QND measurement of a superconducting qubit in the weakly projective regime

Quantum state detectors based on switching of hysteretic Josephson junctions biased close to their critical current are simple to use but have strong back-action. We show that the back-action of a DC-switching detector can be considerably reduced by limiting the switching voltage and using a fast cryogenic amplifier, such that a single readout can be completed within 25 ns at a repetition rate of 1 MHz without loss of contrast. Based on a sequence of two successive readouts we show that the measurement has a clear quantum non-demolition character, with a QND fidelity of 75 %.Comment: submitted to PR

Partial-measurement back-action and non-classical weak values in a superconducting circuit

We realize indirect partial measurement of a transmon qubit in circuit quantum electrodynamics by interaction with an ancilla qubit and projective ancilla measurement with a dedicated readout resonator. Accurate control of the interaction and ancilla measurement basis allows tailoring the measurement strength and operator. The tradeoff between measurement strength and qubit back-action is characterized through the distortion of a qubit Rabi oscillation imposed by ancilla measurement in different bases. Combining partial and projective qubit measurements, we provide the solid-state demonstration of the correspondence between a non-classical weak value and the violation of a Leggett-Garg inequality.Comment: 5 pages, 4 figures, and Supplementary Information (8 figures

In the Mood for Risk? A Random-Assignment Experiment Addressing the Effects of Moods on Risk Preferences

Recent discussions in decision sciences and behavioral economics stress the potential impact of affect on decision outcomes. In the present study, we conducted random-assignment experiments (N = 253) to investigate whether affect can cause temporary fluctuations in risk preferences. In particular, we employed film clips to vary the valence (positive / negative) and arousal level (low / high) of the affective states of student participants; following this, we elicited and observed risk preferences by asking the participants to make choi

Are tibial angles measured with inertial sensors useful surrogates for frontal plane projection angles using 2-dimensional video analysis during single leg squat tasks? A reliability and agreement analysis in elite football (soccer) players

During single leg squats (SLS), tibial angle (TA) quantification using inertial measurement units (IMU) may offer a practical alternative to frontal plane projection angle (FPPA) measurement using 2-dimensional (2D) video analysis. This study determined: (i) the reliability of IMUs and 2D video analysis for TA measurement, and 2D video analysis for FPPA measurement; (ii) the agreement between IMU TA and both 2D video TA and FPPA measurements during single leg squats in elite footballers. 18 players were tested on consecutive days. Absolute TA (ATA) and relative TA (RTA) were measured with IMUs. ATA and FPPA were measured concurrently using 2D video analysis. Within-session reliability for all measurements varied across days (intraclass correlation coefficient (ICC) range=0.27–0.83, standard error of measurement (SEM) range=2.12–6.23°, minimal detectable change (MDC) range=5.87–17.26°). Between-sessions, ATA reliability was good for both systems (ICCs=0.70–0.74, SEMs=1.64–7.53°, MDCs=4.55–7.01°), while IMU RTA and 2D FPPA reliability ranged from poor to good (ICCs=0.39–0.72, SEMs=2.60–5.99°, MDCs=7.20–16.61°). All limits of agreement exceeded a 5° acceptability threshold. Both systems were reliable for between-session ATA, although agreement was poor. IMU RTA and 2D video FPPA reliability was variable. For SLS assessment, IMU derived TAs are not useful surrogates for 2D video FPPA measures in this population

Microalgae for municipal wastewater nutrient remediation: mechanisms, reactors and outlook for tertiary treatment

