Bulletin of the American Physical Society
39th Annual Meeting of the APS Division of Atomic, Molecular, and Optical Physics
Volume 53, Number 7
Tuesday–Saturday, May 27–31, 2008; State College, Pennsylvania
Session P5: Coherent Control/Slow and Stopped Light |
Hide Abstracts |
Chair: Marin Pichler, Goucher College Room: Nittany Lion Inn Boardroom I |
Friday, May 30, 2008 11:00AM - 11:12AM |
P5.00001: Population transfer between two quantum states by piecewise chirping of femtosecond pulses Sergey Zhdanovich, Evgeny Shapiro, Moshe Shapiro, John Hepburn, Valery Milner We show that by using a sequence of mutually coherent transform limited femtosecond pulses one can achieve complete and robust population transfer between quantum states in a two-level system. We compare this piecewise process with the conventional adiabatic passage performed with a single frequency chirped pulse by studying the excitation of $5s_{1/2}$ - $5p_{1/2}$ transition in Rubidium atoms. We introduced ``piecewise chirp,'' a parameter of the pulse sequence defined by phase shift between two sequential pulses in the train. We demonstrate that similarly to the conventional adiabatic passage, the piecewise excitation is insensitive to the total energy of the pulse and the value of the piecewise chirp if adiabaticity conditions are satisfied. We discuss the influence of amplitudes and phases of pulses in the sequence on the excitation process. Prospects of using the piecewise method for selective population transfer in multilevel system are discussed. [Preview Abstract] |
Friday, May 30, 2008 11:12AM - 11:24AM |
P5.00002: Robust control by two chirped pulse trains in the presence of decoherence Svetlana Malinovskaya We propose the adiabatic passage control method implementing chirped femtosecond laser pulses in the Raman configuration to optimize coherence in a selected vibrational mode. We investigate vibrational energy relaxation and collisional dephasing as factors of the coherence loss, and demonstrate the possibility for preventing decoherence by two pulse trains chirped in accordance with the proposed method. [Preview Abstract] |
Friday, May 30, 2008 11:24AM - 11:36AM |
P5.00003: Quantum state control of a Raman-coupled spinor BEC K.C. Wright, L.S. Leslie, N.P. Bigelow We have investigated the conditions under which it is possible to coherently prepare a BEC in a desired spinor state using a series of off-resonant Raman-detuned laser pulses. We find that over a wide range of experimental parameters it is possible to design a pulse-sequence protocol for controlling both the amplitudes and relative phases of the components of the spinor order parameter of alkali metal BECs. We apply these results specifically to $^{87}$Rb in the F=2 ground hyperfine state, and compare the predictions of the theoretical model against experimental results. [Preview Abstract] |
Friday, May 30, 2008 11:36AM - 11:48AM |
P5.00004: Strong Field Coherent Control of Atomic Population Transfer Stephen Clow, Uvo Holscher, Carlos Trallero, Thomas Weinacht There is significant interest in controlling atomic and molecular dynamics using shaped ultrafast laser pulses, an important aspect of which is selectively populating a particular target state with high efficiency. In order to achieve this beyond the limits of single photon excitation, one has to consider multiple interfering pathways and dynamic Stark shifts (DSS), which make resonance conditions time-dependent and substantially modify the phase advance of the bare states during the atom/molecule-field interaction. In this work, we demonstrate strong field atomic population transfer in a three level system via three-photon absorption from a single shaped ultrafast laser pulse. The optimal pulse shape for efficient population transfer is discovered using closed-loop learning control and interpreted via pulse shape parameter scans and numerical integration of the Schr\"odinger equation. We show a population inversion can be achieved and measured using a combination of spontaneous and stimulated emission. Our results illustrate the importance of dynamic Stark shifts in coherent multi-photon excitation and give rise to the possibility of lasing in the deep ultraviolet. [Preview Abstract] |
Friday, May 30, 2008 11:48AM - 12:00PM |
P5.00005: Orientation of ``asymmetric-top'' water molecules with shaped terahertz fields Catherine Herne, Philip Bucksbaum We demonstrate orientation of the asymmetric top water molecule with a programmable series of half-cycle terahertz pulses. Molecular orientation or alignment controls initial conditions and reduces random spatial orientations of molecules, and is essential for efficient generation of high-order harmonics and many other processes. Our experimental evidence confirms what has until now only been theoretically considered; the orientation of asymmetric tops. The application of a sequence of broadband half-cycle pulses to an ensemble of water molecules in the gas phase initiates a sequence of orientation revivals. Two parallel pulses with optimal pulse separation are shown to enhance the degree of orientation and restrict motion about the most polarizable molecular axes. [Preview Abstract] |
Friday, May 30, 2008 12:00PM - 12:12PM |
P5.00006: Continuous Measurement Quantum State Reconstruction in an Almost Decoherence-Free Protocol Carlos Riofrio, Seth Merkel, Ivan Deutsch Quantum state reconstruction techniques based on weak continuous measurement have the advantage of being fast, accurate, and almost non-perturbative. Moreover, they have been successfully implemented in experiments on large spin systems (PRL 97, 180403 (2006)). The performance of these techniques is generally limited by decoherence, however, as controlling optical fields lead to spontaneous emission. In this talk, an application of the reconstruction algorithm developed by Silberfarb et al. (PRL 95, 030402 (2005)) is presented for the reconstruction of quantum states stored in the ground-electronic hyperfine manifolds (F=3, F=4) of an ensemble of $^{133}$Cs atoms controlled by microwaves and radio- frequency magnetic fields. This system is advantageous in the sense that its evolution only depends on the dynamics of the ground state, giving as a result an almost decoherence-free protocol. [Preview Abstract] |
