Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session X3: Single Spin Detection |
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Sponsoring Units: DCMP GMAG Chair: Daniel Ralph, Cornell University Room: LACC 515B |
Friday, March 25, 2005 8:00AM - 8:36AM |
X3.00001: Single spin detection by magnetic resonance force microscopy Invited Speaker: Single spin detection by magnetic resonance force microscopy (MRFM) is based on ultrasensitive measurements of the attonewton magnetic force between a spin and a nearby magnetic tip. Interest in the technique is driven by potential applications to three-dimensional atomic resolution imaging and by fundamental interest in the detection and manipulation of individual quantum objects. This talk describes the basic principles of MRFM and discusses recent results that demonstrated the detection of an individual electron spin buried below the surface of a silicon dioxide sample. Various innovations that led to single spin detection will be described, including ultrasensitive force detection, spin-friendly micromechanical cantilevers and methods to measure and control statistical polarization in small spin ensembles. Future prospects for quantum state readout and for extension to nuclear spin detection will be discussed. This work was performed in collaboration with H. J. Mamin, R. Budakian and B. W. Chui. [Preview Abstract] |
Friday, March 25, 2005 8:36AM - 9:12AM |
X3.00002: Electrical Detection of a Single Electron Spin in the SiO2 of a Si Field Effect Transistor Invited Speaker: For electron spin based quantum information processing in semiconductor, it is necessary to determine the spin orientation of a single electron. We have been able to identify the spin state and perform magnetic resonance measurements, for a single paramagnetic spin center residing in the SiO$_{2}$ of a sub-micrometer Si field effect transistor. At certain bias points, the transistor current experiences random telegraph signal (RTS), arising from the stochastic switching of the paramagnetic spin center between two charge states. RTS turns out to be a sensitive probe of the center's spin orientation. Using microwave radiation at frequencies ranging from 16 - 50 GHz, electron spin resonance (ESR) for our paramagnetic spin center was obtained, corresponding to a g-factor of 2.02$\pm $0.015. On the basis of these results, we will introduce a scheme for an electrical projective single-shot spin-state read-out and our preliminary experimental results. [Preview Abstract] |
Friday, March 25, 2005 9:12AM - 9:48AM |
X3.00003: Single-shot read-out of an individual electron spin in a quantum dot Invited Speaker: We demonstrate a fully electrical technique to read out the spin state of a single electron confined in a semiconductor quantum dot [1]. The quantum dot is formed by metal surface gates on top of a GaAs/AlGaAs heterostructure that contains a two-dimensional electron gas. The spin measurement relies on the Zeeman splitting of the orbital states, induced by a large in-plane magnetic field. We tune the dot potential such that a spin-up electron is trapped on the dot, whereas a spin-down electron has enough energy to tunnel to the reservoir. By detecting whether or not a single-electron tunneling event occurs, using a nearby quantum point contact, the original spin state is revealed. Using this single-shot spin measurement technique (with a visibility of $\sim $65 {\%}), we observe very long single-spin energy relaxation times (up to $\sim $0.85 ms at a magnetic field of 8 T). Finally, we discuss improvements to the spin read-out technique, which could allow it to work for smaller Zeeman energy, and to be less sensitive to charge noise. [1] J.M. Elzerman, R. Hanson, L.H. Willems van Beveren, B. Witkamp, L.M.K. Vandersypen and L.P. Kouwenhoven, Nature 430, 431 (2004) [Preview Abstract] |
Friday, March 25, 2005 9:48AM - 10:24AM |
X3.00004: Spectroscopy of Spontaneous Spin Noise for Probes of Spin Dynamics and Magnetic Resonance Invited Speaker: Not all noise in experimental measurements in unwelcome. Certain fundamental noise sources contain valuable information about the system itself -- a notable example being the small, inherent fluctuations of electrical current (current shot noise), which both demonstrates the discrete nature of the current carriers, and also directly yields the electron charge. In magnetic systems, fundamental noise can exist in the form of random spin fluctuations. As pointed out by F. Bloch in 1946, stochastic fluctuations of $N$ paramagnetic spins will generate measurable noise of order $\sqrt{N}$ spins, even in zero magnetic field. As such, the relative amplitude of the noise signature compared with the signal from spins driven into saturation scales as $1/\sqrt{N}$, which approaches unity in the single-spin limit. In this work we address precisely these same $\sqrt{N}$ spin fluctuations, using off-resonant Faraday rotation to passively ``listen" to the magnetization noise in an equilibrium ensemble of paramagnetic rubidium or potassium atoms near room temperature [1]. These random spin fluctuations generate measurable spontaneous spin coherences, which precess and decay with the same characteristic energy and time scales as the macroscopic magnetization of an intentionally polarized or driven ensemble. Spin-spin correlation spectra of the measured noise reveals g-factors, nuclear spin, isotope abundance ratios, hyperfine splittings, nuclear moments, and spin coherence lifetimes -- without having to excite, optically pump, or otherwise drive the system away from thermal equilibrium. These noise signatures scale inversely with interaction volume, suggesting routes towards non-perturbative, sourceless magnetic resonance of small systems containing few spins. [1] S.A. Crooker, D.G. Rickel, A.V. Balatsky, D.L. Smith, Nature {\bf 431}, 49 (2004). [Preview Abstract] |
Friday, March 25, 2005 10:24AM - 11:00AM |
X3.00005: Observation of Coherent Oscillations in a Single Electron Spin Invited Speaker: |
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