64 research outputs found
Coherent oscillations in a Cooper-pair box
This paper is devoted to an analysis of the experiment by Nakamura {\it et
al.} (Nature {\bf 398}, 786 (1999)) on the quantum state control in Josephson
junctions devices. By considering the relevant processes involved in the
detection of the charge state of the box and a realistic description of the
gate pulse we are able to analyze some aspects of the experiment (like the
amplitude of the measurement current) in a quantitative way
Current noise of a superconducting single electron transistor coupled to a resonator
We analyze the current and zero-frequency current noise properties of a
superconducting single electron resonator (SSET) coupled to a resonator,
focusing on the regime where the SSET is operated in the vicinity of the
Josephson quasiparticle resonance. We consider a range of coupling strengths
and resonator frequencies to reflect the fact that in practice the system can
be tuned to quite a high degree with the resonator formed either by a
nanomechanical oscillator or a superconducting stripline fabricated in close
proximity to the SSET. For very weak couplings the SSET acts on the resonator
like an effective thermal bath. In this regime the current characteristics of
the SSET are only weakly modified by the resonator. Using a mean field
approach, we show that the current noise is nevertheless very sensitive to the
correlations between the resonator and the SSET charge. For stronger couplings,
the SSET can drive the resonator into limit cycle states where self-sustained
oscillation occurs and we find that regions of well-defined bistability exist.
Dynamical transitions into and out of the limit cycle state are marked by
strong fluctuations in the resonator energy, but these fluctuations are
suppressed within the limit cycle state. We find that the current noise of the
SSET is strongly influenced by the fluctuations in the resonator energy and
hence should provide a useful indicator of the resonator's dynamics.Comment: Reduced quality figures for arXiv version; v2 minor correction
EXOPOLYMERS OF PROBIOTIC LACTOBACILLI AND BIFIDOBACTERIA (NEW APPROACHES AND FEATURES)
This paper summarizes the results of electrophoretic and other studies of exopolymeric substances (EPS) of probiotic lactobacilli and. bifidobacteria of human origin. It finds that EPS of lactobacilli were significantly less produced and. low stained with fluorescent dye compared to bifidobacterial ones. For the first time, the systems of biosurfactants of bacilli and. bifidobacteria were identified. Also the pictures of physical layer EPS gradients of bifidobacteria were described for the first time. Part of EPS included cationic latent biosurfactants. Perspective features of EPS are described. The used approaches are suitable for both screening probiotic producers of EPS and. monitoring EPS consumption or degradation. Electrophoresis in pore gels can be used for obtaining directed 3D gradients of EPS associated with (glyco)proteins and. (glyco)lipids
Charge Transport Processes in a Superconducting Single-Electron Transistor Coupled to a Microstrip Transmission Line
We have investigated charge transport processes in a superconducting
single-electron transistor (S-SET) fabricated in close proximity to a
two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure. The
macroscopic bonding pads of the S-SET along with the 2DEG form a microstrip
transmission line. We observe a variety of current-carrying cycles in the S-SET
which we attribute to simultaneous tunneling of Cooper pairs and emission of
photons into the microstrip. We find good agreement between these experimental
results and simulations including both photon emission and photon-assisted
tunneling due to the electromagnetic environment.Comment: 4 pages, 4 figures, REVTeX
Superlattice Based on Graphene on a Strip Substrate
A graphene-based superlattice formed due to the periodic modulation of the
band gap has been investigated. Such a modulation is possible in graphene
deposited on a strip substrate made of silicon oxide and hexagonal boron
nitride. The advantages and some possible problems in the superlattice under
consideration are discussed. A model describing such a superlattice is proposed
and the dispersion relation between the energy and momentum of carriers has
been obtained using the transfer matrix method within this model.Comment: 6 pages, 3 figure
Carrier Recombination, LongâWavelength Photoluminescence, and Stimulated Emission in HgCdTe Quantum Well Heterostructures
The Mode Competition, Instability, and Second Harmonic Generation in Dual-Frequency InGaAsâGaAsâInGaP Lasers
A new approach for computing the geometry of the moduli spaces for a CalabiâYau manifold
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