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Center for Engineering Science Advanced Research (CESAR)
Computer Science and Mathematics Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee 37831 USA
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Listed in descending chronological order. |
We report the design and experimental characterization of a down-conversion source optimized for high spectral and spatial purity. Spatial and spectral entanglement are minimized through careful control of pump properties and material parameters.
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40.
J. Schaake, R. Bennink, P. Evans, W. Grice, and T. Humble, "Bright Photon Pair Source with High Spectral and Spatial Purity," Nonlinear Optics, 42nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics, 56 http
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We report the design and experimental characterization of a down-conversion source that has been optimized for high spectral and spatial purity. Spectral purity is achieved through the choices of the pump properties and phase-matching characteristics. Spatial entanglement is minimized via a collinear configuration in non-critically phase-matched periodically poled potassium titanyl phosphate. This geometry eliminates walk-off effects and maximizes the overlap of the pump, signal, and idler fields. With a properly focused pump, nearly all of the photons are emitted into a single spatial mode, thus yielding a single-mode emission rate of 123,000 pairs/s/mW. With its high brightness and spectral and spatial purity, this source is ideal for experiments requiring multiple pairs of identical photons, or for use as a heralded single-photon source. In addition to describing the methods for eliminating the spectral and spatial entanglement, we also show how the source can be configured to produce \emph{N}-photon polarization-entangled states.
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39.
B. Williams, R. Bennink, D. Earl, P. Evans, W. Grice, T. Humble, R. Pooser, and J. Schaake, "Multi-Client Quantum Key Distribution using Wavelength Division Multiplexing," Novel Optical Technologies and Quantum Information, 42nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics, 56 http.
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Quantum Key Distribution (QKD) exploits the rules of quantum mechanics to generate and securely distribute a random sequence of bits to two spatially separated clients. Typically a QKD system can support only a single pair of clients at a time. We overcome this limitation with the design and characterization of a multi-client entangled-photon QKD system with the capacity for up to 100 clients simultaneously. The telecom-wavelength entangled photon pairs are generated in a broadband down-conversion source configured for time-bin entangled QKD. The photons are strongly correlated in energy and are emitted across a large spectrum. Using standard wavelength division multiplexing hardware, the photons can be routed to different parties on a quantum communication network, while the strong spectral correlations ensure that each client is ``linked'' only to the client receiving the conjugate wavelength. In this way, a single down-conversion source can support dozens of channels simultaneously.
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38.
T. Humble, D. Earl, and W. Grice, "Tamper-indicating Quantum Optical Sensing," 42nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics, 56 http
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Monitoring systems based on fiber-optic seals actively monitor inventories of closed containers for tampering. However, the physics underlying these tamper-indicating optical systems make them susceptible to deception. The basis for this deception lies in the description of the electromagnetic field transmitted through the fiber. Within classical physics, knowledge of the light source, e.g., carrier frequency and pseudo-random modulation, can be used by an intruder to replicate the transmission. Once a replicated field is injected into the fiber, the downstream detector cannot discriminate it from the original transmission. Motivated by this context, we demonstrate a quantum optical, tamper-indicating device inherently immune to replication. We use time-bin entanglement (TBE) distributed through a pair of fibers, where each fiber couples to a Mach-Zehnder interferometer (MZI) detector. We monitor coincident detection as a function of the combined MZI phase $\phi = \phi_{1} + \phi_{2}$ to statistically quantify entanglement in terms of TBE visibility. The presence or absence of the expected interference consequently serves as a test for tampering, and we quantity the probability of detection and false alarm using this statistic. We anticipate this form of quantum-based sensing to support future intrusion detection technologies.
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37.
T. S. Humble, "Quantum Spread Spectrum Communication," Quantum Communication, Theoretical Entanglement, and Cryptography, APS March Meeting 2011, 56, A29.0005 http.
