Collective dynamics of multimode bosonic systems induced by weak quantum measurement

TL;DR

This paper explores how weak quantum measurements on ultracold bosonic systems induce collective oscillatory dynamics, revealing a new regime of measurement-driven many-body quantum behavior with potential applications in various quantum platforms.

Contribution

It introduces an effective model and analytic solutions for measurement-induced collective dynamics in multimode bosonic systems, extending understanding beyond strong measurement regimes.

Findings

Weak measurement causes quasi-periodic collective oscillations.

Quantum jumps destabilize the system's stable point.

Analytic solutions describe the stochastic evolution of modes.

Abstract

In contrast to the fully projective limit of strong quantum measurement, where the evolution is locked to a small subspace (quantum Zeno dynamics), or even frozen completely (quantum Zeno effect), the weak non-projective measurement can effectively compete with standard unitary dynamics leading to nontrivial effects. Here we consider global weak measurement addressing collective variables, thus preserving quantum superpositions due to the lack of which path information. While for certainty we focus on ultracold atoms, the idea can be generalized to other multimode quantum systems, including various quantum emitters, optomechanical arrays, and purely photonic systems with multiple-path interferometers (photonic circuits). We show that light scattering from ultracold bosons in optical lattices can be used for defining macroscopically occupied spatial modes that exhibit long-range coherent dynamics. Even if the measurement strength remains constant, the quantum measurement backaction acts on the atomic ensemble quasi-periodically and induces collective oscillatory dynamics of all the atoms. We introduce an effective model for the evolution of the spatial modes and present an analytic solution showing that the quantum jumps drive the system away from its stable point. We confirm our finding describing the atomic observables in terms of stochastic differential equations.