gradient-echo-quantum-memory-in-warm-atomic-vapor

Gradient Echo Quantum Memory in Warm Atomic Vapor

Gradient  echo memory (GEM) is a protocol for storing optical quantum states of light in  atomic ensembles. The primary motivation for such a technology ...

The Australian National University

The micro-Wilhelmy method is a well-established method of determining surface tension by measuring the force of withdrawing a tens of microns to millimeters in diameter cylindrical wire or fiber from a liquid. A comparison of insertion force to retraction force can also be used to determine the contact angle with the fiber. Given the limited availability of atomic force microscope (AFM) probes that have long constant diameter tips, force-distance (F-D) curves using probes with standard tapered tips have been difficult to relate to surface tension. In this report, constant diameter metal alloy nanowires (referred to as "nanoneedles") between 7.2 and 67 microm in length and 108 and 1006 nm in diameter were grown on AFM probes. F-D and Q damping AFM measurements of wetting and drag forces made with the probes were compared against standard macroscopic models of these forces on slender cylinders to estimate surface tension, contact angle, meniscus height, evaporation rate, and viscosity. The surface tensions for several low molecular weight liquids that were measured with these probes were between -4.2% and +8.3% of standard reported values. Also, the F-D curves show well-defined stair-step events on insertion and retraction from partial wetting liquids, compared to the continuously growing attractive force of standard tapered AFM probe tips. In the AFM used, the stair-step feature in F-D curves was repeatably monitored for at least 0.5 h (depending on the volatility of the liquid), and this feature was then used to evaluate evaporation rates (as low as 0.30 nm/s) through changes in the surface height of the liquid. A nanoneedle with a step change in diameter at a known distance from its end produced two steps in the F-D curve from which the meniscus height was determined. The step features enable meniscus height to be determined from distance between the steps, as an alternative to calculating the height corresponding to the AFM measured values of surface tension and contact angle. All but one of the eight measurements agreed to within 13%. The constant diameter of the nanoneedle also is used to relate viscous damping of the vibrating cantilever to a macroscopic model of Stokes drag on a long cylinder. Expected increases in drag force with insertion depth and viscosity are observed for several glycerol-water solutions. However, an additional damping term (associated with drag of the meniscus on the sidewalls of the nanoneedle) limits the sensitivity of the measurement of drag force for low-viscosity solutions, while low values of Q limit the sensitivity for high-viscosity solutions. Overall, reasonable correspondence is found between the macroscopic models and the measurements with the nanoneedle-tipped probes. Tighter environmental control of the AFM and treatments of needles to give them more ideal surfaces are expected to improve repeatability and make more evident subtle features that currently appear to be present on the F-D and Q damping curves.

Micro-wilhelmy and related liquid property measurements using constant-diameter nanoneedle-tipped atomic force microscope probes.

The bandwidth and versatility of optical devices have revolutionized information technology systems and communication networks. Precise and arbitrary control of an optical field that preserves optical coherence is an important requisite for many proposed photonic technologies. For quantum information applications, a device that allows storage and on-demand retrieval of arbitrary quantum states of light would form an ideal quantum optical memory. Recently, significant progress has been made in implementing atomic quantum memories using electromagnetically induced transparency, photon echo spectroscopy, off-resonance Raman spectroscopy and other atom-light interaction processes. Single-photon and bright-optical-field storage with quantum states have both been successfully demonstrated. Here we present a coherent optical memory based on photon echoes induced through controlled reversible inhomogeneous broadening. Our scheme allows storage of multiple pulses of light within a chosen frequency bandwidth, and stored pulses can be recalled in arbitrary order with any chosen delay between each recalled pulse. Furthermore, pulses can be time-compressed, time-stretched or split into multiple smaller pulses and recalled in several pieces at chosen times. Although our experimental results are so far limited to classical light pulses, our technique should enable the construction of an optical random-access memory for time-bin quantum information, and have potential applications in quantum information processing.

Coherent optical pulse sequencer for quantum applications.

There is growing interest in the identification of novel therapeutic agents for the treatment of affective disorders, with modafinil being one promising substance. The purpose of the present investigation was to compare the efficacy of a combination of fluoxetine plus modafinil with that of fluoxetine plus placebo in the treatment of major depression in a 6-week double blind and placebo-controlled trial.

Double-blind randomized parallel-group clinical trial of efficacy of the combination fluoxetine plus modafinil versus fluoxetine plus placebo in the treatment of major depression.

A total of 230 goats and 185 sheep were evaluated in this cross-sectional observational study. After emptying the gastrointestinal tract, the size, location, adhesion and obstruction were examined. Twenty seven and half percent of sheep and 24 point 3 % of goats had foreign bodies. Most foreign bodies were plastic materials in sheep and goats. Forty percent of pregnant animals had foreign bodies. Drought and lack of adequate pastures in the past years have been a major cause of the swallowing of foreign objects by sheep and goats.

Mahdi Hosseini

ARC Centre for Quantum Computation and Communication Technology,
Department of Quantum Science,
ARC Centre for Quantum Computation and Communication Technology, Department of Quantum Science

The Australian National University

Gradient Echo Quantum Memory in Warm Atomic Vapor

Mahdi Hosseini

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}ARC Centre for Quantum Computation and Communication Technology,Department of Quantum Science,ARC Centre for Quantum Computation and Communication Technology, Department of Quantum Science

The Australian National University

Gradient Echo Quantum Memory in Warm Atomic Vapor

ARC Centre for Quantum Computation and Communication Technology,
Department of Quantum Science,
ARC Centre for Quantum Computation and Communication Technology, Department of Quantum Science