13,050 research outputs found
Vacuum induced Berry phases in single-mode Jaynes-Cummings models
Motivated by the work [Phys. Rev. Lett. 89, 220404 (2002)] for detecting the
vacuum-induced Berry phases with two-mode Jaynes-Cummings models (JCMs), we
show here that, for a parameter-dependent single-mode JCM, certain atom-field
states also acquire the photon-number-dependent Berry phases after the
parameter slowly changed and eventually returned to its initial value. This
geometric effect related to the field quantization still exists, even the filed
is kept in its vacuum state. Specifically, a feasible Ramsey interference
experiment with cavity quantum electrodynamics (QED) system is designed to
detect the vacuum-induced Berry phase.Comment: 10 pages, 4 figures
Controllable coupling between a nanomechanical resonator and a coplanar-waveguide resonator via a superconducting flux qubit
We study a tripartite quantum system consisting of a coplanar-waveguide (CPW)
resonator and a nanomechanical resonator (NAMR) connected by a flux qubit,
where the flux qubit has a large detuning from both resonators. By a unitray
transformation and a second-order approximation, we obtain a strong and
controllable (i.e., magnetic-field-dependent) effective coupling between the
NAMR and the CPW resonator. Due to the strong coupling, vacuum Rabi splitting
can be observed from the voltage-fluctuation spectrum of the CPW resonator. We
further study the properties of single photon transport as inferred from the
reflectance or equivalently the transmittance. We show that the reflectance and
the corresponding phase shift spectra both exhibit doublet of narrow spectral
features due to vacuum Rabi splitting. By tuning the external magnetic field,
the reflectance and the phase shift can be varied from 0 to 1 and to
, respectively. The results indicate that this hybrid quantum system can
act as a quantum router.Comment: 8 pages, 6 figure
Switchable coupling between charge and flux qubits
We propose a hybrid quantum circuit with both charge and flux qubits
connected to a large Josephson junction that gives rise to an effective
inter-qubit coupling controlled by the external magnetic flux. This switchable
inter-qubit coupling can be used to transfer back and forth an arbitrary
superposition state between the charge qubit and the flux qubit working at the
optimal point. The proposed hybrid circuit provides a promising quantum memory
because the flux qubit at the optimal point can store the tranferred quantum
state for a relatively long time.Comment: 5 pages, 1 figur
Pharmacokinetic/Pharmacodynamic Correlation of Cefquinome Against Experimental Catheter-Associated Biofilm Infection Due to Staphylococcus aureus.
Biofilm formations play an important role in Staphylococcus aureus pathogenesis and contribute to antibiotic treatment failures in biofilm-associated infections. The aim of this study was to evaluate the pharmacokinetic/pharmacodynamic (PK/PD) profiles of cefquinome against an experimental catheter-related biofilm model due to S. aureus, including three clinical isolates and one non-clinical isolate. The minimal inhibitory concentration (MIC), minimal biofilm inhibitory concentration (MBIC), biofilm bactericidal concentration (BBC), minimal biofilm eradication concentration (MBEC) and biofilm prevention concentration (BPC) and in vitro time-kill curves of cefquinome were studied in both planktonic and biofilm cells of study S. aureus strains. The in vivo post-antibiotic effects (PAEs), PK profiles and efficacy of cefquinome were performed in the catheter-related biofilm infection model in murine. A sigmoid E max model was utilized to determine the PK/PD index that best described the dose-response profiles in the model. The MICs and MBICs of cefquinome for the four S. aureus strains were 0.5 and 16 μg/mL, respectively. The BBCs (32-64 μg/mL) and MBECs (64-256 μg/mL) of these study strains were much higher than their corresponding BPC values (1-2 μg/mL). Cefquinome showed time-dependent killing both on planktonic and biofilm cells, but produced much shorter PAEs in biofilm infections. The best-correlated PK/PD parameters of cefquinome for planktonic and biofilm cells were the duration of time that the free drug level exceeded the MIC (fT > MIC, R (2) = 96.2%) and the MBIC (fT > MBIC, R (2) = 94.7%), respectively. In addition, the AUC24h/MBIC of cefquinome also significantly correlated with the anti-biofilm outcome in this model (R (2) = 93.1%). The values of AUC24h/MBIC for biofilm-static and 1-log10-unit biofilm-cidal activity were 22.8 and 35.6 h; respectively. These results indicate that the PK/PD profiles of cefquinome could be used as valuable guidance for effective dosing regimens treating S. aureus biofilm-related infections
Optical selection rules and phase-dependent adiabatic state control in a superconducting quantum circuit
We analyze the optical selection rules of the microwave-assisted transitions
in a flux qubit superconducting quantum circuit (SQC). We show that the
parities of the states relevant to the superconducting phase in the SQC are
well-defined when the external magnetic flux , then the
selection rules are same as the ones for the electric-dipole transitions in
usual atoms. When , the symmetry of the potential of
the artificial "atom'' is broken, a so-called -type "cyclic"
three-level atom is formed, where one- and two-photon processes can coexist. We
study how the population of these three states can be selectively transferred
by adiabatically controlling the electromagnetic field pulses. Different from
-type atoms, the adiabatic population transfer in our three-level
-atom can be controlled not only by the amplitudes but also by the
phases of the pulses
Reconstructing diffusion kurtosis tensors from sparse noisy measurements
Diffusion kurtosis imaging (DKI) is a recent MRI based method that can quantify deviation from Gaussian behavior using a kurtosis tensor. DKI has potential value for the assessment of neurologic diseases. Existing techniques for diffusion kurtosis imaging typically need to capture hundreds of MRI images, which is not clinically feasible on human subjects. In this paper, we develop robust denoising and model fitting methods that make it possible to accurately reconstruct a kurtosis tensor from 75 or less noisy measurements. Our denoising method is based on subspace learning for multi-dimensional signals and our model fitting technique uses iterative reweighting to effectively discount the influences of outliers. The total data acquisition time thus drops significantly, making diffusion kurtosis imaging feasible for many clinical applications involving human subjects. © 2010 IEEE.published_or_final_versionThe 17th IEEE International Conference on Image Processing (ICIP 2010), Hong Kong, China, 26-29 September 2010. In Proceedings of the 17th ICIP, 2010, p. 4185-418
Measuring the quality factor of a microwave cavity using superconduting qubit devices
We propose a method to create superpositions of two macroscopic quantum
states of a single-mode microwave cavity field interacting with a
superconducting charge qubit. The decoherence of such superpositions can be
determined by measuring either the Wigner function of the cavity field or the
charge qubit states. Then the quality factor Q of the cavity can be inferred
from the decoherence of the superposed states. The proposed method is
experimentally realizable within current technology even when the value is
relatively low, and the interaction between the qubit and the cavity field is
weak.Comment: 8 page
Generation and control of Greenberger-Horne-Zeilinger entanglement in superconducting circuits
Going beyond the entanglement of microscopic objects (such as photons, spins,
and ions), here we propose an efficient approach to produce and control the
quantum entanglement of three macroscopic coupled superconducting qubits. By
conditionally rotating, one by one, selected Josephson charge qubits, we show
that their Greenberger-Horne-Zeilinger (GHZ) entangled states can be
deterministically generated. The existence of GHZ correlations between these
qubits could be experimentally demonstrated by effective single-qubit
operations followed by high-fidelity single-shot readouts. The possibility of
using the prepared GHZ correlations to test the macroscopic conflict between
the noncommutativity of quantum mechanics and the commutativity of classical
physics is also discussed.Comment: 4 Pages with 1 figure. to appear in Physical Review Letter
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