5,669 research outputs found
Fast all-optical nuclear spin echo technique based on EIT
We demonstrate an all-optical Raman spin echo technique, using
Electromagnetically Induced Transparency (EIT) to create the different pulses
of the spin echo sequence: initialization, pi-rotation, and readout. The first
pulse of the sequence induces coherence directly from a mixed state, and the
technique is used to measure the nuclear spin coherence of an inhomogeneously
broadened ensemble of rare-earth ions (Pr). In contrast to previous
experiments it does not require any preparatory hole burning pulse sequences,
which greatly shortens the total duration of the sequence. The effect of the
different pulses is characterized by quantum state tomography and is compared
with simulations. We demonstrate two applications of the technique by using the
spin echo sequence to accurately compensate a magnetic field across our sample,
and to measure the coherence time at high temperatures up to 11 K, where
standard preparation techniques are difficult to implement. We explore the
potential of the technique and possible applications.Comment: 8 pages, 6 figure
Fatal lymphoproliferation and acute monocytic leukemia-like disease following infectious mononucleosis in the elderly
Three elderly patients are reported, in whom serologically confirmed recent infectious mononucleosis is followed by fatal lymphoproliferation (case 1), by acute monocytic leukemia (case 2), and by acute probably monocytic leukemia (case 3)
Study to establish cost projections for production of Redox chemicals
A cost study of four proposed manufacturing processes for redox chemicals for the NASA REDOX Energy Storage System yielded favorable selling prices in the range 1.91/kg of chromic chloride, anhydrous basis, including ferrous chloride. The prices corresponded to specific energy storage costs from under 17/kWh. A refined and expanded cost analysis of the most favored process yielded a price estimate corresponding to a storage cost of $11/kWh. The findings supported the potential economic viability of the NASA REDOX system
Storage and recall of weak coherent optical pulses with an efficiency of 25%
We demonstrate experimentally a quantum memory scheme for the storage of weak
coherent light pulses in an inhomogeneously broadened optical transition in a
Pr^{3+}: YSO crystal at 2.1 K. Precise optical pumping using a frequency stable
(about 1kHz linewidth) laser is employed to create a highly controllable Atomic
Frequency Comb (AFC) structure. We report single photon storage and retrieval
efficiencies of 25%, based on coherent photon echo type re-emission in the
forward direction. The coherence property of the quantum memory is proved
through interference between a super Gaussian pulse and the emitted echo.
Backward retrieval of the photon echo emission has potential for increasing
storage and recall efficiency.Comment: 5,
High fidelity readout scheme for rare-earth solid state quantum computing
We propose and analyze a high fidelity readout scheme for a single instance
approach to quantum computing in rare-earth-ion-doped crystals. The scheme is
based on using different species of qubit and readout ions, and it is shown
that by allowing the closest qubit ion to act as a readout buffer, the readout
error can be reduced by more than an order of magnitude. The scheme is shown to
be robust against certain experimental variations, such as varying detection
efficiencies, and we use the scheme to predict the expected quantum fidelity of
a CNOT gate in these solid state systems. In addition, we discuss the potential
scalability of the protocol to larger qubit systems. The results are based on
parameters which we believed are experimentally feasible with current
technology, and which can be simultaneously realized.Comment: 7 pages, 5 figure
A new, temporarily confined population in the polar cap during the August 27, 1996 geomagnetic field distortion period
On August 27, 1996, a two-hour energetic heavy ion event (∼1 MeV) was detected at 8:25 UT at apogee (∼9 Re and an invariant latitude of ∼80°), by the Charge and Mass Magnetospheric Ion Composition Experiment onboard POLAR. The event, with a maximum spin averaged peak flux of ∼150 particles/(cm²-sr-s-MeV), showed three local peaks corresponding to three localized regions; the ion pitch angle distributions in the three regions were different from an isotropic distribution and different from each other. No comparable flux was observed by the WIND spacecraft. The appearance of lower energy He++ and O \u3e +2 during the event period indicates a solar source for these particles. From region 1 to 2 to 3, the helium energy spectra softened. A distorted magnetic field with three local minima corresponding to the three He peak fluxes was also observed by POLAR. A possible explanation is that the energetic He ions were energized from lower energy helium by a local acceleration mechanism that preferred smaller rigidity ions in the high altitude polar cusp region
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