Topological Protection of Coherence in Noisy Open Quantum Systems

TL;DR

This paper explores how topological mechanisms can protect qubit coherence in noisy, disordered open quantum systems by analyzing non-Hermitian models and revealing disorder-induced coherence enhancements.

Contribution

It introduces a framework for defining winding numbers in disordered non-Hermitian systems and maps topological phase diagrams under realistic noise conditions.

Findings

Winding numbers can be defined in disordered non-Hermitian systems with symmetry.

Topological phase diagrams are constructed for disordered SSH and trimer models.

Disorder can induce re-entrance phenomena, increasing qubit coherence times.

Abstract

We consider topological protection mechanisms in dissipative quantum systems in the presence of quenched disorder, with the intent to prolong coherence times of qubits. The physical setting is a network of qubits and dissipative cavities whose coupling parameters are tunable, such that topological edge states can be stabilized. The evolution of a fiducial qubit is entirely determined by a non-Hermitian Hamiltonian which thus emerges from a bona-fide physical process. It is shown how even in the presence of disorder winding numbers can be defined and evaluated in real space, as long as certain symmetries are preserved. Hence we can construct the topological phase diagrams of noisy open quantum models, such as the non-Hermitian disordered Su-Schrieffer- Heeger dimer model and a trimer model that includes longer-range couplings. In the presence of competing disorder parameters, interesting re-entrance phenomena of topologically non-trivial sectors are observed. This means that in certain parameter regions, increasing disorder drastically increases the coherence time of the fiducial qubit.