Quantum optics of strongly correlated many-body systems
Igor Mekhov, University of Oxford
We show that quantum backaction of weak measurement constitutes a novel source of competitions in many-body systems, thus leading to new phenomena. We consider a system of ultracold atoms in optical lattices trapped inside a high-Q cavity, which requires a fully quantum description of both light and matter waves. The QND measurements lead to the generation of genuinely multipartite entangled modes of the matter fields, which have analogies in quantum optics (e.g. two-mode squeezing), but are non-Gaussian. Interestingly, non-QND weak measurements lead to nontrivial conditional dynamics even at single quantum trajectories: non-Hermitian evolution beyond quantum Zeno dynamics, long-range correlated tunneling, measurement-based protection and break-up of fermion pairs, as well as generation of antiferromagnetic order and multimode global NOON states. The weak global measurement also allows engineering correlated reservoirs for open systems. The quantization of cavity light creates a paradigm of quantum optical lattices. This enables quantum simulations of various long-range interacting systems unobtainable using classical optical lattices. The novel quantum phases include dimers, trimers, etc. of matter waves, beyond density orders (e.g. supersolids) utilizing the collective enhancement of light-matter interaction. Our approach can be applied to other arrays of quantum emitters, including natural and artificial atoms, as well as to purely photonic multimode systems with multiple-path interference.