[Show abstract][Hide abstract] ABSTRACT: An integrated coherent matter wave circuit is a single device, analogous to
an integrated optical circuit, in which coherent de Broglie waves are created
and then propagate freely in waveguides where they can be switched, divided,
recombined, and detected. Applications of such circuits include guided atom
interferometers, atomtronic circuits, and precisely controlled delivery of
atoms. Here we report experiments demonstrating integrated matter wave circuits
for guided coherent matter waves. The circuit elements are created with the
painted potential technique, a form of time-averaged optical dipole potential
in which a rapidly-moving, tightly-focused laser beam exerts forces on atoms
through their electrical polarizability. The source of coherent matter waves is
a Bose-Einstein condensate (BEC). We launch BECs into painted waveguides that
guide them around bends and form switches, phase coherent beamsplitters, and
closed circuits. These developments open the door to creating arbitrary and
dynamic coherent matter wave circuits.
New Journal of Physics 10/2014; 17(9). DOI:10.1088/1367-2630/17/9/092002 · 3.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Radio-frequency (RF) atomic magnetometers (AMs) can be used in many applications, such as magnetic resonance imaging and nuclear quadrupole resonance. High-density AMs provide both superior sensitivity and large bandwidth. Previously, high-density potassium AMs were demonstrated, but these magnetometers have various disadvantages, such as high-temperature of operation and bulky design. We demonstrate a rubidium-87 RF AM with 5 fT/Hz1/2 sensitivity (3 fT Hz1/2 probe noise), which is comparable to that of the best potassium magnetometers. Our magnetometer also features a simple fiber-optic design, providing maximum flexibility for magnetic-field measurements.
[Show abstract][Hide abstract] ABSTRACT: Bessel beams are plane waves with amplitude profiles described by Bessel functions. They are important because they propagate ‘diffraction-free’ and because they can carry orbital angular momentum. Here we report the creation of a Bessel beam of de Broglie matter waves. The Bessel beam is produced by the free evolution of a thin toroidal atomic Bose-Einstein condensate (BEC) which has been set into rotational motion. By attempting to stir it at different rotation rates, we show that the toroidal BEC can only be made to rotate at discrete, equally spaced frequencies, demonstrating that circulation is quantized in atomic BECs. The method used here can be viewed as a form of wavefunction engineering which might be developed to implement cold atom matter wave holography.
New Journal of Physics 12/2013; 16(1). DOI:10.1088/1367-2630/16/1/013046 · 3.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We show that repulsive neutral-atom impurities in a dilute gas Bose-Einstein condensate (BEC) can self-localize in bubble polaron states formally analogous to electron bubbles in helium. The BEC is then the first impurity host medium known to exhibit both Landau-Pekar polaron states akin to that of self-localized electrons in a dielectric lattice and self-localized bubble polaron states. We find that the neutral BEC-impurity system is fully characterized by only two dimensionless coupling constants and that a single BEC impurity can be steered adiabatically from the Landau-Pekar to the bubble region. The adiabatic change is that of a crossover, not a transition.
Physical Review A 11/2013; 88(5). DOI:10.1103/PhysRevA.88.053610 · 2.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Non-zero curvature in a waveguide leads to the appearance of an attractive
quantum potential which crucially affects the dynamics in matter-wave circuits.
Using methods of supersymmetric quantum mechanics, pairs of bent waveguides are
found whose geometry-induced potentials share the same scattering properties.
As a result, reflectionless waveguides, dual to the straight waveguide, are
identified. Strictly isospectral waveguides are also found by modulating the
depth of the trapping potential. Numerical simulations are used to demonstrate
the efficiency of these approaches.
[Show abstract][Hide abstract] ABSTRACT: We report the creation of ideal Josephson junctions in a toroidal dilute gas
Bose-Einstein condensate (BEC). The demonstrated configuration of a pair of
junctions on a multiply-connected BEC is the cold atom analog of the well-known
dc Superconducting Quantum Inteference Device (SQUID). We measure the critical
current of the junctions, observe Josephson effects, and find dynamic behavior
that is in good agreement with the simple Josephson equations for an ideal
tunnel junction with a sinusoidal current-phase relation. The junctions and
toroidal trap are created with the Painted Potential, a time-averaged optical
dipole potential technique which will allow scaling to more complex BEC circuit
geometries than the single Atom-SQUID case reported here. Since rotation plays
the same role in the Atom SQUID as magnetic field does in the dc SQUID
magnetometer, the device has potential as a compact rotation sensor. It may
also be useful for creating macroscopic Schr\"odinger Cat states.
