Publications (180)565.6 Total impact
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ABSTRACT: We employ spindependent optical dipole forces to characterize the transverse centerofmass (COM) motional mode of a twodimensional Wigner crystal of hundreds of $^9$Be$^+$. By comparing the measured spin dephasing produced by the spindependent force with the predictions of a semiclassical dephasing model, we obtain absolute mode temperatures in excellent agreement with both the Doppler laser cooling limit and measurements obtained from a previously published technique (B. C. Sawyer et al. Phys. Rev. Lett. \textbf{108}, 213003 (2012)). Furthermore, the structure of the dephasing histograms allows for discrimination between initial thermal and coherent states of motion. We also apply the techniques discussed here to measure, for the first time, the ambient heating rate of the COM mode of a 2D Coulomb crystal in a Penning trap. This measurement places an upper limit on the anomalous singleion heating rate due to electric field noise from the trap electrode surfaces of $\frac{d\bar{n}}{dt}\sim 5$ s$^{1}$ for our trap at a frequency of 795 kHz, where $\bar{n}$ is the mean occupation of quantized COM motion in the axial harmonic well.01/2014; 89(3). 
Conference Paper: Quantum Simulation and ManyBody Physics with Hundreds of Trapped Ions
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ABSTRACT: The Coulomb energy of lasercooled trappedion arrays can be modified with spindependent forces to mimic quantum spin Hamiltonians. I will review recent progress, concentrating on 2D triangular arrays generated in Penning traps. 150word Biography: John Bollinger joined the NIST ion storage group in 1982 after PhD work in atomic, molecular, and optical physics at Harvard University. At NIST John's research focused on Penning trap microwave frequency standards and on the collective and cold plasma behavior of trapped ions in a Penning trap. Current research interests include quantum metrology and quantum simulation experiments involving many trapped ions. John is a member of OSA and an APS fellow.CLEO: QELS_Fundamental Science; 06/2013  [Show abstract] [Hide abstract]
ABSTRACT: Ising models, and the physical systems described by them, play a central role in generating entangled states for use in quantum metrology and quantum information. In particular, ultracold atomic gases, trapped ion systems, and Rydberg atoms realize longranged Ising models, which even in the absence of a transverse field can give rise to highly nonclassical dynamics and longrange quantum correlations. In the first part of this paper, we present a detailed theoretical framework for studying the dynamics of such systems driven (at time t=0) into arbitrary unentangled nonequilibrium states, thus greatly extending and unifying the work of Ref. [1]. Specifically, we derive exact expressions for closedtimepath ordered correlation functions, and use these to study experimentally relevant observables, e.g. Bloch vector and spinsqueezing dynamics. In the second part, these correlation functions are then used to derive closedform expressions for the dynamics of arbitrary spinspin correlation functions in the presence of both T_1 (spontaneous spin relaxation/excitation) and T_2 (dephasing) type decoherence processes. Even though the decoherence is local, our solution reveals that the competition between Ising dynamics and T_1 decoherence gives rise to an emergent nonlocal dephasing effect, thereby drastically amplifying the degradation of quantum correlations. In addition to identifying the mechanism of this deleterious effect, our solution points toward a scheme to eliminate it via measurementbased coherent feedback.New Journal of Physics 06/2013; · 4.06 Impact Factor 
Article: Nonequilibrium dynamics of arbitraryrange Ising models with decoherence: An exact analytic solution
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ABSTRACT: The interplay between interactions and decoherence in manybody systems is of fundamental importance in quantum physics. In a step toward understanding this interplay, we obtain an exact analytic solution for the nonequilibrium dynamics of Ising models with arbitrary couplings (and therefore in arbitrary dimension) and subject to local Markovian decoherence. Our solution shows that decoherence significantly degrades the nonclassical correlations developed during coherent Ising spin dynamics, which relax much faster than predicted by treating decoherence and interactions separately. We also show that the competition of decoherence and interactions induces a transition from oscillatory to overdamped dynamics that is absent at the singleparticle or meanfield level. These calculations are applicable to ongoing quantum information and emulation efforts using a variety of atomic, molecular, optical, and solidstate systems. In particular, we apply our results to the NIST Penning trappedion experiment and show that the current experiment is capable of producing entanglement amongst hundreds of quantum spins.Physical Review A 04/2013; 87(4). · 3.04 Impact Factor 
Article: Spectroscopy and Thermometry of Drumhead Modes in a Mesoscopic 2D Coulomb Crystal of ^9Be^+
