Collective dynamics of multimode bosonic systems induced by weak quantum measurement

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.

Quantum measurement-induced antiferromagnetic order and density modulations in ultracold Fermi gases in optical lattices

“…Specifically, in the strong measurement regime the detection process freezes to a specific value stochastically determined by a particular series of quantum jumps. However, if the measurement cannot inhibit the dynamics and the tunneling of atoms across the optical lattice leads to an oscillatory behavior, that, in the case of bosons, can be described analytically 42 .…”

Cavityless self-organization of ultracold atoms due to the feedback-induced phase transition

“…In particular, one can measure light scattered at an angle that does not satisfy the condition (1), which would contain different information about the distribution of the atoms [58][59][60][61] . The feedback-induced maximization of this signal might result in more exotic states of the atomic ensembles, both bosons and fermions 28,29,[62][63][64][65][66][67][68][69][70] . We leave this interesting possibility for future research.…”

Quantum State Reduction by Matter-Phase-Related Measurements in Optical Lattices

“…The main major concern is photon detector inefficiency. It has been shown 31 that as long as there is a sufficient number of photons detected such that the true instantaneous rate can be reliably estimated it is possible to use detectors with very low efficiencies. Another, possible issue is the sensitivity of the relative angle between the cavity and the probe beams.…”