Dynamical phases and quantum correlations in an emitter-waveguide system with feedback

Abstract

We investigate the creation and control of emergent collective behavior and quantum correlations using feedback in an emitter-waveguide system using a minimal model. Employing homodyne detection of photons emitted from a laser-driven emitter ensemble into the modes of a waveguide allows to generate intricate dynamical phases. In particular, we show the emergence of a time-crystal phase, the transition to which is controlled by the feedback strength. Feedback enables furthermore the control of many-body quantum correlations, which become manifest in spin squeezing in the emitter ensemble. Developing a theory for the dynamics of fluctuation operators we discuss how the feedback strength controls the squeezing and investigate its temporal dynamics and dependence on system size. The largely analytical results allow to quantify spin squeezing and fluctuations in the limit of large number of emitters, revealing critical scaling of the squeezing close to the transition to the time-crystal. Our study corroborates the potential of integrated emitter-waveguide systems -which feature highly controllable photon emission channels -for the exploration of collective quantum phenomena and the generation of resources, such as squeezed states, for quantum enhanced metrology.

Quantum engineering of a synthetic thermal bath for bosonic atoms in a one-dimensional optical lattice via Markovian feedback control

“…Here, we consider the quantum engineering of a synthetic thermal bath via Markovian feedback control [54,55]. As an important measurement-based feedback method, Markovian feedback control has been applied to various problems, including the stabilization of arbitrary one-qubit quantum states [56,57], the manipulation of quantum entanglement between two qubits [58][59][60][61], as well as optical and spin squeezing [62][63][64].…”

Tuning the universality class of phase transitions by feedback: Open quantum systems beyond dissipation

“…Such tunable feedback-induced phase transitions maybe be obtained in many-body problems, e.g., the feedback-induced supersolid-like, antiferromagnetic, and other states in optical lattices [3,13], time crystals [1,14], etc. The influence of quantum measurements on phase transitions in many-body systems was considered without feedback, e.g., in Refs.…”

A versatile quantum simulator for coupled oscillators using a 1D chain of atoms trapped near an optical nanofiber

“…The individual atom-atom coupling via resonant photon emission by one atom followed by absorption by a second atom is typically rather small [12,13], but it can already lead to spatial self-ordering of the atoms [14]. The induced force can be significantly increased if the atoms are transversely illuminated far off any internal atomic resonance to induce collective coherent scattering into the fiber [15,16,17]. Here the interference between the mode amplitudes created by scattering from different particles leads to gradient or dipole forces, which appear without changing the internal atomic state from spontaneous emission [18].…”