278 research outputs found
Water vapor at a translational temperature of one kelvin
We report the creation of a confined slow beam of heavy-water (D2O) molecules
with a translational temperature around 1 kelvin. This is achieved by filtering
slow D2O from a thermal ensemble with inhomogeneous static electric fields
exploiting the quadratic Stark shift of D2O. All previous demonstrations of
electric field manipulation of cold dipolar molecules rely on a predominantly
linear Stark shift. Further, on the basis of elementary molecular properties
and our filtering technique we argue that our D2O beam contains molecules in
only a few ro-vibrational states.Comment: 4 pages, 4 figures, 1 tabl
Spatially encoded light for Large-alphabet Quantum Key Distribution
Most Quantum Key Distribution protocols use a two-dimensional basis such as
HV polarization as first proposed by Bennett and Brassard in 1984. These
protocols are consequently limited to a key generation density of 1 bit per
photon. We increase this key density by encoding information in the transverse
spatial displacement of the used photons. Employing this higher-dimensional
Hilbert space together with modern single-photon-detecting cameras, we
demonstrate a proof-of-principle large-alphabet Quantum Key Distribution
experiment with 1024 symbols and a shared information between sender and
receiver of 7 bit per photon.Comment: 9 pages, 6 figures, Added references, Updated Fig. 1 in the main
text, Updated Fig.1 in supplementary material, Added section Trojan-horse
attacks in supplementary material, title changed, Added paragraphs about
final key rate and overfilling the detector to result sectio
Characterization of a Quantum Light Source Based on Spontaneous Parametric Down-Conversion
We have built a quantum light source capable of producing different types of
quantum states. The quantum light source is based on entangled state
preparation in the process of spontaneous parametric down-conversion. The
single-photon detection rate of eight-hundred thousand per second demonstrates
that we have created a bright state-of-the-art quantum light source. As a part
of the characterization we measured two-photon quantum interference in a
Hong-Ou-Mandel interferometer.Comment: 33 page
Continuous loading of an electrostatic trap for polar molecules
A continuously operated electrostatic trap for polar molecules is
demonstrated. The trap has a volume of ~0.6 cm^3 and holds molecules with a
positive Stark shift. With deuterated ammonia from a quadrupole velocity
filter, a trap density of ~10^8/cm^3 is achieved with an average lifetime of
130 ms and a motional temperature of ~300 mK. The trap offers good starting
conditions for high-precision measurements, and can be used as a first stage in
cooling schemes for molecules and as a "reaction vessel" in cold chemistry.Comment: 4 pages, 3 figures v2: several small improvements, new intr
Normal-mode spectroscopy of a single bound atom-cavity system
The energy-level structure of a single atom strongly coupled to the mode of a
high-finesse optical cavity is investigated. The atom is stored in an
intracavity dipole trap and cavity cooling is used to compensate for inevitable
heating. Two well-resolved normal modes are observed both in the cavity
transmission and the trap lifetime. The experiment is in good agreement with a
Monte Carlo simulation, demonstrating our ability to localize the atom to
within at a cavity antinode.Comment: 4 pages, 4 figure
Trapping of Neutral Rubidium with a Macroscopic Three-Phase Electric Trap
We trap neutral ground-state rubidium atoms in a macroscopic trap based on
purely electric fields. For this, three electrostatic field configurations are
alternated in a periodic manner. The rubidium is precooled in a magneto-optical
trap, transferred into a magnetic trap and then translated into the electric
trap. The electric trap consists of six rod-shaped electrodes in cubic
arrangement, giving ample optical access. Up to 10^5 atoms have been trapped
with an initial temperature of around 20 microkelvin in the three-phase
electric trap. The observations are in good agreement with detailed numerical
simulations.Comment: 4 pages, 4 figure
The rotational memory effect of a multimode fiber
We demonstrate the rotational memory effect in a multimode fiber. Rotating
the incident wavefront around the fiber core axis leads to a rotation of the
resulting pattern of the fiber output without significant changes in the
resulting speckle pattern. The rotational memory effect can be exploited for
non-invasive imaging or ultrafast high-resolution scanning through a multimode
fiber. Our experiments demonstrate this effect over a full range of angles in
two experimental configurations.Comment: 7 pages, 3 figure
Calculating the Fine Structure of a Fabry-Perot Resonator using Spheroidal Wave Functions
A new set of vector solutions to Maxwell's equations based on solutions to
the wave equation in spheroidal coordinates allows laser beams to be described
beyond the paraxial approximation. Using these solutions allows us to calculate
the complete first-order corrections in the short-wavelength limit to
eigenmodes and eigenfrequencies in a Fabry-Perot resonator with perfectly
conducting mirrors. Experimentally relevant effects are predicted. Modes which
are degenerate according to the paraxial approximation are split according to
their total angular momentum. This includes a splitting due to coupling between
orbital angular momentum and spin angular momentum
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