Combined feedback and sympathetic cooling of a mechanical oscillator coupled to ultracold atoms

Abstract

A promising route to novel quantum technologies are hybrid quantum systems, which combine the advantages of several individual quantum systems. We have realized a hybrid atomic-mechanical experiment consisting of a Si 3 N 4 membrane oscillator cryogenically precooled to 500 mK and optically coupled to a cloud of laser cooled 87 Rb atoms. Here, we demonstrate active feedback cooling of the oscillator to a minimum mode occupation of n 16 1 m =  corresponding to a mode temperature of T min ≈200 μK. Furthermore, we characterize in detail the coupling of the membrane to the atoms by means of sympathetic cooling. By simultaneously applying both cooling methods we demonstrate the possibility of preparing the oscillator near the motional ground state while it is coupled to the atoms. Realistic modifications of our setup will enable the creation of a ground state hybrid quantum system, which opens the door for coherent quantum state transfer, teleportation and entanglement as well as quantum enhanced sensing applications.

Tuning the order of the nonequilibrium quantum phase transition in a hybrid atom-optomechanical system

“…The currently realized motional coupling schemes utilize membranes in the kHz-regime [14,15], resulting in realistic experimental parameters 70…”

“…The vibrational motion of a nanomembrane in an optical cavity is coupled to the spatial motion of a distant cloud of cold 87 Rb atoms that reside in the optical lattice of the outcoupled light field. By combining different cooling mechanisms such as optical feedback cooling [15] and sympathetic cooling by utilizing the atom gas as a coolant [12][13][14][15], the nanooscillator can be cooled close to its quantum mechanical ground state. Quantum many-body effects lead to collective atomic motion with an instability [16] and a second-order NQPT [17,18] to a state with a spatially shifted optical lattice.…”

Nonequilibrium quantum phase transition in a spinor quantum gas in a lattice coupled to a membrane

“…one mirror of the cavity is designed to reflect incident light on resonance and forms a standing wave in front of the cavity, in which a spinor Bose-Einstein condensate (BEC) can be trapped. Our setup is of immediate relevance in the context of experiments for the one-component hybrid mechanical-atomic system [1][2][3][4]. Furthermore, the spin degree of freedom can be encoded by two atomic internal states or sub-lattices [19].…”

“…In recent years, the hybrid atom-optomechanical systems [1][2][3][4], where a membrane is coupled to ultra-cold quantum gases, have attracted considerable interests as a novel and versatile alternative to more conventional optomechanical setups. Combining mechanical oscillators and ultra-cold atoms, such hybrid systems [5][6][7][8][9][10] provide opportunities for cooling, detection and quantum control of mechanical motion, with applications in precision sensing, quantum-level signal transduction, as well as for fundamental tests of quantum mechanics [11][12][13][14][15].…”

“…Combining mechanical oscillators and ultra-cold atoms, such hybrid systems [5][6][7][8][9][10] provide opportunities for cooling, detection and quantum control of mechanical motion, with applications in precision sensing, quantum-level signal transduction, as well as for fundamental tests of quantum mechanics [11][12][13][14][15]. For example, state-of-the-art optomechanics is nowadays able to realize optical feedback cooling of the mechanical oscillator to its quantum-mechanical ground state [2]. Being intrinsically non-equilibrium, such hybrid mechanical atomic system further provides a natural setting for non-equilibrium many-body quantum systems.…”