Bulletin of the American Physical Society
41st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 55, Number 5
Tuesday–Saturday, May 25–29, 2010; Houston, Texas
Session Q6: EIT and Coherence Effects |
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Chair: George Welch, Texas A&M University Room: Arboretum IV-V |
Friday, May 28, 2010 8:00AM - 8:12AM |
Q6.00001: Slow light in a pure nuclear spin system Mei-Ju Lu, Jonathan Weinstein Atomic ensembles have found use in a variety of important experiments in quantum information: quantum memory, quantum repeaters, and deterministic single photon generation. In these experiments, quantum information is transferred between photons and atomic hyperfine states. Unfortunately, the hyperfine states involve electron spin, and electronic angular momentum is highly susceptible to decoherence from inelastic collisions and inhomogeneous magnetic fields. On the other hand, it has been long known from NMR experiments that long coherence times can be obtained with pure nuclear spin states. By using standard electromagnetically-induced-transparency techniques with atoms with a J=0 ground state and non-zero nuclear spin, we have obtained strong coupling between photons and pure nuclear spin states. We use laser ablation and helium buffer-gas cooling to produce a sample of cryogenically-cooled ground-state atomic Yb-173 with optical density up to 80. We have obtained a narrow ($<$ 100 Hz) and deep transparency window, showing good atom-field coherence, and have demonstrated slow light in this pure nuclear-spin system. [Preview Abstract] |
Friday, May 28, 2010 8:12AM - 8:24AM |
Q6.00002: Spinor Slow-Light and unusual midgap states Johannes Otterbach, Razmik G. Unanyan, Michael Fleischhauer, Julius Ruseckas, Viaceslav Kudriasov, Gediminas Juzeliunas Since the discovery of a Dirac-like band structure in graphene there is a constantly growing interest in systems evolving under the influence of an effective Dirac-like Hamiltonian. We here show that the interaction of weak probe fields with a coherently driven atomic ensemble under conditions of electromagnetically induced transparency (EIT) leads to a Dirac-like spectrum for light-matter quasi-particles, with multiple dark-states, called spinor slow-light polaritons (SSP). They posses an ``effective speed of light'' given by the group-velocity of slow-light, which can be externally controlled and be made many orders of magnitude smaller than the vacuum speed of light. By inducing a small two-photon detuning a mass is created for the SSPs. It has been shown that a 1D model of Dirac particles having a spatially random varying mass exhibits unusual spatial correlations. For a vanishing mean value of the mass there exists a zero energy (mid-gap) state with a power-law decay of correlations. We use the property of a locally adjustable two-photon detuning to create a random varying mass of the SSP and hence to observe the unusual mid-gap state correlations. A possible implementation and its limitations are discussed. [Preview Abstract] |
Friday, May 28, 2010 8:24AM - 8:36AM |
Q6.00003: Heterodyne coherent anti-Stokes Raman scattering for spectral phase retrieval and signal amplification Xi Wang, Aihua Zhang, Miaochan Zhi, Alexei Sokolov, George Welch, Marlan Scully We study interference between local oscillator and coherent anti-Stokes Raman scattering signal fields by controlling their relative phase and amplitude. This control allows direct observation of the real and imaginary components of the third-order nonlinear susceptibility of the sample. Unlike previous heterodyne schemes, we use broad-band femtosecond preparatory pulses and a narrow-band probe pulse to coherently excite and detect multiple Raman lines simultaneously. In addition, we demonstrate that this heterodyne method can be used to amplify the signal. We also show that the combination of the spectral interferometry and a phase scan reveals how the background resonance affects the detected susceptibility in aqueous methanol solution. Our work has important applications to Raman microscopy and spectroscopy. [Preview Abstract] |
Friday, May 28, 2010 8:36AM - 8:48AM |
Q6.00004: Broadband light generation in CVD single crystal diamond Miaochan Zhi, Kai Wang, Alexei Sokolov We study broadband light generation in Raman-active crystals, such as diamond, aiming to produce few-femtosecond and sub-femtosecond pulses. Diamond has high Raman gain and has the widest transparency range of all materials. We generated up to 16 sidebands (wavelength down to 550 nm) when we focus two pump beams into a high optical quality chemical vapor deposition (CVD) single crystal diamond with 1 mm thickness. The two 50 femtosecond pump pulses have peak wavelength at 1237 and 1040 nm and have about 5$\mu $J pulse energy. The first and 2$^{nd}$ frequency up-converted sidebands have pulse energy of 0.31 and 0.15 $\mu $J. The pump pulse at 1040 nm has a conversion efficiency of 23{\%} to the sidebands. The peak frequency of the sidebands has a linear dependence on the external output angle. We combine the sidebands using a spherical mirror and a fused silica prism. A nice round beam is obtained after the prism. Our next step will be to use our pulse shaper to adjust the relative phases of the sidebands and characterize the pulses synthesized. [Preview Abstract] |
Friday, May 28, 2010 8:48AM - 9:00AM |
Q6.00005: Omni-directional collective emission of paired photons from atomic vapors Michael Moore, Yuping Huang Spontaneous four-wave mixing can generate highly correlated photon pairs from atomic vapors. We show that multi-photon pumping of dipole-forbidden transitions in a `recoil-free' geometry can result in ultra-bright pair-emission in the full $4\pi$ solid angle with strongly suppressed background Rayleigh scattering. Pair production rates of $\sim 10^{12}$ per second are predicted, given only moderate optical depths of $10\sim100$, with subnatural bandwidth biphotons obtainable at lower rates. Collective excitation and coherence dynamics are studied numerically, via a nonlinear extension of the optical Bloch equations, for two realistic schemes, based on $^{133}$Cs and $^{171}$Yb level structures. Dark-state adiabatic following (EIT) and/or a timescale hierarchy are shown to protect the paired photons from reabsorption. [Preview Abstract] |
