Poul S Jessen

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• Jessen, P. S., Lysne, N. K., Kuper, K. W., Poggi, P. M., & Deutsch, I. H. (2020). A Small, Highly Accurate Quantum Processor for Intermediate-Depth Quantum Simulations. Physical Review Letters, 6.
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  In first round of review at Physical Review LettersPreprint available at arXiv:1911:02694Abstract: Analog quantum simulation is widely considered a step on the path to fault tolerant quantum computation. If based on current noisy hardware, the accuracy of an analog simulator will degrade after just a few time steps, especially when simulating complex systems that are likely to exhibit quantum chaos. Here we describe a small, highly accurate quantum simulator and its use to run high fidelity simulations of three different model Hamiltonians for >100 time steps. While not scalable to exponentially large Hilbert spaces, this platform provides the accuracy and programmability required for systematic exploration of the interplay between dynamics, imperfections, and accuracy in quantum simulation.
• Jessen, P. S., Munoz, M. H., Poggi, P. M., & Deutsch, I. H. (2020). Simulating nonlinear dynamics of collective spins via quantum measurement and feedback. Physical Review Letters, 7.
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  Currently in 2nd round of review at Phys. Rev. Lett.Preprint available at arXiv:1907.12606Abstract: We study a method to simulate quantum many-body dynamics of spin ensembles using measurement-based feedback. By performing a weak collective measurement on a large ensemble of two-level quantum systems and applying global rotations conditioned on the measurement outcome, one can simulate the dynamics of a mean-field quantum kicked top, a standard paradigm of quantum chaos. We analytically show that there exists a regime in which individual quantum trajectories adequately recover the classical limit, and show the transition between noisy quantum dynamics to full deterministic chaos described by classical Lyapunov exponents. We also analyze the effects of decoherence, and show that the proposed scheme represents a robust method to explore the emergence of chaos from complex quantum dynamics in a realistic experimental platform based on an atom-light interface.
• Jessen, P. S., Munoz-Ariaz, M. H., Deutsch, I. H., & Poggi, P. M. (2020). Simulation of the complex dynamics of mean-field p -spin models using measurement-based quantum feedback control. Physical Review A.
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  ABSTRACTWe study the application of a new method for simulating nonlinear dynamics of many-body spin systems using quantum measurement and feedback [Muñoz-Arias et al., Phys. Rev. Lett. 124, 110503 (2020)] to a broad class of many-body models known as p-spin Hamiltonians, which describe Ising-like models on a completely connected graph with p-body interactions. The method simulates the desired mean-field dynamics in the thermodynamic limit by combining nonprojective measurements of a component of the collective spin with a global rotation conditioned on the measurement outcome. We apply this protocol to simulate the dynamics of the p-spin Hamiltonians and demonstrate how different aspects of criticality in the mean-field regime are readily accessible with our protocol. We study applications including properties of dynamical phase transitions and the emergence of spontaneous symmetry breaking in the adiabatic dynamics of the collective spin for different values of the parameter p. We also demonstrate how this method can be employed to study the quantum-to-classical transition in the dynamics continuously as a function of system size.
• Jessen, P. S., Poggi, P. M., Lysne, N. K., Kuper, K. W., & Deutsch, I. H. (2020). Quantifying the Sensitivity to Errors in Analog Quantum Simulation. PRX-Quantum.
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  ABSTRACTQuantum simulators are widely seen as one of the most promising near-term applications of quantum technologies. However, it remains unclear to what extent a noisy device can output reliable results in the presence of unavoidable imperfections. Here we propose a framework to characterize the performance of quantum simulators by linking the robustness of measured quantum expectation values to the spectral properties of the output observable, which in turn can be associated with its macroscopic or microscopic character. We show that, under general assumptions and on average over all states, imperfect devices are able to reproduce the dynamics of macroscopic observables accurately, while the relative error in the expectation value of microscopic observables is much larger on average. We experimentally demonstrate the universality of these features in a state-of-the-art quantum simulator and show that the predicted behavior is generic for a highly accurate device, without assuming any detailed knowledge about the nature of the imperfections.
• Sosa-Martinez, H., Lysne, N. K., Baldwin, C. H., Kalev, A., Deutsch, I. H., & Jessen, P. S. (2017). Experimental Study of Optimal Measurements for Quantum State Tomography. PHYSICAL REVIEW LETTERS, 119(15).
• Qi, X., Baragiola, B. Q., Jessen, P. S., & Deutsch, I. H. (2016). Dispersive response of atoms trapped near the surface of an optical nanofiber with applications to quantum nondemolition measurement and spin squeezing. PHYSICAL REVIEW A, 93(2).
• Jessen, P. S. (2015). Accurate and robust unitary transformations of a high-dimensional quantum system. Physical Review Letters, 114, 240401. doi:10.1103/PhysRevLett.114.240401
• Baragiola, B. Q., Norris, L. M., Montano, E., Mickelson, P. G., Jessen, P. S., & Deutsch, I. H. (2014). Three-dimensional light-matter interface for collective spin squeezing in atomic ensembles. PHYSICAL REVIEW A, 89(3).
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  We study the three-dimensional nature of the quantum interface between an ensemble of cold, trapped atomic spins and a paraxial laser beam, coupled through a dispersive interaction. To achieve strong entanglement between the collective atomic spin and the photons, one must match the spatial mode of the collective radiation of the ensemble with the mode of the laser beam while minimizing the effects of decoherence due to optical pumping. For ensembles coupling to a probe field that varies over the extent of the cloud, the set of atoms that indistinguishably radiates into a desired mode of the field defines an inhomogeneous spin wave. Strong coupling of a spin wave to the probe mode is not characterized by a single parameter, the optical density, but by a collection of different effective atom numbers that characterize the coherence and decoherence of the system. To model the dynamics of the system, we develop a full stochastic master equation, including coherent collective scattering into paraxial modes, decoherence by local inhomogeneous diffuse scattering, and backaction due to continuous measurement of the light entangled with the spin waves. This formalism is used to study the squeezing of a spin wave via continuous quantum nondemolition measurement. We find that the greatest squeezing occurs in parameter regimes where spatial inhomogeneities are significant, far from the limit in which the interface is well approximated by a one-dimensional, homogeneous model.
• Jessen, P., Lee, J. H., Montano, E., Deutsch, I. H., & Jessen, P. S. (2013). Robust site-resolvable quantum gates in an optical lattice via inhomogeneous control. Nature communications, 4.
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  The power of optical lattices for quantum simulation and computation is greatly enhanced when atoms at individual lattice sites can be accessed for measurement and control. Experiments routinely use high-resolution microscopy to obtain site-resolved images in real time, and site-resolved spin flips have been implemented using microwaves resonant with frequency-shifted target atoms in focused light fields. Here we show that methods adapted from inhomogeneous control can greatly increase the performance of such resonance addressing, allowing the targeting of arbitrary single-qubit quantum gates on selected sites with minimal cross-talk to neighbouring sites and significant robustness against uncertainty in the atom position. We further demonstrate the simultaneous implementation of different gates at adjacent sites with a single global microwave pulse. Coherence is verified through two-pulse experiments, and the average gate fidelity is measured to be 95±3%. Our approach may be useful in other contexts such as ion traps and nitrogen-vacancy centres in diamond.
• Smith, A., Anderson, B. E., Sosa-Martinez, H., Riofrío, C., Deutsch, I. H., & Jessen, P. S. (2013). Quantum control in the Cs 6S_1/2 ground manifold using radio-frequency and microwave magnetic fields. Physical Review Letters, 111(17).
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  Abstract: We implement arbitrary maps between pure states in the 16-dimensional Hilbert space associated with the ground electronic manifold of Cs133. This is accomplished by driving atoms with phase modulated radio-frequency and microwave fields, using modulation waveforms found via numerical optimization and designed to work robustly in the presence of imperfections. We evaluate the performance of a sample of randomly chosen state maps by randomized benchmarking, obtaining an average fidelity >99%. Our protocol advances state-of-the-art quantum control and has immediate applications in quantum metrology and tomography. © 2013 American Physical Society.
• Smith, A., Riofrío, C., Anderson, B. E., Sosa-Martinez, H., Deutsch, I. H., & Jessen, P. S. (2013). Quantum state tomography by continuous measurement and compressed sensing. Physical Review A - Atomic, Molecular, and Optical Physics, 87(3).