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Spread spectrum techniques are widely used in classical contexts, including sensing and communication, for establishing low probability of intercept, resistance to narrowband jamming, and multiuser access protocols. In SS, the spectrum of the signal is spread much larger than the minimal information bandwidth to yield a boost in channel capacity. In this contribution, we apply SS modulation to the transmission and detection of the single-photon spectral probability amplitude (as opposed to SS of the field). We draw upon previous methods for coherently dilating single-photon spectral states to motivate our ideas. Techniques for direct modulation of the spectral amplitude, modulation via pumped single-photon up-conversion, and modulation via spread spectral teleportation are developed as particular modulation schemes for quantum spread spectrum communication. We quantify QSSC performance using the channel capacity and process gain expressed in terms of the spread bandwidth, and we investigate its behavior for a frequency-selective fading model. We conclude by discussing the potential for QSSC to underlie a QKD multiuser access control (MAC) protocol.
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Spontaneous parametric down-conversion (SPDC) is a reliable and robust source of photons for quantum information applications. For applications that involve operations such as entanglement swapping or single-photon heralding, two-photon states are required to be factorable (uncorrelated) in their spectral and spatial degrees of freedom. We report the design and experimental characterization of an SPDC source that has been optimized for high spectral and spatial purity. The source is pumped by the 776 nm output of a mode-locked Ti:Sapphire laser and consists of a periodically-poled Potassium Titanyl Phosphate (PPKTP) crystal phase-matched for collinear type-II SPDC. The dispersive properties of PPKTP at these wavelengths is such that it is possible to minimize the spectral entanglement by matching the widths of the pump to the spectral phase-matching function. The spatial entanglement is minimized through careful control of the pump focus, yielding nearly single-mode emission. An advantage of this approach is that the emission rate into the collection modes is very high, resulting in a very bright SPDC source. We also report a scheme that employs the output of collinear sources such as these to produce polarization-entangled photon pairs. The scheme, which requires only simple polarization elements, can be scaled to N-photon GHZ states.
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Spread spectrum techniques have seen widespread use in classical contexts, including sensing and communication, for establishing low probability of intercept, resistance to narrowband jamming, and multiuser access protocols. In this contribution, we investigate the extension of spread spectrum techniques to the transmission of quantum information encoded into single-photon states. We develop forms of quantum spread spectrum communication based on direct-sequence and frequency-hopping modulations, and we discuss the benefits attributed to these protocols by quantifying the associated channel capacities and process gains due to broadening of the spectral probability amplitude and transmission though a medium populated by narrowband absorbers.
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34.
T. S. Humble, R. S. Bennink, and W. P. Grice, "Simultaneous Teleportation of Multiple Single-Photon Degrees of Freedom," J. Mod. Opt. 58, 288 (2011); Special Issue: Single-Photon Technologies. Selected Papers from the 4th International Workshop on Single and Entangled Photons: Sources, Detectors, Components, and Applications, 3-6 November 2009 pdf http
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ABSTRACT: We report how quantum information encoded into multiple photonic degrees of freedom may be simultaneously teleported using a single, common physical process. The application of teleportation to the complete quantum state of a photon, i.e., the spectral, spatial, and polarization component states, permits the full photonic Hilbert space to be used for encoding information while simultaneously enabling subspaces to be addressed individually, e.g., for quantum information processing. We analyze the feasibility of teleporting the full quantum state through numerical analysis of the fidelity under nominal experimental conditions and for different types of input states, e.g., single-photon states that are separable and entangled in the physical degrees of freedom.
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ABSTRACT:The emergence of streaming multicore processors with multi-SIMD architectures and
ultra-low power operation combined with real-time compute and I/O reconfigurability opens
unprecedented opportunities for executing sophisticated signal processing algorithms faster and
within a much lower energy budget. Here, we present an unconventional FFT implementation
scheme for the IBM Cell, named transverse vectorization. It is shown to outperform (both in
terms of timing and GFLOP throughput) the fastest FFT results reported to date for the Cell in
the open literature. We also provide the first results for multi-FFT implementation and
application on the novel, ultra-low power Coherent Logix HyperX processor.
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ABSTRACT: The emergence of streaming multicore processors with multi-SIMD architectures opens unprecedented opportunities for executing many sophisticated signal processing algorithms faster and within a much lower energy budget. Here we report on the development, implementation, and demonstration of a novel, massively parallel computational scheme for inverting the spatio-temporal covariance matrix associated with ambient noise in signal detection algorithms. Our methodology involves extensive use of the FFT, for which we exploit the capabilities of leading hybrid multicore processors, including the IBM Cell, the Nvidia Tesla, and the Coherent Logix HyperX.
