Sensitivity to initial noise in measurement-induced nonlinear quantum dynamics

TL;DR

This paper studies how initial noise affects measurement-induced nonlinear quantum dynamics, showing that noise can turn a chaotic ergodic system into one with a stable mixed state fixed point.

Contribution

It demonstrates that initial noise can fundamentally alter the behavior of measurement-induced nonlinear quantum protocols, turning chaos into stability.

Findings

Initial pure states exhibit chaotic dynamics.

Initial noise drives the system toward a mixed state.

The completely mixed state becomes an attractive fixed point.

Abstract

We consider a special iterated quantum protocol with measurement-induced nonlinearity for qubits, where all pure initial states on the Bloch sphere can be considered chaotic. The dynamics is ergodic with no attractive fixed cycles. We show that initial noise radically changes this behavior. The completely mixed state is an attractive fixed point of the dynamics induced by the protocol. Our numerical simulations strongly indicate that initially mixed states all converge to the completely mixed state. The presented protocol is an example, where gaining information from measurements and employing it to control an ensemble of quantum systems enables us to create ergodicity, which in turn is destroyed by any initial noise.