arXiv subjects

M. G. Boshier

Publications and source records attributed to M. G. Boshier.

12 recordsLinked to original sources

arXiv2015

Integrated coherent matter wave circuits

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 launched into waveguides where they can be switched, divided, recombined, and detected as they propagate. Applications of such circuits include guided atom interferometers, atomtronic circuits, and precisely controlled delivery of atoms. Here we report experiments demonstrating integrated 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 electric 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 are the basic elements that are needed to engineer arbitrarily complex matter wave circuitry.

cond-mat.quant-gas↗

arXiv2014

Shortcuts to adiabaticity in a time-dependent box

A method is proposed to drive an ultrafast non-adiabatic dynamics of an ultracold gas trapped in a 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 analogous to those used in soliton control. The method is extended to a broad family of 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.

cond-mat.quant-gas↗

arXiv2013

Experimental realization of Josephson junctions for an Atom SQUID

We report the creation of a pair of Josephson junctions on a toroidal dilute gas Bose-Einstein condensate (BEC), a configuration that is the cold atom analog of the well-known dc superconducting quantum interference device (SQUID). We observe Josephson effects, measure the critical current of the junctions, and find dynamic behavior that is in good agreement with the simple Josephson equations for a tunnel junction with the ideal sinusoidal current-phase relation expected for the parameters of the experiment. 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.

cond-mat.quant-gas↗

arXiv2013

Creation of matter wave Bessel beams

Bessel beams are plane waves with amplitude profiles described by Bessel functions. They are important because of their property of limited diffraction and their capacity to 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 to generate matter wave Bessel beams with a Painted Potential can be viewed as a form of wavefunction engineering which might be extended to implement arbitrary cold atom matter wave holography.

cond-mat.quant-gas↗

arXiv2013

Single impurities in a Bose-Einstein condensate can make two polaron flavors

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.

cond-mat.quant-gas↗

arXiv2009

Experimental demonstration of painting arbitrary and dynamic potentials for Bose-Einstein condensates

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.

cond-mat.other↗

arXiv2008

Lifetime of the A(v'=0) state and Franck-Condon factor of the A-X(0-0) transition of CaF measured by the saturation of laser-induced fluorescence

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.

physics.atom-ph↗

arXiv2003

Adaptive reflection and focusing of Bose-Einstein condensates

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.

cond-mat.soft↗

arXiv2001

Destabilization of dark states and optical spectroscopy in Zeeman-degenerate atomic systems

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.

quant-ph↗

arXiv2001

An adaptive inelastic magnetic mirror for Bose-Einstein condensates

We report the reflection and focussing of a Bose-Einstein condensate by a new pulsed magnetic mirror. The mirror is adaptive, inelastic, and of extremely high optical quality. The deviations from specularity are less than 0.5 mrad rms, making this the best atomic mirror demonstrated to date. We have also used the mirror to realize the analog of a beam-expander, producing an ultra-cold collimated fountain of matter waves

cond-mat.soft↗

arXiv2000

A two wire waveguide and interferometer for cold atoms

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 sub-micron scale. These include controlled and coherent splitting of the wavefunction as well as cooling, trapping and guiding. In particular we discuss a novel microscopic atom interferometer with the potential to be exceedingly sensitive.

physics.atom-ph↗

arXiv1999

Measurement of the 1s-2s energy interval in muonium

The 1s-2s interval has been measured in the muonium ({$μ^+e^-$}) atom by Doppler-free two-photon laser spectroscopy. The frequency separation of the states was determined to be 2 455 528 941.0(9.8) MHz in good agreement with quantum electrodynamics. The muon-electron mass ratio can be extracted and is found to be 206.768 38(17). The result may be interpreted as measurement of the muon-electron charge ratio as $-1- 1.1(2.1)\cdot 10^{-9}$.

hep-ex↗