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ABSTRACT: We present results of a bright polarization-entangled photon source operating at 1552 nm via type-II collinear degenerate spontaneous parametric down-conversion in a periodically poled potassium titanyl phosphate crystal. We report a conservative inferred pair generation rate of 123,000 pairs/s/mW into collection modes. Minimization of spectral and spatial entanglement was achieved by group velocity matching the pump, signal, and idler modes and through properly focusing the pump beam. By utilizing a pair of calcite beam displacers, we are able to overlap photons from adjacent down-conversion processes to obtain polarization-entanglement visibility of 94.7+/-1.1% with accidentals subtracted.
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30.
W. Grice, R. Bennink, P. Evans, T. Humble, R. Pooser, J. Schaake, and B. Williams, "Strong spectral entanglement in spontaneous parametric down-conversion," Frontiers in Optics (2010). pdf
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ABSTRACT: Photon pairs with a high degree of spectral entanglement have a very large capacity for
carrying information. We describe methods for generating this type of entanglement and discuss
applications.
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ABSTRACT:We report how quantum information encoded into the spectral degree of freedom of a single-photon state may be teleported using a finite spectrally entangled biphoton state. We further demonstrate how the bandwidth of the teleported wave form can be controllably and coherently dilated using a spread-spectral variant of teleportation. We calculate analytical expressions for the fidelities of spectral and spread-spectral teleportation when complex-valued Gaussian states are transferred using a proposed experimental approach. Finally, we discuss the utility of these techniques for integrating broad-bandwidth photonic qubits with narrow-bandwidth receivers in quantum communication systems.
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ABSTRACT: While many techniques exist for local spectrum sensing of a primary user, each represents a computationally demanding task to secondary user receivers. In software-defined radio, computational complexity lengthens the time for a cognitive radio to recognize changes in the transmission environment. This complexity is even more significant for spatially multiplexed receivers, e.g., in SIMO and MIMO, where the spatio-temporal data sets grow in size with the number of antennae. Limits on power and space for the processor hardware further constrain SDR performance. In this report, we discuss improvements in spatio-temporal twice whitening (STTW) for real-time local spectrum sensing by demonstrating a form of STTW well suited for MIMO environments. We implement STTW on the Coherent Logix hx3100 processor, a multicore processor intended for low-power, high-throughput software-defined signal processing. These results demonstrate how coupling the novel capabilities of emerging multicore processors with algorithmic advances can enable real-time, software-defined processing of large spatio-temporal data sets.
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ABSTRACT: Importance of achieving high performance Fourier transforms for Cognitive Radio applications can not be over-emphasized. This includes signal detection in the presence of noise power uncertainty, multi-resolution spectrum sensing, minimization of subcarriers' side lobes in OFDM modulators, multi-stream processing, or spectrum loading, for example. With the emergence of advanced multicore processors, there is a remarkable opportunity to develop novel, massively parallel implementations of the FFT. This paper reviews recent advances in the area, and presents results for three classes of devices: the IBM Cell multi-SIMD processor, the Nvidia Tesla SIMT processor, and the EnLight digital optical core device.
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ABSTRACT:We demonstrate that spectral teleportation can coherently dilate the spectral probability amplitude of a single photon. In preserving the encoded quantum information, this variant of teleportation subsequently enables a form of quantum spread spectrum communication.
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25.
J. Barhen, J. Polcari, M. Traweek, T. S. Humble, N. Imam, and P. Mitra, "Vector-sensor array algorithms for advanced multicore processors," U.S. Navy J. Underwater Acoustics (2010).
