Phonon arithmetic in a trapped ion system

Single-quantum level operations are important tools to manipulate a quantum state. Annihilation or creation of single particles translates a quantum state to another by adding or subtracting a particle, depending on how many are already in the given state. The operations are probabilistic and the success rate has yet been low in their experimental realization. Here we experimentally demonstrate (near) deterministic addition and subtraction of a bosonic particle, in particular a phonon of ionic motion in a harmonic potential. We realize the operations by coupling phonons to an auxiliary two-level system and applying transitionless adiabatic passage. We show handy repetition of the operations on various initial states and demonstrate by the reconstruction of the density matrices that the operations preserve coherences. We observe the transformation of a classical state to a highly non-classical one and a Gaussian state to a non-Gaussian one by applying a sequence of operations deterministically

A definitive number of atoms on demand: controlling the number of atoms in a-few-atom magneto-optical trap

A few 85Rb atoms were trapped in a micron-size magneto-optical trap with a high quadrupole magnetic-field gradient and the number of atoms was precisely controlled by suppressing stochastic loading and loss events via real-time feedback on the magnetic field gradient. The measured occupation probability of single atom was as high as 99%. Atoms up to five were also trapped with high occupation probabilities. The present technique could be used to make a deterministic atom source.Comment: 3 pages, 4 figure

Heteroepitaxal fabrication and structural characterizations of ultrafine GaN/ZnO coaxial nanorod heterostructures

We report on heteroepitaxial fabrication and structural characterizations of ultrafine GaN/ZnO coaxial nanorod heterostructures. The coaxial nanorod heterostructures were fabricated by epitaxial growth of a GaN layer on ultrafine ZnO nanorods. Epitaxial growth and precise control of GaN overlayer thickness were obtained by low pressure metalorganic vapor-phase epitaxy. ZnO nanorods grown on Si and sapphire substrates using catalyst-free metalorganic chemical vapor deposition exhibited diameters as small as 7 nm. Furthermore, structural properties of the coaxial nanorod heterostructures were investigated using both synchrotron-radiation x-ray diffraction and high resolution transmission electron microscopy. (C) 2004 American Institute of Physics.open115462sciescopu

How Accurate Are Wearable Activity Trackers For Measuring Steps?

Wearable activity trackers have become popular for tracking individual’s daily physical activity, but little or no information is available to substantiate the validity of these devices in step counts. PURPOSE: The purpose of this study was to systemically examine the validity of newly developed wearable activity trackers for measuring steps compared to the criterion measure (hand tally) in two different conditions. METHODS: Twenty (28.2±4.8 years) healthy males (n=19) and females (n=17) participated in the study. The participants were fitted with eight wearable activity trackers while walking and running on a treadmill (speeds of 2, 2.5, 3, 3.5, 4, and 5 mph) for 3-minutes at each speed. For overground protocol, participants walked at three-self-determined speeds; gradually becoming faster (slow, normal, and fast) for one lap on an indoor track (200 meter track). The number of actual steps taken was manually tallied by researchers using a hand-tally counter. The monitors included the Basis B1 band (BB), Misfit Shine (MS), Polar Loop (PL), and Jawbone UP (UP) worn on the right wrist; the Nike+Fuelband (NF), Garmin VivoFit (GV), and Fitbit Flex (FF) worn on the left wrist; and Withings Pulse (WP) and Fitbit Zip (FZ) worn with a clip on the waist. Step counts from each monitor were compared with criterion values from manually counted steps. RESULTS: Total step counts (means ±SD) were 329.5±71.0, 267.8±89.9, 290.6±105.1, 326.2 ±73.2, 282.2±85.1, 294.3±85.8, 329.2±70.0, 322.1±75.7, 310.8±82.8, and 318.±76.7, for manual counts, NF, MS, WP, PL, FF, FZ, UP, GV, and BB, respectively. Corresponding absolute error rates (computed as the average absolute value of the individuals’ errors) were 19.8±16.4%, 18.9±12.2%, 17.4±15.8%, 11.3±13.1%, 0.7±1.4%, 4.5±7.8%, 6.6±12.6%, and 3.5±6.0%, respectively. ANOVA and Post hoc analyses with Bonferroni revealed the MS, WP, FZ, UP, GV, and BB were the devices to give non-significant differences (p\u3e .05) compared to the manual step counts, but significant differences were found with NF, PL, and FF. CONCLUSION: The results demonstrate that the waist-oriented trackers, FZ and WP, show the most accuracy in measuring steps. However, promising preliminary findings were observed with the wrist-oriented trackers, BB, UP, and GV

High current-carrying capability in c-axis-oriented superconducting MgB2 thin films

In high-quality c-axis-oriented MgB2 thin films, we observed high critical current densities (Jc) of 16 MA/cm^2 at 15 K under self fields comparable to those of cuprate high-temperature superconductors. The extrapolated value of Jc at 5 K was estimated to be 40 MA/cm^2. For a magnetic field of 5 T, a Jc of 0.1 MA/cm^2 was detected at 15 K, suggesting that this compound would be a very promising candidate for practical applications at high temperature and lower power consumption. The vortex-glass phase is considered to be a possible explanation for the observed high current-carrying capability.Comment: 3 pages and 4 figures, to be published in Physical Review Letter