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ABSTRACT: We demonstrate spectroscopy and thermometry of individual motional modes in a mesoscopic 2D ion array using entanglement between ion valence electron spins and collective motion. Our system is a ˜400 μmdiameter planar crystal of several hundred ^9Be^+ ions exhibiting complex drumhead modes in the confining potential of a Penning trap. Exploiting precise control over the ^9Be^+ valence electron spins, we apply a homogeneous spindependent optical dipole force to excite arbitrary transverse modes with wavelengths ranging from the array diameter to the interparticle spacing of ˜20 μm. In addition to temperature measurements, this spinmotion entanglement induced by the spindependent optical dipole force allows for extremely sensitive detection of external forces (˜100 yN) acting on the ion crystal. Characterization of mode frequencies and temperatures is critical for quantum simulation experiments that make use of the ion spins.04/2013;  [Show abstract] [Hide abstract]
ABSTRACT: By employing forces that depend on the internal electronic state (or spin) of an atomic ion, the Coulomb potential energy of a strongly coupled array of ions can be modified in a spindependent way to mimic effective quantum spin Hamiltonians. Both ferromagnetic and antiferromagnetic interactions can be implemented. We use simple models to explain how the effective spin interactions are engineered with trappedion crystals. We summarize the type of effective spin interactions that can be readily generated, and discuss an experimental implementation using singleplane ion crystals in a Penning trap.02/2013; 
Article: Relaxation timescales and decay of correlations in a longrange interacting quantum simulator
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ABSTRACT: We study the time evolution of correlation functions in longrange interacting quantum Ising models. For a large class of initial conditions, exact analytic results are obtained in arbitrary lattice dimension, both for ferromagnetic and antiferromagnetic coupling, and hence also in the presence of geometric frustration. In contrast to the nearestneighbour case, we find that correlations decay like stretched or compressed exponentials in time. Provided the longrange character of the interactions is sufficiently strong, pronounced prethermalization plateaus are observed and relaxation timescales are widely separated. Specializing to a triangular lattice in two spatial dimensions, we propose to utilize these results for benchmarking of a recently developed iontrap based quantum simulator.New Journal of Physics 09/2012; 15(8). · 4.06 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Experimental progress in atomic, molecular, and optical physics has enabled exquisite control over ensembles of cold trapped ions. We have recently engineered longrange Ising interactions in a twodimensional, 1mK Coulomb crystal of hundreds of ^9Be^+ ions confined within a Penning trap. Interactions between the ^9Be^+ valence spins are mediated via spindependent optical dipole forces (ODFs) coupling to transverse motional modes of the planar crystal. A continuous range of inverse powerlaw spinspin interactions from infinite (1/r^0) to dipolar (1/r^3) are accessible by varying the ODF drive frequency relative to the transverse modes. The ions naturally form a triangular lattice structure within the planar array, allowing for simulation of spin frustration using our generated antiferromagnetic couplings. We report progress toward simulating the ferromagnetic/antiferromagnetic transverse quantum Ising Hamiltonians in this large ensemble. We also report spectroscopy, thermometry, and sensitive displacement detection (˜100 pm) via entanglement of valence spin and drumhead oscillations.06/2012;  [Show abstract] [Hide abstract]
ABSTRACT: The presence of longrange quantum spin correlations underlies a variety of physical phenomena in condensedmatter systems, potentially including hightemperature superconductivity. However, many properties of exotic, strongly correlated spin systems, such as spin liquids, have proved difficult to study, in part because calculations involving Nbody entanglement become intractable for as few as N ≈ 30 particles. Feynman predicted that a quantum simulatora specialpurpose 'analogue' processor built using quantum bits (qubits)would be inherently suited to solving such problems. In the context of quantum magnetism, a number of experiments have demonstrated the feasibility of this approach, but simulations allowing controlled, tunable interactions between spins localized on two or threedimensional lattices of more than a few tens of qubits have yet to be demonstrated, in part because of the technical challenge of realizing largescale qubit arrays. Here we demonstrate a variablerange Isingtype spinspin interaction, J(i,j), on a naturally occurring, twodimensional triangular crystal lattice of hundreds of spinhalf particles (beryllium ions stored in a Penning trap). This is a computationally relevant scale more than an order of magnitude larger than previous experiments. We show that a spindependent optical dipole force can produce an antiferromagnetic interaction J(i,j) proportional variant d(a)(i,j), where 0 ≤ a ≤ 3 and d(i,j) is the distance between spin pairs. These power laws correspond physically to infiniterange (a = 0), Coulomblike (a = 1), monopoledipole (a = 2) and dipoledipole (a = 3) couplings. Experimentally, we demonstrate excellent agreement with a theory for 0.05 ≲ a ≲ 1.4. This demonstration, coupled with the high spin count, excellent quantum control and low technical complexity of the Penning trap, brings within reach the simulation of otherwise computationally intractable problems in quantum