Sympathetic cooling with ultracold atoms [1] and atomic ions [2] enables ultralow temperatures in systems where direct laser or evaporative cooling is not possible. It has so far been limited to the cooling of other microscopic particles, with masses up to 90 times larger than that of the coolant atom [3]. Here we use ultracold atoms to sympathetically cool the vibrations of a Si 3 N 4 nanomembrane [4,5], whose mass exceeds that of the atomic ensemble by a factor of 10 10 . The coupling of atomic and membrane vibrations is mediated by laser light over a macroscopic distance [6,7] and enhanced by placing the membrane in an optical cavity [8]. We observe cooling of the membrane vibrations from room temperature to 650 ± 230 mK, exploiting the large atom-membrane cooperativity [9] of our hybrid optomechanical system [10,11]. Our scheme enables ground-state cooling and quantum control of low-frequency oscillators such as nanomembranes or levitated nanoparticles [12], in a regime where purely optomechanical techniques cannot reach the ground state [8,9].The control over micro-and nanomechanical oscillators has recently made impressive progress [13]. First experiments cooled high-frequency mechanical oscillators to the quantum ground state [14][15][16][17] and demonstrated single-phonon control [14] using cryogenic cooling and the techniques of cavity optomechanics [18]. A current challenge is to couple engineered mechanical structures to microscopic quantum systems with good coherence properties, such as atoms [7,19,20], solid-state spin systems [21][22][23], semiconductor quantum dots [24], or superconducting devices [14,25]. The resulting hybrid mechanical systems offer new possibilities for quantum control of mechanical vibrations, precision sensing, and quantum-level signal transduction [10,11,13,18]. Ultracold atoms are an attractive choice for hybrid systems because a well-developed toolbox exists for atomic laser cooling and quantum manipulation [26]. It has been proposed to use hybrid mechanical-atomic systems for sympathetic cooling [6,8,27], creating atom-oscillator entanglement [27,28] and controlling the oscillator on the single-phonon level [29]. However, in the experiments reported so far [7,19,20], the mechanical-atomic coupling was far too weak to realize any of these possibilities.Sympathetic cooling of mechanical oscillators with laser-cooled atoms has received particular interest, as it would allow one to relax the constraints of cavity optomechanical and feedback cooling techniques [8,9]. Up to now, sympathetic cooling with atoms and atomic ions has been used to cool other microscopic particles such as different atoms or molecular ions up to the size of proteins [1][2][3], with applications in cold chemistry and quantum technology [26,30]. In these experiments, the coolant and the target species thermalize through shortrange collisional or electrostatic interactions in a trap. A large difference in their mass reduces the cooling performance, which has prevented extensions to more massive objects.In...
We report on the observation of cooperative radiation of exactly two neutral atoms strongly coupled to the single mode field of an optical cavity, which is close to the lossless-cavity limit. Monitoring the cavity output power, we observe constructive and destructive interference of collective Rayleigh scattering for certain relative distances between the two atoms. Because of cavity backaction onto the atoms, the cavity output power for the constructive two-atom case (N=2) is almost equal to the single-emitter case (N=1), which is in contrast to free-space where one would expect an N^{2} scaling of the power. These effects are quantitatively explained by a classical model as well as by a quantum mechanical model based on Dicke states. We extract information on the relative phases of the light fields at the atom positions and employ advanced cooling to reduce the jump rate between the constructive and destructive atom configurations. Thereby we improve the control over the system to a level where the implementation of two-atom entanglement schemes involving optical cavities becomes realistic.
We experimentally demonstrate the elementary case of electromagnetically induced transparency with a single atom inside an optical cavity probed by a weak field. We observe the modification of the dispersive and absorptive properties of the atom by changing the frequency of a control light field. Moreover, a strong cooling effect has been observed at two-photon resonance, increasing the storage time of our atoms twenty-fold to about 16 seconds. Our result points towards all-optical switching with single photons.
The intention of the paper is to give an example on how different plasma diagnostics can be combined in a synergistic way in order to investigate new physics. The link between the individual diagnostics has to be provided by theoretical concepts that predict certain relations between the different plasma parameters. The example chosen here is the effect of self-excited plasma series resonances in asymmetric capacitively coupled RF discharges. These resonance oscillations lead to high frequency current oscillations and are caused by a series resonance between the capacitive sheath and the effective inductance of the bulk which results from electron inertia. The non-linearity of the sheath is essential for the self-excitation of these oscillations. Laser spectroscopic electric field measurements, phase and space resolved optical emission spectroscopy, current, voltage, and Langmuir probe measurements are combined. The synergistic effect of these diagnostics in combination with a simple analytical model for the modification of the electron energy distribution function by electron beams yields information on cause and effect of electron heating and a better understanding of these fundamental phenomena.
We experimentally investigate the interaction between one and two atoms and the field of a high-finesse optical resonator. Laser-cooled caesium atoms are transported into the cavity using an optical dipole trap. We monitor the interaction dynamics of a single atom strongly coupled to the resonator mode for several hundred milliseconds by observing the cavity transmission. Moreover, we investigate the position-dependent coupling of one and two atoms by shuttling them through the cavity mode. We demonstrate an alternative method, which suppresses heating effects, to analyze the atom-field interaction by retrieving the atom from the cavity and by measuring its final state.
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