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  Abstract: The need to perform quantum state tomography on ever-larger systems has spurred a search for methods that yield good estimates from incomplete data. We study the performance of compressed sensing (CS) and least squares (LS) estimators in a fast protocol based on continuous measurement on an ensemble of cesium atomic spins. They both efficiently reconstruct nearly pure states in the 16-dimensional ground manifold, reaching average fidelities F ̄CS=0.92 and F̄LS=0.88 using similar amounts of incomplete data. Surprisingly, the main advantage of CS in our protocol is an increased robustness to experimental imperfections. © 2013 American Physical Society.
• Norris, L. M., Trail, C. M., Jessen, P. S., & Deutsch, I. H. (2012). Enhanced squeezing of a collective spin via control of its qudit subsystems. Physical Review Letters, 109(17).
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  Abstract: Unitary control of qudits can improve the collective spin squeezing of an atomic ensemble. Preparing the atoms in a state with large quantum fluctuations in magnetization strengthens the entangling Faraday interaction. The resulting increase in interatomic entanglement can be converted into metrologically useful spin squeezing. Further control can squeeze the internal atomic spin without compromising entanglement, providing an overall multiplicative factor in the collective squeezing. We model the effects of optical pumping and study the tradeoffs between enhanced entanglement and decoherence. For realistic parameters we see improvements of ∼10dB. © 2012 American Physical Society.
• Riofrío, C. A., Jessen, P. S., & Deutsch, I. H. (2011). Quantum tomography of the full hyperfine manifold of atomic spins via continuous measurement on an ensemble. Journal of Physics B: Atomic, Molecular and Optical Physics, 44(15).
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  Abstract: Quantum state reconstruction based on weak continuous measurement has the advantage of being fast, accurate and almost non-perturbative. In this work we present a pedagogical review of the protocol proposed by Silberfarb et al (2005 Phys. Rev. Lett. 95 030402), whereby an ensemble of identically prepared systems is collectively probed and controlled in a time-dependent manner so as to create an informationally complete continuous measurement record. The measurement history is then inverted to determine the state at the initial time through a maximum-likelihood estimate. The general formalism is applied to the case of reconstruction of the quantum state encoded in the magnetic sublevels of a large-spin alkali atom, 133Cs. We detail two different protocols for control. Using magnetic interactions and a quadratic ac Stark shift, we can reconstruct a chosen hyperfine manifold F, e.g. the seven-dimensional F = 3 manifold in the electronic ground state of Cs. We review the procedure as implemented in experiments (Smith et al 2006 Phys. Rev. Lett. 97 180403). We extend the protocol to the more ambitious case of reconstruction of states in the full 16-dimensional electronic ground subspace (F = 3⊕F = 4), controlled by microwaves and radio-frequency (RF) magnetic fields. We give detailed derivations of all physical interactions, approximations, numerical methods and fitting procedures, tailored to the realistic experimental setting. For the case of light-shift and magnetic control, reconstruction fidelities of ∼0.95 have been achieved, limited primarily by inhomogeneities in the light-shift. For the case of microwave/RF-control we simulate fidelity >0.97, limited primarily by signal-to-noise. © 2011 IOP Publishing Ltd.
• Smith, A., Anderson, B. E., Chaudhury, S., & Jessen, P. S. (2011). Three-axis measurement and cancellation of background magnetic fields to less than 50 μg in a cold atom experiment. Journal of Physics B: Atomic, Molecular and Optical Physics, 44(20).
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  Abstract: Many experiments involving cold and ultracold atomic gases require very precise control of magnetic fields that couple to and drive the atomic spins. Examples include quantum control of atomic spins, quantum control and quantum simulation in optical lattices, and studies of spinor Bose condensates. This makes accurate cancellation of the (generally time dependent) background magnetic field a critical factor in such experiments. We describe a technique that uses the atomic spins themselves to measure dc and ac components of the background field independently along three orthogonal axes, with a resolution of a few tens of μG in a bandwidth of ∼1 kHz. Once measured, the background field can be cancelled with three pairs of compensating coils driven by arbitrary waveform generators. In our laboratory, the magnetic field environment is sufficiently stable for the procedure to reduce the field along each axis to less than ∼50 μG rms, corresponding to a suppression of the ac part by about one order of magnitude. This suggests that our approach can provide access to a new low-field regime in cold atom experiments. © 2011 IOP Publishing Ltd.
• Deutsch, I. H., & Jessen, P. S. (2010). Quantum control and measurement of atomic spins in polarization spectroscopy. Optics Communications, 283(5), 681-694.
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  Abstract: Quantum control and measurement are two sides of the same coin. To affect a dynamical map, well-designed time-dependent control fields must be applied to the system of interest. To read out the quantum state, information about the system must be transferred to a probe field. We study a particular example of this dual action in the context of quantum control and measurement of atomic spins through the light-shift interaction with an off-resonant optical probe. By introducing an irreducible tensor decomposition, we identify the coupling of the Stokes vector of the light field with moments of the atomic spin state. This shows how polarization spectroscopy can be used for continuous weak measurement of atomic observables that evolve as a function of time. Simultaneously, the state-dependent light shift induced by the probe field can drive nonlinear dynamics of the spin, and can be used to generate arbitrary unitary transformations on the atoms. We revisit the derivation of the master equation in order to give a unified description of spin dynamics in the presence of both nonlinear dynamics and photon scattering. Based on this formalism, we review applications to quantum control, including the design of state-to-state mappings, and quantum-state reconstruction via continuous weak measurement on a dynamically controlled ensemble. © 2009 Elsevier B.V. All rights reserved.
• Jessen, P. S., Deutsch, I. H., & Stock, R. (2010). Quantum Information Processing with Trapped Neutral Atoms. QUANTUM INFORMATION PROCESSING, 3(1-5), 91-103.
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  Quantum information can be processed using large ensembles of ultracold and trapped neutral atoms, building naturally on the techniques developed for high-precision spectroscopy and metrology. This article reviews some of the most important protocols for universal quantum logic with trapped neutrals, as well as the history and state-of-the-art of experimental work to implement these in the laboratory. Some general observations are made concerning the different strategies for qubit encoding, transport and interaction, including trade-offs between decoherence rates and the likelihood of two-qubit gate errors. These trade-offs must be addressed through further refinements of logic protocols and trapping technologies before one can undertake the design of a general-purpose neutral-atom quantum processor.
• Mischuck, B., Deutsch, I. H., & Jessen, P. S. (2010). Coherent control of atomic transport in spinor optical lattices. Physical Review A - Atomic, Molecular, and Optical Physics, 81(2).
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  Abstract: Coherent transport of atoms trapped in an optical lattice can be controlled by microwave-induced spin flips that correlate with site-to-site hopping. We study the controllability of homogeneous one-dimensional systems of noninteracting atoms in the absence of site addressability. Given these restrictions, we construct a deterministic protocol to map an initially localized Wannier state to a wave packet that is coherently distributed over n sites. As an example, we consider a one dimensional quantum walk in the presence of both realistic photon scattering and inhomogeneous broadening of the microwave transition due to the optical lattice. Using composite pulses to suppress errors, fidelities of over 95% can be achieved for a 25-step walk. We extend the protocol for state preparation to analytic solutions for arbitrary unitary maps given homogeneous systems and in the presence of time-dependent uniform forces. Such control is important for applications in quantum information processing, such as quantum computing and quantum simulations of condensed matter phenomena. © 2010 The American Physical Society.
• Trail, C. M., Jessen, P. S., & Deutsch, I. H. (2010). Strongly enhanced spin squeezing via quantum control. Physical Review Letters, 105(19).
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  Abstract: We describe a new approach to spin squeezing based on a double-pass Faraday interaction between an optical probe and an optically dense atomic sample. A quantum eraser is used to remove residual spin-probe entanglement, thereby realizing a single-axis twisting unitary map on the collective spin. This interaction can be phase matched, resulting in exponential enhancement of squeezing as a function of optical density for times short compared to the decoherence time. In practice the scaling and peak squeezing depends on decoherence, technical loss, and noise. Including these imperfections, our model indicates that ∼10dB of squeezing should be achievable with laboratory parameters. © 2010 The American Physical Society.
• Förster, L., Karski, M., Choi, J., Steffen, A., Alt, W., Meschede, D., Widera, A., Montano, E., Lee, J. H., Rakreungdet, W., & Jessen, P. S. (2009). Microwave control of atomic motion in optical lattices. Physical Review Letters, 103(23).
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  Abstract: We control the quantum mechanical motion of neutral atoms in an optical lattice by driving microwave transitions between spin states whose trapping potentials are spatially offset. Control of this offset with nanometer precision allows for adjustment of the coupling strength between different motional states, analogous to an adjustable effective Lamb-Dicke factor. This is used both for efficient one-dimensional sideband cooling of individual atoms to a vibrational ground state population of 97% and to drive coherent Rabi oscillation between arbitrary pairs of vibrational states. We further show that microwaves can drive well resolved transitions between motional states in maximally offset, shallow lattices, and thus in principle allow for coherent control of long-range quantum transport. © 2009 The American Physical Society.