Friday, May 28, 2010 9:00AM - 9:12AM |
Q6.00006: Resonances in Four-Level N-Scheme Atomic Systems in the Bare and Dressed States Pictures Tony Abi-Salloum, Bryan Henry, Jon Davis, Frank Narducci The theoretical study of three resonances that comprise the probe absorption and dispersion lines in the case of four-level N-scheme atomic systems explains the observed behaviors of these systems under different conditions. In this work we derive the three constituent resonances, study their dynamics as a function of the varying strengths of the interacting fields, and match each resonance in both the bare and dressed states pictures with a microscopic pathway that is followed by the system when absorbing a probe photon. The theoretical understanding of the different resonances and their conditions brings clarity to the absorptive versus non-absorptive and slow and fast versus negative group velocities experienced by a probe passing through a four-level N-scheme medium by changing the strengths of the fields. [Preview Abstract] |
Friday, May 28, 2010 9:12AM - 9:24AM |
Q6.00007: Phase Jumps in an Electro-magnetically Induced Transparency System F.A. Narducci, J. Noble, G.R. Welch, J.P. Davis We have taken a closer look at the dynamics of an EIT system when the relative phase of the two lasers is abruptly changed. The absorption of the probe field rapidly increases to a value that can exceed even the ordinary two-level absorption, then slowly decays back down to the induced transparency level. This system has been previously studied by some of us theoretically [1] and experimentally [2,3]. We show that the timescale for the rapid rise is set by the inverse bandwidth of the medium in the absence of the pump field and is therefore dramatically different for a room temperature cell as for a laser cooled sample. We also show that, surprisingly, the slow decay is not dependent on the ground state coherence time, but rather, the interplay between the Rabi frequencies and the excited state spontaneous emission rate. This suggests that, theoretically, the rise time can be made arbitrarily fast, while, simultaneously, the decay time can be made arbitrarily small or even zero. We draw a comparison with experiments performed in a warm cell and in experiments being conducted in a cold sample of atoms. [1] T. Abi-salloum, J.P. Davis, C. Lehman, E. Elliott, F.A. Narducci, {\em J. Mod. Opt}, {\bf 54}, 2459-2471, (2007). [2] V.A. Sautenkov, H. Li, Y.V. Rostovtsev, G.R. Welch, J.P. Davis, F.A. Narducci, M. O. Scully, {\em J. Mod. Opt}, {\bf 55}, 3093-3099, (2008). [3] V.A. Sautenkov, H. Li, Y.V. Rostovtsev, G.R. Welch, J.P. Davis, F.A. Narducci, M.O. Scully, {\em J. Mod. Opt}, {\bf 56}, 975-979, (2009). [Preview Abstract] |
Friday, May 28, 2010 9:24AM - 9:36AM |
Q6.00008: Control of Lamb shift by driving field Shuai Yang, Hang Zheng, Ran Hong, Shi-Yao Zhu, Suhail Zubairy The energy level shift of the atom coupled with both vacuum electromagnetic field and a driving laser is studied by using a unitary transformation approach, which directly includes the effect of the counter-rotating terms of the interaction between the atom and the vacuum field. The Lamb shift of the energy levels is shown to depend on the Rabi frequency and the detuning of the driving laser which couples another two levels. This relation provides a way to control the Lamb shift coherently. [Preview Abstract] |
Friday, May 28, 2010 9:36AM - 9:48AM |
Q6.00009: Coherent Excitation of Rydberg Atoms in Micron Sized Vapor Cells James Shaffer, Harold Kubler, Thomas Baluktsian, Robert Low, Tilman Pfau The coherent control of mesoscopic ensembles of atoms and Rydberg atom blockade are the basis for proposed quantum devices such as integrable gates and single photon sources. So far, experimental progress has been limited to complex experimental setups that use ultracold atoms. Here, we show that coherence times of 100 ns are achievable with coherent Rydberg atom spectroscopy in micron sized thermal vapour cells. We investigated states with principle quantum numbers between 30 and 50. Our results demonstrate that microcells with a size on the order of the blockade radius, 2 microns, at temperatures of 100-300 C are robust, promising candidates to investigate low dimensional strongly interacting Rydberg gases, construct quantum gates and build single photon sources. [Preview Abstract] |
Friday, May 28, 2010 9:48AM - 10:00AM |
Q6.00010: Impossibility of large phase shifts via the ``giant Kerr effect'' with single-photon wavepackets Julio Gea-Banacloche For a system of two single-photon wavepackets interacting via an ideal, localized Kerr medium, it is shown that, because of spontaneous emission into the initially unoccupied temporal modes, the cross-phase modulation in the Schr\" odinger picture is very small as long as the spectral width of the single-photon pulses is well within the medium's bandwidth. In this limit, the Hamiltonian used can be derived from the ``giant Kerr effect'' for a four-level atom, under conditions of electromagnetically-induced transparency; it is shown explicitly that the linear absorption in this system increases as the pulse's spectral width approaches the medium's transparency bandwidth, and hence, as long as the absorption probability remains small, the maximum cross-phase modulation is limited to essentially useless values. These results are in agreement with the general, causality- and unitarity-based arguments of Shapiro and co-workers. [Preview Abstract] |
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