magnetism.Nature 04/2012; 484(7395):48992. · 38.60 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We demonstrate spectroscopy and thermometry of individual motional modes in a mesoscopic 2D ion array using entanglementinduced decoherence as a method of transduction. Our system is a $\sim$400 $\mu$mdiameter planar crystal of several hundred $^9$Be$^+$ ions exhibiting complex drumhead modes in the confining potential of a Penning trap. Exploiting precise control over the $^9$Be$^+$ valence electron spins, we apply a homogeneous spindependent optical dipole force to excite arbitrary transverse modes with an effective wavelength approaching the interparticle spacing ($\sim$20 \nolinebreak$\mu$m). Centerofmass displacements below 1 nm are detected via entanglement of spin and motional degrees of freedom.Physical Review Letters 01/2012; 108(21). · 7.73 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Building robust instruments capable of making interferometric measurements with precision beyond the standard quantum limit remains an important goal in many metrology laboratories. We describe here the basic concepts underlying spin squeezing experiments that allow one to surpass this limit. In priniciple it is possible to reach the socalled Heisenberg limit, which constitutes an improvement in precision by a factor $\sqrt{N}$, where $N$ is the number of particles on which the measurement is carried out. In particular, we focus on recent progress toward implementing spin squeezing with a cloud of beryllium ions in a Penning ion trap, via the geometric phase gate used more commonly for performing twoqubit entangling operations in quantum computing experiments.11/2011;  [Show abstract] [Hide abstract]
ABSTRACT: We report on a new technique for exciting and sensitively detecting plasma modes in small, cold nonneutral ion plasmas. The technique uses an optical dipole force generated from laser beams to excite plasma modes. By making the force spin dependent (i.e. depend on the internal state of the atomic ion) very small mode excitations (< 100 nm) can be detected through spinmotion entanglement. Even when the optical dipole force is homogeneous throughout the plasma, short wavelength modes on the order of the interparticle spacing can in principle be excited and detected through the spin dependence of the force. We use this technique to study the drumhead modes of single plane triangular arrays of a few hundred Be^+ ions. Spindependent mode excitation is interesting in this system because it provides a means of engineering an Ising interaction on a 2D triangular lattice.ootnotetextPorras and Cirac, PRL 92, 207901 (2004) For the case of an antiferromagnetic interaction, this system exhibits spin frustration on a scale that is at present computationally intractable.11/2011;  [Show abstract] [Hide abstract]
ABSTRACT: We report an experimental determination of the diamagnetic correction to the {sup 9}Be{sup +} ground state hyperfine constant A. We measured A = 625 008 837.371(11) Hz at a magnetic field B of 4.4609 T. Comparison with previous results, obtained at lower values of B (0.68 T and 0.82 T), yields the diamagnetic shift coefficient k = 2.63(18)x10{sup 11} T{sup 2}, where A(B)=A{sub 0}(1+kB{sup 2}). The zerofield hyperfine constant A{sub 0} is determined to be 625 008 837.044(12) Hz. The gfactor ratio g{sub I}{sup '}/g{sub J} is determined to be 2.134 779 852 7(10)x10{sup 4}, which is equal to the value measured at lower B to within experimental error. Upper limits are placed on some other corrections to the BreitRabi formula. The measured value of k agrees with theoretical estimates.Physical Review A 07/2011; 84(1). · 3.04 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Dynamical decoupling is a promising technique for fighting the unwanted effects of decoherence in the context of quantum information. Decoupling techniques span two extremes from pulsed spinecho sequences to optimized, continuous amplitude and phase modulation allowing arbitrary rotations on the Bloch sphere. On the one hand spinecho techniques have the advantage of simplicity, while on the other optimized continuous modulation is expected to achieve better performance results at the cost complexity. That complexity exists both in the implementation and the modulation design, which either requires intimate knowledge of the relevant noise environment for numerical optimization or experimental optimization through feedback. Rotary echos represent an intermediate approach which have the advantage of continuous averaging of dephasing noise and pulsed compensation of fluctuations in the control field amplitude. Here we consider a classical dephasing noise environment and compare the performance of rotary echos to both pulsed and optimized continuous control decoupling techniques.06/2011;  [Show abstract] [Hide abstract]
ABSTRACT: Experimental progress in the fields of atomic and molecular physics has allowed exquisite control over ensembles of cold and ultracold ions, neutral atoms, and polar molecules. A number of theoretical proposals have been put forward concerning direct simulation of quantum Hamiltonians in these systems. We report progress toward simulation of the transverse Ising model in a twodimensional Coulomb crystal of ˜100 ^9Be^+ ions confined within a Penning trap. Coupling between ions is controlled via optical dipole forces, thereby facilitating a wide range of interparticle interactions including infiniterange and nearestneighbor coupling. Furthermore, the triangular lattice structure readily obtained within the planar Coulomb crystal allows for simulation of spin frustration in an antiferromagnetic system. Given our large ensembles of trapped ^9Be^+, it may be possible to perform quantum simulations that are currently intractable with classical computers.06/2011;  [Show abstract] [Hide abstract]
