Experimental Demonstration of a Resonator-Induced Phase Gate in a Multiqubit Circuit-QED System.

The resonator-induced phase (RIP) gate is an all-microwave multiqubit entangling gate that allows a high degree of flexibility in qubit frequencies, making it attractive for quantum operations in large-scale architectures. We experimentally realize the RIP gate with four superconducting qubits in a three-dimensional circuit-QED architecture, demonstrating high-fidelity controlled-z (cz) gates between all possible pairs of qubits from two different 4-qubit devices in pair subspaces. These qubits are arranged within a wide range of frequency detunings, up to as large as 1.8 GHz. We further show a dynamical multiqubit refocusing scheme in order to isolate out 2-qubit interactions, and combine them to generate a 4-qubit Greenberger-Horne-Zeilinger state.

Non-Poissonian quantum jumps of a fluxonium qubit due to quasiparticle excitations.

As the energy relaxation time of superconducting qubits steadily improves, nonequilibrium quasiparticle excitations above the superconducting gap emerge as an increasingly relevant limit for qubit coherence. We measure fluctuations in the number of quasiparticle excitations by continuously monitoring the spontaneous quantum jumps between the states of a fluxonium qubit, in conditions where relaxation is dominated by quasiparticle loss. Resolution on the scale of a single quasiparticle is obtained by performing quantum nondemolition projective measurements within a time interval much shorter than T1, using a quantum-limited amplifier (Josephson parametric converter). The quantum jump statistics switches between the expected Poisson distribution and a non-Poissonian one, indicating large relative fluctuations in the quasiparticle population, on time scales varying from seconds to hours. This dynamics can be modified controllably by injecting quasiparticles or by seeding quasiparticle-trapping vortices by cooling down in a magnetic field.

Prevalence of obesity among Arab school children in Nazareth, Israel: comparison with national (Jewish) and international data.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: Lack of published data. Absence of Ethnic specific data. Lack of focus on obesity prevention in Arab schools. WHAT THIS STUDY ADDS: First set of data on obesity for Arab children. Data will be used as reference data. Alert health/school official for intervention. SUMMARY: Objective The objective is to produce the first set of obesity prevalence data and use the data as reference values of body mass index (BMI) trends for Arab children in Israel and compare with Jewish and international data. Methods A prevalence study was carried out in 2009 in which 4130 children aged 6-12, were selected from eight Arab sector schools representing the Nazareth Municipality. Height, weight and BMI measurements were obtained and presented by age, mean age, size, weight, gender and percentile. Appropriate epidemiological and statistical methods used for comparison. Results The obesity and overweight prevalence rates in Arab children by age ranges from 0% to 2.6% and 0% to 11.2%, respectively. Comparison with international and Jewish data revealed differences in almost all age groups but higher rates in Arabs, especially boys. Discussion The higher rates/trends in Arab children may be explained by more Arab women entering the workforce, increase in single-parent families and changes in food and physical activity environments. Conclusion Based on our data, we recommend either an ethnic-specific BMI reference curves and/or inclusion of Arab data in the Israeli data system. Research need to focus on reasons for the increase and interventions to reverse/slow the trend.

Quantum back-action of an individual variable-strength measurement.

Measuring a quantum system can randomly perturb its state. The strength and nature of this back-action depend on the quantity that is measured. In a partial measurement performed by an ideal apparatus, quantum physics predicts that the system remains in a pure state whose evolution can be tracked perfectly from the measurement record. We demonstrated this property using a superconducting qubit dispersively coupled to a cavity traversed by a microwave signal. The back-action on the qubit state of a single measurement of both signal quadratures was observed and shown to produce a stochastic operation whose action is determined by the measurement result. This accurate monitoring of a qubit state is an essential prerequisite for measurement-based feedback control of quantum systems.