Bulletin of the American Physical Society
42nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 56, Number 5
Monday–Friday, June 13–17, 2011; Atlanta, Georgia
Session N4: Quantum Measurement and Control of Spin Ensembles |
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Chair: Luis Orozco, JQI and University of Maryland Room: A704 |
Thursday, June 16, 2011 10:30AM - 11:00AM |
N4.00001: Entanglement generated by dissipation and steady state entanglement of two atomic ensembles Invited Speaker: Room temperature atomic ensembles in spin protecting cells have become a versatile resource for quantum memory and quantum sensing [1,2,3]. Dissipation has always been the main factor limiting the life time of entanglement. We have demonstrated [4] that using both vector and tensor parts of the atomic polarizability we can engineer forward scattering from two ensembles which works as a dissipation process into a reservoir joint for both ensembles. This collective dissipation leads to generation of entanglement between the two ensembles of atoms which can be sustained for up to 40 msec, much longer than the decoherence - limited entanglement life time of 2 msec. Combining the dissipation mechanism with the continuous measurement, we demonstrate steady state atomic entanglement observed for up to an hour. At any unspecified moment the dissipation mechanism can be switched off and such ready-to-use entanglement of two atomic systems can be used for teleportation or other operations. \\[4pt] [1] K. Hammerer et al RMP 82, 1041 (2010).\\[0pt] [2] K. Jensen et al Nature Physics 7, 13 (2011)\\[0pt] [3] W. Wasilewski et al. Phys. Rev. Lett., 104, 133601 (2010).\\[0pt] [4] H. Krauter, C. Muschik, K. Jensen, W. Wasilewski, J. M. Petersen, J. I. Cirac, and E. S. Polzik. arXiv:1006.4344; and 22nd ICAP Proceeding. J. Phys.: Conf. Ser. 264, 012022 (2011). 5. C. A. Muschik, E. S. Polzik, J. I. Cirac arXiv:1007.2209. [Preview Abstract] |
Thursday, June 16, 2011 11:00AM - 11:30AM |
N4.00002: Enhanced Spin Squeezing via Collective and Individual Atomic Control Invited Speaker: Spin squeezed states of atomic ensembles are of interest for their application in quantum metrology and their connection with continuous variable quantum information processing. We study new mechanisms for strongly enhancing the degree of squeezing that can be achieved by employing the tools of quantum control. Through coherent quantum feedback, a laser pulse acts as a quantum bus with creates entanglement between atoms. By employing a quantum eraser and phase-matching, we can realize exponential growth of the squeezing for a time short compared to decoherence. Through initial quantum control on the individual atomic hyperfine spins, we can further enhance the squeezing parameter by increasing the resolvable quantum fluctuations. Final quantum control multiplicatively increases the squeezing on the individual atoms. We predict $>$10 dB squeezing, including decoherence and loss. [Preview Abstract] |
Thursday, June 16, 2011 11:30AM - 12:00PM |
N4.00003: Entangled-state generation via light-induced atom-atom interaction Invited Speaker: The performance of the best atomic clocks is limited by the quantum projection noise in the final readout measurement, a situation referred to as the standard quantum limit. Entangled states of the many-body system can be used to overcome the standard quantum limit. We show how to generate such states in an ensemble of distant atoms using their common interaction with a driven mode of an optical resonator. We also demonstrate an atomic clock operated with a phase-squeezed input state that achieves a given precision almost three times faster than a clock operating at the standard quantum limit. [Preview Abstract] |
Thursday, June 16, 2011 12:00PM - 12:30PM |
N4.00004: Quantum metrology with collective atomic spins Invited Speaker: Quantum metrology uses quantum features such as entanglement and squeezing to improve the sensitivity of quantum-limited measurements. Long established as a valuable technique in optical measurements such as gravitational-wave detection, quantum metrology is increasingly being applied to atomic instruments such as matter-wave interferometers, atomic clocks, and atomic magnetometers. Several of these new applications involve dual optical/atomic quantum systems, presenting both new challenges and new opportunities. I will describe an optical magnetometry system based on cold rubidium-87 in an optical trap, which achieves both shot-noise- and projection-noise-limited performance, allowing study of optical magnetometry in a fully-quantum regime [1,2]. The versatility of this system allows us to design both linear and non-linear atom- light couplings, and to apply dynamical decoupling and quantum non-demolition measurement, for application in quantum-enhanced magnetometry [3]. As an example, we have recently developed a method for generating metrologically-advantageous optical nonlinearities and performed the first interaction-based quantum-noise-limited measurements of atomic magnetisation [4]. With this technique we implement a non-linear metrology scheme proposed by Boixo et al. with the surprising feature of precision scaling better than the 1/N ``Heisenberg limit'' [5]. \\[4pt] [1] M. Koschorreck, M. Napolitano, B. Dubost, and M. W. Mitchell. Sub-projection-noise sensitivity in broadband atomic magnetometry. Phys. Rev. Lett., 104(9):093602, 2010. \\[0pt] [2] M. Koschorreck, M. Napolitano, B. Dubost, and M. W. Mitchell. Quantum nondemolition measurement of large-spin ensembles by dynamical decoupling. Phys. Rev. Lett., 105 (9):093602, 2010. \\[0pt] [3] S R de Echaniz, M Koschorreck, M Napolitano, M Kubasik, and MWMitchell. Hamiltonian design in atom-light interactions with rubidium ensembles: A quantum-information toolbox. Phys. Rev. A, 77(3):032316, 2008. \\[0pt] [4] M Napolitano and M W Mitchell. Nonlinear metrology with a quantum interface. New J. Phys., 12(9):093016, 2010. \\[0pt] [5] Sergio Boixo, Animesh Datta, Matthew J Davis, Steven T Flammia, Anil Shaji, and Carlton M Caves. Quantum metrology: dynamics versus entanglement. Phys. Rev. Lett., 101(4):040403, 2008. \\[0pt] [6] M. Napolitano, M. Koschorreck, B. Dubost, N. Behbood, R. J. Sewell, and M. W. Mitchell. Interaction-based quantum metrology showing scaling beyond the Heisenberg limit. Nature (in press) arXiv:1012.5787v1, 2011. [Preview Abstract] |
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