480 research outputs found
Tunable Whispering Gallery Mode Resonators for Cavity Quantum Electrodynamics
We theoretically study the properties of highly prolate shaped dielectric
microresonators. Such resonators sustain whispering gallery modes that exhibit
two spatially well separated regions with enhanced field strength. The field
per photon on the resonator surface is significantly higher than e.g. for
equatorial whispering gallery modes in microsphere resonators with a comparable
mode volume. At the same time, the frequency spacing of these modes is much
more favorable, so that a tuning range of several free spectral ranges should
be attainable. We discuss the possible application of such resonators for
cavity quantum electrodynamics experiments with neutral atoms and reveal
distinct advantages with respect to existing concepts.Comment: 4 pages, 3 figure
Ultra-sensitive surface absorption spectroscopy using sub-wavelength diameter optical fibers
The guided modes of sub-wavelength diameter air-clad optical fibers exhibit a
pronounced evanescent field. The absorption of particles on the fiber surface
is therefore readily detected via the fiber transmission. We show that the
resulting absorption for a given surface coverage can be orders of magnitude
higher than for conventional surface spectroscopy. As a demonstration, we
present measurements on sub-monolayers of 3,4,9,10-perylene-tetracarboxylic
dianhydride (PTCDA) molecules at ambient conditions, revealing the
agglomeration dynamics on a second to minutes timescale.Comment: 4 pages, Fig.1a corrected y-axis, p.2 minor text changes to
facilitate the understanding of eq. 4 and
Revealing quantum statistics with a pair of distant atoms
Quantum statistics have a profound impact on the properties of systems
composed of identical particles. In this Letter, we demonstrate that the
quantum statistics of a pair of identical massive particles can be probed by a
direct measurement of the exchange symmetry of their wave function even in
conditions where the particles always remain spatially well separated and thus
the exchange contribution to their interaction energy is negligible. We present
two protocols revealing the bosonic or fermionic nature of a pair of particles
and discuss possible implementations with a pair of trapped atoms or ions.Comment: 4+13 pages, v2 corresponds to the version published by PR
Cold Atom Physics Using Ultra-Thin Optical Fibers: Light-Induced Dipole Forces and Surface Interactions
The strong evanescent field around ultra-thin unclad optical fibers bears a
high potential for detecting, trapping, and manipulating cold atoms.
Introducing such a fiber into a cold atom cloud, we investigate the interaction
of a small number of cold Caesium atoms with the guided fiber mode and with the
fiber surface. Using high resolution spectroscopy, we observe and analyze
light-induced dipole forces, van der Waals interaction, and a significant
enhancement of the spontaneous emission rate of the atoms. The latter can be
assigned to the modification of the vacuum modes by the fiber.Comment: 4 pages, 4 figure
A neutral atom quantum register
We demonstrate the realization of a quantum register using a string of single
neutral atoms which are trapped in an optical dipole trap. The atoms are
selectively and coherently manipulated in a magnetic field gradient using
microwave radiation. Our addressing scheme operates with a high spatial
resolution and qubit rotations on individual atoms are performed with 99%
contrast. In a final read-out operation we analyze each individual atomic
state. Finally, we have measured the coherence time and identified the
predominant dephasing mechanism for our register.Comment: 4 pages, 4 figure
Precision preparation of strings of trapped neutral atoms
We have recently demonstrated the creation of regular strings of neutral
caesium atoms in a standing wave optical dipole trap using optical tweezers [Y.
Miroshnychenko et al., Nature, in press (2006)]. The rearrangement is realized
atom-by-atom, extracting an atom and re-inserting it at the desired position
with sub-micrometer resolution. We describe our experimental setup and present
detailed measurements as well as simple analytical models for the resolution of
the extraction process, for the precision of the insertion, and for heating
processes. We compare two different methods of insertion, one of which permits
the placement of two atoms into one optical micropotential. The theoretical
models largely explain our experimental results and allow us to identify the
main limiting factors for the precision and efficiency of the manipulations.
Strategies for future improvements are discussed.Comment: 25 pages, 18 figure
Adiabatic Quantum State Manipulation of Single Trapped Atoms
We use microwave induced adiabatic passages for selective spin flips within a
string of optically trapped individual neutral Cs atoms. We
position-dependently shift the atomic transition frequency with a magnetic
field gradient. To flip the spin of a selected atom, we optically measure its
position and sweep the microwave frequency across its respective resonance
frequency. We analyze the addressing resolution and the experimental robustness
of this scheme. Furthermore, we show that adiabatic spin flips can also be
induced with a fixed microwave frequency by deterministically transporting the
atoms across the position of resonance.Comment: 4 pages, 4 figure
Preprint arXiv: 2208.12253 Submitted on 25 Aug 2022
Sampling from a quantum distribution can be exponentially hard for classicalcomputers and yet could be performed efficiently by a noisy intermediate-scalequantum device. A prime example of a distribution that is hard to sample isgiven by the output states of a linear interferometer traversed by identical boson particles. Here, we propose a scheme to implement such a bosonsampling machine with ultracold atoms in a polarization-synthesized opticallattice. We experimentally demonstrate the basic building block of such amachine by revealing the Hong-Ou-Mandel interference of two bosonic atoms in afour-mode interferometer. To estimate the sampling rate for large , wedevelop a theoretical model based on a master equation. Our results show that aquantum advantage compared to today's best supercomputers can be reached with
Coherence properties and quantum state transportation in an optical conveyor belt
We have prepared and detected quantum coherences with long dephasing times at
the level of single trapped cesium atoms. Controlled transport by an "optical
conveyor belt" over macroscopic distances preserves the atomic coherence with
slight reduction of coherence time. The limiting dephasing effects are
experimentally identified and are of technical rather than fundamental nature.
We present an analytical model of the reversible and irreversible dephasing
mechanisms. Coherent quantum bit operations along with quantum state transport
open the route towards a "quantum shift register" of individual neutral atoms.Comment: 4 pages, 3 figure
Coherent imaging of extended objects
When used with coherent light, optical imaging systems, even
diffraction-limited, are inherently unable to reproduce both the amplitude and
the phase of a two-dimensional field distribution because their impulse
response function varies slowly from point to point (a property known as
non-isoplanatism). For sufficiently small objects, this usually results in a
phase distortion and has no impact on the measured intensity. Here, we show
that the intensity distribution can also be dramatically distorted when objects
of large extension or of special shapes are imaged. We illustrate the problem
using two simple examples: the pinhole camera and the aberration-free thin
lens. The effects predicted by our theorical analysis are also confirmed by
experimental observations.Comment: 10 pages, 9 figures, submitted to Optics Communication
- …