• Jessen, P., Chaudhury, S., Smith, A., Anderson, B. E., Ghose, S., & Jessen, P. S. (2009). Quantum signatures of chaos in a kicked top. Nature, 461(7265).
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  Chaotic behaviour is ubiquitous and plays an important part in most fields of science. In classical physics, chaos is characterized by hypersensitivity of the time evolution of a system to initial conditions. Quantum mechanics does not permit a similar definition owing in part to the uncertainty principle, and in part to the Schrödinger equation, which preserves the overlap between quantum states. This fundamental disconnect poses a challenge to quantum-classical correspondence, and has motivated a long-standing search for quantum signatures of classical chaos. Here we present the experimental realization of a common paradigm for quantum chaos-the quantum kicked top- and the observation directly in quantum phase space of dynamics that have a chaotic classical counterpart. Our system is based on the combined electronic and nuclear spin of a single atom and is therefore deep in the quantum regime; nevertheless, we find good correspondence between the quantum dynamics and classical phase space structures. Because chaos is inherently a dynamical phenomenon, special significance attaches to dynamical signatures such as sensitivity to perturbation or the generation of entropy and entanglement, for which only indirect evidence has been available. We observe clear differences in the sensitivity to perturbation in chaotic versus regular, non-chaotic regimes, and present experimental evidence for dynamical entanglement as a signature of chaos.
• Merkel, S. T., Brennen, G., Jessen, P. S., & Deutsch, I. H. (2009). Constructing general unitary maps from state preparations. Physical Review A - Atomic, Molecular, and Optical Physics, 80(2).
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  Abstract: We present an efficient algorithm for generating unitary maps on a d -dimensional Hilbert space from a time-dependent Hamiltonian through a combination of stochastic searches and geometric construction. The protocol is based on the eigendecomposition of the map. A unitary matrix can be implemented by sequentially mapping each eigenvector to a fiducial state, imprinting the eigenphase on that state, and mapping it back to the eigenvector. This requires the design of only d state-to-state maps generated by control wave forms that are efficiently found by a gradient search with computational resources that scale polynomially in d. In contrast, the complexity of a stochastic search for a single wave form that simultaneously acts as desired on all eigenvectors scales exponentially in d. We extend this construction to design maps on an n -dimensional subspace of the Hilbert space using only n stochastic searches. Additionally, we show how these techniques can be used to control atomic spins in the ground-electronic hyperfine manifold of alkali metal atoms in order to implement general qudit logic gates as well to perform a simple form of error correction on an embedded qubit. © 2009 The American Physical Society.
• Rakreungdet, W., Lee, J. H., Lee, K. F., Mischuck, B. E., Montano, E., & Jessen, P. S. (2009). Accurate microwave control and real-time diagnostics of neutral-atom qubits. Physical Review A - Atomic, Molecular, and Optical Physics, 79(2).
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  Abstract: We demonstrate accurate single-qubit control in an ensemble of atomic qubits trapped in an optical lattice. The qubits are driven with microwave radiation, and their dynamics tracked by optical probe polarimetry. Real-time diagnostics is crucial to minimize systematic errors and optimize the performance of single-qubit gates, leading to fidelities of 0.99 for single-qubit π rotations. We show that increased robustness to large, deliberately introduced errors can be achieved through the use of composite rotations. However, during normal operation the combination of very small intrinsic errors and additional decoherence during the longer pulse sequences precludes any significant performance gain in our current experiment. © 2009 The American Physical Society.
• Ghose, S., Stock, R., Jessen, P., Lal, R., & Silberfarb, A. (2008). Chaos, entanglement, and decoherence in the quantum kicked top. Physical Review A - Atomic, Molecular, and Optical Physics, 78(4).
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  Abstract: We analyze the interplay of chaos, entanglement, and decoherence in a system of qubits whose collective behavior is that of a quantum kicked top. The dynamical entanglement between a single qubit and the rest can be calculated from the mean of the collective spin operators. This allows the possibility of efficiently measuring entanglement dynamics in an experimental setting. We consider a deeply quantum regime and show that signatures of chaos are present in the dynamical entanglement for parameters accessible in an experiment that we propose using cold atoms. The evolution of the entanglement depends on the support of the initial state on regular versus chaotic Floquet eigenstates, whose phase-space distributions are concentrated on the corresponding regular or chaotic eigenstructures. We include the effect of decoherence via a realistic model and show that the signatures of chaos in the entanglement dynamics persist in the presence of decoherence. In addition, the classical chaos affects the decoherence rate itself. © 2008 The American Physical Society.
• Merkel, S. T., Jessen, P. S., & Deutsch, I. H. (2008). Quantum control of the hyperfine-coupled electron and nuclear spins in alkali-metal atoms. Physical Review A - Atomic, Molecular, and Optical Physics, 78(2).
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  Abstract: We study quantum control of the full hyperfine manifold in the ground-electronic state of alkali-metal atoms based on applied radio frequency and microwave fields. Such interactions should allow essentially decoherence-free dynamics and the application of techniques for robust control developed for NMR spectroscopy. We establish the conditions under which the system is controllable in the sense that one can generate an arbitrary unitary map on the system. We apply this to the case of Cs133 with its d=16 dimensional Hilbert space of magnetic sublevels in the 6 S1 2 state, and design control wave forms that generate an arbitrary target state from an initial fiducial state. We develop a generalized Wigner function representation for this space consisting of the direct sum of two irreducible representations of SU(2), allowing us to visualize these states. The performance of different control scenarios is evaluated based on the ability to generate a high-fidelity operation in an allotted time with the available resources. We find good operating points commensurate with modest laboratory requirements. © 2008 The American Physical Society.
• Chaudhury, S., Merkel, S., Herr, T., Silberfarb, A., Deutsch, I. H., & Jessen, P. S. (2007). Quantum control of the hyperfine Spin of a Cs atom ensemble. Physical Review Letters, 99(16).
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  Abstract: We demonstrate quantum control of a large spin angular momentum associated with the F=3 hyperfine ground state of Cs133. Time-dependent magnetic fields and a static tensor light shift are used to implement near-optimal controls and map a fiducial state to a broad range of target states, with yields in the range 0.8-0.9. Squeezed states are produced also by an adiabatic scheme that is more robust against errors. Universal control facilitates the encoding and manipulation of qubits and qudits in atomic ground states and may lead to the improvement of some precision measurements. © 2007 The American Physical Society.
• Chaudhury, S., Smith, G. A., Schulz, K., & Jessen, P. S. (2006). Continuous nondemolition measurement of the Cs clock transition pseudospin. Physical Review Letters, 96(4).
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  Abstract: We demonstrate a weak continuous measurement of the pseudospin associated with the clock transition in a sample of Cs atoms. Our scheme uses an optical probe tuned near the D1 transition to measure the sample birefringence, which depends on the z component of the collective pseudospin. At certain probe frequencies the differential light shift of the clock states vanishes, and the measurement is nonperturbing. In dense samples the measurement can be used to squeeze the collective clock pseudospin and has the potential to improve the performance of atomic clocks and interferometers. © 2006 The American Physical Society.
• Sebby-Strabley, J., Anderlini, M., Jessen, P. S., & Porto, J. V. (2006). Lattice of double wells for manipulating pairs of cold atoms. Physical Review A - Atomic, Molecular, and Optical Physics, 73(3).
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  Abstract: We describe the design and implementation of a two-dimensional optical lattice of double wells suitable for isolating and manipulating an array of individual pairs of atoms in an optical lattice. Atoms in the square lattice can be placed in a double well with any of their four nearest neighbors. The properties of the double well (the barrier height and relative energy offset of the paired sites) can be dynamically controlled. The topology of the lattice is phase stable against phase noise imparted by vibrational noise on mirrors. We demonstrate the dynamic control of the lattice by showing the coherent splitting of atoms from single wells into double wells and observing the resulting double-slit atom diffraction pattern. This lattice can be used to test controlled neutral atom motion among lattice sites and should allow for testing controlled two-qubit gates. © 2006 The American Physical Society.
• Smith, G. A., Silberfarb, A., Deutsch, I. H., & Jessen, P. S. (2006). Efficient quantum-state estimation by continuous weak measurement and dynamical control. Physical Review Letters, 97(18).
