Measurement-induced dynamics and stabilization of spinor-condensate domain walls

Abstract

Weakly measuring many-body systems and allowing for feedback in real-time can simultaneously create and measure new phenomena in quantum systems. We theoretically study the dynamics of a continuously measured two-component Bose-Einstein condensate (BEC) potentially containing a domain wall, and focus on the trade-off between usable information obtained from measurement and quantum backaction. Each weakly measured system yields a measurement record from which we extract real-time dynamics of the domain wall. We show that quantum backaction due to measurement causes two primary effects: domain wall diffusion and overall heating. The system dynamics and signal-to-noise ratio depend on the choice of measurement observable. We propose a feedback protocol to dynamically create a stable domain wall in the regime where domain walls are unstable, giving a prototype example of Hamiltonian engineering using measurement and feedback.

Synthetic Mechanical Lattices with Synthetic Interactions

“…We have experimentally demonstrated the basic elements of this approach, including the control of real and imaginary site energies, complex and non-reciprocal inter-site hopping terms, and engineered nonlinear interactions. The presented approach is general, directly applicable to classical emulators based on mechanics or electronics and photonics [60], but also intimately related to recent ideas for the steering of quantum systems into new many-body phases via measurement-based feedback [61][62][63][64]. Looking forward, as this approach is expanded to many-site arrays of classical oscillators, the ability to synthesize near-arbitrary mean-field lattice Hamiltonians will open up new opportunities for exploring exotic transport phenomena in a highly accessible laboratory setting.…”

Relaxation of ferromagnetic domains in a disordered lattice in 2D

“…The manuscript here presented sets a platform for the design of specific protocols appropriate to study demagnetization processes or frustration effects associated to geometry and energy disorder [41][42][43][44]. Also, our study aims for the investigation of the dynamics induced by measurement in the sense that sources of disorder can be either internal as those here considered, or external as those associated to reservoirs in contact with assessable quantum systems [45]. We expect that our work will trigger further theoretical analysis as for instance, the long range character proper of the dipole-dipole mag-netic interactions, as well as the homogeneous environment where the elemental constituents move.…”

Feedback Induced Magnetic Phases in Binary Bose-Einstein Condensates

“…We model dispersive imaging of a quasi-onedimensional (1D) multicomponent Bose-Einstein condensate of length L via spin resolved phase-contrast imaging [39] and we label individual components by an index s. We consider time and space resolved measurements of atomic density ns (x, t) in each component using the Gaussian measurement model developed in detail in Ref. [40]. Stroboscopic weak measurements with strength ϕ result in the measurement signal…”

“…(1) the measurement results at the meanfield level therefore depend on the field amplitude via ns (x) → |ψ s (x)| 2 . Measurement backaction leads to stochastic evolution of the order parameter, which results in condensate heating [40,42] in the absence of a cooling protocol, which we describe in Sec. III.…”