Quantum noise in a transversely-pumped-cavity Bose-Hubbard model

Abstract

We investigate the quantum measurement noise effects on the dynamics of an atomic Bose lattice gas inside an optical resonator. We describe the dynamics by means of a hybrid model consisting of a Bose-Hubbard Hamiltonian for the atoms and a Heisenberg-Langevin equation for the lossy cavity field mode. We assume that the atoms are prepared initially in the ground state of the lattice Hamiltonian and then start to interact with the cavity mode. We show that the cavity field fluctuations originating from the dissipative outcoupling of photons from the resonator lead to vastly different effects in the different possible ground state phases, i.e., the superfluid, the supersolid, the Mott-and the charge-density-wave phases. In the former two phases with the presence of a superfluid wavefunction, the quantum measurement noise appears as a driving term leading to depletion of the ground state. The time scale for the system to leave the ground state is presented in a simple analytical form. For the latter two incompressible phases, the quantum noise results in the fluctuation of the chemical potential. We derive an analytical expression for the corresponding broadening of the quasiparticle resonances. arXiv:1803.06014v2 [cond-mat.quant-gas]

Cavity QED with Quantum Gases: New Paradigms in Many-Body Physics

“…We now consider lattice scenarios where the atoms are already initially trapped in a strong 2D "external", static optical lattice below the superradiant phase transition. As before, photons scattered by the atoms from a transverse pump field into the cavity result in cavity-mediated long-range interactions, competing directly with the kinetic energy and the local interactions of the strongly correlated atoms [75,84,98,99,104,105,[223][224][225][226][227][228][229][230][231][232][233][234][235][236][237]. Here, for instance, the cavity-mediated long-range interactions can be incommensurate with respect to the external static lattice spacing, leading to frustration.…”

“…Indeed, coupling atoms to a lossy cavity field is known to lead to the redistribution of the atoms and hence an effective temperature for the atoms-referred to as cavity cooling or heating in quantum optics [70]-roughly set by the loss rate. The cavity-induced redistribution has recently been studied also for quantum gases [97][98][99][100] and can even lead to non-thermal steady states [97]. Since the corrections to the noiseless mean-field approach are suppressed by a factor 1/V , the characteristic time for a cavity-induced redistribution to set in scales with the volume V [97].…”

“…Let us now consider a generic lattice model inside a linear cavity [84,98,99,104,105,[225][226][227][228][229][230]233]. Ultracold bosonic atoms are trapped in a three dimensional external static lattice, generated by three mutually orthogonal standing-wave laser fields not interfering with each other.…”

Light-induced quantum droplet phases of lattice bosons in multimode cavities

“…Already for a single-mode cavity, which mediates global-range interactions, a rich phase diagram has been experimentally observed, featuring, besides the known superfluid and Mott-insulating phases, a lattice supersolid as well as an incompressible density-wave phase [3]. Such experiments implement a Bose-Hubbard (BH) model extended by a global-range sign-changing interaction, which has been intensively studied in recent years [4][5][6][7][8][9][10][11][12][13][14].…”

Extended Bose-Hubbard Model with Cavity-Mediated Infinite-Range Interactions at Finite Temperatures

“…It presents in total four quantum phases: superfluid (SF), supersolid (SS), Mott insulator (MI), and charge density wave (CDW). Previous theoretical studies [30][31][32][33][34][35][36][37][38] mainly concentrate on the ground-state phase diagram and associated phase transitions of the model, leaving the finite-temperature physics which is experimentally relevant and interesting, largely intact.…”