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  Abstract: We demonstrate a fast, robust, and nondestructive protocol for quantum-state estimation based on continuous weak measurement in the presence of a controlled dynamical evolution. Our experiment uses optically probed atomic spins as a test bed and successfully reconstructs a range of trial states with fidelities of ∼90%. The procedure holds promise as a practical diagnostic tool for the study of complex quantum dynamics, the testing of quantum hardware, and as a starting point for new types of quantum feedback control. © 2006 The American Physical Society.
• Jessen, P. S., Deutsch, I. H., & Stock, R. (2005). Quantum information processing with trapped neutral atoms. Experimental Aspects of Quantum Computing, 91-103.
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  Abstract: Quantum information can be processed using large ensembles of ultracold and trapped neutral atoms, building naturally on the techniques developed for high-precision spectroscopy and metrology. This article reviews some of the most important protocols for universal quantum logic with trapped neutrals, as well as the history and state-of-the-art of experimental work to implement these in the laboratory. Some general observations are made concerning the different strategies for qubit encoding, transport and interaction, including trade-offs between decoherence rates and the likelihood of two-qubit gate errors. These trade-offs must be addressed through further refinements of logic protocols and trapping technologies before one can undertake the design of a general-purpose neutral-atom quantum processor. © 2005 Springer Science+Business Media, Inc.
• Silberfarb, A., Jessen, P. S., & Deutsch, I. H. (2005). Quantum state reconstruction via continuous measurement. Physical Review Letters, 95(3).
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  Abstract: We present a new procedure for quantum state reconstruction based on weak continuous measurement of an ensemble average. By applying controlled evolution to the initial state, new information is continually mapped onto the measured observable. A Bayesian filter is then used to update the state estimate in accordance with the measurement record. This generalizes the standard paradigm for quantum tomography based on strong, destructive measurements on separate ensembles. This approach to state estimation induces minimal perturbation of the measured system, giving information about observables whose evolution cannot be described classically in real time and opening the door to new types of quantum feedback control. © 2005 The American Physical Society.
• Jessen, P. S., Deutsch, I. H., & Stock, R. (2004). Quantum information processing with trapped neutral atoms. Quantum Information Processing, 3(1-5), 91-103.
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  Abstract: Quantum information can be processed using large ensembles of ultracold and trapped neutral atoms, building naturally on the techniques developed for high-precision spectroscopy and metrology. This article reviews some of the most important protocols for universal quantum logic with trapped neutrals, as well as the history and state-of-the-art of experimental work to implement these in the laboratory. Some general observations are made concerning the different strategies for qubit encoding, transport and interaction, including trade-offs between decoherence rates and the likelihood of two-qubit gate errors. These trade-offs must be addressed through further refinements of logic protocols and trapping technologies before one can undertake the design of a general-purpose neutral-atom quantum processor. © 2004 Springer Science+Business Media, Inc.
• Smith, G. A., Chaudhury, S., Silberfarb, A., Deutsch, I. H., & Jessen, P. S. (2004). Continuous weak measurement and nonlinear dynamics in a cold spin ensemble. Physical Review Letters, 93(16), 163602-1-163602-4.
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  PMID: 15524989;Abstract: The continuous weak measurement of cold spin in an ensemble of laser cooled Cs atoms was carried out using linear Faraday effect. It was showed that the probe light shift lead to nonlinearity in the spin dynamics which limited the Fraraday measurement window. A nonperturbing measurement on the much longer time scale set by decoherence was possible by removing the nonlinearity. The nonlinear spin Hamiltonian was found to be useful for the studies of quantum chaos and real-time quantum state estimation.
• Smith, G. A., Chaudhury, S., & Jessen, P. S. (2003). Faraday spectroscopy in an optical lattice: A continuous probe of atom dynamics. Journal of Optics B: Quantum and Semiclassical Optics, 5(4), 323-329.
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  Abstract: The linear Faraday effect is used to implement a continuous; measurement of the spin of a sample of laser-cooled atoms trapped in an optical lattice. One of the optical lattice beams serves also as a probe beam, thereby allowing one to monitor the atomic dynamics in real time and with minimal perturbation. A simple theory is developed to predict the measurement sensitivity and associated cost in terms of decoherence caused by the scattering of probe photons. Calculated signal-to-noise ratios in measurements of Larmor precession are found to agree with experimental data for a wide range of lattice intensity and detuning. Finally, quantum back-action is estimated by comparing the measurement sensitivity to spin projection noise, and shown to be insignificant in the current experiment. A continuous quantum measurement based on Faraday spectroscopy in optical lattices may open up new possibilities for the study of quantum feedback and classically chaotic quantum systems.
• Jessen, P. S., Haycock, D. L., Klose, G., Smith, G. A., Deutsch, I. H., & Brennen, G. K. (2001). Quantum control and information processing in optical lattices. Quantum Information and Computation, 1(SUPPL. 1), 20-32.
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  Abstract: Neutral atoms offer a promising platform for single- and many-body quantum control, as required for quantum information processing. This includes excellent isolation from the decohering influence of the environment, and the existence of well developed techniques for atom trapping and coherent manipulation. We present a review of our work to implement quantum control and measurement for ultra-cold atoms in far-off-resonance optical lattice traps. In recent experiments we have demonstrated coherent behavior of mesoscopic atomic spinor wavepackets in optical double-well potentials, and carried out quantum state tomography to reconstruct the full density matrix for the atomic spin degrees of freedom. This model system shares a number of important features with proposals to implement quantum logic and quantum computing in optical lattices. We present a theoretical analysis of a protocol for universal quantum logic via single qubit operations and an entangling gate based on electric dipole-dipole interactions. Detailed calculations including the full atomic hyperfine structure suggests that high-fidelity quantum gates are possible under realistic experimental conditions.
• Klose, G., Smith, G., & Jessen, P. S. (2001). Measuring the quantum state of a large angular momentum. Physical Review Letters, 86(21), 4721-4724.
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  PMID: 11384332;Abstract: A new method to measure the unknown quantum state for an angular momentum of arbitrary magnitude is presented. For demonstration purposes, the implementation of this protocol for laser cooled Cesium atoms in the 6S1/2(F=4) hyperfine ground state is discussed.
• Brennen, G. K., Deutsch, I. H., & Jessen, P. S. (2000). Entangling dipole-dipole interactions for quantum logic with neutral atoms. Physical Review A - Atomic, Molecular, and Optical Physics, 61(6), 1-10.
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  Abstract: We study a means of creating multiparticle entanglement of neutral atoms using pairwise controlled dipole-dipole interactions. For tightly trapped atoms the dipolar interaction energy can be much larger than the photon scattering rate and substantial coherent evolution of the two-atom state can be achieved before decoherence occurs. Excitation of the dipoles can be made conditional on the atomic states, allowing for deterministic generation of entanglement. We derive selection rules and a figure of merit for the dipole-dipole interaction matrix elements, for alkali atoms with hyperfine structure and trapped in localized center of mass states. Different protocols are presented for implementing two-qubit quantum logic gates such as the controlled-phase and swap gates. We analyze the error probability of our gate designs, finite due to decoherence from cooperative spontaneous emission and coherent couplings outside the logical basis. Outlines for extending our model to include the full molecular interactions potentials are discussed. ©2000 The American Physical Society.
• Deutsch, I. H., Alsing, P. M., Grondalski, J., Ghose, S., Haycock, D. L., & Jessen, P. S. (2000). Quantum transport in magneto-optical double-potential wells. Journal of Optics B: Quantum and Semiclassical Optics, 2(5), 633-644.
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  Abstract: We review the quantum transport of ultra-cold alkali atoms trapped in a one-dimensional optical lattice of double-potential wells, engineered through a combination of ac-Stark shifts and Zeeman interactions. The system is modelled numerically through analysis of the bandstructure and integration of the time-dependent Schrodinger equation. By these means we simulate coherent control of the atomic wavepackets. We present results from ongoing experiments on laser-cooled caesium, including the demonstration of quantum state preparation and preliminary evidence for coherent tunnelling. Entanglement between the internal and motional degrees of freedom allows us to access the tunneling dynamics by Stern-Gerlach measurements of the ground state magnetic populations. A scheme to extend this into a full reconstruction of the density matrix for the ground state angular momentum is presented. We further consider the classical dynamics of our system, which displays deterministic chaos. This has important implications for the distinction between classical and quantum mechanical transport.
• Deutsch, I. H., Brennen, G. K., & Jessen, P. S. (2000). Quantum computing with neutral atoms in an optical lattice. Fortschritte der Physik, 48(9-11), 925-943.
