Atomic Mirror Research Articles

A high-reflectivity atom-focusing mirror stable at room temperature

It is shown that the Pb(√3×√3)R30/Si(111) ordered layer is an excellent mirror for neutral He atoms. It focuses more than 15% of the incoming He atoms into the specular peak, and is stable up to 450 K. Moreover, the reflectivity remains almost unchanged in a time scale of several weeks in ultrahigh vacuum. As a consequence, this system is a very good candidate to be used as a mirror in the next generation of the scanning helium atom microscope.

Intrinsic cavity QED and emergent quasinormal modes for a single photon

We propose a special cavity design that is constructed by terminating a one-dimensional waveguide with a perfect mirror at one end and doping a two-level atom at the other. We show that this atom plays the intrinsic role of a semitransparent mirror for single-photon transports such that quasinormal modes emerge spontaneously in the cavity system. This atomic mirror has its reflection coefficient tunable through its level spacing and its coupling to the cavity field, for which the cavity system can be regarded as a two-end resonator with a continuously tunable leakage. The overall investigation predicts the existence of quasibound states in the waveguide continuum. Solid-state implementations based on a dc-superconducting quantum interference device circuit and a defected line resonator embedded in a photonic crystal are illustrated to show the experimental accessibility of the generic model.

Controlled acceleration of a modulated quantum bouncer

Cold atoms bouncing on a modulated atomic mirror exhibit dynamic localization and acceleration subject to modulated strength. We explain the characteristics of acceleration using accelerated mapping and define control parameters. We show that the effective Planck’s constant plays a vital role in limiting overall linear growth of accelerated atoms with time. For large values of the effective Planck’s constant, the atomic quantum accelerated is seized if the localization window overlaps the accelerated window.

Acceleration of Material Waves in Fermi Accelerator

Cold Atoms bouncing on modulated atomic mirror exhibits acceleration and dynamical localization subject to modulated strength. We explain characteristics of acceleration and define control parameters in terms of effective Planck′s constant. We show that the effective Planck′s constant plays a vital role in limiting classical‐like overall linear growth of the variance of accelerated atoms with time. For large values of the effective Planck′s constant the atomic quantum acceleration is seized as localization window overlaps the accelerated window.

Flexible Optical Dipole Mirror for Cold Atoms

A flexible and relatively simple and cheap optical dipole mirror for cold rubidium atoms from magneto-optical trap is described, being a very modern and efficient tool for atomic physicists. Emphasis is put on physical processes responsible for the mirror parameters and their optimization. Promising perspectives are provided for evanescent wave properties investigation and atom–surface interaction measurements.

Isotopic separation of silicon atoms by atomic mirror

The isotopic separation of silicon by an atomic mirror has been demonstrated numerically, by which each silicon isotope encounters a different dipole force depending on the frequency detuning due to the different frequencies resonant to the silicon isotopes. It was found that the atomic mirror, which comprised a wave guide structure designed for the enhancement of evanescent waves at 252 nm, allows us to discriminate 29Si from the other isotopes.

A Quantum‐Stabilized Mirror for Atoms

Because of the lowenergies used (ca. 100meV), neutral He atoms probe thetop-most surface layer of any material in an inert, completelynondestructive manner. This means that a scanning heliumatommicroscopeusingafocusedbeamofHeatomsasimagingprobe would be a unique tool for reflection or transmissionmicroscopy, with a potential lateral resolution of ca. 50nm. Itcould be used to investigate insulating glass surfaces, delicatebiological materials, and fragile samples, which are difficult toexamine by other methods because of sample charging orelectron excitation effects. The practical realization of such amicroscoperequiresthedevelopmentofamirrorthatisabletofocus a beam of low-energy He atoms into a small spot on thesampletobeexamined.HolstandAllison

Controlling Chaotic Behavior in a Bose–Einstein Condensate with Linear Feedback

The spatial structure of a Bose–Einstein condensate (BEC) loaded into an optical lattice potential is investigated and the spatially chaotic distributions of the condensates are revealed. A method of chaos control with linear feedback is presented in this paper. By using the method, we propose a scheme of controlling chaotic behavior in a BEC with atomic mirrors. The results of the computer simulation show that controlling the chaos into the stable states could be realized by adjusting the coefficient of feedback only if the maximum Lyapunov exponent of the system is negative.

Atomic reflection off conductor walls as a tool in cold atom traps

We explain why a system of cold 85Rb atoms at temperatures of the order T≈ 7.78× 10-5 K and below, but not too low to lie in the quantum reflection regime, should be automatically repelled from the surface of a conductor without the need of an evanescent field, as in a typical atom mirror, to counteract the van der Waals attraction. The repulsive potential arises naturally outside the conductor and is effective at distances from the conductor surface of about 400 nm, intermediate between the van der Waals and the Casimir-Polder regions of variation. We propose that such a field-free reflection capability should be useful as a component in cold atom traps. It should be practically free of undesirable field fluctuations and would be operative at distances for which surface roughness, dissipative effects and other finite conductivity effects should be negligibly small.

COHERENT ACCELERATION OF MATERIAL WAVE PACKETS

We study the quantum dynamics of a material wave packet bouncing off a modulated atomic mirror in the presence of a gravitational field. We find the occurrence of coherent accelerated dynamics for atoms. The acceleration takes place for certain initial phase space data and within specific windows of modulation strengths. The realization of the proposed acceleration scheme is within the range of present day experimental possibilities.

Atom trapping with a thin magnetic film

We have created a $^{87}$Rb Bose-Einstein condensate in a magnetic trapping potential produced by a hard disk platter written with a periodic pattern. Cold atoms were loaded from an optical dipole trap and then cooled to BEC on the surface with radiofrequency evaporation. Fragmentation of the atomic cloud due to imperfections in the magnetic structure was observed at distances closer than 40 $\mu$m from the surface. Attempts to use the disk as an atom mirror showed dispersive effects after reflection.

