113 research outputs found
Two-Color Magneto-Optical Trap with Small Magnetic Field for Ytterbium
We report a two-color magneto-optical trap (MOT) for ytterbium atoms
operating at a low magnetic field gradient down to 2 G/cm where a conventional
MOT using the singlet transition (6s^2 1S0 -> 6s6p 1P1) is unable to trap
atoms. By simultaneously applying laser light on both the broad-linewidth
singlet transition and the narrow-linewidth triplet transition (6s^2 1S0 ->
6s6p 3P1), we load and trap 4.0 x 10^5 atoms directly from an atomic beam at
700 K. In the two-color MOT, the slowing and trapping functions are separately
performed by the singlet transition light and the triplet transition light,
respectively. The two-color MOT is highly robust against laser power imbalance
even at very low magnetic field gradients.Comment: 6 pages, 5 figure
Implementation of Cavity Squeezing of a Collective Atomic Spin
We squeeze unconditionally the collective spin of a dilute ensemble of
laser-cooled rubidium-87 atoms using their interaction with a driven optical
resonator. The shape and size of the resulting spin uncertainty region are well
described by a simple analytical model [M.H.S., I.D.L., V.V., arXiv:0911.3936]
through two orders of magnitude in the effective interaction strength, without
free parameters. We deterministically generate states with up to 5.6(6) dB of
metrologically relevant spin squeezing on the canonical rubidium-87 hyperfine
clock transition.Comment: 4 pages, 2 figures. To be published in Phys. Rev. Lett. Some
additional details and clarified wording in response to referee comments.
Figures and results unchange
Fast Compact Laser Shutter Using a Direct Current Motor and 3D Printing
We present a mechanical laser shutter design that utilizes a DC electric
motor to rotate a blade which blocks and unblocks a light beam. The blade and
the main body of the shutter are modeled with computer aided design (CAD) and
are produced by 3D printing. Rubber flaps are used to limit the blade's range
of motion, reducing vibrations and preventing undesirable blade oscillations.
At its nominal operating voltage, the shutter achieves a switching speed of
(1.22 0.02) m/s with 1 ms activation delay and 10 s jitter in its
timing performance. The shutter design is simple, easy to replicate, and highly
reliable, showing no failure or degradation in performance over more than
cycles.Comment: 4 pages, 6 figures; supplementary materials for shutter replication
added under "Ancillary files
Large conditional single-photon cross-phase modulation
Deterministic optical quantum logic requires a nonlinear quantum process that
alters the phase of a quantum optical state by through interaction with
only one photon. Here, we demonstrate a large conditional cross-phase
modulation between a signal field, stored inside an atomic quantum memory, and
a control photon that traverses a high-finesse optical cavity containing the
atomic memory. This approach avoids fundamental limitations associated with
multimode effects for traveling optical photons. We measure a conditional
cross-phase shift of up to between the retrieved signal and control
photons, and confirm deterministic entanglement between the signal and control
modes by extracting a positive concurrence. With a moderate improvement in
cavity finesse, our system can reach a coherent phase shift of at low
loss, enabling deterministic and universal photonic quantum logic.Comment: 22 pages, 5 figures, 1 table, includes supplementary informatio
Squeezing the Collective Spin of a Dilute Atomic Ensemble by Cavity Feedback
We propose and analyze a simple method to squeeze dynamically and
unconditionally the collective spin of a dilute atomic ensemble by interaction
with a driven mode of an optical resonator, as recently demonstrated [I. D. L.,
M. H. S., and V. V., Phys. Rev. Lett. 104, 073602 (2010)]. We show that
substantial squeezing can be achieved in the regime of strong collective
ensemble-resonator coupling. The squeezing is ultimately limited either by
photon emission into free space or by the curvature of the Bloch sphere. We
derive both limits and show where each prevails.Comment: 4 pages, 2 figures. Minor revision. To appear in Phys. Rev.
Entangled collective-spin states of atomic ensembles under non-uniform atom-light interaction
We consider the optical generation and verification of entanglement in atomic
ensembles under non-uniform interaction between the ensemble and an optical
mode. We show that for a wide range of parameters a system of non-uniformly
coupled atomic spins can be described as an ensemble of uniformly coupled spins
with a reduced effective atom-light coupling and a reduced effective atom
number, with a reduction factor of order unity given by the ensemble-mode
geometry. This description is valid even for complex entangled states with
arbitrary phase-space distribution functions as long as the detection does not
resolve single spins. Furthermore, we derive an analytic formula for the
observable entanglement in the case, of relevance in practice, where the
ensemble-mode coupling differs between state generation and measurement.Comment: 5 pages, 3 figure
Partially Nondestructive Continuous Detection of Individual Traveling Optical Photons
We report the continuous and partially nondestructive measurement of optical
photons. For a weak light pulse traveling through a slow-light optical medium
(signal), the associated atomic-excitation component is detected by another
light beam (probe) with the aid of an optical cavity. We observe strong
correlations of between the transmitted signal and probe
photons. The observed (intrinsic) conditional nondestructive quantum efficiency
ranges between 13% and 1% (65% and 5%) for a signal transmission range of 2% to
35%, at a typical time resolution of 2.5 s. The maximal observed
(intrinsic) device nondestructive quantum efficiency, defined as the product of
the conditional nondestructive quantum efficiency and the signal transmission,
is 0.5% (2.4%). The normalized cross-correlation function violates the
Cauchy-Schwarz inequality, confirming the non-classical character of the
correlations
Two-axis-twisting spin squeezing by multi-pass quantum erasure
Many-body entangled states are key elements in quantum information science
and quantum metrology. One important problem in establishing a high degree of
many-body entanglement using optical techniques is the leakage of the system
information via the light that creates such entanglement. We propose an
all-optical interference-based approach to erase this information. Unwanted
atom-light entanglement can be removed by destructive interference of three or
more successive atom-light interactions, with only the desired effective
atom-atom interaction left. This quantum erasure protocol allows implementation
of Heisenberg-limited spin squeezing using coherent light and a cold or warm
atomic ensemble. Calculations show that significant improvement in the
squeezing exceeding 10 dB is obtained compared to previous methods, and
substantial spin squeezing is attainable even under moderate experimental
conditions. Our method enables the efficient creation of many-body entangled
states with simple setups, and thus is promising for advancing technologies in
quantum metrology and quantum information processing.Comment: 10 pages, 4 figures. We have improved the presentation and added a
new section, in which we have generalized the scheme from a three-pass scheme
to multi-pass schem
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