[Show abstract][Hide abstract] ABSTRACT: Polarons, self-localized composite objects formed by the interaction of a
single impurity particle with a host medium, are a paradigm of strong
interaction many-body physics. We show that dilute gas Bose-Einstein
condensates (BEC's) are the first medium known to self-localize the same
impurity particles both in a Landau-Pekar polaron state akin to that of
self-localized electrons in a dielectric lattice, and in a bubble state akin to
that of electron bubbles in helium. We also show that the BEC-impurity system
is fully characterized by just two dimensionless coupling constants, and that
it can be adiabatically steered from the Landau-Pekar regime to the bubble
regime in a smooth crossover trajectory.
[Show abstract][Hide abstract] ABSTRACT: A method is proposed to drive an ultrafast non-adiabatic dynamics of an ultracold gas trapped in a time-dependent box potential. The resulting state is free from spurious excitations associated with the breakdown of adiabaticity, and preserves the quantum correlations of the initial state up to a scaling factor. The process relies on the existence of an adiabatic invariant and the inversion of the dynamical self-similar scaling law dictated by it. Its physical implementation generally requires the use of an auxiliary expulsive potential. The method is extended to a broad family of interacting many-body systems. As illustrative examples we consider the ultrafast expansion of a Tonks-Girardeau gas and of Bose-Einstein condensates in different dimensions, where the method exhibits an excellent robustness against different regimes of interactions and the features of an experimentally realizable box potential.
[Show abstract][Hide abstract] ABSTRACT: Quantized circulation, one of the most important consequences of Bose-Einstein condensation, is fundamental to the understanding of superfluid phenomena. In a toroidal trap, Bose- condensed atoms should flow with a well defined winding number, which makes it an ideal system to demonstrate the quantized nature of circulation. We used a scanning laser beam to create a toroidal trap [1]. To rotate the atoms, a small potential barrier within the toroidal trap was rotated at a certain frequency and then the barrier was lowered to create a quantized flow state. The winding number of the flow was determined by the diameter of the central hole seen in a time of flight image of the condensate. The measurement showed diameters increasing stepwise with the stirring frequency. We observed flows with winding number up to 5. This is a clear demonstration of the quantization of the flow of atoms in a toroidal trap. Further study of critical velocity and metastability of flow of atoms will be very important in understanding the nature of superfluidity of atoms in a toroidal trap, especially in a 1D limit.[4pt] [1] K. Henderson, C. Ryu, C. MacCormick, and M. G. Boshier, New Journal of Physics 11, 043030 (2009).
[Show abstract][Hide abstract] ABSTRACT: We describe a method ootnotetextT. E. Wall et al., Phys. Rev. A 78, 062509 (2008) for determining the radiative decay properties of a molecule by studying the saturation of laser-induced fluorescence and the associated power broadening of spectral lines. The fluorescence saturates because the molecules decay to states that are not resonant with the laser. The amplitudes and widths of two hyperfine components of a spectral line are measured over a range of laser intensities and the results compared to a model of the laser-molecule interaction. Using this method we measure the lifetime of the A(v'=0) state of CaF to be tau=19.2±0.7 ns, and the Franck-Condon factor for the transition to the X(v=0) state to be Z=0.987-0.019^+0.013. In addition, our analysis provides a measure of the hyperfine interval in the lowest-lying state of A(v'=0), deltae=4.8±1.1 MHz. A Franck-Condon factor close to 1 opens the possiblity of implementing a cycling transition with a small number of additional repump frequencies. We discuss possible schemes of laser cooling CaF or other alkaline earth monofluorides.
[Show abstract][Hide abstract] ABSTRACT: There is a pressing need for robust and straightforward methods to create potentials for trapping Bose-Einstein condensates which are simultaneously dynamic, fully arbitrary, and sufficiently stable to not heat the ultracold gas. We show here how to accomplish these goals, using a rapidly-moving laser beam that "paints" a time-averaged optical dipole potential in which we create BECs in a variety of geometries, including toroids, ring lattices, and square lattices. Matter wave interference patterns confirm that the trapped gas is a condensate. As a simple illustration of dynamics, we show that the technique can transform a toroidal condensate into a ring lattice and back into a toroid. The technique is general and should work with any sufficiently polarizable low-energy particles. Comment: Minor text changes and three references added. This is the final version published in New Journal of Physics
New Journal of Physics 02/2009; 11(4). DOI:10.1088/1367-2630/11/4/043030 · 3.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We describe a method for determining the radiative decay properties of a
molecule by studying the saturation of laser-induced fluorescence and the
associated power broadening of spectral lines. The fluorescence saturates
because the molecules decay to states that are not resonant with the laser. The
amplitudes and widths of two hyperfine components of a spectral line are
measured over a range of laser intensities and the results compared to a model
of the laser-molecule interaction. Using this method we measure the lifetime of
the A(v'=0) state of CaF to be tau=19.2 \pm 0.7 ns, and the Franck-Condon
factor for the transition to the X(v=0) state to be Z=0.987 (+0.013 || -0.019).
