Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session Y8: Pushing the Limits of Mechanical Detection |
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Sponsoring Units: GIMS Chair: Dan Rugar, IBM Almaden Room: 414/415 |
Friday, March 20, 2009 8:00AM - 8:36AM |
Y8.00001: Quantum Optical Control of Micromechanics Invited Speaker: Massive mechanical resonators are now approaching the quantum regime. This opens up not only a spectrum of new applications but also a previously inaccessible parameter range for macroscopic quantum experiments on systems consisting of up to $10^{20}$ atoms. Quantum optics provides a rich toolbox to prepare and detect quantum states of mechanical systems, in particular by combining nano- and micromechanical resonators with high-finesse cavities. I will report on our recent experiments in Vienna on laser cooling micromechanical systems towards the quantum ground state by using radiation pressure. I will also discuss the prospects and experimental challenges of generating and detecting optomechanical entanglement, which is at the heart of Schr\"{o}dinger's cat paradox. [Preview Abstract] |
Friday, March 20, 2009 8:36AM - 9:12AM |
Y8.00002: Measurement of Dispersive Coupling Between a Nanoresonator and a Superconducting Qubit Invited Speaker: Incorporating superconducting qubit technology into nanoelectromechanical systems (NEMS) should enable the observation of quantum behavior in NEMS. Ultimately, it is expected that coupled qubit-NEMS systems could serve as a test bed for studying fundamental issues of quantum mechanics including the quantum limits of measurement and the quantum-classical divide. Proposals in the literature posit the qubits as veritable toolboxes for preparing, manipulating and measuring quantum states of a nanomechanical resonator (or `nanoresonator'), and range from the nondestructive read-out of quantized-energy states (or `Fock states') to the generation of Schrodinger-cat states. In an initial step toward implementing these advanced strategies, we have performed the first measurements of a nanoresonator coupled to a superconducting qubit, the Cooper-pair box (CPB). We find that the coupling produces a CPB-state-dependent shift in the frequency of the nanoresonator that is analogous to the single-atom phase shifts experienced by superconducting resonators in the dispersive limit of cavity quantum electrodynamics (CQED). In my talk, I will report on our latest measurements of the dispersive interaction between the CPB and nanoresonator, including how we utilize it to read-out quantum interference effects in the CPB. In the end, I will discuss how the interaction could soon be utilized for exploring the quantum limit of NEMS. [Preview Abstract] |
Friday, March 20, 2009 9:12AM - 9:48AM |
Y8.00003: Nanoscale Magnetic Resonance Imaging Based on Ultrasensitive Force Detection Invited Speaker: Magnetic Resonance Force Microscopy (MRFM) seeks to dramatically improve the sensitivity and resolution of magnetic resonance imaging (MRI), perhaps ultimately down to the molecular scale. It uses force detection to circumvent the sensitivity limits inherent in conventional inductively-detected MRI. By using an ultrasensitive, single crystal silicon cantilever cooled to 300 mK, we can detect forces smaller than 1 aN, allowing us to sense the magnetism from small ensembles of nuclear spins. We have used tobacco mosaic virus as a test object, detecting the hydrogen signal. Using three-dimensional scans and mathematical deconvolution algorithms, we have made 3D reconstructions of the viruses with resolution down to roughly 4 nm. This represents a 10$^{8}\times $ improvement in minimum detectable volume compared to the best conventional MRI. Advancing the technique further will require reducing the force noise, increasing the achieved magnetic field gradients, and making use of the inherent chemical sensitivity of magnetic resonance. [Preview Abstract] |
Friday, March 20, 2009 9:48AM - 10:24AM |
Y8.00004: A Cantilever-based apparatus for detecting micron-scale deviations from Newtonian gravity Invited Speaker: To test new theories of physics beyond the Standard Model, we have built a low temperature probe to measure forces as small as 10$^{-18}$ N between masses separated by distances on the order of 20 microns. Our experiment is fundamentally a Cavendish-type experiment in the sense that its purpose is to directly measure the force between two masses [1]. A cryogenic helium gas bearing is used to rotate a disc containing a drive mass pattern of alternating density under a small test mass mounted on a micromachined cantilever. Any mass-dependent force between the two will produce a time-varying force on the test mass, and consequently a time-varying displacement of the cantilever. This displacement is read out with a laser interferometer, and the position of the drive mass is simultaneously recorded using an optical encoder. The displacement is then averaged over many cycles and converted to a force using measured properties of the cantilever. This AC ``lock-in'' type measurement enables significant noise rejection and allows us to operate on resonance to take advantage of the cantilever's high quality factor. A novel feature of the apparatus is the utilization of feedback regulation of the response of the microcantilever using the radiation pressure of a laser. Our approach does not require a high-finesse cavity, and the feedback force is due solely to the momentum of the photons in the second laser. \\[4pt] [1] D.M. Weld, J. Xia, B. Cabrera, and A. Kapitulnik, Phys. Rev. D 77, 062006 (2008). [Preview Abstract] |
Friday, March 20, 2009 10:24AM - 11:00AM |
Y8.00005: The quantum limit and beyond in gravitational wave detection Invited Speaker: The sensitivity of current and next generation interferometric gravitational wave detectors is limited by quantum mechanics. We will explore this quantum limit, one aspect of which arises from the radiation pressure that laser light exerts on the movable mirrors of the interferometer. I will describe experiments in which the light force dominates the mechanical forces to such an extent that the mirror oscillators are optically trapped and cooled. Laser cooling of macroscopic mechanical oscillators has applications in high precision force and position measurements, gravitational wave detection, and exploration of the classical-quantum boundary. I will discuss the status of a variety of experimental efforts worldwide are working to approach the quantum regime, with the goal of observing non-classical effects such as quantum back-action, squeezing and entanglement of the light and mirror states, and conclude with an outlook on prospects for observation of quantum effects in macroscopic human-scale objects. [Preview Abstract] |
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