29,358 research outputs found
Amplitude squeezed light from a laser
Intensity squeezed light was successfully generated using semiconductor lasers with sub-Poissonian pumping. Control of the pumping statistics is crucial and is achieved by a large series resistor which regulates the pump current; its sub-Poissonian statistics are then transferred to the laser output. The sub-Poissonian pumping of other laser systems is not so simple, however, and their potential as squeezed states sources is apparently diminished. We consider a conventional laser incoherently pumped well above threshold, and allow for pump depletion of the ground state. In this regime, sub-Poissonian photon statistics and squeezed amplitude fluctuations are produced
Analytic Relations between Localizable Entanglement and String Correlations in Spin Systems
We study the relation between the recently defined localizable entanglement
and generalized correlations in quantum spin systems. Differently from the
current belief, the localizable entanglement is always given by the average of
a generalized string. Using symmetry arguments we show that in most spin 1/2
and spin 1 systems the localizable entanglement reduces to the spin-spin or
string correlations, respectively. We prove that a general class of spin 1
systems, which includes the Heisenberg model, can be used as perfect quantum
channel. These conclusions are obtained in analytic form and confirm some
results found previously on numerical grounds.Comment: 5 pages, RevTeX
Evaluation of materials and design modifications for aircraft brakes
A test program is described which was carried out to evaluate several proposed design modifications and several high-temperature friction materials for use in aircraft disk brakes. The evaluation program was carried out on a specially built test apparatus utilizing a disk brake and wheel half from a small het aircraft. The apparatus enabled control of brake pressure, velocity, and braking time. Tests were run under both constant and variable velocity conditions and covered a kinetic energy range similar to that encountered in aircraft brake service. The results of the design evaluation program showed that some improvement in brake performance can be realized by making design changes in the components of the brake containing friction material. The materials evaluation showed that two friction materials show potential for use in aircraft disk brakes. One of the materials is a nickel-based sintered composite, while the other is a molybdenum-based material. Both materials show much lower wear rates than conventional copper-based materials and are better able to withstand the high temperatures encountered during braking. Additional materials improvement is necessary since both materials show a significant negative slope of the friction-velocity curve at low velocities
Computer aids for worst case electronic circuit design
Computer aids for worst case electronic circuit desig
Making the small oblique parameters large
We compute the oblique parameters, including the three new parameters ,
and introduced recently by the Montreal group, for the case of one
scalar multiplet of arbitrary weak isospin and weak hypercharge . We
show that, when the masses of the heaviest and lightest components of the
multiplet remain constant, but increases, the oblique parameter and
the three new oblique parameters increase like , while only
increases like . For large multiplets with masses not much higher than , the oblique parameters and may become much larger than
and .Comment: 9 pages, standard LATEX, 3 figures available from the authors, report
CMU-HEP93-17 and DOE-ER/40682-4
Tracking ground state Ba+ ions in an expanding laser–plasma plume using time-resolved vacuum ultraviolet photoionization imaging
We report results from a study of the integrated column density and expansion dynamics of ground-state-selected Ba+ ions in a laser–plasma plume using a new experimental system—VPIF (vacuum-ultraviolet photoabsorption imaging facility). The ions are tracked by recording the attenuation of a pulsed and collimated vacuum ultraviolet beam, tuned to the 5p–6d inner-shell resonance of singly ionized barium, as the expanding plasma plume moves across it. The attenuated beam is allowed to fall on a CCD array where the spatial distribution of the absorption is recorded. Time-resolved ion velocity and integrated column density maps are readily extracted from the photoionization images
High-resolution width-modulated pulse rebalance electronics for strapdown gyroscopes and accelerometers
Three different rebalance electronic loops were designed, implemented, and evaluated. The loops were width-modulated binary types using a 614.4 kHz keying signal; they were developed to accommodate the following three inertial sensors with the indicated resolution values: (1) Kearfott 2412 accelerometer - resolution = 260 micro-g/data pulse, (2) Honeywell GG334 gyroscope - resolution = 3.9 milli-arc-sec/data pulse, (3) Kearfott 2401-009 accelerometer - resolution = 144 milli-g/data pulse. Design theory, details of the design implementation, and experimental results for each loop are presented
Electroweak Theory Without Higgs Bosons
A perturbative SU(2)_L X U(1)_Y electroweak theory containing W, Z, photon,
ghost, lepton and quark fields, but no Higgs or other fields, gives masses to
W, Z and the non-neutrino fermions by means of an unconventional choice for the
unperturbed Lagrangian and a novel method of renormalisation. The
renormalisation extends to all orders. The masses emerge on renormalisation to
one loop. To one loop the neutrinos are massless, the A -> Z transition drops
out of the theory, the d quark is unstable and S-matrix elements are
independent of the gauge parameter xi.Comment: 27 pages, LaTex, no figures; revised for publication; accepted by
Int. J. Mod. Phys. A; includes biographical note on A. F. Nicholso
Thermodynamic limit of the density matrix renormalization for the spin-1 Heisenberg chain
The density matrix renormalization group (``DMRG'') discovered by White has
shown to be a powerful method to understand the properties of many one
dimensional quantum systems. In the case where renormalization eventually
converges to a fixed point we show that quantum states in the thermodynamic
limit with periodic boundary conditions can be simply represented by a special
type of product ground state with a natural description of Bloch states of
elementary excitations that are spin-1 solitons. We then observe that these
states can be rederived through a simple variational ansatz making no reference
to a renormalization construction. The method is tested on the spin-1
Heisenberg model.Comment: 13 pages uuencoded compressed postscript including figure
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