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  Abstract: We present a proposal for quantum information processing with neutral atoms trapped in optical lattices as qubits. Initialization and coherent control of single qubits can be achieved with standard laser cooling and spectroscopic techniques. We consider entangling two-qubit logic gates based on optically induced dipole-dipole interactions, calculating a figure-of-merit for various protocols. Massive parallelism intrinsic to the lattice geometry makes this an intriguing system for scalable, fault-tolerant quantum computation.
• Haycock, D. L., Alsing, P. M., Deutsch, I. H., Grondalski, J., & Jessen, P. S. (2000). Mesoscopic quantum coherence in an optical lattice. Physical Review Letters, 85(16), 3365-3368.
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  Abstract: Rabi oscillations of atomic spinor wave packets in the optical double-well potentials of a far-off-resonance 1D lin-θ-lin optical lattice were observed. Extensive data were taken for a relative polarization angle θ=80°, plus additional data at = 85°. Both data sets show Rabi frequencies in excellent agreement with theory.
• Brennen, G. K., Caves, C. M., Jessen, P. S., & Deutsch, I. H. (1999). Quantum Logic Gates in Optical Lattices. Physical Review Letters, 82(5), 1060-1063.
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  Abstract: We propose a new system for implementing quantum logic gates: neutral atoms trapped in a very far-off-resonance optical lattice. Pairs of atoms are made to occupy the same well by varying the polarization of the trapping lasers, and then a near-resonant electric dipole is induced by an auxiliary laser. A controlled-NOT can be implemented by conditioning the target atomic resonance on a resolvable level shift induced by the control atom. Atoms interact only during logical operations, thereby suppressing decoherence.
• Deutsch, I. H., & Jessen, P. S. (1998). Quantum-state control in optical lattices. Physical Review A - Atomic, Molecular, and Optical Physics, 57(3), 1972-1986.
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  Abstract: We study the means of preparing and coherently manipulating atomic wave packets in optical lattices, with particular emphasis on alkali-metal atoms in the far-detuned limit. We derive a general, basis-independent expression for the lattice potential operator, and show that its off-diagonal elements can be tailored to couple the vibrational manifolds of separate magnetic sublevels. Using these couplings one can evolve the state of a trapped atom in a quantum coherent fashion, and prepare pure quantum states by resolved-sideband Raman cooling. We explore the use of atoms bound in optical lattices to study quantum tunneling and the generation of macroscopic superposition states in a double-well potential. Far-off-resonance optical potentials lend themselves particularly well to reservoir engineering via well-controlled fluctuations in the potential, making the atom-lattice system attractive for the study of decoherence and the connection between classical and quantum physics.
• Hamann, S. E., Haycock, D. L., Klose, G., Pax, P. H., Deutsch, I. H., & Jessen, P. S. (1998). Resolved-sideband raman cooling to the ground state of an optical lattice. Physical Review Letters, 80(19), 4149-4152.
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  Abstract: We trap neutral Cs atoms in a two-dimensional optical lattice and cool them close to the zero point of motion by resolved-sideband Raman cooling. Sideband cooling occurs via transitions between the vibrational manifolds associated with a pair of magnetic sublevels, and the required Raman coupling is provided by the lattice potential itself. We obtain mean vibrational excitations n̄x ≈ n̄y < 0.024, corresponding to a population >95% in the vibrational ground state. Atoms in the ground state of an optical lattice provide a new system in which to explore quantum state control and subrecoil laser cooling.
• Haycock, D. L., Hamann, S. E., Klose, G., Raithel, G., & Jessen, P. S. (1998). Enhanced laser cooling and state preparation in an optical lattice with a magnetic field. Physical Review A - Atomic, Molecular, and Optical Physics, 57(2), R705-R708.
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  Abstract: We demonstrate that weak magnetic fields can significantly enhance laser cooling and state preparation of Cs atoms in a one-dimensional optical lattice. A field parallel to the lattice axis increases the vibrational ground-state population of the stretched state |m = F) to 28%. A transverse field reduces the kinetic temperature. Quantum Monte Carlo simulations agree with the experiment, and predict 45% ground-state population for optimal parallel and transverse fields. Our results show that coherent mixing and local energy relaxation play important roles in laser cooling of large-F atoms.
• Gatzke, M., Birkl, G., Jessen, P. S., Katsberg, A., Rolston, S. L., & Phillips, W. D. (1997). Temperature and localization of atoms in three-dimensional optical lattices. Physical Review A - Atomic, Molecular, and Optical Physics, 55(6), R3987-R3990.
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  Abstract: We report temperature measurements of atoms trapped in a three-dimensional (3D) optical lattice, a well-defined laser-cooling situation that can be treated with currently available theoretical tools. We also obtain fluorescence spectra from a 3D optical lattice, from which we obtain quantitative information about the trapping atoms, including the oscillation frequencies, spatial localization, and a temperature, which is in good agreement with our direct measurements. For comparison we study a 1D lattice using the same atom (cesium).
• Haycock, D. L., Hamann, S. E., Klose, G., & Jessen, P. S. (1997). Atom trapping in deeply bound states of a far-off-resonance optical lattice. Physical Review A - Atomic, Molecular, and Optical Physics, 55(6), R3991-R3994.
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  Abstract: We form a one-dimensional optical lattice for Cs atoms using light tuned a few thousand linewidths below atomic resonance. Atoms are selectively loaded into deeply bound states by adiabatic transfer from a super-imposed, near-resonance optical lattice. The yields a mean vibrational excitation n̄≈0.3 and localization Δz ≈λ/20. Light scattering subsequently heats the atoms, but the initial rate is only of order 10-3 vibrational quanta per oscillation period. Low vibrational excitation, strong localization, and low heating rates make these atoms good candidates for resolved-sideband Raman cooling.
• Jessen, P. S., & Deutsch, I. H. (1996). Optical Lattices. Advances in Atomic, Molecular and Optical Physics, 37(C), 95-138.
• Wright, E., Jessen, P., & Lapeyere, G. (1996). Two-dimensional motion of cold atoms in a near-resonant annular laser beam: Artificial two-dimensional molecules. OPTICS COMMUNICATIONS, 129(5-6), 423-432.
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  We develop the theory of the two-dimensional motion of cold atoms in a near-resonant annular laser beam. For a reddetuned field the laser beam provides an annular light shift potential and the atomic motion divides into vibrational and rotational normal motions analogous to a two-dimensional molecule. In the ground vibrational state we obtain an atom optics realization of a two-dimensional rotator. We illustrate the novel physics which may be explored with this system by showing that gravity acts analogously to a static electric field applied to a charged rotator.
• Kastberg, A., Phillips, W. D., Rolston, S. L., Spreeuw, R. J., & Jessen, P. S. (1995). Adiabatic cooling of cesium to 700 nK in an optical lattice. Physical Review Letters, 74(9), 1542-1545.
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  Abstract: We localize Cs atoms in wavelength-sized potential wells of an optical lattice, and cool them to a three-dimensional temperature of 700 nK by adiabatic expansion. In the optical lattice we precool the atoms to ≈1 μK. We then reduce the trapping potential in a few hundred μs, causing the atomic center-of-mass distribution to expand and the temperature to decrease by an amount which agrees with a simple 3D band theory. These are the lowest 3D kinetic temperatures ever measured.
• GERZ, C., HODAPP, T., JESSEN, P., JONES, K., PHILLIPS, W., WESTBROOK, C., & MOLMER, K. (1993). THE TEMPERATURE OF OPTICAL MOLASSES FOR 2 DIFFERENT ATOMIC ANGULAR MOMENTA. EUROPHYSICS LETTERS, 21(6), 661-666.
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  We have measured the temperature of laser-cooled Rb atoms in optical molasses as a function of laser intensity and detuning. For both Rb-85 and Rb-87, cooled on the F = 3 --> F' = 4 and F = 2 --> F' = 3 transitions, respectively, the temperatures are proportional to the ratio of laser power and detuning for a wide range of these parameters. We observe a small but significant difference between the two isotopes. We also show the results of three-dimensional semi-classical numerical calculations. Our results favor a model which includes atomic localization in optical standing waves.
• Hangst, J. S., Berg-Sørensen, K., Jessen, P. S., Kristensen, M., Mølmer, K., Nielsen, J. S., Poulsen, P., Schiffer, J. P., & Shi, P. (1992). Laser cooling of stored ions in ASTRID: a storage ring for ions and electrons. Nuclear Inst. and Methods in Physics Research, B, 68(1-4), 17-22.
