Stephan Camerer

Bose-Einstein Condensate Coupled to a Nanomechanical Resonator on an Atom Chip

We theoretically study the coupling of Bose-Einstein condensed atoms to the mechanical oscillations of a nanoscale cantilever with a magnetic tip. This is an experimentally viable hybrid quantum system which allows one to explore the interface of quantum optics and condensed matter physics. We propose an experiment where easily detectable atomic spin flips are induced by the cantilever motion. This can be used to probe thermal oscillations of the cantilever with the atoms. At low cantilever temperatures, as realized in recent experiments, the backaction of the atoms onto the cantilever is significant and the system represents a mechanical analog of cavity quantum electrodynamics. With high but realistic cantilever quality factors, the strong coupling regime can be reached, either with single atoms or collectively with Bose-Einstein condensates. We discuss an implementation on an atom chip.

Resonant Coupling of a Bose-Einstein Condensate to a Micromechanical Oscillator

We report experiments in which the vibrations of a micromechanical oscillator are coupled to the motion of Bose-condensed atoms in a trap. The interaction relies on surface forces experienced by the atoms at about 1 microm distance from the mechanical structure. We observe resonant coupling to several well-resolved mechanical modes of the condensate. Coupling via surface forces does not require magnets, electrodes, or mirrors on the oscillator and could thus be employed to couple atoms to molecular-scale oscillators such as carbon nanotubes.

Realization of an Optomechanical Interface Between Ultracold Atoms and a Membrane

We have realized a hybrid optomechanical system by coupling ultracold atoms to a micromechanical membrane. The atoms are trapped in an optical lattice, which is formed by retroreflection of a laser beam from the membrane surface. In this setup, the lattice laser light mediates an optomechanical coupling between membrane vibrations and atomic center-of-mass motion. We observe both the effect of the membrane vibrations onto the atoms as well as the backaction of the atomic motion onto the membrane. By coupling the membrane to laser-cooled atoms, we engineer the dissipation rate of the membrane. Our observations agree quantitatively with a simple model.

Optical cooling of a micromirror of wavelength size

The authors report on the passive optical cooling of the Brownian motion of a cantilever suspended micromirror. They show that laser cooling is possible for a mirror of size in the range of the diffraction limit (at λ=1.3μm). This represents the tiniest mirror optically cooled so far, with a mass of 11.3pg, more than four orders of magnitude lighter than current mirrors used in cavity cooling. The reciprocal effect of cooling is also investigated and opens the way to the optical excitation of megahertz vibrational modes under continuous wave laser illumination.

Spectroscopy of mechanical dissipation in micro-mechanical membranes

We measure the frequency dependence of the mechanical quality factor (Q) of SiN membrane oscillators and observe a resonant variation of Q by more than two orders of magnitude. The frequency of the fundamental mechanical mode is tuned reversibly by up to 40% through local heating with a laser. Several distinct resonances in Q are observed that can be explained by coupling to membrane frame modes. Away from the resonances, the background Q is independent of frequency and temperature in the measured range.

Optical lattices with micromechanical mirrors

We investigate a setup where a cloud of atoms is trapped in an optical lattice potential of a standing-wave laser field which is created by retroreflection on a micromembrane. The membrane vibrations itself realize a quantum mechanical degree of freedom. We show that the center-of-mass mode of atoms can be coupled to the vibrational mode of the membrane in free space. Via laser cooling of atoms a significant sympathetic cooling effect on the membrane vibrations can be achieved. Switching off laser cooling brings the system close to a regime of strong coherent coupling. This setup provides a controllable segregation between the cooling and coherent dynamics regimes, and allows one to keep the membrane in a cryogenic environment and atoms at a distance in a vacuum chamber.

Observation of Backaction of Ultracold Atoms onto a Mechanical Oscillator

An optical lattice formed by reflection from a SiN

Magnetic coupling of a Bose-Einstein condensate to a nanomchanical resonator

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Hybrid atom-membrane optomechanics

membrane creates a bi-directional coupling of atomic and membrane motion. Experimental demonstrations of both direct-action and backaction in this system are reported.

Non-linear operation of nanomechnical systems combining photothermal excitation and magneto-motive detection

The experiment aims at coupling the thermal oscillations of a nanomechanical resonator to the spin of a nearby Bose-Einstein condensate via a magnetic interaction. The coupling is mediated by a small island of ferromagnetic material on the cantilever. In this way, the resonator motion causes an oscillating magnetic field that can drive atomic spin-flip transitions. If the eigenfrequency of the beam is resonant with transitions to untrapped magnetic sublevels, observable trap loss occurs.