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ABSTRACT: While modern signal detection theory fully accounts for spatially distributed sensors, exploiting these techniques for real-time sensing using large, underwater acoustic arrays requires advances in the spatio-temporal signal processing algorithms. In particular, the computational complexity of many spatio-temporal processing techniques is so large that conventional computer processors lack sufficient throughput to provide real-time processing of large spatio-temporal data sets. These limits are exacerbated when constraints, such as power consumption or footprint, reduce the available computational resources. In this report, we demonstrate an implementation of a signal twice-whitening algorithm that is better suited for processing spatio-temporal data in real time. We emphasize these advances by implementing data whitening on the Coherent Logix hx3100 processor, a programmable multicore processor intended for low-power and high-throughput signal processing. These results serve as an example of how the novel capabilities available from emerging multicore processor platforms can provide real-time, software-defined processing of large data sets acquired by spatially distributed sensing.
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ABSTRACT: This paper describes the optimized design and implementation of sonar signal processing algorithms (matched filter) on the CELL multi-core processor. The algorithm is modified to achieve maximum parallelism to enhance time performance on the multi-core platform. In this proof-of-concept effort, we show a factor of 10 speedup by parallelizing the matched filter code on 16 separate computing nodes on the CELL processor for broadband matched filter implementation. This demonstration of considerably faster signal processing capability should be of substantial interest to the signal processing community in general, and the oceanic engineering community in particular.
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ABSTRACT: The emergence of streaming multicore processors with multi-SIMD architectures and ultra-low power operation combined with real-time compute and I/O reconfigurability opens unprecedented opportunities for executing sophisticated signal processing algorithms faster and within a much lower energy budget. Here, we present an unconventional FFT implementation scheme for the IBM Cell, named transverse vectorization. It is shown to outperform (both in terms of timing or GFLOP throughput) the fastest FFT results reported to date in the open literature."
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ABSTRACT: We describe an entangled photon source based on collinear down-conversion in periodically-poled KTP at 1552 nm. The pump bandwidth, crystal length, and pump spatial mode are chosen so as to minimize spectral and spatial entanglement.
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ABSTRACT: We describe the use of quantum-mechanically entangled photons for sensing intrusions across a physical perimeter. Our approach to intrusion detection uses the no-cloning principle of quantum information science as protection against an intruder's ability to spoof a sensor receiver using a 'classical' intercept-resend attack. Moreover, we employ the correlated measurement outcomes from polarization-entangled photons to protect against 'quantum' intercept-resend attacks, i.e., attacks using quantum teleportation. We explore the bounds on detection using quantum detection and estimation theory, and we experimentally demonstrate the underlying principle of entanglement-based detection using the visibility derived from polarization-correlation measurements.
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ABSTRACT: Recent demonstrations of teleportation have transferred quantum information encoded into either polarization or field-quadrature degrees of freedom (DOFs), but an outstanding question is how to simultaneously teleport quantum information encoded into multiple photonic DOFs. We describe how the spatial-spectral-polarization state of a single photon can be teleported using a pair of multimode, polarization-entangled photons derived from spontaneous parametric down conversion.
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ABSTRACT: We examine how spectral entanglement in polarization-entangled photon states generated from bulk-crystal, spontaneous parametric down-conversion affects the success of entanglement swapping and type-I fusion gates. We quantify the success of the entanglement swapping and fusion gates by calculating the bipartite concurrence and residual tangle, respectively, in terms of the joint spectral probability amplitudes of the initial broad-bandwidth polarization-entangled states. We find that both polarization-entanglement measures depend strongly on the initial spectral entanglement, as well as on the configuration of the independent sources. Specifically, when spectral differences correlate with polarization, the optimal source configuration is different for the two protocols. We conclude that this distinction is founded in how the underlying Bell-state measurement and quantum-erasure techniques respond differently to distinguishing spectral information.
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ABSTRACT: We show how adjunct spectral entanglement affects polarization-based entanglement swapping and type-I fusion gates and we explain why the concurrence of the subsequently entangled states are distinctively dependent on the initial joint spectral amplitudes.
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16.
T. S. Humble, "Quantum Teleportation Tutorial", program review, March 2007. pdf
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ABSTRACT: We provide an introductory tutorial to quantum teleportation with a brief emphasis on the motivation of our current research.
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15.
