Towards Laser Control of Open Quantum Systems: Memory Effects

TL;DR

This paper explores laser control of open quantum systems by tuning system parameters to manipulate non-Markovian memory effects, aiming to optimize decoherence processes for various quantum applications.

Contribution

It demonstrates how external laser fields can be used to enhance non-Markovianity in open quantum systems, providing a new approach for quantum control.

Findings

Non-Markovianity can be continuously tuned via laser-induced Stark shifts.

Decoherence rates are calculated using a Nakajima-Zwanzig master equation with HEOM.

Control of open quantum systems through memory effects is feasible.

Abstract

Laser control of Open Quantum Systems (OQS) is a challenging issue as compared to its counterpart in isolated small size molecules, basically due to very large numbers of degrees of freedom to be accounted for. Such a control aims at appropriately optimizing decoherence processes of a central two-level system (a given vibrational mode, for instance) towards its environmental bath (including, for instance, all other normal modes). A variety of applications could potentially be envisioned, either to preserve the central system from decaying (long duration molecular alignment or orientation, qubit decoherence protection) or, to speed up the information flow towards the bath (efficient charge or proton transfers in long chain organic compounds). Achieving such controls require some quantitative measures of decoherence in relation with memory effects in the bath response, actually given by the degree of non-Markovianity. Characteristic decoherence rates of a Spin-Boson model are calculated using a Nakajima-Zwanzig type master equation with converged HEOM expansion for the memory kernel. It is shown that, by adequately tuning the two-level transition frequency through a controlled Stark shift produced by an external laser field, non-Markovianity can be enhanced in a continuous way leading to a first attempt towards the control of OQS.