Enhancing correlation times for edge spins through dissipation

TL;DR

This paper explores how dissipation can unexpectedly extend the coherence times of edge spins in quantum spin chains, generalizing strong zero modes to dissipative systems and suggesting potential benefits for quantum information storage.

Contribution

It introduces the concept of dissipative strong zero maps, showing dissipation can enhance correlation times and preserve quantum information in open quantum systems.

Findings

Dissipation can extend edge spin coherence times beyond unitary cases.

Weak end-to-end coupling induces stable harmonic oscillations of zero modes.

Dissipative environments can be harnessed to improve quantum information storage.

Abstract

Spin chains with open boundaries, such as the transverse field Ising model, can display coherence times for edge spins that diverge with the system size as a consequence of almost conserved operators, the so-called strong zero modes. Here, we discuss the fate of these coherence times when the system is perturbed in two different ways. First, we consider the effects of a unitary coupling connecting the ends of the chain; when the coupling is weak and non-interacting, we observe stable long-lived harmonic oscillations between the strong zero modes. Second, and more interestingly, we consider the case when dynamics becomes dissipative. While in general dissipation induces decoherence and loss of information, here we show that particularly simple environments can actually enhance correlation times beyond those of the purely unitary case. This allows us to generalise the notion of strong zero modes to irreversible Markovian time-evolutions, thus defining conditions for {\em dissipative strong zero maps}. Our results show how dissipation could, in principle, play a useful role in protocols for storing information in quantum devices.