibility under control of the capacitive coupling strength and the externally applied flux results in experimentally measurable differences between a number of these models. In particular, one should be able to determine whether a squeezing term of the form ˆX ˆ P + ˆ P ˆX should be present in the effective Hamiltonian or not. If model generation is not performed correctly, device characterization will be prone to systemic errors.

History

School

  • Mechanical, Electrical and Manufacturing Engineering

Published in

Physical review B: Condensed Matter and Materials Physics

Volume

96

Issue

13

Citation

DWYER, V.M., DUFFUS, S.N.A. and EVERITT, M.J., 2017. Open quantum systems, effective Hamiltonians, and device characterization. Physical Review B: Condensed Matter and Materials Physics, 96, 134520

Publisher

© American Physical Society

Version

VoR (Version of Record)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Acceptance date

13/10/2017

Publication date

2017-10-27

ISSN

2469-9950

eISSN

2469-9969

Language

en

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Keywords

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