5,753 research outputs found
Composite oscillator systems for meeting user needs for time and frequency
Frequency standards are used in most navigation and telecommunications systems to provide a long term memory of either frequency, phase, or time epoch. From a systems point of view, the performance aspects of the frequency standard are weighed against other systems characteristics, such as overall performance, cost, size, and accessibility; a number of examples are very briefly reviewed. The theory of phase lock and frequency lock systems is outlined in sufficient detail that total oscillator system performance can be predicted from measurements on the individual components. As an example, details of the performance of a high spectral purity oscillator phase locked to a long term stable oscillator are given. Results for several systems, including the best system stability that can be obtained from present commercially available 5-MHz sources, are shown
Single photon absorption and dynamic control of a coupled quantum dot-cavity system
We theoretically investigate the dynamic interaction of a quantum dot in a
nanocavity with timesymmetric single photon pulses. The simulations, based on a
wavefunction approach, reveal that almost perfect single photon absorption
occurs for quantum dot-cavity systems operating on the edge between strong and
weak coupling regime. The computed maximum absorptions probability is close to
unity for pulses with a typical length comparable to the half of the Rabi
period. Furthermore, the dynamic control of the quantum dot energy via electric
fields allows the freezing of the light-matter interaction leaving the quantum
dot in its excited state. Shaping of single photon wavepackets by the electric
field control is limited by the occurrence of chirping of the single photon
pulse. This understanding of the interaction of single photon pulses with the
quantum dot-cavity system provides the basis for the development of advanced
protocols for quantum information processing in the solid state.Comment: 7 pages, 4 figure
Quantum atom optics with fermions from molecular dissociation
We study a fermionic atom optics counterpart of parametric down-conversion
with photons. This can be realized through dissociation of a Bose-Einstein
condensate of molecular dimers consisting of fermionic atoms. We present a
theoretical model describing the quantum dynamics of dissociation and find
analytic solutions for mode occupancies and atomic pair correlations, valid in
the short time limit. The solutions are used to identify upper bounds for the
correlation functions, which are applicable to any fermionic system and
correspond to ideal particle number-difference squeezingComment: Changes in response to referees' comments, updated reference
The emotional health of senior pastors in the Christian and Missionary Alliance of Canada and its connection to the spiritual health of their churches
https://place.asburyseminary.edu/ecommonsatsdissertations/1275/thumbnail.jp
Non-classical Photon Statistics For Two-mode Optical Fields
The non-classical property of subpoissonian photon statistics is extended
from one to two-mode electromagnetic fields, incorporating the physically
motivated property of invariance under passive unitary transformations.
Applications to squeezed coherent states, squeezed thermal states, and
superposition of coherent states are given. Dependences of extent of
non-classical behaviour on the independent squeezing parameters are graphically
displayed.Comment: 15 pages, RevTex, 5 figures, available by sending email to
[email protected]
A high bandwidth quantum repeater
We present a physical- and link-level design for the creation of entangled
pairs to be used in quantum repeater applications where one can control the
noise level of the initially distributed pairs. The system can tune
dynamically, trading initial fidelity for success probability, from high
fidelity pairs (F=0.98 or above) to moderate fidelity pairs. The same physical
resources that create the long-distance entanglement are used to implement the
local gates required for entanglement purification and swapping, creating a
homogeneous repeater architecture. Optimizing the noise properties of the
initially distributed pairs significantly improves the rate of generating
long-distance Bell pairs. Finally, we discuss the performance trade-off between
spatial and temporal resources.Comment: 5 page
Analysis of photon-atom entanglement generated by Faraday rotation in a cavity
Faraday rotation based on AC Stark shifts is a mechanism that can entangle
the polarization variables of photons and atoms. We analyze the structure of
such entanglement by using the Schmidt decomposition method. The
time-dependence of entanglement entropy and the effective Schmidt number are
derived for Gaussian amplitudes. In particular we show how the entanglement is
controlled by the initial fluctuations of atoms and photons.Comment: 6 pages, 3 figure
Theory of collective Raman scattering from a Bose-Einstein condensate
Recent experiments have demonstrated superradiant Raman scattering from a
Bose-Einstein condensate driven by a single off-resonant laser beam. We present
a quantum theory describing this phenomenon, showing Raman amplification of
matter wave due to collective atomic recoil from 3-level atoms in a
-configuration. When atoms are initially in a single lower internal
state, a closed two-level system is realized between atoms with different
internal states, and entangled atom-photon pairs can be generated. When atoms
are initially prepared in both the lower internal states, a fraction of atoms
recoiling in the backward direction can be generated.Comment: 5 pages, 2 figure
Relationships Between the Performance of Time/Frequency Standards and Navigation/Communication Systems
The relationship between system performance and clock or oscillator performance is discussed. Tradeoffs discussed include: short term stability versus bandwidth requirements; frequency accuracy versus signal acquisition time; flicker of frequency and drift versus resynchronization time; frequency precision versus communications traffic volume; spectral purity versus bit error rate, and frequency standard stability versus frequency selection and adjustability. The benefits and tradeoffs of using precise frequency and time signals are various levels of precision and accuracy are emphasized
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