T. S. Humble and W. P. Grice, "Spectral entanglement in entanglement swapping and type-I fusion gates", rejected, December 2006. pdf
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ABSTRACT: Correlations in the spectral degrees of freedom affect polarization-based entanglement swapping and type-I fusion gates, with the coherence of the subsequently entangled states essentially and similarly dependent on the initial spectral entanglement.
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ABSTRACT: We use a multimode description of polarization-encoded qubits to analyze the quantum teleportation protocol. Specifically, we investigate how the teleportation fidelity depends on the spectral correlations inherent to polarization-entangled photons generated by type-II spontaneous parametric down conversion. We find that the maximal obtainable fidelity depends on the spectral entanglement carried by the joint probability amplitude, a result which we quantify for the case of a joint spectrum approximated by a correlated Gaussian function. We contrast these results with a similar analysis of the visibility obtained in a polarization-correlation experiment.
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13.
T. S. Humble, "An Overview of Quantum Teleportation", accepted October 2007. pdf
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ABSTRACT: Quantum teleportation is a communication protocol for the exchange of information between remotely separated parties. We survey some prominent applications of quantum teleportation that show potential for collecting and analyzing information. In addition to a background review of the underlying principles, we highlight the use of quantum teleportation in quantum key distribution, long-distance quantum communication networks, and quantum computing. The latter applications are significant as they show promise for cracking conventional public-key encryption systems and providing alternate key distribution systems that are secure against attack.
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ABSTRACT: Quantum teleportation is analyzed in the context of multi-mode interference effects.
The teleportation fidelity depends on the spectral relationship between the entangled photons and
on the spectral overlap between the photons in the Bell-state measurement.
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ABSTRACT: We formulate two-color nonlinear wave-packet interferometry (WPI) for application to a diatomic molecule in the gas phase and show that this form of heterodyne-detected multidimensional electronic spectroscopy will permit the reconstruction of photoinduced rovibrational wave packets from experimental data. Using two phase-locked pulse-pairs, each resonant with a different electronic transition, nonlinear WPI detects the quadrilinear interference contributions to the population of an excited electronic state. Combining measurements taken with different phase-locking angles isolates various quadrilinear interference terms. One such term gives the complex overlap between a propagated one-pulse target wave packet and an unpropagated three-pulse reference wave packet. The two-dimensional interferogram in the time domain specifies the overlap of the given target state with a collection of variable reference states. An inversion procedure based on singular-value decomposition enables reconstruction of the target wave packet from the interferogram without prior characterization of the nuclear Hamiltonian under which the target propagates. With numerically calculated nonlinear WPI signals subject to Gaussian noise, we demonstrate the reconstruction of a rovibrational wave packet launched from the A-state and propagated in the E-state of Li2.
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10.
T. S. Humble and J. A. Cina, "Nonlinear wave packet interferometry and molecular state reconstruction", Optics in the Southeast, 6-8 October 2005, Atlanta, Georgia, USA.
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ABSTRACT:Nonlinear WPI uses two phase-locked pulse-pairs to excite a molecular electronic population and measures contributions arising from a one-pulse target state overlapping with a three-pulse reference state. Combined with knowledge of the three-pulse reference states, the detected wave-packet interference enables reconstruction of the one-pulse target state at the probability-amplitude level.
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ABSTRACT: Nonlinear wave packet interferometry (WPI) uses two phase-locked pulse-pairs to excite a molecular electronic population and measures those contributions arising from a
one-pulse nuclear wave packet overlapping with a three-pulse nuclear wave packet. The
interferogram quantifies the wave-packet interference at the probability-amplitude level
and, with knowledge of the three-pulse (reference) wave packets, enables reconstruction
of the one-pulse (target) wave packet.