This review explores the use of microalgae for nutrient removal in municipal wastewater treatment, considering recent improvements in the understanding of removal mechanisms and developments of both suspended and non-suspended systems. Nutrient removal is associated to both direct and indirect uptake, with the former associated to the biomass concentration and growth environment (reactor). Importantly, direct uptake is influenced by the Nitrogen:Phosphorus content in both the cells and the surrounding wastewater, with opposite trends observed for N and P. Comparison of suspended and non-suspended systems revealed that whilst all were capable of achieving high levels of nutrient removal, only non-suspended immobilized systems could do so with reduced hydraulic retention times of less than 1 day. As microalgae are photosynthetic organisms, the metabolic processes associated with nutrient assimilation are driven by light. Optimization of light delivery remains a key area of development with examples of improved mixing in suspended systems and the use of pulsating lights to enhance light utilization and reduce costs. Recent data provide increased confidence in the use of microalgae for nutrient removal in municipal wastewater treatment, enabling effluent discharges below 1 mg L−1 to be met whilst generating added value in terms of bioproducts for energy production or nutrient recovery. Ultimately, the review suggests that future research should focus on non-suspended systems and the determination of the added value potential. In so doing, it is predicted that microalgae systems will be significant in the delivery of the circular economy

Interqubit coupling mediated by a high-excitation-energy quantum object

We consider a system composed of two qubits and a high-excitation-energy quantum object used to mediate coupling between the qubits. We treat the entire system quantum mechanically and analyze the properties of the eigenvalues and eigenstates of the total Hamiltonian. After reproducing well-known results concerning the leading term in the mediated coupling, we obtain an expression for the residual coupling between the qubits in the off state. We also analyze the entanglement between the three objects, i.e. the two qubits and the coupler, in the eigenstates of the total Hamiltonian. Although we focus on the application of our results to the recently realized parametric-coupling scheme with two qubits, we also discuss extensions of our results to harmonic-oscillator couplers, couplers that are near resonance with the qubits and multi-qubit systems. In particular, we find that certain errors that are absent for a two-qubit system arise when dealing with multi-qubit systems.Comment: 15 pages (two-column

Role of relaxation in the quantum measurement of a superconducting qubit using a nonlinear oscillator

We analyze the relaxation of a superconducting flux qubit during measurement. The qubit state is measured with a nonlinear oscillator driven across the threshold of bifurcation, acting as a switching dispersive detector. This readout scheme is of quantum non-demolition type. Two successive readouts are used to analyze the evolution of the qubit and the detector during the measurement. We introduce a simple transition rate model to characterize the qubit relaxation and the detector switching process. Corrected for qubit relaxation the readout fidelity is at least 95%. Qubit relaxation strongly depends on the driving strength and the state of the oscillator.Comment: 4 pages, 4 figure

A Multi-Level View of the Antecedents and Consequences of Trust in Virtual Leaders

Although trust is widely acknowledged as critical to virtual teams, little is known regarding the causes and consequences of trust in leaders of virtual teams. This paper examines the antecedents and consequences of trust in virtual team leaders. Using survey and archival data from a massively multiplayer online game (MMOG), this study’s findings show that trust in the leader is affected by team members’ use of synchronous communication and breadth of communication with leaders as well as team members’ distance from each other. Furthermore, reasoning that team size and culture create a shared context qualifying team members’ experiences, we found that team size and collectivistic values diminished the benefits of synchronous communication and breadth of communication, respectively. The findings also revealed that trust in leaders had a positive relationship to team performance. Detailed discussion of the findings is provided in the conclusion of the paper

Effect of a 6-month brisk walking program on walking endurance in sedentary and physically deconditioned women aged 60 or older: A randomized trial

International audienceBACKGROUND:Walking endurance is a predictor of healthy ageing.OBJECTIVE:To examine if a 6-month brisk walking program can increase walking endurance in sedentary and physically deconditioned older women.TRIAL DESIGN:Randomized controlled trial.SETTING:Women recruited from public meetings aimed at promoting physical activity in women aged 60 or older.SUBJECTS:121 women aged 65.7 ± 4.3 years, with sedentary lifestyle (Physical Activity Questionnaire for the Elderly score 46%) were those with baseline lowest values of 6MWD (p=0.001) and highest values of body mass index (BMI) (p<0.01).CONCLUSION:Present results support recommendation that brisk walking programs should be encouraged to improve walking endurance in physically deconditioned women aged 60 or older, especially in those with high BMI