Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session X4: Approaching Quantum Limits in Optomechanical Systems |
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Sponsoring Units: DCMP GQI Chair: Konrad Lehnert, JILA, NIST/University of Colorado Room: Morial Convention Center 206 |
Friday, March 14, 2008 8:00AM - 8:36AM |
X4.00001: Sensing nanomechanical motion with a microwave cavity interferometer Invited Speaker: Optomechanical and electromechanical systems utilizing micro and nanomechanical oscillators offer a promising route towards manipulation of macroscopic objects at the quantum level. In this talk I present experiments that use principles of popular optomechanical systems yet employ light at microwave frequencies. Operating at microwave frequencies allows us to also harness technology associated with electromechanical systems, such as very light nanoscale mechanical objects and on- chip circuit elements compatible with a dilution refrigerator environment. Specifically, in our work we embed a nanomechanical flexural resonator inside a superconducting transmission-line microwave cavity, where the mechanical resonator's position couples to the cavity capacitance and thus to the resonant frequency of the cavity. With our device we realize near state-of-the-art force sensitivity (3 aN/$\rm{\sqrt {Hz}}$) and thus add to only a handful of techniques able to measure thermomechanical motion at 10's of milliKelvin temperatures. Our current measurements achieve a promising total displacement uncertainty at 140 times the quantum limit and a measurement imprecision as low as 30 times the quantum limit, as well as elucidate the important steps that will be required to progress towards the full quantum limit of displacement detection with this new system. [Preview Abstract] |
Friday, March 14, 2008 8:36AM - 9:12AM |
X4.00002: Strong dispersive coupling between a micromechanical oscillator and a high finesse optical cavity. Invited Speaker: Very sensitive mechanical detectors spanning roughly seventeen orders of magnitude in size are rapidly approaching a regime in which either the mechanical device itself or its readout should demonstrate quantum behavior. One of the main technical barriers to actually reaching this regime has been the difficulty of integrating ultrasensitive micromechanical devices with high-finesse optical cavities. Recently we have developed a robust means for addressing this issue, and have integrated a 50 nm-thick membrane (with a quality factor $>$ 1,000,000) into an optical cavity with a finesse $\sim $ 20,000. Although the membrane is nearly transparent, it couples to the optical cavity dispersively. This coupling is strong enough to laser-cool the membrane from room temperature to 7 mK. In addition, the dispersive nature of the optomechanical coupling allows us to realize a sensitive ``displacement squared'' readout of the membrane. Such a readout is a crucial requirement for measuring quantum jumps in a mechanical oscillator. We will describe these results, as well as our progress towards observing quantum effects in this system. [Preview Abstract] |
Friday, March 14, 2008 9:12AM - 9:48AM |
X4.00003: Cavity Assisted Sideband Cooling of Mechanical Motion Invited Speaker: This talk will provide a pedagogical introduction to the theoretical ideas that form the basis for cooling a mechanical cantilever using light-induced forces. During recent years, these concepts have been realized in a series of experiments by various groups, that have demonstrated impressive progress in cooling. Several of them will be discussed in the following talks of this session. Ultimately, this line of research may lead to the quantum-mechanical ground state of the center-of-mass motion of objects composed of many billions of atoms. A common ingredient is the use of an optical cavity to resonantly enhance the radiation pressure force affecting the motion of the cantilever. I will start by reviewing the classical description of how a time-retarded force leads to enhanced friction and thus cooling. Then I will present a fully quantum-mechanical description, that takes into account the opposing effect of the photon shot noise [F. Marquardt, J. P. Chen, A. A. Clerk and S. M. Girvin, Phys. Rev. Lett. 99, 093902 (2007); see also I. Wilson-Rae, N. Nooshi, W. Zwerger and T. J. Kippenberg, Phys. Rev. Lett. 99, 093901 (2007)]. This theory yields a quantum-limit for the reachable photon number that can be made arbitrarily small, provided a high-finesse cavity is combined with a high-frequency mirror (the ``resolved sideband limit,'' analogous to ion cooling). Various different ways of experimentally measuring the photon number will be mentioned. Finally, I will briefly give an outlook regarding the opportunities for quantum-coherent experiments that will open up once the ground state has been reached. This talk primarily reports joint work with A. Clerk, J. P. Chen, and S. Girvin. [Preview Abstract] |
Friday, March 14, 2008 9:48AM - 10:24AM |
X4.00004: Laser Cooling of Gram Scale Objects Invited Speaker: Laser cooling of macroscopic mechanical oscillators is a rapidly growing field with applications in high precision measurements, gravitational wave detectors, and exploration of the classical-quantum transition. Here I will describe a series of cooling experiments, which are inspired by gravitational wave detectors, to trap and cool gram scale mirror oscillators. To approach quantum limits of oscillators with such a high mass requires the use of a variety of cooling techniques. The techinques employ non-mechanical forces both to trap the mirror by increasing its effective mechanical resonant frequency, and to cool the mirror by damping its motion within the trap. The non-mechanical forces are created from either radiation pressure in a detuned optical resonator, or from electronic feedback forces in an active servo. As the experiments approach the quantum regime, an assortment of non-classical behavior and effects should become evident, such as quantum radiation pressure noise, and squeezing and entanglement of the light and mirror states. I will discuss the prospects for observation of these effects, in light of current performance and expected upgrades. [Preview Abstract] |
Friday, March 14, 2008 10:24AM - 11:00AM |
X4.00005: Towards experimental optomechanical entanglement between a movable mirror and a cavity field. Invited Speaker: The quantum regime of mechanical systems offers fascinating new possibilities for both applied and fundamental physics. Quantum optics provides a well-developed tool box to help entering and controlling this regime as is evidenced by the recent successes in laser-cooling of micromirrors that promise cooling capabilities to the mechanical quantum ground state. I will discuss the prospects and challenges to generate (opto-mechanical) quantum entanglement, which is an important resource for quantum information processing and is also at the heart of Schr\"{o}dinger's ``cat paradox.`` [Preview Abstract] |
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