In one-color nonlinear WPI, both pulse-pairs resonate with the same electronic transition and the interferogram measures a sum of wave-packet overlaps. Experimental conditions often minimize mixing of these overlaps and hence permit molecular state reconstruction, as demonstrated by numerical calculations for model harmonic and photodissociative systems. Yet, a one-color reconstruction technique requires information about the Hamiltonian under which the target and reference states propagate. The latter knowledge obviates the practical need for experimental state determination, since computational methods are then a viable, alternative solution. Two-color nonlinear WPI, in which the pulse-pairs drive different electronic transitions, circumvents the need for information about the target-state Hamiltonian by using an auxiliary electronic level for preparing the reference states. Furthermore, in a two-color experiment, the interferogram measures a single wave-packet overlap, definitely identifying the information necessary for molecular state reconstruction. These features suggest two-color nonlinear WPI could serve as a diagnostic tool for identifying optically-controlled, yet unknown, molecular dynamics. Simulations for model systems and the lithium dimer demonstrate that target states can be reconstructed in the presence of signal noise, thermal mixtures, and rovibrational coupling and in the absence of information about the target-state Hamiltonian. In the presence of electronic-energy transfer, the interferogram reveals changes in the probability amplitude first-order in the inter-chromophore scalar coupling J. Controlling the polarization of the pulse-pairs enables selective excitation of the components in a model dimer complex and isolation of the overlap between a three-pulse reference wave packet, independent of J, and a one-pulse target wave packet, whose electronic and nuclear degrees of freedom are entangled. The processes underlying coherent energy transfer are identified by interpreting the interferogram with the help of quasi-classical phase-space diagrams. This dissertation includes both my previously published and my co-authored materials. |
8.
T. S. Humble and J. A. Cina, "Molecular state reconstruction by nonlinear wave packet interferometry," Ultrafast Phenomena XIV : Proceedings of the 14th International Conference, Niigata, Japan, July 25-30, 2004, (Springer). pdf.
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ABSTRACT:We investigate reconstruction of optically prepared vibrational wave packets using nonlinear wave packet interferometry. Simulated results for a model photodissociative diatomic demonstrate the technique's effectiveness in identifying dynamics induced by shaped laser pulses.
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7.
T. S. Humble and J. A. Cina, "Molecular state reconstruction by nonlinear wave packet interferometry", Phys. Rev. Lett. 93, 060402 (2004). pdf.
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ABSTRACT:We show that time- and phase-resolved two-color nonlinear wave packet interferometry can be used to reconstruct the probability amplitude of an optically prepared molecular wave packet without prior knowledge of the underlying potential surface.We analyze state reconstruction in pure- and mixed-state model systems excited by shaped laser pulses and propose nonlinear wave packet interferometry as a tool for identifying optimized wave packets in coherent control experiments. |
6.
T. S. Humble and J. A. Cina, "Molecular state reconstruction by nonlinear wave packet interferometry," 51th Annual Western Spectroscopy Association Conference, 28-30 January 2004 Pacific Grove, CA.
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ABSTRACT: The time and phase-resolved signals measured in a nonlinear wave packet interferometry (nl-WPI) experiment probe the overlaps between vibronic wave packets prepared by a pair of phase-locked pulse-pairs. Making use of the phase-control between pulse-pairs to measure and isolate the real and imaginary components to a molecular response which is linear in all four fields (i.e. a quadrilinear contribution), we consider the application of nl-WPI to isolated, gas phase species as a potential method for characterizing laser induced, photochemical reactions. In particular, we show that two-color nl-WPI can be used to reconstruct the probability amplitude of an optically prepared vibronic wave packet without prior detailed knowledge of the underlying potential energy surface. We analyze this form of vibronic state reconstruction in a model system excited by shaped laser pulses, and propose nl-WPI as a diagnostic tool for identifying optimized wave packets in adaptive coherent control experiments. Additionally, we demonstrate how knowledge of a propagating wave packet on an unknown surface gained using nl-WPI can be used to invert the Schrodinger equation, providing a potential method for mapping out multidimensional potential energy surfaces.
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5.
