Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session J6: Squeezing |
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Chair: Frank Narducci, American Physical Society Room: 302 |
Wednesday, June 5, 2013 2:00PM - 2:12PM |
J6.00001: Squeezing of Spin Waves in Atomic Ensembles Ben Baragiola, Leigh Norris, Enrique Montano, Pascal Michelson, Poul Jessen, Ivan Deutsch Squeezing the collective spin of an atomic ensemble via QND measurement is based on the lighhift interaction between a cloud of atoms and a laser probe. When the shot noise resolution of the laser probe is below the projection noise of the atoms, the resulting backaction can reduce the uncertainty for a collective atomic observable. Most current models of this process rely on idealized one-dimensional plane wave approximations of the underlying light-matter interaction, which are not appropriate for describing a real system consisting of an atomic cloud in dipole trap interacting with a paraxial probe laser. We derive from first principles a model for three-dimensional QND spin squeezing of an ensemble of alkali atoms. The model includes spin waves, diffraction, propagation phase, paraxial modes, and optical pumping, based on a full master equation description. Our model easily generalizes to atoms with hyperfine spin f \textgreater 1/2, for which initial state preparation of the ensemble using internal hyperfine control can enhance the entangling power of the Faraday interaction [Norris et al., PRL 109, 173603 (2012)]. Including dissipative dynamics, we find optimal geometries to maximize spin squeezing for a variety of state preparations and spin sizes. [Preview Abstract] |
Wednesday, June 5, 2013 2:12PM - 2:24PM |
J6.00002: Simultaneous observation of super-Heisenberg scaling and spin squeezing in a nonlinear measurement of atomic spins Robert Sewell, Mario Napolitano, Naeimeh Behbood, Giorgio Colangelo, Ferran Martin Ciurana, Morgan Mitchell We report a nonlinear alignment-to-orientation conversion (AOC) [PRL 85, 2088 (2000)] measurement of atomic spins that simultaneously shows super-Heisenberg scaling and achieves projection-noise limited sensitivity. Using this technique, we have recently demonstrated conditional spin squeezing of the atomic ensemble, and entanglement-enhanced measurement sensitivity useful for optical magnetometry [PRL 109, 253605 (2012)]. In addition, we use a novel technique to explicitly certify that the measurement fulfills all the conditions required for quantum non-demolition measurement [NJP 14, 085021 (2012)], which is non-trivial in large spin (J $>$ 1/2) systems. Lastly, we demonstrate that the measurement shows super-Heisenberg scaling with photon number due to the nonlinearity of the AOC technique. This scaling was recently demonstrated in a proof-of-principle experiment [Nature 471, 486-489 (2011)], however in this experiment the measurement sensitivity was more than an order of magnitude worse than the projection noise limit. Here we achieve a sensitivity (observed read-out noise) of 990 spins, competitive with the best observed sensitivity in an equivalent linear measurement [PRL 104, 093602 (2010)], and 20 dB more sensitive than the previous best nonlinear measurement. [Preview Abstract] |
Wednesday, June 5, 2013 2:24PM - 2:36PM |
J6.00003: Dynamical Decoupling to Preserve Spin Squeezing in a Dephasing Bath Bhaskar Roy Bardhan, Jonathan Dowling Spin-squeezed states (SSS) are quantum-correlated states of a collection of spins or two-level atoms with reduced fluctuations in one of the collective spin components. They are also used to generate as well as detect multipartite quantum entanglement. We show that the amount of spin-squeezing, and hence the entanglement, is significantly deteriorated in presence of individual phase-damping channel and demonstrate that dynamical decoupling technique of repeatedly applying external pulses collectively on the spin-squeezed state can be successfully used to preserve the squeezing in presence of such dephasing bath. Various schemes of the dynamical decoupling technique are studied and they efficiencies n preserving the spin squeezing are compared. [Preview Abstract] |
Wednesday, June 5, 2013 2:36PM - 2:48PM |
J6.00004: Conditional Spin Squeezing Through Cavity-Aided Measurements Kevin Cox, Joshua Weiner, Matthew Norcia, Zilong Chen, Justin Bohnet, James Thompson Spin squeezed states of large atomic ensembles exploit inter-particle entanglement to suppress fundamental quantum noise, with applications for precision measurements and tests of fundamental physics. We produce spin squeezed states by performing entanglement-generating measurements of $10^5$ $^{87}$Rb atoms confined in an optical lattice, collectively probing the ensemble through an optical cavity. Previous demonstrations of conditional spin squeezing have been limited by decoherence due to Raman scattering. Here, we report recent results towards creating squeezed states with greatly reduced decoherence by utilizing the maximal $m_F$ ground states and probing on a closed optical transition. [Preview Abstract] |
Wednesday, June 5, 2013 2:48PM - 3:00PM |
J6.00005: Multi-photon interference and quantum optical interferometry Richard Birrittella, Jihane Mimih, Christopher Gerry We study multi-photon quantum interference effects at a beam splitter and its connection to the prospect of attaining interferometic phase shift measurements with noise levels below the standard quantum limit. Specifically, we consider the mixing of the most classical states of light, coherent states, with the most non-classical states of light, number states, at a 50:50 beam splitter. Multi-photon quantum interference effects from mixing photon number states of small photon numbers with coherent states of arbitrary amplitudes are dramatic even at the level of a single photon. For input vacuum and coherent states, the joint photon number distribution after the beam splitter is unimodal, a product of Poisson distributions for each of the output modes, but with the input of a single photon, the original distribution is symmetrically bifurcated into a bi-modal distribution. With a two-photon number state mixed with a coherent state a tri-modal distribution is obtained, etc. The obtained distributions are shown to be structured so as to be conducive for approaching Heisenberg-limited sensitivities in photon number parity based interferometry. We show that mixing a coherent state with even a single photon results in a significant reduction in noise over that of the shot-noise limit. Based on the results of mixing coherent light with single photons, we consider the mixing coherent light with the squeezed vacuum and the squeezed one-photon states and find the latter yields higher sensitivity in phase-shift measurements for the same squeeze parameter owing to the absence of the vacuum state. [Preview Abstract] |
Wednesday, June 5, 2013 3:00PM - 3:12PM |
J6.00006: ABSTRACT WITHDRAWN |
Wednesday, June 5, 2013 3:12PM - 3:24PM |
J6.00007: Biological measurement beyond the quantum limit Michael Taylor, Jiri Janousek, Vincent Daria, Joachim Knittel, Boris Hage, Hans Bachor, Warwick Bowen Biology is an important frontier for quantum metrology, with quantum enhanced sensitivity allowing optical intensities to be lowered, and a consequent reduction in specimen damage and photochemical intrusion upon biological processes. Here we demonstrate the first biological measurement with precision surpassing the quantum noise limit. Naturally occurring lipid granules within living yeast cells were tracked in real time with sensitivity surpassing the quantum noise limit by 42{\%} as they diffuse through the cytoplasm and interact with embedded polymer networks. This allowed dynamic mechanical properties of the cytoplasm to be determined with a 64{\%} higher measurement rate than possible classically. To enable this, a new microscopy system was developed which is compatible with squeezed light, and which utilized a novel optical lock-in technique to allow quantum enhancement down to 10 Hz. This method is widely applicable, extending the reach of quantum enhanced measurement to many dynamic biological processes. [Preview Abstract] |
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