Topological protection of coherence in a dissipative environment

Lorenzo Campos Venuti (1) , Zhengzhi Ma (1) , Hubert Saleur (2, 1) , Stephan Haas (1)

1 USC - University of Southern California
2 IPHT - Institut de Physique Théorique - UMR CNRS 3681

One dimensional topological insulators are characterized by edge states with exponentially small energies. According to one generalization of topological phase to non-Hermitian systems, a finite system in a non-trivial topological phase displays surface states with exponentially long life times. In this work we explore the possibility of exploiting such non-Hermitian topological phases to enhance the quantum coherence of a fiducial qubit embedded in a dissipative environment. We first show that a network of qubits interacting with lossy cavities can be represented, in a suitable super-one-particle sector, by a non-Hermitian " Hamiltonian " of the desired form. We then study, both analytically and numerically, one-dimensional geometries with up to three sites per unit cell, and up to a topological winding number $W$ = 2. For finite-size systems the number of edge modes is a complicated function of $W$ and the system size $N$. However we find that there are precisely $W$ modes localized at one end of the chain. In such topological phases the quibt's coherence lifetime is exponentially large in the system size. We verify that, for $W$ > 1, at large times, the Lindbladian evolution is approximately a non-trivial unitary. For $W$ = 2 this results in Rabi-like oscillations of the qubit's coherence measure.

Domains: Physics [physics]

Lorenzo Campos Venuti, Zhengzhi Ma, Hubert Saleur, Stephan Haas. Topological protection of coherence in a dissipative environment. Physical Review A, 2017, 96, pp.053858. ⟨10.1103/PhysRevA.96.053858⟩. ⟨cea-01540332v2⟩