Fractional adiabatic passage in two-level systems: Mirrors and beam splitters for atomic interferometry

Atom interferometers require atom mirrors and beam splitters that can maintain high fidelity even when experimental parameters vary from the ideal. We address the use of chirped laser pulses to provide such elements via rapid adiabatic passage, and present a prescription for practical pulses that offer controlled adiabaticity throughout. Full- and half-adiabatic pulses, providing mirrors and beam splitters, respectively, are derived, and the latter examined for robustness and suitability for experimental implementations.

Coherent acceleration of material wave packets in modulated optical fields

We study the quantum dynamics of a material wave packet bouncing off a modulated atomic mirror in the presence of a gravitational field. We find the occurrence of coherent accelerated dynamics for atoms beyond the familiar regime of dynamical localization. The acceleration takes place for certain initial phase-space data and within specific windows of modulation strengths. The realization of the proposed acceleration scheme is within the range of present-day experimental possibilities.

Coherent Slowing of a Supersonic Beam with an Atomic Paddle

We report the slowing of a supersonic beam by elastic reflection from a receding atomic mirror. We use a pulsed supersonic nozzle to generate a 511+/-9 m/s beam of helium that we slow by reflection from a Si(111)-H(1x1) crystal placed on the tip of a spinning rotor. We were able to reduce the velocity of helium by 246 m/s and show that the temperature of the slowed beam is lower than 250 mK in the comoving frame.

Experiments on the reflection of cold atoms from magnetic thin films

We report the results from a series of experiments in which ferromagnetic thin films were used as atom mirrors for laser-cooled rubidium atoms released from a magneto-optical trap. The thin films were made of cobalt and lanthanum calcium manganite (LCMO) with thicknesses between 20 and 300 nm. The magnetic domains in these thin films have a periodic structure where the spatial period is of the order of the thickness of the film, and the field decays exponentially above the film over a length scale comparable to the domain size. Thus, the neutral atoms reflect off these films from distances comparable to the thickness of the film, resulting in modification of the reflectivity due to the competition between the repulsive magnetic force and the attractive short-range forces such as van der Waals and Casimir forces. The smoothness of the atom mirror is also modified due to the proximity of the magnetic domains. The reflectivity is sensitive to the domain structure and size, which can be modified in LCMO by applying a modest external magnetic field. In this paper, we discuss the evaluation of the thin films as magnetic mirrors for atom optics, and the measurement of the van der Waals force with an accuracy of about 15%, using cobalt thin films. We also discuss some preliminary results on the temperature-dependent reflectivity for atoms near the ferromagnetic transition at 250 K in the LCMO film, and on the domain dynamics and relaxation.

Controlling the Motion of Silicon Isotopes with Atomic Mirror

Controlling the motion of silicon isotopes with an atomic mirror which is comprised of dielectric dual layers is numerically demonstrated under the realistic condition. The performance of the atomic mirror depends on the power and the effective detune frequency of the deep-ultraviolet light source which is enhanced in the dielectric waveguide layer. Taking advantage of these features and the frequency separation in isotopes, we can control silicon isotopes, furthermore, nuclear spin with the atomic mirror.

Si(1 1 1)–H(1 × 1): A mirror for atoms characterized by AFM, STM, He and H 2 diffraction

AFM, STM and diffraction of He and H 2 have been used to assess Si(1 1 1)–H(1 × 1) surfaces for their potential as mirrors for matter-waves. The H-passivated samples are produced by wet-chemical methods and delivered to a different laboratory for diffraction measurements. We show that the surface is flat and homogenous over lateral scales of microns and that absolute He and H 2 reflectivities of the order of ∼3% are obtained, even after 20 h storage under Ar and several days’ storage in UHV. These characteristics allow the use of Si(1 1 1)–H(1 × 1) as a highly reflective mirror for atoms and molecules, with application in a future He microscope or focused hydrogen nano-lithography system.

Normal-Incidence Electrostatic Rydberg Atom Mirror

A Rydberg atom mirror has been designed and its operational principle tested experimentally. A supersonic expansion containing H atoms moving with a velocity of 720 m/s initially propagates toward a quadrupolar electrostatic mirror. The H atoms are then photoexcited to n=27 Rydberg states with a positive Stark shift and move in a rapidly increasing electric field. The H atom beam is stopped in 4.8 micros, only 1.9 mm away from the photoexcitation spot, and is then reflected back. The reflection process is monitored by pulsed field ionization and imaging.

Single-atom mirror for one-dimensional atomic lattice gases

We propose a scheme utilizing quantum interference to control the transport of atoms in a one-dimensional optical lattice by a single impurity atom. The two internal state of the impurity represent a spin-$1∕2$ (qubit), which in one spin state is perfectly transparent to the lattice gas, and in the other spin state acts as a single atom mirror, confining the lattice gas. This allows one to ``amplify'' the state of the qubit, and provides a single-shot quantum nondemolition measurement of the state of the qubit. We derive exact analytical expression for the scattering of a single atom by the impurity, and give approximate expressions for the dynamics of a gas of many interacting bosonic or fermionic atoms.

Recurrence tracking microscope

In order to probe nanostructures on a surface we present a microscope based on the quantum recurrence phenomena. A cloud of atoms bounces off an atomic mirror connected to a cantilever and exhibits quantum recurrences. The times at which the recurrences occur depend on the initial height of the bouncing atoms above the atomic mirror, and vary following the structures on the surface under investigation. The microscope has inherent advantages over existing techniques of scanning tunneling microscope and atomic force microscope. Presently available experimental technology makes it possible to develop the device in the laboratory.