5,335 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
Automation in the Space Station module power management and distribution Breadboard
The Space Station Module Power Management and Distribution (SSM/PMAD) Breadboard, located at NASA's Marshall Space Flight Center (MSFC) in Huntsville, Alabama, models the power distribution within a Space Station Freedom Habitation or Laboratory module. Originally designed for 20 kHz ac power, the system is now being converted to high voltage dc power with power levels on a par with those expected for a space station module. In addition to the power distribution hardware, the system includes computer control through a hierarchy of processes. The lowest level process consists of fast, simple (from a computing standpoint) switchgear, capable of quickly safing the system. The next level consists of local load center processors called Lowest Level Processors (LLP's). These LLP's execute load scheduling, perform redundant switching, and shed loads which use more than scheduled power. The level above the LLP's contains a Communication and Algorithmic Controller (CAC) which coordinates communications with the highest level. Finally, at this highest level, three cooperating Artificial Intelligence (AI) systems manage load prioritization, load scheduling, load shedding, and fault recovery and management. The system provides an excellent venue for developing and examining advanced automation techniques. The current system and the plans for its future are examined
Distributing fully optomechanical quantum correlations
We present a scheme to prepare quantum correlated states of two mechanical
systems based on the pouring of pre-available all-optical entanglement into the
state of two micro-mirrors belonging to remote and non-interacting
optomechanical cavities. We show that, under realistic experimental conditions,
the protocol allows for the preparation of a genuine quantum state of a
composite mesoscopic system whose non-classical features extend far beyond the
occurrence of entanglement. We finally discuss a way to access such mechanical
correlations.Comment: 5 pages, 4 figures, to appear in Physical Review
Entanglement detection by Bragg scattering
We show how to measure the structural witnesses proposed in [P. Krammer et
al., Phys. Rev. Lett. 103, 100502 (2009)] for detecting entanglement in a spin
chain using photon scattering. The procedure, moreover, allows one to measure
the two-point correlation function of the spin array. This proposal could be
performed in existing experimental platforms realizing ion chains in Paul traps
or atomic arrays in optical lattices.Comment: 4 pages, 2 figures, final version (refs added + minor changes
Optical wavelength conversion of quantum states with optomechanics
An optomechanical interface that converts quantum states between optical
fields with distinct wavelengths is proposed. A mechanical mode couples to two
optical modes via radiation pressure and mediates the quantum state mapping
between the two optical modes. A sequence of optomechanical pulses
enables state-swapping between optical and mechanical states as well as the
cooling of the mechanical mode. Theoretical analysis shows that high fidelity
conversion can be realized for states with small photon numbers in systems with
experimentally achievable parameters. The pulsed conversion process also makes
it possible to maintain high conversion fidelity at elevated bath temperatures.Comment: 4 pages, 4 figures, Fig. 4 looks weird (possible latex style problem
Quantum decoherence reduction by increasing the thermal bath temperature
The well-known increase of the decoherence rate with the temperature, for a
quantum system coupled to a linear thermal bath, holds no longer for a
different bath dynamics. This is shown by means of a simple classical
non-linear bath, as well as a quantum spin-boson model. The anomalous effect is
due to the temperature dependence of the bath spectral profile. The decoherence
reduction via the temperature increase can be relevant for the design of
quantum computers
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