430 research outputs found
Mesoscopic entanglement of noninteracting qubits using collective spontaneous emission
We describe an experimentally straightforward method for preparing an
entangled W state of up to 100 qubits. Our repeat-until-success protocol relies
on detection of single photons from collective spontaneous emission in free
space. Our method allows entanglement preparation in a wide range of qubit
implementations that lack entangling qubit-qubit interactions. We give detailed
numerical examples for entanglement of neutral atoms in optical lattices and of
nitrogen-vacancy centres in diamond. The simplicity of our method should enable
preparation of mesoscopic entangled states in a number of physical systems in
the near future.Comment: replaced; corrected per referee comment
Wavelength-Scale Imaging of Trapped Ions using a Phase Fresnel lens
A microfabricated phase Fresnel lens was used to image ytterbium ions trapped
in a radio frequency Paul trap. The ions were laser cooled close to the Doppler
limit on the 369.5 nm transition, reducing the ion motion so that each ion
formed a near point source. By detecting the ion fluorescence on the same
transition, near diffraction limited imaging with spot sizes of below 440 nm
(FWHM) was achieved. This is the first demonstration of imaging trapped ions
with a resolution on the order of the transition wavelength.Comment: 8 pages, 3 figure
Low-loss flake-graphene saturable absorber mirror for laser mode-locking at sub-200-fs pulse duration
Saturable absorbers are a key component for mode-locking femtosecond lasers.
Polymer films containing graphene flakes have recently been used in
transmission as laser mode-lockers, but suffer from high nonsaturable loss,
limiting their application in low-gain lasers. Here we present a saturable
absorber mirror based on a film of pure graphene flakes. The device is used to
mode lock an erbium-doped fiber laser, generating pulses with state-of-the-art,
sub-200-fs duration. The laser characteristic indicate that the film exhibits
low nonsaturable loss (13% per pass) and large absorption modulation depth (45%
of low-power absorption)
Quantum optical waveform conversion
Currently proposed architectures for long-distance quantum communication rely
on networks of quantum processors connected by optical communications channels
[1,2]. The key resource for such networks is the entanglement of matter-based
quantum systems with quantum optical fields for information transmission. The
optical interaction bandwidth of these material systems is a tiny fraction of
that available for optical communication, and the temporal shape of the quantum
optical output pulse is often poorly suited for long-distance transmission.
Here we demonstrate that nonlinear mixing of a quantum light pulse with a
spectrally tailored classical field can compress the quantum pulse by more than
a factor of 100 and flexibly reshape its temporal waveform, while preserving
all quantum properties, including entanglement. Waveform conversion can be used
with heralded arrays of quantum light emitters to enable quantum communication
at the full data rate of optical telecommunications.Comment: submitte
Laser cooling of trapped ytterbium ions with an ultraviolet diode laser
We demonstrate an ultraviolet diode laser system for cooling of trapped
ytterbium ions. The laser power and linewidth are comparable to previous
systems based on resonant frequency doubling, but the system is simpler, more
robust, and less expensive. We use the laser system to cool small numbers of
ytterbium ions confined in a linear Paul trap. From the observed spectra, we
deduce final temperatures < 270 mK.Comment: submitted to Opt. Let
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