Dephasing of solid-state qubits at optimal points

Motivated by recent experiments with Josephson-junction circuits, we analyze the influence of various noise sources on the dynamics of two-level systems at optimal operation points where the linear coupling to low-frequency fluctuations is suppressed. We study the decoherence due to nonlinear (quadratic) coupling, focusing on the experimentally relevant 1/f and Ohmic noise power spectra. For 1/f noise strong higher-order effects influence the evolution.Comment: minor corrections and clarification

Photon mediated interaction between distant quantum dot circuits

Engineering the interaction between light and matter is an important goal in the emerging field of quantum opto-electronics. Thanks to the use of cavity quantum electrodynamics architectures, one can envision a fully hybrid multiplexing of quantum conductors. Here, we use such an architecture to couple two quantum dot circuits . Our quantum dots are separated by 200 times their own size, with no direct tunnel and electrostatic couplings between them. We demonstrate their interaction, mediated by the cavity photons. This could be used to scale up quantum bit architectures based on quantum dot circuits or simulate on-chip phonon-mediated interactions between strongly correlated electrons

HSV2 acute retinal necrosis: diagnosis and monitoring with quantitative polymerase chain reaction

Purpose To describe a case of HSV2 acute retinal necrosis (ARN) diagnosed and monitored with quantitative polymerase chain reaction (PCR) in ocular fluids. Design Case report. Methods Quantitative PCR was performed in the aqueous humor (AH) and vitreous using primers specific for herpes virus. Results A positive PCR was found for HSV2 in the AH (>100,000,000 viral copies − 8.00log/ml). After therapy, another anterior chamber tap showed a reduction of the viral load at 4.28log/ml (19205 copies), confirming the efficacy of the treatment. After six months, PCR on the vitreous still showed the presence of HSV2 viral particles in the eye (3.14 log DNA copies/ml, 1379 copies) although the lesion was healed. Conclusions This case demonstrates that PCR is useful to detect viral DNA in AH and vitreous and to monitor viral activity and therapeutic response. Viral DNA persists in ocular fluids for months in the presence of a healed infectio

Using Spontaneous Emission of a Qubit as a Resource for Feedback Control

Persistent control of a transmon qubit is performed by a feedback protocol based on continuous heterodyne measurement of its fluorescence. By driving the qubit and cavity with microwave signals whose amplitudes depend linearly on the instantaneous values of the quadratures of the measured fluorescence field, we show that it is possible to stabilize permanently the qubit in any targeted state. Using a Josephson mixer as a phase-preserving amplifier, it was possible to reach a total measurement efficiency $\eta$=35%, leading to a maximum of 59% of excitation and 44% of coherence for the stabilized states. The experiment demonstrates multiple-input multiple-output analog Markovian feedback in the quantum regime.Comment: Supplementary material can be found as an ancillary objec

Modeling a Schottky-barrier carbon nanotube field-effect transistor with ferromagnetic contacts

In this study, a model of a Schottky-barrier carbon nanotube field- effect transistor (CNT-FET), with ferromagnetic contacts, has been developed. The emphasis is put on analysis of current-voltage characteristics as well as shot (and thermal) noise. The method is based on the tight-binding model and the non- equilibrium Green's function technique. The calculations show that, at room temperature, the shot noise of the CNT FET is Poissonian in the sub-threshold region, whereas in elevated gate and drain/source voltage regions the Fano factor gets strongly reduced. Moreover, transport properties strongly depend on relative magnetization orientations in the source and drain contacts. In particular, one observes quite a large tunnel magnetoresistance, whose absolute value may exceed 50%.Comment: 8 pages, 4 figure

Principles and Implementation of an Ultrafast Transmission Electron Microscope

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 - August 2, 201

Nanospintronics with carbon nanotubes

One of the actual challenges of spintronics is the realization of a spin-transistor allowing to control spin transport through an electrostatic gate. In this review, we report on different experiments which demonstrate a gate control of spin transport in a carbon nanotube connected to ferromagnetic leads. We also discuss some theoretical approaches which can be used to analyze spin transport in these systems. We emphasize the roles of the gate-tunable quasi-bound states inside the nanotube and the coherent spin-dependent scattering at the interfaces between the nanotube and its ferromagnetic contacts.Comment: 35 pages, 15 figures, some figures in gi

Translation, cross-cultural adaptation, and validation of the Italian version of the anterior cruciate ligament–return to sport after injury (ACL-RSI) scale and its integration into the K-STARTS test

Background: The timing of a return to sport (RTS) after anterior cruciate ligament reconstruction (ACLR) represents a major subject of debate in sports medicine practice. Recently, the Knee Santy Athletic Return to Sport (K‐STARTS) composite test was validated. This consists of a battery of physical tests and a psychological evaluation using the anterior cruciate ligament–return to sport after injury scale (ACL‐RSI). This study aimed to translate the ACL‐RSI and K‐STARTS from English to Italian and determine the scale’s reliability and validity in an Italian context. Methods: The translation and cultural adaptation process was performed according to the guidelines for the cross‐ cultural adaptation of self‐report measures. The patients were asked to fill an anonymized online form created for this purpose that included the KOOS, the Lysholm, the IKDC‐SKF, and the Italian translation of the ACL‐RSI (ACL‐RSI‐It). After 1 week, the attendees were asked to repeat the ACL‐RSI‐It to investigate the test–retest reliability. Results: The final study population comprised 115 patients who underwent ACLR, with a mean follow‐up of 37.37 ± 26.56 months. The ACL‐RSI‐It showed axcellent internal consistency (Cronbach’s α = 0.963), reliability (test– retest ICC = 0.966), and good construct validity (positive correlations with the other scales were above 75%). Conclusions: The ACL‐RSI‐It is valid, reliable, and comparable to the original English version of the questionnaire for Italian‐speaking patients. It can be used to assess the psychological readiness of patients for a RTS after primary and unilateral ACLR, and can be integrated into the Italian K‐STARTS test

Entanglement and decoherence of a micromechanical resonator via coupling to a Cooper box

We analyse the quantum dynamics of a micromechanical resonator capacitively coupled to a Cooper box. With appropriate quantum state control of the Cooper box, the resonator can be driven into a superposition of spatially separated states. The Cooper box can also be used to probe the environmentally-induced decoherence of the resonator superposition state.Comment: 4 pages, 3 figure