880 research outputs found
Charge and Isospin Fluctuations in High Energy pp-Collisions
Charge and isospin event-by-event fluctuations in high-energy pp-collisions
are predicted within the Unitary Eikonal Model, in particular the fluctuation
patterns of the ratios of charged-to-charged and neutral-to-charged pions.
These fluctuations are found to be sensitive to the presence of unstable
resonances, such as and mesons. We predict that the
charge-fluctuation observable should be restricted to the interval
depending on the production ratio. Also, the
isospin fluctuations of the DCC-type of the ratio of neutral-to-charged pions
are suppressed if pions are produced together with mesons.Comment: Latex, 5 pages, no figures. To appear in the proceedings of 9th
Adriatic Meeting, Dubrovnik, Croatia, 4 - 14 September 2003. Added reference
into reference no.
The Sunyaev-Zeldovich Effect at 1 and 2 mm towards ROSAT Clusters
An observing campaign was devoted to the search for the Sunyaev-Zeldovich
(S-Z) effect towards X-ray ROSAT Clusters in the millimetric spectral domain. A
double channel (1.2 and 2 {\it mm}) photometer was installed at the focus of
the 15m Swedish ESO Submillimeter Telescope (SEST) in Chile in september 1994
and 1995 and observations of the targets S1077, A2744, S295 and RXJ0658-5557
were gathered. Detections were found for A2744 at 1 {\it mm} and in both
channels (at 1.2 and 2 {\it mm}) towards RXJ0658-5557. For the first time there
is evidence for the S-Z enhancement and both the latter and the decrement were
detected on the same source. We discuss astrophysical and systematic effects
which could give origin to these signals.Comment: 6 pg Latex file (style file included) including 1 ps figure, XVIth
Moriond Astrophysics Meeting "The Anisotropies of the Cosmic Microwave
Background", Les Arcs, Savoie-France, March 16-23 199
Direct Wigner tomography of a superconducting anharmonic oscillator
The analysis of wave-packet dynamics may be greatly simplified when viewed in
phase-space. While harmonic oscillators are often used as a convenient platform
to study wave-packets, arbitrary state preparation in these systems is more
challenging. Here, we demonstrate a direct measurement of the Wigner
distribution of complex photon states in an anharmonic oscillator - a
superconducting phase circuit, biased in the small anharmonicity regime. We
test our method on both non-classical states composed of two energy eigenstates
and on the dynamics of a phase-locked wavepacket. This method requires a simple
calibration, and is easily applicable in our system out to the fifth level.Comment: 5 figures, 1 table and supplementary materia
Observation of quantum oscillations between a Josephson phase qubit and a microscopic resonator using fast readout
We have detected coherent quantum oscillations between Josephson phase qubits
and microscopic critical-current fluctuators by implementing a new state
readout technique that is an order of magnitude faster than previous methods.
The period of the oscillations is consistent with the spectroscopic splittings
observed in the qubit's resonant frequency. The results point to a possible
mechanism for decoherence and reduced measurement fidelity in superconducting
qubits and demonstrate the means to measure two-qubit interactions in the time
domain
Coherent photon assisted cotunneling in a Coulomb blockade device
We study cotunneling in a double junction Coulomb blockade device under the
influence of time dependent potentials. It is shown that the ac-bias leads to
photon assisted cotunneling which in some cases may dominate the transport. We
derive a general non-perturbative expression for the tunneling current in the
presence of oscillating potentials and give a perturbative expression for the
photon assisted cotunneling current.Comment: Replaced with a longer paper which includes a non-perturbative
calculation. 13 pages with 1 figure. To be published in Physical Review
Decoherence in Josephson Qubits from Dielectric Loss
Dielectric loss from two-level states is shown to be a dominant decoherence
source in superconducting quantum bits. Depending on the qubit design,
dielectric loss from insulating materials or the tunnel junction can lead to
short coherence times. We show that a variety of microwave and qubit
measurements are well modeled by loss from resonant absorption of two-level
defects. Our results demonstrate that this loss can be significantly reduced by
using better dielectrics and fabricating junctions of small area . With a redesigned phase qubit employing low-loss
dielectrics, the energy relaxation rate has been improved by a factor of 20,
opening up the possibility of multi-qubit gates and algorithms.Comment: shortened version submitted to PR
A glycine hinge for tRNA-dependent translocation of editing substrates to prevent errors by leucyl-tRNA synthetase
AbstractAminoacyl-tRNA synthetases often rely on a proofreading mechanism to clear mischarging errors before they can be incorporated into newly synthesized proteins. Leucyl-tRNA synthetase (LeuRS) houses a hydrolytic editing pocket in a domain that is distinct from its aminoacylation domain. Mischarged amino acids are transiently translocated ∼30Å between active sites for editing by an unknown tRNA-dependent mechanism. A glycine within a flexible β-strand that links the aminoacylation and editing domains of LeuRS was determined to be important to tRNA translocation. The translocation-defective mutation also demonstrated that the editing site screens both correctly and incorrectly charged tRNAs prior to product release
Microwave response of vortices in superconducting thin films of Re and Al
Vortices in superconductors driven at microwave frequencies exhibit a
response related to the interplay between the vortex viscosity, pinning
strength, and flux creep effects. At the same time, the trapping of vortices in
superconducting microwave resonant circuits contributes excess loss and can
result in substantial reductions in the quality factor. Thus, understanding the
microwave vortex response in superconducting thin films is important for the
design of such circuits, including superconducting qubits and photon detectors,
which are typically operated in small, but non-zero, magnetic fields. By
cooling in fields of the order of 100 T and below, we have characterized
the magnetic field and frequency dependence of the microwave response of a
small density of vortices in resonators fabricated from thin films of Re and
Al, which are common materials used in superconducting microwave circuits.
Above a certain threshold cooling field, which is different for the Re and Al
films, vortices become trapped in the resonators. Vortices in the Al resonators
contribute greater loss and are influenced more strongly by flux creep effects
than in the Re resonators. This different behavior can be described in the
framework of a general vortex dynamics model.Comment: Published in Physical Review B 79,174512(2009); preprint version with
higher resolution figures available at
http://physics.syr.edu/~bplourde/bltp-publications.ht
Coherent dynamics of a Josephson charge qubit
We have fabricated a Josephson charge qubit by capacitively coupling a
single-Cooper-pair box (SCB) to an electrometer based upon a single-electron
transistor configured for radio-frequency readout (RF-SET). Charge quantization
of 2e is observed and microwave spectroscopy is used to extract the Josephson
and charging energies of the box. We perform coherent manipulation of the SCB
by using very fast DC pulses and observe quantum oscillations in time of the
charge that persist to ~=10ns. The observed contrast of the oscillations is
high and agrees with that expected from the finite E_J/E_C ratio and finite
rise-time of the DC pulses. In addition, we are able to demonstrate nearly 100%
initial charge state polarization. We also present a method to determine the
relaxation time T_1 when it is shorter than the measurement time T_{meas}.Comment: accepted for publication in Phys. Rev.
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