1,054 research outputs found
NrsZ: a novel, processed, nitrogen-dependent, small non-coding RNA that regulates Pseudomonas aeruginosa PAO1 virulence.
The opportunistic pathogen Pseudomonas aeruginosa PAO1 has a remarkable capacity to adapt to various environments and to survive with limited nutrients. Here, we report the discovery and characterization of a novel small non-coding RNA: NrsZ (nitrogen-regulated sRNA). We show that under nitrogen limitation, NrsZ is induced by the NtrB/C two component system, an important regulator of nitrogen assimilation and P. aeruginosa's swarming motility, in concert with the alternative sigma factor RpoN. Furthermore, we demonstrate that NrsZ modulates P. aeruginosa motility by controlling the production of rhamnolipid surfactants, virulence factors notably needed for swarming motility. This regulation takes place through the post-transcriptional control of rhlA, a gene essential for rhamnolipids synthesis. Interestingly, we also observed that NrsZ is processed in three similar short modules, and that the first short module encompassing the first 60 nucleotides is sufficient for NrsZ regulatory functions
Improving the Coherence Time of Superconducting Coplanar Resonators
The quality factor and energy decay time of superconducting resonators have
been measured as a function of material, geometry, and magnetic field. Once the
dissipation of trapped magnetic vortices is minimized, we identify surface
two-level states (TLS) as an important decay mechanism. A wide gap between the
center conductor and the ground plane, as well as use of the superconductor Re
instead of Al, are shown to decrease loss. We also demonstrate that classical
measurements of resonator quality factor at low excitation power are consistent
with single-photon decay time measured using qubit-resonator swap experiments.Comment: 3 pages, 4 figures for the main paper; total 5 pages, 6 figures
including supplementary material. Submitted to Applied Physics Letter
Energy decay and frequency shift of a superconducting qubit from non-equilibrium quasiparticles
Quasiparticles are an important decoherence mechanism in superconducting
qubits, and can be described with a complex admittance that is a generalization
of the Mattis-Bardeen theory. By injecting non-equilibrium quasiparticles with
a tunnel junction, we verify qualitatively the expected change of the decay
rate and frequency in a phase qubit. With their relative change in agreement to
within 4% of prediction, the theory can be reliably used to infer quasiparticle
density. We describe how settling of the decay rate may allow determination of
whether qubit energy relaxation is limited by non-equilibrium quasiparticles.Comment: Main paper: 4 pages, 3 figures, 1 table. Supplementary material: 8
pages, 3 figure
Multiplexed dispersive readout of superconducting phase qubits
We introduce a frequency-multiplexed readout scheme for superconducting phase
qubits. Using a quantum circuit with four phase qubits, we couple each qubit to
a separate lumped-element superconducting readout resonator, with the readout
resonators connected in parallel to a single measurement line. The readout
resonators and control electronics are designed so that all four qubits can be
read out simultaneously using frequency multiplexing on the one measurement
line. This technology provides a highly efficient and compact means for reading
out multiple qubits, a significant advantage for scaling up to larger numbers
of qubits.Comment: 4 pages, 4 figure
Quantum process tomography of two-qubit controlled-Z and controlled-NOT gates using superconducting phase qubits
We experimentally demonstrate quantum process tomography of controlled-Z and
controlled-NOT gates using capacitively-coupled superconducting phase qubits.
These gates are realized by using the state of the phase qubit. We
obtain a process fidelity of 0.70 for the controlled-phase and 0.56 for the
controlled-NOT gate, with the loss of fidelity mostly due to single-qubit
decoherence. The controlled-Z gate is also used to demonstrate a two-qubit
Deutsch-Jozsa algorithm with a single function query.Comment: 10 pages, 8 figures, including supplementary informatio
Deterministic entanglement of photons in two superconducting microwave resonators
Quantum entanglement, one of the defining features of quantum mechanics, has
been demonstrated in a variety of nonlinear spin-like systems. Quantum
entanglement in linear systems has proven significantly more challenging, as
the intrinsic energy level degeneracy associated with linearity makes quantum
control more difficult. Here we demonstrate the quantum entanglement of photon
states in two independent linear microwave resonators, creating N-photon NOON
states as a benchmark demonstration. We use a superconducting quantum circuit
that includes Josephson qubits to control and measure the two resonators, and
we completely characterize the entangled states with bipartite Wigner
tomography. These results demonstrate a significant advance in the quantum
control of linear resonators in superconducting circuits.Comment: 11 pages, 11 figures, and 3 tables including supplementary materia
Reduced phase error through optimized control of a superconducting qubit
Minimizing phase and other errors in experimental quantum gates allows higher
fidelity quantum processing. To quantify and correct for phase errors in
particular, we have developed a new experimental metrology --- amplified phase
error (APE) pulses --- that amplifies and helps identify phase errors in
general multi-level qubit architectures. In order to correct for both phase and
amplitude errors specific to virtual transitions and leakage outside of the
qubit manifold, we implement "half derivative" an experimental simplification
of derivative reduction by adiabatic gate (DRAG) control theory. The phase
errors are lowered by about a factor of five using this method to per gate, and can be tuned to zero. Leakage outside the qubit
manifold, to the qubit state, is also reduced to for
faster gates.Comment: 4 pages, 4 figures with 2 page supplementa
Denaturation transition of stretched DNA
We generalize the Poland-Scheraga model to consider DNA denaturation in the
presence of an external stretching force. We demonstrate the existence of a
force-induced DNA denaturation transition and obtain the temperature-force
phase diagram. The transition is determined by the loop exponent for which
we find the new value such that the transition is second order
with in . We show that a finite stretching force
destabilizes DNA, corresponding to a lower melting temperature , in
agreement with single-molecule DNA stretching experiments.Comment: 5 pages, 3 figure
Does the group leader matter? The impact of monitoring activities and social ties of group leaders on the repayment performance of groupbased lending Eritrea
This paper analyzes whether the effects of monitoring and social ties of the group leader and other group members on repayment performance of groups differ, using data from an extensive questionnaire held in Eritrea among participants of 102 groups. We hypothesize that the monitoring activities and social ties of the group leader have a stronger positive impact on the repayment performance of groups. The results show that social ties of the group leader do have a positive effect on repayment performance of groups, whereas this is not true for social ties of other group members. We do not find evidence for the hypothesis that monitoring activities of the group leader have a stronger positive impact on group repayment performance. All variables measuring monitoring activities, either of the group leader or the other group members, are found to be statistically insignificant.
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