Bulletin of the American Physical Society
49th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 63, Number 5
Monday–Friday, May 28–June 1 2018; Ft. Lauderdale, Florida
Session R05: Coherent Quantum Control with Ultrafast Fields |
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Chair: Wendell Hill, University of Maryland Room: Grand E |
Thursday, May 31, 2018 10:30AM - 10:42AM |
R05.00001: Turning ethanol into water and hydronium: experimentally determining the roles of each hydrogen site T. Severt, B. Kaderiya, P. Feizollah, B. Jochim, F. Ziaee, K. Borne, Kanaka Raju P., K. D. Carnes, D. Rolles, A. Rudenko, I. Ben-Itzhak, N. Ekanayake, M. Nairat, N. P. Weingartz, B. M. Farris, B. G. Levine, J. E. Jackson, M. Dantus Ultrafast hydrogen migration has been extensively studied in a variety of small hydrocarbons such as the acetylene-vinylidene isomerization reaction. In this talk, we study the formation of water and hydronium cations from ethanol induced by an ultrafast intense laser-field, where one or two hydrogens migrate, respectively, and form bonds with the OH moiety. Due to the complexity of the ethanol molecule, the migrating hydrogens can originate from multiple sites within the molecule. By studying various isotopologues of ethanol and employing coincidence momentum imaging, the origins of the migrating hydrogens can be determined. In particular for the formation of hydronium, we experimentally determine that both hydrogens can migrate from either the CH$_3$ or the CH$_2$ sites, or one hydrogen can migrate from each of these sites. [Preview Abstract] |
Thursday, May 31, 2018 10:42AM - 10:54AM |
R05.00002: Chirp control of the formation of excited neutral D fragments in intense ultrafast laser pulses Peyman Feizollah, Ben Berry, T. Severt, Bethany Jochim, M. Zohrabi, Kanaka Raju P., K.D. Carnes, B.D. Esry, I. Ben-Itzhak Excited neutral D fragments ($n$$\geq$2) are formed by the interaction of intense laser pulses with D$_2$ molecules [1]. One of the suggested interpretations of this process is that one (or both) of the electrons that were ejected recombine with the parent ion(s) and form the excited neutral fragment(s) [1]. In the present study, 400 nm laser pulses were used, and a single-prism pulse compressor [2] was implemented, which allows the generation of both positively- and negatively-chirped laser pulses. The kinetic energy release spectrum of neutral D fragments is observed to be extremely sensitive to the laser parameters. In particular, we report control of this spectrum using the chirp of the laser pulses. \\ {[1]} T. Nubbemeyer \emph{et al.}, Phys. Rev. Lett \textbf{101}, 233001 (2008). \\ {[2]} Selcuk Akturk \emph{et al.}, Opt. Express \textbf{14}, 10101 (2006). [Preview Abstract] |
Thursday, May 31, 2018 10:54AM - 11:06AM |
R05.00003: Strong-field ionization control via adiabatic passage Ulf Saalmann, Jan-Michael Rost It is shown that rapid adiabatic passage, an almost perfect coherent population transfer by means of chirped pulses, can be extended to transitions into the continuum. In contrast to the traditional scheme, hereby, the chirp serves as a control parameter that allows to switch between excitation and ionization with very high contrast. The underlying mechanism of this new control scheme for strong laser pulses is discussed in detail. Extensive calculations for atoms show that this scheme is efficient and robust. Due to locking to either of the two adiabatic states and the essentially different coupling to the continuum, contrasts as large as 80\,\% can be reached by simply reversing the chirp. [Preview Abstract] |
Thursday, May 31, 2018 11:06AM - 11:18AM |
R05.00004: Experimental quantum simulation of ultrafast-equivalent dynamics Toshihiko Shimasaki, Ruwan Senaratne, Shankari V. Rajagopal, Peter E. Dotti, David M. Weld We discuss the experimental realization of a physical quantum simulator of ultrafast phenomena, in which time-varying forces on neutral atoms in a tunable optical trap emulate the electric fields of a pulsed laser acting on electrons or nuclei in a binding potential [1]. The simulator operates in regimes equivalent to those of ultrafast and strong-field pulsed-laser experiments, opening up a hitherto unexplored application of quantum simulation techniques and a complementary path towards investigating open questions in ultrafast science. Counter-intuitively, this approach emulates some of the fastest processes in atomic physics with some of the slowest, giving rise to a temporal magnification factor of up to twelve orders of magnitude [2]. This allows straightforward access to temporal regimes that are difficult to reach in pulsed-laser experiments. The correspondence with ultrafast science is demonstrated by a sequence of experiments: we perform nonlinear spectroscopy of a many-body bound state, control the excitation spectrum by shaping the potential, observe sub-cycle unbinding dynamics during strong few-cycle pulses, and directly measure carrier-envelope phase dependence of the response to an ultrafast-equivalent pulse. We will also discuss future experimental directions for extending the capabilities of the quantum simulator and strengthening the ultracold/ultrafast correspondence. [1] R. Senaratne \textit{et al}., arXiv:1711.02654 (2017). [2] S. Sala \textit{et al}., Phys. Rev. A 95, 011403 (2017). [Preview Abstract] |
Thursday, May 31, 2018 11:18AM - 11:30AM |
R05.00005: The application of coherent anti-Stokes Raman spectroscopy technique in remote molecular detection Gengyuan Liu, Frank Narducci, Svetlana Malinovskaya The demand for remote molecular detection has been rising in recent years. The technique of coherent anti-Stokes Raman spectroscopy (CARS) is becoming one of the most optimal solutions due to its high efficiency, fast response time and ease of use. In this work, we present a new method of open air molecular detection technique by using CARS. A semiclassical theory of nonlinear scattering is introduced to estimate the number of detectable photons in a CARS signal from the target molecule clusters in the background of open air. Several key parameters are studied to provide an optimal solution. Here the novelty in implementing CARS technique is in using optical frequency combs to estimate the sustainable CARS signal. In addition, the accumulating propagation of the signal is obtained by solving the Maxwell-Liouville-von Neumann equations numerically. [Preview Abstract] |