In addition, our analysis provides a measure of the hyperfine interval in the
lowest-lying state of A(v'=0), Delta_e=4.8 \pm 1.1 MHz.
Physical Review A 12/2008; 78(6). DOI:10.1103/PhysRevA.78.062509 · 2.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report progress towards making a precise measurement of the 2S Lamb shift in singly-ionised helium by spectroscopy of the
2S-3S transition. The motivation for the experiment is discussed with reference to recent developments in the theory of quantum
electrodynamics (QED) and a description of the apparatus and techniques used is given.
[Show abstract][Hide abstract] ABSTRACT: This paper discusses some recent and ongoing experiments involving the application of laser spectroscopy to light hydrogenic atoms. Several theoretical groups have recently made substantial advances in the calculation of energy level corrections due to quantum electrodynamics, the theory most directly tested by these experiments. At the same time optical spectroscopy of hydrogen has reached the point where uncertainties due to strong interactions are an important limitation in the interpretation of measurements. This problem is much less severe in the case of the singly-ionised He+ ion, motivating laser spectroscopic measurements of Lamb shifts in that system. New experiments on muonium complement this work on more conventional atoms.
Physica Scripta 09/2006; 2000(T86):21. DOI:10.1238/Physica.Topical.086a00021 · 1.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Adjustable magnetic reflection and focusing of an 87Rb Bose–Einstein condensate was achieved using a particularly smooth mirror and a very straightforward apparatus. In this paper, we discuss a simple Thomas–Fermi model and a Monte Carlo method for analysing the bouncing. Both models are in close agreement with the observed condensate evolution. Additionally, the theory predicts very tight condensate focusing, and atomic matter-wave diffraction should be observable. The effect of mirror anharmonicities on the condensate focusing is investigated.
Journal of Physics B Atomic Molecular and Optical Physics 12/2003; 37(2):485. DOI:10.1088/0953-4075/37/2/015 · 1.98 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report adjustable magnetic `bouncing' and focusing of a dilute $^{87}$Rb Bose gas. Both the condensate production and manipulation are realised using a particularly straight-forward apparatus. The bouncing region is comprised of approximately concentric ellipsoidal magnetic equipotentials with a centre that can be adjusted vertically. We extend, and discuss the limitations of, simple Thomas-Fermi and Monte-Carlo theoretical models for the bouncing, which at present find close agreement with the condensate's evolution. Very strong focusing has been inferred and the observation of atomic matter-wave diffraction should be possible. Prospects look bright for applications in matter-wave atom-optics, due to the very smooth nature of the mirror.
[Show abstract][Hide abstract] ABSTRACT: We present a general discussion of the techniques of destabilizing dark states in laser-driven atoms with either a magnetic field or modulated laser polarization. We show that the photon scattering rate is maximized at a particular evolution rate of the dark state. We also find that the atomic resonance curve is significantly broadened when the evolution rate is far from this optimum value. These results are illustrated with detailed examples of destabilizing dark states in some commonly-trapped ions and supported by insights derived from numerical calculations and simple theoretical models. Comment: 14 pages, 10 figures
Physical Review A 11/2001; 65(3). DOI:10.1103/PhysRevA.65.033413 · 2.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Magnetic videotape is of great interest for trapping and guiding cold atomic vapors, but was hitherto considered unsuitable
for manipulating Bose–Einstein condensates (BEC) because of the presumed evolution of gas under vacuum. We have studied the
outgassing in vacuum of the most promising tape, Ampex 398 Betacam SP. We find that after cleaning in ethanol and baking for
200h at 100°C the magnetic patterns are undisturbed and the outgassing is remarkably small: 4×10-10Torr l s-1cm-2, due mostly to hydrogen. This makes the tape exceedingly attractive for manipulation of BEC.
Applied Physics B 06/2001; 73(1):51-54. DOI:10.1007/s003400100607 · 1.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report the reflection and focusing of a Bose-Einstein condensate by a pulsed magnetic mirror. The mirror is adaptive, inelastic, and has extremely high optical quality. Deviations from specularity are below 1 mrad rms - almost an order of magnitude better than other atomic mirrors. The mirror has been used to realize the atom-optical analog of a beam expander, producing an ultracold collimated fountain of matter waves. The results of these experiments are in good agreement with simple theoretical models.
Physical Review A 03/2001; 65(3). DOI:10.1103/PhysRevA.65.031601 · 2.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A versatile miniature de Broglie waveguide is formed by two parallel current-carrying wires in the presence of a uniform bias field. We derive a variety of analytical expressions to describe the guide and present a quantum theory to show that it offers a remarkable range of possibilities for atom manipulation on the submicron scale. These include controlled and coherent splitting of the wave function as well as cooling, trapping, and guiding. In particular, we discuss a novel microscopic atom interferometer with the potential to be exceedingly sensitive.