ABSTRACT: We report phasecoherent Doppler detection of optical dipole forces using large ion crystals in a Penning trap. The technique is based on laser Doppler velocimetry using a cycling transition in 9Be+ near 313 nm and the centerofmass (COM) ion motional mode. The optical dipole force is tuned to excite the COM mode, and measurements of photon arrival times synchronized with the excitation potential show oscillations with a period commensurate with the COM motional frequency. Experimental results compare well with a quantitative model for a driven harmonic oscillator. This technique permits characterization of motional modes in ion crystals; the measurement of both frequency and phase information relative to the driving force is a key enabling capabilitycomparable to lockin detection  providing access to a parameter that is typically not available in timeaveraged measurements. This additional information facilitates discrimination of nearly degenerate motional modes.Optics Express 05/2011; 19(11):1030416. · 3.55 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: In the science of measurement, increasing the sensitivity to the quantity being measured while minimizing the susceptibility to noise is a challenge. A technique demonstrated with a single electron spin may help to tackle it. See Letter p.61Nature 05/2011; 473(7345):3940. · 38.60 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A scalable, multiplexed ion trap for quantum information processing is fabricated and tested. The trap design and fabrication process are optimized for scalability to small trap size and large numbers of interconnected traps, and for integration of control electronics and optics. Multiple traps with similar designs are tested with Cd+, Mg+, and Sr+ ions at room temperature and with Sr+ at 6 K, with respective ion lifetimes of 90 s, 300 +/ 30 s, 56 +/ 6 s, and 4.5 +/ 1.1 hours. The motional heating rate for Mg+ at room temperature and a trap frequency of 1.6 MHz is measured to be 7 +/ 3 quanta per millisecond. For Sr+ at 6 K and 540 kHz the heating rate is measured to be 220 +/ 30 quanta per second.Quantum Information & Computation. 01/2011; 9:901919.  [Show abstract] [Hide abstract]
ABSTRACT: We present theoretical and experimental studies of the decoherence of hyperfine groundstate superpositions due to elastic Rayleigh scattering of light off resonant with higher lying excited states. We demonstrate that under appropriate conditions, elastic Rayleigh scattering can be the dominant source of decoherence, contrary to previous discussions in the literature. We show that the elasticscattering decoherence rate of a twolevel system is given by the square of the difference between the elasticscattering amplitudes for the two levels, and that for certain detunings of the light, the amplitudes can interfere constructively even when the elasticscattering rates from the two levels are equal. We confirm this prediction through calculations and measurements of the total decoherence rate for a superposition of the valence electron spin levels in the ground state of 9Be+ in a 4.5 T magnetic field.Physical Review Letters 11/2010; 105(20):200401. · 7.73 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The ability to detect extremely small forces and nanoscale displacements is vital for disciplines such as precision spinresonance imaging, microscopy, and tests of fundamental physical phenomena. Current forcedetection sensitivity limits have surpassed 1 aN Hz(1/2) (refs 6,7) through coupling of nanomechanical resonators to a variety of physical readout systems. Here, we demonstrate that crystals of trapped atomic ions behave as nanoscale mechanical oscillators and may form the core of exquisitely sensitive force and displacement detectors. We report the detection of forces with a sensitivity of 390 +/ 150 yN Hz(1/2), which is more than three orders of magnitude better than existing reports using nanofabricated devices(7), and discriminate ion displacements of approximately 18 nm. Our technique is based on the excitation of tunable normal motional modes in an ion trap and detection through phasecoherent Doppler velocimetry, and should ultimately allow force detection with a sensitivity better than 1 yN Hz(1/2) (ref. 16). Trappedionbased sensors could enable scientists to explore new regimes in materials science where augmented force, field and displacement sensitivity may be traded against reduced spatial resolution.Nature Nanotechnology 09/2010; 5(9):64650. · 31.17 Impact Factor
Publication Stats
4k  Citations  
565.60  Total Impact Points  
Top Journals
 Physical Review A (20)
 Physical Review Letters (11)
 Physical Review Letters (11)
 Hyperfine Interactions (4)
 Physics of Plasmas (4)
Institutions

1991–2014

National Institute of Standards and Technology
 Time and Frequency Division
Maryland, United States


2010

University of Sydney
 School of Physics
Sydney, New South Wales, Australia


2002–2003

University of Delaware
 Department of Physics and Astronomy
Newark, DE, United States


1999

Brigham Young University  Hawaii
Kahuku, Hawaii, United States