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  Abstract: A small storage ring, ASTRID, for ions and electrons has been constructed. It is a dual-purpose machine, serving as a storage ring for either ions or electrons for synchrotronradiation production. The ring has for more than one year been operational with ions and has recently been commissioned for electron storage. Both these running modes will be described as well as results given from the first experiments with laser cooled ions. Finally, prospects for experiments with superhigh mass and isotope selectivity will be discussed. © 1992.
• JESSEN, P., & KRISTENSEN, M. (1992). GENERATION OF A FREQUENCY COMB WITH A DOUBLE ACOUSTOOPTIC MODULATOR RING. APPLIED OPTICS.
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  We use an acousto-optic modulator ring setup to impose an asymmetric frequency comb on a dye laser. Applications include laser cooling of stored heavy ions.
• Jessen, P. S., Gerz, C., Lett, P. D., Phillips, W. D., Rolston, S. L., Spreeuw, R. J., & Westbrook, C. I. (1992). Observation of quantized motion of Rb atoms in an optical field. Physical Review Letters, 69(1), 49-52.
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  Abstract: We observe transitions of laser-cooled Rb between vibrational levels in subwavelength-sized optical potential wells, using high-resolution spectroscopy of resonance fluorescence. We measure the spacing of the levels and the population distribution, and find the atoms to be localized to 1/15 of the optical wavelength. We find up to 60% of the population of trapped atoms in the vibrational ground state. The dependence of the spectrum on the parameters of the optical field provides detailed information about the dynamics of laser-cooled atoms.
• Kristensen, M., Hangst, J. S., Jessen, P. S., Nielsen, J. S., Poulsen, O., & Shi, P. (1992). Laser-rf double-resonance spectroscopy in a storage ring. Physical Review A, 46(7), 4100-4109.
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  Abstract: Laser-rf double-resonance spectroscopy of the hyperfine transition between F=0 and F=1 in the metastable 3S1 state of Li+6 was performed in 100-keV beam in the storage ring ASTRID. High efficiency of optical pumping was demonstrated for complex pumping schemes. A broadband (dc6 GHz) rf device was designed and used for rf spectroscopy in the storage ring. The possibility of obtaining coherent rf signals (Ramsey fringes) from successive interactions with the same field was investigated. Important limitations for the coherences due to magnetic-field inhomogeneities were observed. These led to randomization of the atomic polarization during only one turn in the storage ring and completely prevented observation of Ramsey fringes. This situation is different from the case of fundamental particles in a storage ring, where the polarization may be preserved for many round-trips. Limits were put on the demands to beam quality, beam positioning, and magnetic-field quality to overcome the problem. The effects of the rf device on the external degrees of freedom of the ion beam were investigated. Its small aperture substantially reduced the beam lifetime, and at very low rf frequencies the electric field in the rf device was able to excite external transverse resonances in the beam. © 1992 The American Physical Society.
• Lett, P. D., Jessen, P. S., Phillips, W. D., Rolston, S. L., Westbrook, C. I., & Gould, P. L. (1991). Laser modification of ultracold collisions: Experiment. Physical Review Letters, 67(16), 2139-2142.
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  Abstract: Julienne recently predicted a dramatic laser-intensity-dependent modification of the associative ionization (AI) rate in ultracold collisions. We observe such a modification, but with a behavior inconsistent with the originally proposed mechanism. Furthermore, we find resonant structure in the spectrum of AI rate versus laser frequency, showing the importance of molecular bound states in the AI process. These observations are explained in a new theoretical treatment by Julienne and Heather (preceding Letter).
• SIMONSEN, H., WORM, T., JESSEN, P., & POULSEN, O. (1988). LIFETIME MEASUREMENTS AND ABSOLUTE OSCILLATOR-STRENGTHS FOR SINGLE IONIZED THORIUM (THII). PHYSICA SCRIPTA, 38(3), 370-373.

Proceedings Publications

• Jessen, P. S. (2014, August). Quantum control and a novel atom-light quantum interface. In Proceedings of SPIE, 9186, 91860E.
• Ghose, S., Chaudhury, S., Smith, A., Anderson, B., Jessen, P., & Cunningham, B. (2013, april). Quantum Chaos in the Dynamics of Cold Atoms. In WOMEN IN PHYSICS.
• Jessen, P. S., Deutsch, I. H., & Ghose, S. (2010, January). From order to chaos with a spin and a twist. In Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference: 2010 Laser Science to Photonic Applications, CLEO/QELS 2010.
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  Abstract: Laboratory techniques to manipulate and observe ultracold atoms make these an attractive platform for testing new ideas in quantum control and measurement. Over the last decade we have revisited the tensor interaction between light fields and multilevel atoms, and have developed a theoretical framework suited for applications in quantum control and measurement (see [1] for a review). One important finding is that the combined action of a light shift and magnetic field on an atomic ground state can be used to implement a non-linear Hamiltonian for a hyperfine spin, and that its action can lead to nonlinear spin dynamics such as wavepacket collapse and revival. Using concepts from classical control theory it is straightforward to show that this Hamiltonian is sufficiently general for full control of an arbitrarily large spin. On this foundation we have developed a new protocol for quantum state reconstruction, based on continuous weak measurement of a spin observable during carefully designed coherent evolution [2]. We have further used our tools for control and state reconstruction to implement and verify protocols for optimal control of Cs hyperfine spins (Fig. 1), showing that an initial fiducial state can be transformed into any desired target state with a fidelity in the 80-90% range [3]. © 2010 IEEE.
• Ghose, S., Alsing, P., Deutsch, I., Jessen, P., Haycock, D., Bhattacharya, T., Habib, S., Jacobs, K., In, ., Kocarev, L., Carroll, T., Gluckman, B., Boccaletti, S., & Kurths, J. (2003). Quantum and classical dynamics of atoms in a magneto-optical lattice. In EXPERIMENTAL CHAOS, 676, 283-294.
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  The transport of ultra-cold atoms in magneto-optical potentials provides a clean setting in which to investigate the distinct predictions of classical versus quantum dynamics for a system with coupled degrees of freedom. In this system, entanglement at the quantum level and chaos at the classical level arise from the coupling between the atomic spin and its center-of-mass motion. Experiments, performed deep in the quantum regime, correspond to dynamic quantum tunneling. This nonclassical behavior is contrasted with the predictions for an initial phase space distribution produced in the experiment, but undergoing classical Hamiltonian flow. We study conditions under which the trapped atoms can be made to exhibit classical dynamics through the process of continuous measurement, which localizes the probability distribution to phase space trajectories, consistent with the uncertainty principle and quantum "back-action" noise. This method allows us to analytically and numerically identify the quantum-classical boundary.
• Smith, G. A., Chaudhury, S., & Jessen, P. S. (2003, January). Probing the motion of cold atoms by Faraday spectroscopy. In Proceedings of SPIE - The International Society for Optical Engineering, 5111, 396-400.
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  Abstract: We have implemented a continuous measurement of the mean magnetic moment of an ensemble of atoms trapped in a far-off-resonance optical lattice, by detecting the Faraday rotation of one of the lattice beams after it has passed through the atom cloud. In a first demonstration experiment we have observed Larmor precession with high signal-to-noise ratio, and compared the performance of the measurement with a simple theory. Faraday spectroscopy offers an ideal method to monitor the atomic dynamics and will be applied to the study of quantum chaos in magneto-optical lattices. In principle the measurement sensitivity can be increased to the point where quantum backaction becomes significant, thereby opening the door to studies of quantum feedback, spin squeezing and the role played by quantum measurement in quantum/classical correspondence.
• Klose, G., Smith, G. A., & Jessen, P. S. (2000, January). Density matrix reconstruction of atoms with large angular momentum. In Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 152-153.
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  Abstract: A method to reconstruct the complete density matrix of a generally mixed spin state of trapped neutral atoms has been described. The numerical simulation of the reconstruction showed that this time of flight analysis is robust against expected experimental uncertainties.
• Brennen, G. K., Caves, C. M., Deutsch, I. H., & Jessen, P. S. (1999, January). Controlling atom-atom interactions in optical lattices. In IQEC, International Quantum Electronics Conference Proceedings, 106-107.
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  Abstract: The main source of decoherence in optical lattices is spontaneous emission, but this can be negligible if all manipulations are performed rapidly compared to the phonon scattering rate. A study was conducted to consider the possibility of using resonantly induced electric dipole-dipole interactions to engineer two-qubit operations such as the swap gate and the controlled-phase which, together with single qubit operations, can perform arbitrary quantum computations.
• Haycock, D. L., Cheong, K., Jessen, P. S., & Deutsch, I. H. (1999, January). Quantum state control via tunneling in an optical potential. In IQEC, International Quantum Electronics Conference Proceedings, 80-81.