Thursday, May 31, 2018 11:30AM - 11:42AM |
R05.00006: Maximum coherence control technique in a super-effective two-level CARS system Neil Pandya, Gengyuan Lui, Svetlana Malinovskaya Advances in ultrafast laser technology have brought new opportunities and challenges to investigations of light-matter interaction as well as applications at the frontier of science and technology. Owing to the accuracy and instantaneity, the technique of Coherent anti-Stokes Raman Spectroscopy (CARS) is widely studied and used in the area of remote detection. Preparing the maximum coherence between vibrational states in target molecules is the essential condition of generating CARS signal. In this work, we present a new adiabatic control method to achieve the maximum coherence between target vibrational states. We reduced the four-level CARS system to a super-effective two-level system based on the adiabatic condition produced by several key parameters. The study shows that the control conditions which result in optimal coherence include but are not limited to a roof chirped probe pulse. [Preview Abstract] |
Thursday, May 31, 2018 11:42AM - 11:54AM |
R05.00007: Dynamics of Quantum Superposition States and Quantum Beating in Rubidium Vapor William Goldshlag, Gary Eden We have developed a high-resolution all-optical experimental technique for studying dynamics of coherent atomic superposition states. Coherent superpositions of pairs of low quantum number ($n=5-8$) states were formed in heated Rb vapor with ultrafast laser pulses, and their dynamics was observed with nearly ps resolution by an all-optical technique of parametric four-wave mixing (PFWM). Observed phenomena and behaviors included concurrent formation of multiple superposition states and interactions between them, nonlinear oscillations inside an atom, atomic oscillator frequency pulling and quantum beat revivals. A regeneratively amplified Ti:sapphire laser produced 60 fs pulses centered near 770 nm and having the bandwidth of 20 nm. Pairs of interferometrically cloned pulses excited and subsequently probed the region near the 7S$_{1/2}$ and 5D$_{5/2}$ states in Rb vapor, which was sealed in a cylindrical cell and heated to achieve number densities between $10^{14}$ and $10^{16}$ cm$^{-3}$. Coherent emission at 420 nm from the 6P$_{3/2} \rightarrow$ 5S transition was generated by PFWM, and its intensity, recorded as a function of pump-probe delay, displayed Ramsey fringes resulting from quantum beating. Dynamics of state interactions were observed with time-frequency analysis. [Preview Abstract] |
Thursday, May 31, 2018 11:54AM - 12:06PM |
R05.00008: Quantum versus classical dynamics in the optical centrifuge Tsafrir Armon, Lazar Friedland The optical centrifuge (OC) allows to control and excite molecules' rotational degree of freedom. In this work we study the interplay between classical and quantum-mechanical evolution in the OC. The analysis is based on the quantum-mechanical formalism starting from either the ground state or a thermal ensemble. Two resonant mechanisms are identified, i.e., the classical autoresonance and the quantum-mechanical ladder climbing, yielding different dynamics and rotational excitation efficiencies. The rotating-wave approximation is used to analyze the two resonant regimes in the associated dimensionless two-parameter space and calculate several characteristic values of the excited bunch such as the efficiency and spectral width. The results show good agreement between numerical simulations and theory and are relevant to existing experimental setups. [Preview Abstract] |
Thursday, May 31, 2018 12:06PM - 12:18PM |
R05.00009: Interactions between (8s-6d) and (7s-5d) wavepackets in Rb examined by parametric four-wave mixing Rui Su, William Goldshlag, J. Gary Eden Quantum beating resulting from the coherent superposition of states in the Rb atom with pairs of femtosecond pulses has allowed for weak interaction between the 7S-5D$_{5/2}$ and 8S-6d$_{5/2}$ wavepackets to be examined. The dominant 7S-5D$_{5/2}$ beating was identified at 18.225 THz with an accuracy on par with NIST data and was demonstrated to persist in excess of 1 ns after excitation. A weaker beating of the 8s-6d$_{5/2}$ oscillation is measured at 10.732 $\pm$ 0.002 THz (where the uncertainty represents the frequency resolution when no zero padding is used in the discrete Fourier transform), which is 0.5 cm$^{-1}$, or 10 times the frequency resolution, above that given by NIST data. This measured impact of the 7S-5D$_{5/2}$ wavepacket on the 8S-6d$_{5/2}$ superposition is consistent with the classical model of coupled oscillators. [Preview Abstract] |
Thursday, May 31, 2018 12:18PM - 12:30PM |
R05.00010: State selective excitation of a trapped ion qubit with broadband laser pulses Anthony Ransford, Conrad Roman, Michael Ip, Wesley Campbell Excitation by picosecond pulses can be used for background-free detection of fluorescence by temporally separating the prompt incidental scatter from the subsequent atomic emission. This scheme can be applied to state detection of trapped ion qubits to eliminate the need for expensive, high-NA imaging optics (trading spatial filtering for temporal filtering, which should allow for even higher NA). For hyperfine structure, however, the necessarily large bandwidth of the pulse is greater than the qubit splitting and the excitation will not be state selective or state preserving. We present a technique using sub-nanosecond pulse pairs to recover the requisite state selectivity. Using fast electronics the fluorescence from the ion can be detected unambiguously in the presence of large amounts of laser scatter and used to readout the original state. [Preview Abstract] |
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