T. S. Humble and J. A. Cina, "Direct method for molecular wavepacket reconstruction on an unknown potential: Two-color nonlinear wavepacket interferometry on a photodissociative system," Scientific Program Bulletin of the American Physical Society, 3-7 March 2003, Austin, TX. http
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ABSTRACT: Nonlinear wavepacket interferometry (WPI) is a nonlinear optical technique that measures the contribution to molecular excited-state population that is quadrilinear in the electric fields of four femtosecond laser pulses comprising a pair of phase-locked pulse-pairs. The complex-valued overlap between one-pulse target and three-pulse reference vibrational wavepackets in an excited electronic state can be isolated from the nonlinear WPI signal by adding signals with different combinations of intrapulse-pair optical phase shifts. Using calculated WPI signals for a photodissociative model system of three electronic levels and nonzero pulse durations, we demonstrate that the set of isolable complex overlaps for a range of interpulse delays provides sufficient information to systematically reconstruct a time-dependent vibrational wavepacket prepared on an unknown potential by an unknown optical waveform. We apply our reconstruction procedure, based on singular-value decomposition in the position representation, to a shaped wavepacket prepared by linearly chirped pulses. The robustness of the reconstruction procedure is examined for various levels of signal noise and the presence of initial thermal population in multiple vibrational levels. It should be possible to incorporate nonlinear WPI measurements along the lines discussed here with closed-loop learning algorithms using existing pulse-shaping technology. In that context, the wavepacket reconstruction process could yield insights into the design and mechanism of action of shaped matter waves created by optimally crafted optical waveforms.
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4.
J. A. Cina, D. Kilin, and T. S. Humble, "Wave packet interferometry for short-time electronic energy transfer: Multidimensional optical spectroscopy in the time domain," J. Chem. Phys. 118, 46 (2003). pdf.
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ABSTRACT: We develop a wave packet interferometry description of multidimensional ultrafast electronic
spectroscopy for energy-transfer systems. After deriving a general perturbation-theory-based expression for the interference signal quadrilinear in the electric field amplitude of four phase-locked pulses, we analyze its form in terms of the underlying energy-transfer wave packet dynamics in a simplified oriented model complex. We show that a combination of optical-phase cycling and polarization techniques will enable the experimental isolation of complex-valued overlaps between a ‘‘target’’ vibrational wave packet of first order in the energy-transfer coupling J, characterizing the one-pass probability amplitude for electronic energy transfer, and a collection of variable ‘‘reference’’ wave packets prepared independently of the energy-transfer process. With the help of quasiclassical phase-space arguments and analytic expressions for local signal variations, the location and form of peaks in the two-dimensional interferogram are interpreted in terms of the wave packet surface-crossing dynamics accompanying and giving rise to electronic energy transfer.
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ABSTRACT: We present one-color nonlinear wavepacket interferometry (WPI) signal calculations for a system of two electronic levels and one vibrational degree of freedom. We consider two cases, a displaced harmonic oscillator system, which can be treated analytically, and a model photodissociative system, whose WPI signal must be calculated by numerical wavepacket propagation. We show how signals obtained with different combinations of intrapulse-pair phase shifts can be combined to isolate the complex-valued overlap between a given onepulse target wavepacket and a variable three-pulse reference wavepacket. We demonstrate that with a range of inter- and intrapulse-pair delays the complex overlaps and variable reference states can be used to reconstruct the target wavepacket. We compare our results with previous methods for vibronic state reconstruction based on linear WPI and discuss further generalizations of our method.
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2.
J. A. Cina and T. S. Humble, "Molecular wave packet decomposition by nonlinear interferometry," Bull. Chem. Soc. Jpn. 75, 1135 (2002). pdf.
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ABSTRACT:We show that nonlinear interferometry with pairs of phase-locked pulse-pairs can determine the complex overlap of an evolving excited-state nuclear wavepacket with a collection of wavepackets moving in specified ways in the ground-state potential. We outline a procedure through which this information can be inverted to yield the form of an evolving wavepacket directly from experimental data.
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ABSTRACT: The fractionation factor is defined as the equilibrium constant for the reaction; R-H + DOH <=> R-D + HOH. Of interest
are values of fractionation factors that obtain for reactions where reactants and/or products form intra-molecular low-barrier
hydrogen bonds. Experimentally measured isotopic fractionation factors are usually interpreted via a one-dimensional
potential energy surface along the intrinsic proton hydrogen bond coordinate. Here we show that coupling the intrinsic
proton coordinate to an intra-molecular vibrational mode has large effects on the values of isotopic fractionation factors and
offer a picture for the fractionation factor for low-barrier hydrogen bonds based on the one-dimensional potential of mean
force on the intrinsic proton coordinate.
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