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  Abstract: Tunneling of neutral cesium atoms in a one-dimensional, far-off resonance optical lattice formed by a pair of counterpropagating laser beams with linear polarizations at an angle θ was studied. A lattice whose lowest adiabatic potential is a regular array of double wells is formed with a proper choice of θ and application of a small transverse field. Tunneling creates an avoided crossing of the energy levels and the atoms can be adiabatically transferred from one side of the barrier to the other. A Schrodinger cat state can also be produced. The effect of photon scattering on tunneling is discussed, along with the possibility of observing coherent tunneling oscillations.
• Deutsch, I. H., & Jessen, P. S. (1998, January). Coherent quantum tunneling and macroscopic superposition states in optical lattices. In Technical Digest - European Quantum Electronics Conference, 220-.
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  Abstract: The optical lattice offers a flexible environment for quantum-state control and measurement. In addition, once the intrinsic incoherent processes have been suppressed, dissipation may be re-engineered into the system in the form of well-characterized fluctuations in the lattice parameters, allowing for a detailed study of the decoherence process.
• Hamann, S. E., Haycock, D. L., Jessen, P. S., & Deutsch, I. H. (1998, January). Resolved-sideband Raman cooling in an optical lattice. In Technical Digest - European Quantum Electronics Conference, 220-221.
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  Abstract: Periodic dipole force potentials, commonly known as optical lattices, are a powerful means of trapping neutral atoms in the regime of quantum center-of-mass motion. Dissipation from photon scattering can be virtually eliminated if the lattice is formed by light detuned a few thousand linewidths from atomic resonance, in which case the frequency of oscillation in the optical potential wells can be several orders of magnitude larger than the rate of vibrational excitation. The atoms are then good candidates for resolved-sideband Raman cooling. In this context, a time resolved-sideband Raman cooling of neutral cesium atoms close to the zero-point of motion in a two-dimensional optical lattice was demonstrated.
• Deutsch, I. H., & Jessen, P. S. (1997, January). Quantum state preparation in optical lattices. In Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 12, 66-.
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  Abstract: A method to cool the atoms to the vibrational ground state using resolved-sideband Raman cooling between different magnetic sublevels is investigated. A novel scheme for implementing unitary operations based on adiabatic rapid passage is discussed. Once atoms are cooled to the ground states, the same adiabatic passage technique can be used to perform unitary transformations that prepare the atomic wave packet in a given quantum state. The characteristics of the potential, such as well shape and depth, can be easily adjusted through simple changes in the laser geometry, polarization, and intensity. Lattice vibrations can be added at will with an arbitrary noise spectrum.
• Haycock, D. L., Hamann, S. E., Klose, G., & Jessen, P. S. (1997, January). Atom-trapping in the Lamb-Dicke regime in a far-off-resonance optical lattice. In Proceedings of SPIE - The International Society for Optical Engineering, 2995, 163-172.
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  Abstract: We form a 1D optical lattices for Cs atoms using light tuned a few thousand linewidths below the 6S1/2(F equals 4) yields 6P 3/2(F′ equals 5) transition at 852 nm. In this far-off- resonance lattice the time scale for damping of motional coherences and kinetic energy can be orders of magnitude longer than the vibrational oscillation period for atoms trapped in the lattice potential wells. Atoms are loaded directly into deeply bound states, by adiabatic transfer from a superimposed, near-resonance optical lattice. This yields a mean vibrational excitation n approximately equals 0.3, and localization (Delta) z approximately (lambda) /20 deep in the Lamb-Dicke regime. Light scattering subsequently heats the atoms, but the initial rate is only of order 10-3 vibrational quanta per oscillation period. Low vibrational excitation, localization in the Lamb-Dicke regime and low heating rates make these atoms good candidates for resolved- sideband Raman cooling, and for the generation and study of non-classical states of center-of-mass motion. We propose a scheme for resolved-sideband Raman cooling and quantum state preparation; the scheme employs Raman coupling between magnetic sublevels induced by the lattice light field itself. ©2004 Copyright SPIE - The International Society for Optical Engineering.
• Haycock, D. L., Hamann, S. E., Pax, P. H., & Jessen, P. S. (1996, January). Cooling to the recoil limit in an optical lattice. In Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series, 9, 227-228.
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  Abstract: In this work the authors cool and trap cesium in a 1D lin ⊥ lin optical lattice, formed by light that is detuned 25 linewidths below the 62S 1/2 (F = 4) → 62P3/2(F = 5) transition at 852 nm. They then adiabatically cool the atoms by decreasing the intensity of the lattice laser beams, and thus the potential depth, over a few 100 μs. The atomic momentum distribution is measured by a standard time-of-flight technique.
• Jessen, P. S., Kastberg, A., Phillips, W. D., Rolston, S. L., & Spreeuw, R. J. (1994, January). Sub-μK temperatures by adiabatic cooling in a 3D optical lattice. In Proceedings of the International Quantum Electronics Conference (IQEC'94), 236-237.
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  Abstract: In a one-dimensional polarization-gradient cooling scheme, with two counter-propagating laser beams having mutually orthogonal linear polarization, a linear array of potential wells for cold atoms is formed. These optical potential wells are created by the spatially varying light shift of the atomic ground state. Transitions between quantized vibrational states in such wells have been observed by stimulated and spontaneous Raman spectroscopy. Recently, this was extended to three dimensions using both four beams and six beams. In this work, we intersect four travelling-wave laser beams, all polarized in the same plane. This produces a three-dimensional body-centered cubic lattice of potential wells for cesium atoms. We have used fluorescence spectroscopy to measure the temperature and the localization of the atoms, with the temperature as low as 2 μK and the localization about λ/20 rms. We utilize this localization to further cool the atoms by reducing the intensities slowly, thereby reducing the steepness of the potential wells slowly enough to allow the atomic spatial distribution to expand adiabatically. When measuring the temperature of the atoms at different time delays after beginning to decrease the depth of the potential, we find that after 100-300 μs the atoms are cooled to velocities corresponding to less than 700 nK in all directions.
• Kastberg, A., Jessen, P. S., Phillips, W. D., Rolston, S. L., & Spreeuw, R. J. (1994, January). 3-D optical lattices for cesium atoms. In European Quantum Electronics Conference - Technical Digest.
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  Abstract: By intersecting four linearly polarized laser beams, we have produced a three-dimensional optical lattice for cesium atoms. In the interference pattern created by the beams there will be positions where the polarization is purely circular. At such points, optical pumping will put atoms in a state that has a potential minimum at the same location, due to the light shift. Thus, these points will constitute the lattice sites in a lattice of optical potential wells.
• Rolston, S. L., Gerz, C., Helmerson, K., Jessen, P. S., Lett, P. D., Phillips, W. D., Spreeuw, R. J., & Westbrook, C. I. (1992, January). Trapping atoms with optical potentials. In Proceedings of SPIE - The International Society for Optical Engineering, 1726, 205-211.
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  Abstract: Ultralow temperatures produced with polarization-gradient cooling now allow atoms to be trapped in shallow optical potential wells. We present evidence for the quantized motion of atoms in a 1-D optical molasses with the observation of spontaneous Raman transitions between vibrational levels in these wells, observed in fluorescence. In addition, we discuss the features of a far off resonance trap (FORT) - a single focus dipole force trap so far off resonance to be an essentially ground-state trap.
• Hangst, J. S., Berg-Sorensen, K., Jessen, P. S., Kristensen, M., Molmer, K., Nielsen, J. S., Poulsen, O., Schiffer, J. P., & Shi, P. (1991, January). Laser cooling of stored beams in ASTRID. In Conference Record of 1991 IEEE Particle Accelerator Conference, 1764-1766.
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  Abstract: Results of laser cooling experiments on 100 keV Li+ beams in the storage ring ASTRID are reported. The metastable fraction of the lithium beam has been laser cooled to a momentum spread dp/papproximately 10-6, corresponding to a rest frame temperature T∥ = 1 mK. Laser diagnostic methods have been employed to study the dynamics of intrabeam relaxation. A theoretical model of laser cooling has been used to interpret the experimental results. Molecular dynamics simulations of intrabeam interactions and the connection with crystalline beams are also discussed.

Presentations

• Cihak, H., & Jessen, P. S. (2018, August). Improving Quantum Control Waveforms. RiO Final Presentations. Tucson, AZ: College of Optical Sciences.
• Hemmer, D., & Jessen, P. S. (2018, August). Spin Squeezing and Magnetometry with Magnetic Field-Sensitive States. CQuIC Advisory Board Meeting. Albuquerque, NM: Center for Quantum Information and Control.
