Decoherence, relaxation and chaos in a kicked-spin ensemble

TL;DR

This paper investigates how classical dynamical processes like chaos and randomness in kick trains affect quantum decoherence and relaxation in a spin ensemble, revealing a chaos signature called the horizon of coherence.

Contribution

It introduces a model linking classical chaos in kick trains to quantum decoherence, highlighting the horizon of coherence as a chaos signature.

Findings

Chaotic kick trains induce a horizon of coherence.

Decoherence correlates with Lyapunov exponents.

Classical chaos signatures manifest in quantum dynamics.

Abstract

We study the dynamics of a quantum spin ensemble controlled by trains of ultrashort pulses. To model disturbances of the kicks, we consider that the spins are submitted to different kick trains which follow regular, random, stochastic or chaotic dynamical processes. These are described by dynamical systems on a torus. We study the quantum decoherence and the population relaxation of the spin ensemble induced by these classical dynamical processes disturbing the kick trains. For chaotic kick trains we show that the decoherence and the relaxation processes exhibit a signature of chaos directly related to the Lyapunov exponents of the dynamical system. This signature is a horizon of coherence, i.e. a preliminary duration without decoherence followed by a rapid decoherence process.