10,349 research outputs found
Mechanisms for Lasing with Cold Atoms as the Gain Medium
We realize a laser with a cloud of cold rubidium atoms as gain medium, placed
in a low-finesse cavity. Three different regimes of laser emission are observed
corresponding respectively to Mollow, Raman and Four Wave Mixing mechanisms. We
measure an output power of up to 300 W and present the main properties of
these different lasers in each regime
Tunable Oscillations in the Purkinje Neuron
In this paper, we study the dynamics of slow oscillations in Purkinje neurons
in vitro, and derive a strong association with a forced parametric oscillator
model. We demonstrate the precise rhythmicity of the oscillations in Purkinje
neurons, as well as a dynamic tunability of this oscillation using a
photo-switchable compound. We show that this slow oscillation can be induced in
every Purkinje neuron, having periods ranging between 10-25 seconds. Starting
from a Hodgkin-Huxley model, we also demonstrate that this oscillation can be
externally modulated, and that the neurons will return to their intrinsic
firing frequency after the forced oscillation is concluded. These results
signify an additional functional role of tunable oscillations within the
cerebellum, as well as a dynamic control of a time scale in the brain in the
range of seconds.Comment: 12 pages, 5 figure
A quantum algorithm providing exponential speed increase for finding eigenvalues and eigenvectors
We describe a new polynomial time quantum algorithm that uses the quantum
fast fourier transform to find eigenvalues and eigenvectors of a Hamiltonian
operator, and that can be applied in cases (commonly found in ab initio physics
and chemistry problems) for which all known classical algorithms require
exponential time. Applications of the algorithm to specific problems are
considered, and we find that classically intractable and interesting problems
from atomic physics may be solved with between 50 and 100 quantum bits.Comment: 10 page
How groups react to disloyalty in the context of intergroup competition: Evaluations of group deserters and defectors
Groups strongly value loyalty, especially in the context of intergroup competition. However, research has yet to investigate how groups respond to members who leave the group or join a competing outgroup. Three studies investigated groups' reactions to defectors (Experiment 1) and deserting members (Experiments 2 and 3). Experiment 1 used a minimal group paradigm to demonstrate that defectors trigger a stronger derogation of ingroup deviants than outgroup deviants vis-Ã -vis normative members. Experiments 2 and 3 compared group members' responses to defection versus desertion from minimal and self-assigned groups, respectively. Experiment 3 also explored an explanation for the evaluations of disloyalty. Across studies, participants evaluated normative ingroup members more positively than defectors and deserters. Outgroup deserting and defecting members were evaluated similarly. Derogation of ingroup as compared to outgroup targets emerged only for defectors. In addition, Experiment 3 demonstrated that negativity toward the outgroup was related to stronger derogation of disloyal targets. Negative outgroup attitudes trigger stricter criteria for responding to disloyalty. Directions for future research are discussed
Singlet states and the estimation of eigenstates and eigenvalues of an unknown Controlled-U gate
We consider several problems that involve finding the eigenvalues and
generating the eigenstates of unknown unitary gates. We first examine
Controlled-U gates that act on qubits, and assume that we know the eigenvalues.
It is then shown how to use singlet states to produce qubits in the eigenstates
of the gate. We then remove the assumption that we know the eigenvalues and
show how to both find the eigenvalues and produce qubits in the eigenstates.
Finally, we look at the case where the unitary operator acts on qutrits and has
eigenvalues of 1 and -1, where the eigenvalue 1 is doubly degenerate. The
eigenstates are unknown. We are able to use a singlet state to produce a qutrit
in the eigenstate corresponding to the -1 eigenvalue.Comment: Latex, 10 pages, no figure
Development of dispersion strengthened chromium alloys Summary report
Dispersion strengthened chromium alloys with minimal quantities of interstitial impuritie
Detection and mapping of hydrothermally altered rocks in the vicinity of the comstock lode, Virginia Range, Nevada, using enhanced LANDSAT images
The author has identified the following significant results. LANDSAT images enhanced by the band-ratioing method can be used for reconnaissance alteration mapping in moderately heavily vegetated semiarid terrain as well as in sparsely vegetated to semiarid terrain where the technique was originally developed. Significant vegetation cover in a scene, however, requires the use of MSS ratios 4/5, 4/6, and 6/7 rather than 4/5, 5/6, and 6/7, and requires careful interpretation of the results. Supplemental information suitable to vegetation identification and cover estimates, such as standard LANDSAT false-color composites and low altitude aerial photographs of selected areas is desirable
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