• Hemmer, D., & Jessen, P. S. (2018, January). Quantum Control and Squeezing of Collective Spin. 2018 Otics and Photonics Winter School & Workshop. Tucson, AZ: College of Optical Sciences.
• Hemmer, D., Lingasamy, S., & Jessen, P. S. (2018, May). RF Magnetometry with Deterministically Squeezed Atomic Spins. CQuIC Summer Workshop. Flagstaff, AZ: Center for Quantum Information and Control.
• Jessen, P. S. (2018, May). A Universal Analog Quantum Simulator Using Atomic Spins. 2018 Annual Meeting of APS-DAMOP. Ft Lauderdale, FL: APS-DAMOP.
• Jessen, P. S. (2018, May). Quantum Control of Atomis Spins - Experimental Activities at the University of Arizona. CQuIC NSF Site Visit. Albuquerque, NM: University of New Mexico.
• Kuper, K., & Jessen, P. S. (2018, June). Improving Control Over Quantum Systems. RiO Orientation. Tucson, AZ: College of Optical Sciences.
• Kuper, K., Lysne, N., & Jessen, P. S. (2018, May). Analog Quantum Simulation with Cs-133. CQuIC Summer Workshop. Flagstaff, AZ: Center for Quantum Information and Control.
• Lingasamy, S., & Jessen, P. S. (2018, March). RF Magnetometry with Deterministically Squeezed Atomic Spins. CQuIC Group Meeting. Tucson, AZ: Center for Quantum Informantion and Control/UNM.
• Lysne, N., & Jessen, P. S. (2018, January). Analog Quantum Simulation: Quantum Computing in the Near Term. 2018 Optics and Photonics Winter School & Workshop. Tucson, AZ: College of Optical Sciences.
• Lysne, N., & Jessen, P. S. (2018, November). Building a general-purpose analog quantum simulator from cold-atom qudits. CQuIC Group Meeting. Tucson, AZ: Center for Quantum Information and Control.
• Melchior, D., & Jessen, P. S. (2018, January). Trapped Atoms and Polarimetry in a Nanofiber-Based Quantum Interface. 2018 Optics and Photonics Winter School & Workshop. Tucson, AZ: College of Optical Sciences.
• Melchior, D., & Jessen, P. S. (2018, May). Trapping Cold Atoms Around A Nanofiber. QuIC Summer Workshop. Flagstaff, AZ: Center for Quantum Information and Control.
• Hemmer, D., & Jessen, P. S. (2015, May). Improved Spin Squeezing of an Atomic Ensemble Through Internal State Control. CQuIC Summer Workshop. Flagstaff, AZ.
• Hemmer, D., & Jessen, P. S. (2016, May). Improved Spin Squeezing of an Atomic Ensemble Through Internal State Control. 47th Annual DAMOP Meeting. Providence, Rhode Island: APS.
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  Contributed talk at the annual meeting of APS-DAMOP, the major US conference in my field. Given by my PhD student Daniel Hemmer
• Hemmer, D., & Jessen, P. S. (2016, May). Improved Spin Squeezing of an Atomic Ensemble Through Internal State Control. CQuIC Summer Workshop. Flagstaff, AZ.
• Jessen, P. S. (2016, March). Optics and Photonics Winter School and Workshop. Industrial Affiliates Workshop. College of Optical Sciences, University of Arizona.
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  Description of, and fundraising pitch for, the College's Optics and Photonics Winter School and Workshop
• Jessen, P. S. (2016, November). The Spin and the Twist: A Story of Quantum Control and Chaos. Colloquium. University of Miami, Ohio.
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  Colloquium given as part of an Outreach/Recruitment visit
• Lysne, N. (2016, May). Simulating the Kicked Top. CQuIC Group Meeting. UA/UNM (Teleconferenced).
• Lysne, N., & Jessen, P. S. (2016, May). Quantum tomography of near-unitary processes in high-dimensional quantum systems. 47th Annual DAMOP Meeting. Providence, Rhode Island: APS.
  More info

  Contributed talk at the annual meeting of APS-DAMOP, the major US conference in my field. Given by my PhD student Nathan Lysne
• Lysne, N., & Jessen, P. S. (2016, May). SIMULATING THE KICKED TOP. CQuIC Summer Workshop. Flagstaff AZ.
• Melchior, D., & Jessen, P. S. (2016, May). TRAPPING COLD ATOMS AROUND A NANOFIBER. CQuIC Summer Workshop. Flagstaff, AZ.
• Sosa-Martinez, H., & Jessen, P. S. (2016, February). Optimal strategies for quantum state and process tomography: efficiency versus robustness. 18th Annual SQuInT Workshop. Albuquerque, NM.
  More info

  30 minute contributed talk in main session at workshop with ~120 attendees
• Hemmer, D. (2015, October). Control and Squeezing of Collective Spins. CQuIC Group Meeting. UA/UNM (Teleconferenced).
• Hemmer, D., Hemmer, D., Jessen, P. S., & Jessen, P. S. (2015, May). Quantum Control and Squeezing of Collective Spins. CQuIC Summer Workshop. Flagstaff, AZ.
• Jessen, P. S. (2015, July). Quatum Control in a Large Hilbert Space. PRAQSYS 2015. Sydney, Australia: University of New South wales.
• Jessen, P. S. (2015, March). CQuIC Science. CQuIC Site Review.
• Jessen, P. S., & Jessen, P. S. (2015, June). Quantum Control and Squeezing of Collective Spins. 46th Annual DAMOP Meeting. Columbus, Ohio: APS.
• Jessen, P. S., Melchior, D., & Jessen, P. S. (2015, May). Progress In Trapping Ultracold Atoms Around An Optical Nanofiber. CQuIC Summer Workshop. Flagstaff, AZ.
• Lysne, N. (2015, January). Inhomogeneous Control of Qudit Systems. Seminar. Physics Department, University of Arizona.
• Lysne, N., & Jessen, P. S. (2015, May). Comparison of POVM Constructions for Quantum Tomography. CQuIC Summer Workshop. Flagstaff AZ.
• Montano, E., & Jessen, P. S. (2015, February). Quantum Control and Squeezing of Collective Spins. 17th Annual SQuInT Workshop. Berkeley, CA: Center for Quantum Information and Control.
• Montano, E., & Jessen, P. S. (2015, March). Quantum Control and Squeezing of Collective Spins. CQuIC Site Visit. UA/UNM (via teleconference).
• Sosa Martinez, H., & Jessen, P. S. (2015, June). Quantum State Tomography of Cold Atom Qudits. 46th Annual DAMOP Meeting. Columbus, Ohio: APS.
• Jessen, P. S. (2014, August). Quantum control and a novel atom-light quantum interface. SPIE Optics + Photonics. San Diego, California: SPIE.
• Jessen, P. S. (2014, March). Robust and Addressable Control of Atomic Qubits and Qudits. American Physical Society March Meeting. Denver, Colorado: American Physical Society.
• Jessen, P. S. (2014, October). Atoms and Photons: One Perspective on Quantum Optics at the College of Optical Sciences. FIO-LS 2015Optical Society of America.

Poster Presentations

• Cihak, H., & Jessen, P. S. (2018, August). Improving Quantum Control Waveforms. UROC Research Conference. Tucson, AZ: UROC.
• Hemmer, D., & Jessen, P. S. (2018, February). Collective Spin Squeezing of Atoms in Magnetic Field-Sensitive States. SQuInT 2018. Santa Fe, NM: SQuInT.
• Kuper, K., & Jessen, P. S. (2018, February). Compensating for Bandwidth Limitations in Radio-Frequency Control Waveforms. SQuInT 2018. Santa Fe, NM: SQuInT.
• Lingasamy, S., & Jessen, P. S. (2018, February). Deterministic Spin Squeezing with Continuous Feedback Control. SQuInT 2018. Santa Fe, NM: SQuInT.
• Lysne, N., & Jessen, P. S. (2018, August). Building a general-purpose analog quantum simulator from cold-atom qudits. CQuIC Advisory Board Meeting. Albuquerque, NM: Center for Quantum Information and Control.
• Lysne, N., & Jessen, P. S. (2018, February). Building a general-purpose analog quantum simulator from cold-atom qudits. SQuInT 2018. Santa Fe, NM: SQuInT.
• Melchior, D., & Jessen, P. S. (2018, February). Trapped Atoms and Polarimetry in a Nanofiber-Based Quantum Interface. SQuInT 2018. Santa Fe, NM: SQuInT.