1,520 research outputs found
Future Measurements of Deeply Virtual Compton Scattering at HERMES
Prospects for future measurements of Deeply Virtual Compton Scattering at
HERMES are studied using different simple models for parameterizations of
generalized parton distributions (GPDs). Measurements of the lepton charge and
lepton beam helicity asymmetry will yield important input for theoretical
models towards the future extraction of GPDs.Comment: 12 pages, 7 figure
Entanglement of solid-state qubits by measurement
We show that two identical solid-state qubits can be made fully entangled
(starting from completely mixed state) with probability 1/4 just measuring them
by a detector, equally coupled to the qubits. This happens in the case of
repeated strong (projective) measurements as well as in a more realistic case
of weak continuous measurement. In the latter case the entangled state can be
identified by a flat spectrum of the detector shot noise, while the
non-entangled state (probability 3/4) leads to a spectral peak at the Rabi
frequency with the maximum peak-to-pedestal ratio of 32/3.Comment: 5 pages, 2 figure
Spectrum of qubit oscillations from Bloch equations
We have developed a formalism suitable for calculation of the output spectrum
of a detector continuously measuring quantum coherent oscillations in a
solid-state qubit, starting from microscopic Bloch equations. The results
coincide with that obtained using Bayesian and master equation approaches. The
previous results are generalized to the cases of arbitrary detector response
and finite detector temperature.Comment: 8 page
Resonant tunneling through a macroscopic charge state in a superconducting SET transistor
We predict theoretically and observe in experiment that the differential
conductance of a superconducting SET transistor exhibits a peak which is a
complete analogue in a macroscopic system of a standard resonant tunneling peak
associated with tunneling through a single quantum state. In particular, in a
symmetric transistor, the peak height is universal and equal to . Away from the resonance we clearly observe the co-tunneling current
which in contrast to the normal-metal transistor varies linearly with the bias
voltage.Comment: 11 pages, 3 figures, Fig. 1 available upon request from the first
autho
Persistent Rabi oscillations probed via low-frequency noise correlation
The qubit Rabi oscillations are known to be non-decaying (though with a
fluctuating phase) if the qubit is continuously monitored in the weak-coupling
regime. In this paper we propose an experiment to demonstrate these persistent
Rabi oscillations via low-frequency noise correlation. The idea is to measure a
qubit by two detectors, biased stroboscopically at the Rabi frequency. The
low-frequency noise depends on the relative phase between the two combs of
biasing pulses, with a strong increase of telegraph noise in both detectors for
the in-phase or anti-phase combs. This happens because of self-synchronization
between the persistent Rabi oscillations and measurement pulses. Almost perfect
correlation of the noise in the two detectors for the in-phase regime and
almost perfect anticorrelation for the anti-phase regime indicates a presence
of synchronized persistent Rabi oscillations. The experiment can be realized
with semiconductor or superconductor qubits.Comment: 5 page
Nonideal quantum detectors in Bayesian formalism
The Bayesian formalism for a continuous measurement of solid-state qubits is
derived for a model which takes into account several factors of the detector
nonideality. In particular, we consider additional classical output and
backaction noises (with finite correlation), together with quantum-limited
output and backaction noises, and take into account possible asymmetry of the
detector coupling. The formalism is first derived for a single qubit and then
generalized to the measurement of entangled qubits.Comment: 10 page
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