Dynamics, dephasing and clustering of impurity atoms in Bose-Einstein condensates

Abstract

We investigate the influence of a Bose-Einstein condensate (BEC) on the properties of immersed impurity atoms, which are trapped in an optical lattice. Assuming a weak coupling of the impurity atoms to the BEC, we derive a quantum master equation for the lattice system. In the special case of fixed impurities with two internal states the atoms represent a quantum register and the quantum master equation reproduces the exact evolution of the qubits. We characterise the qubit dephasing which is caused by the interspecies coupling and show that the effect of sub- and superdecoherence is observable for realistic experimental parameters. Furthermore, the BEC phonons mediate an attractive interaction between the impurities, which has an important impact on their spatial distribution. If the lattice atoms are allowed to move, there occurs a sharp transition with the impurities aggregating in a macroscopic cluster at experimentally achievable temperatures. We also investigate the impact of the BEC on the transport properties of the impurity atoms and show that a crossover from coherent to diffusive behaviour occurs with increasing interaction strength.

22 pages, 8 figures, some typos corrected

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• Dissipative Quantum Ising model in a cold atomic spin-boson mixture
• Transport of strong-coupling polarons in optical lattices
• Entanglement control via reservoir engineering in ultracold atomic gases
• Toward quantum simulations of biological information flow
• Phonon-induced artificial magnetic fields
• Thermometry by correlated dephasing of impurities in a 1D Fermi gas
• Floquet-heating-induced Bose condensation in a scar-like mode of an open driven optical-lattice system
• Mobile impurity probing a two-dimensional superfluid phase transition
• Lattice Bose polarons at strong coupling and quantum criticality
• Emergent Mott-insulators at non-integer fillings and devil's staircase induced by attractive interaction in many-body polarons
• Dissipative preparation of a Floquet topological insulator in an optical lattice via bath engineering