Friday, May 30, 2008 12:12PM - 12:24PM |
P5.00007: Optimal control of light pulse storage and retrieval Irina Novikova, Nathaniel Phillips, Alexey Gorshkov We experimentally study the efficiency of light storage and retrieval based on the dynamic form of the electromagnetically induced transparency (EIT) in warm Rb vapor. We demonstrate the possibility to achieve the maximum storage efficiency for finite optical depth using both iteration procedure, based on time reversal for the optimization of the input signal pulse-shape, as well as the storage of arbitrary signal pulse-shape using calculated control field. We also discuss the mechanisms that hinder observation of maximum storage efficiency at higher optical depth. [Preview Abstract] |
Friday, May 30, 2008 12:24PM - 12:36PM |
P5.00008: Stored light optimization and optical depth Mason Klein, Yanhong Xiao, Rita Kalra, Michael Hohensee, David F. Phillips, Ronald L. Walsworth Efficient storage of light in an atomic ensemble requires a large optical depth to contain an entire light pulse inside an atomic medium without incoherent absorption. In an idealized theoretical picture, very large optical depths should improve the efficiency of stored light. In practice, however, additional effects such as spin-exchange, radiation trapping, and non-linear processes can reduce the efficiency at large optical depths. Here we present an experimental study of stored light efficiency in Rb vapor as a function of optical depth, varying experimental parameters such as pulse duration and shape, storage time, retrieval field intensity, and cell and beam geometry. [Preview Abstract] |
Friday, May 30, 2008 12:36PM - 12:48PM |
P5.00009: Image Storage in Hot Vapors L. Zhao, T. Wang, Y. Xiao, S.F. Yelin We theoretically investigate image storage in hot atomic vapor. A so-called $4f$ system is adopted for imaging and an atomic vapor cell is placed over the transform plane. The Fraunhofer diffraction pattern of an object in the object plane can thus be transformed into atomic Raman coherence according to the idea of ``light storage''. We investigate how the stored diffraction pattern evolves under diffusion and discuss the essence of the stability of its dark spots. Our result indicates, under appropriate conditions, that an image can be reconstructed with high fidelity. The main reason for this procedure to work is the fact that diffusion of opposite-phase components of the diffraction pattern interfere destructively. [Preview Abstract] |
Friday, May 30, 2008 12:48PM - 1:00PM |
P5.00010: Observation of Refractive Index Enhancement with Vanishing Absorption. Nicholas Proite, Brett Unks, Deniz Yavuz We experimentally demonstrate a scheme where a laser beam which is very far detuned from an atomic resonance experiences a large index of refraction with vanishing absorption. The essential idea is to excite two Raman resonances with appropriately chosen strong control lasers. We observe this effect by utilizing the hyperfine ground states of $^{85}$Rb and $^{87}$Rb simultaneously. [Preview Abstract] |
Friday, May 30, 2008 1:00PM - 1:12PM |
P5.00011: Demostration of Double Electromagnetically Induced Transparency in a Hot Atomic Vapor Andrew MacRae, Geoff Campbell, Alexander Lvovsky We report demonstration of double electromagnetically-induced transparency in a hot rubidium-87 vapor: two transparency windows appear simultaneously on $\|5S_{1/2},F=1\rangle \to \| 5P_{1/2},F=2\rangle$ and $\|5S_{1/2},F=2\rangle \to \| 5P_{1/2},F=2\rangle$ when a single control field is applied. We have been able to simultaneously slow down two optical pulses resonant with these transitions. By switching the control field, we have demonstrated simultaneous storage of these pulses. [Preview Abstract] |
Friday, May 30, 2008 1:12PM - 1:24PM |
P5.00012: Dynamical Evolution in the Propagation of Light in a Four-Level Medium Frank A. Narducci, Jon P. Davis We theoretically study the propagation of a weak probe travelling through a sample of four level atoms being driven by a pump laser and a control laser. We focus on the slow and fast light properties. Although quasi-static pulse propagation in such a medium has been studied before (e..g [1,2]), we are interested in the dynamics of the pulse propagation when characteristics of the controlling fields are suddenly changed while the pulse is in the medium. We present our dynamical model which emphasizes atom dynamics in conjunction with the pulse propagation. We examine the behavior of the system in the neighborhood of the sharp dispersion feature already pointed out in [2]. \newline \newline [1] S.E. Harris and Y. Yamamoto, {\em Phys. Rev. Lett.}, {\bf 81}, 3611 (1998). \newline [2] H. Kang, G. Hernandez and Y. Zhu, {\em Phys. Rev A}, {\bf 70}, 011801(R), (2004). [Preview Abstract] |
Friday, May 30, 2008 1:24PM - 1:36PM |
P5.00013: Observation of Raman self-focusing in an alkali-metal vapor cell Brett Unks, Nicholas Proite, Jonathan Green, Deniz Yavuz We report an experimental demonstration of Raman self-focusing and self-defocusing in a far-off resonant alkali-metal atomic system. The key idea is to drive a hyperfine transition in an alkali-metal atom to a maximally coherent state with two laser beams. In this regime, the two-photon detuning from the Raman resonance controls the nonlinear index of the medium. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700