Guided Matter Wave Research Articles

Guided matter wave inertial sensing in a miniature physics package

We describe an ultra-compact (∼10 cm3 physics package) inertial sensor based on atomic matter waves that are guided within an optical lattice during almost the entire interferometer cycle. We demonstrate a large momentum transfer of up to 8 ℏk photon momentum with a combination of Bragg pulses and Bloch oscillations with scalability to larger numbers of photons. Between momentum transfer steps, we maintain the atoms in a co-moving optical lattice waveguide so that the atoms are in free space only during the Bragg pulses. Our guided matter wave approach paves the way for atomic inertial sensing in dynamic environments in which untrapped atoms would otherwise quickly collide with the walls of a miniature chamber.

Matter-wave scattering on an amplitude-modulated optical lattice

We experimentally study the scattering of guided matter waves on an amplitude-modulated optical lattice. We observe different types of frequency-dependent dips in the asymptotic output density distribution. Their positions are compared quantitatively with numerical simulations. A semiclassical model that combines local Floquet-Bloch bands analysis and Landau-Zener transitions provides a simple picture of the observed phenomena in terms of elementary Floquet photon absorption-emission processes and envelope-induced reflections. Finally, we propose and demonstrate the use of this technique with a bichromatic modulation to design a tunable subrecoil velocity filter. Such a filter can be transposed to all species since it does not rely on a specific internal level configuration of the atoms.

Realization of a Distributed Bragg Reflector for Propagating Guided Matter Waves

We report on the experimental study of a Bragg reflector for guided, propagating Bose-Einstein condensates. A one-dimensional attractive optical lattice of finite length created by red-detuned laser beams selectively reflects some velocity components of the incident matter wave packet. We find quantitative agreement between the experimental data and one-dimensional numerical simulations and show that the Gaussian envelope of the optical lattice has a major influence on the properties of the reflector. In particular, it gives rise to multiple reflections of the wave packet between two symmetric locations where Bragg reflection occurs. Our results are a further step towards integrated atom-optics setups for quasi-cw matter waves.

Planar microwave structures for electron guiding

We present microwave electrode structures suited for guiding electrons propagating in a purely electric, alternating quadrupole field. In a first experiment using a standing wave on an electrically short structure, we previously demonstrated the general concept of electron confinement in microwave fields. Here, we discuss the extension to electrically long structures supporting travelling microwave excitations. This requires a modal decomposition of the voltage patterns on the multiconductor transmission line formed by the electrodes. We show that the use of a general five-wire structure leads to the distortion of the guiding potential upon propagation due to differing modal propagation constants. This can be avoided by implementing a coupled microstrip configuration with elevated signal electrodes. With structures like these, complex geometries connecting different beam manipulation elements can be realized, enabling new forms of electron experiments with guided matter waves.

Observation of atomic speckle and Hanbury Brown–Twiss correlations in guided matter waves

Speckle patterns produced by multiple independent light sources are a manifestation of the coherence of the light field. Second-order correlations exhibited in phenomena such as photon bunching, termed the Hanbury Brown-Twiss effect, are a measure of quantum coherence. Here we observe for the first time atomic speckle produced by atoms transmitted through an optical waveguide, and link this to second-order correlations of the atomic arrival times. We show that multimode matter-wave guiding, which is directly analogous to multimode light guiding in optical fibres, produces a speckled transverse intensity pattern and atom bunching, whereas single-mode guiding of atoms that are output-coupled from a Bose-Einstein condensate yields a smooth intensity profile and a second-order correlation value of unity. Both first- and second-order coherence are important for applications requiring a fully coherent atomic source, such as squeezed-atom interferometry.

Observation of the first excited transverse mode in guided matter waves

In direct analogy to the textbook example of light guided in a few-mode fiber (FMF), we report the observation of the first excited mode of an optically guided atomic beam. We selectively excite the atomic analog of the LP₀₁ optical mode by controlling the energy distribution of ultracold atoms loaded into the guide, resulting in a modal structure dominated by a 47(2)% population in the first excited transverse mode. The ability to guide lower-order modes has been essential to demonstrating optical effects such as multimode interferometry, slow light, and entanglement, and an atomic analog to a FMF may lead to similarly useful applications.

Efficient guiding of cold atoms through a photonic band gap fiber

We demonstrate the first guiding of cold atoms through a 88 mm long piece of photonic band gap fiber. The guiding potential is created by a far-off resonance dipole trap propagating inside the fiber with a hollow core of 12 μm. We load the fiber from a dark spot 85Rb magneto-optical trap and observe a peak flux of more than 105 atoms s−1 at a velocity of 1.5 m s−1. With an additional reservoir optical dipole trap, a constant atomic flux of 1.5 × 104 atoms s−1 is sustained for more than 150 ms. These results open up interesting possibilities to study nonlinear light–matter interaction in a nearly one-dimensional geometry and pave the way for guided matter wave interferometry.

Interaction of a propagating guided matter wave with a localized potential

We provide a theoretical framework to describe the interaction of a propagating guided matter wave with a localized potential in terms of quantum scattering in a confined environment. We analyze how this scattering correlates the longitudinal and transverse degrees of freedom, and work out analytically the output state under the Born approximation using a Gaussian localized potential. In this limit, it is possible to engineer the potential and achieve coherent control of the output channels. The robustness of this approximation is studied by comparing the stationary scattering theory to numerical simulations involving incident wave packets. It remains valid in a domain of weak localized potential that is achievable experimentally. We deduce a possible method to determine the longitudinal coherence length of a guided atom laser. Then, we detail the non-perturbative regime of the interaction of the guided matter wave with the localized potential using a coupled channel approach. This approach is worked out explicitly with a square potential. It yields new non-perturbative effects such as the occurrence of confinement-induced resonances. The perspectives opened up by this work for experiments are discussed.

Transverse mode imaging of guided matter waves

Ultracold atoms whose de Broglie wavelength is of the same order as an extended confining potential can experience waveguiding along the potential. When the transverse kinetic energy of the atoms is sufficiently low, they can be guided in the lowest order mode of the confining potential by analogy with light guided by a single mode optical fiber. We have obtained the first images of the transverse mode structure of guided matter waves in a confining potential with up to $65%$ of atoms in the lowest order mode. The coherence of the guided atomic de Broglie waves is demonstrated by the diffraction pattern produced when incident upon a two dimensional periodic structure. Such coherent waveguides will be important atom optic components in devices with applications such as atom holography and atom interferometry.

Multimode interferometer for guided matter waves.

Atoms can be trapped and guided with electromagnetic fields, using nanofabricated structures. We describe the fundamental features of an interferometer for guided matter waves, built of two combined Y-shaped beam splitters. We find that such a device is expected to exhibit high contrast fringes even in a multimode regime, analogous to a white light interferometer.

Bound states of guided matter waves: An atom and a charged wire.

We argue that it is possible to bind a neutral atom in stable orbits around a wire charged by a time-varying sinusoidal voltage. Both classical and quantum-mechanical theories for this system are discussed, and a unified approach to the Kapitza picture of effective potentials associated with high-frequency fields is presented. It appears that cavities and waveguides for neutral-atomic-matter waves may be fashioned from these considerations.