Energy-level quantization and single-photon control of phase slips in YBa2Cu3O7-x nanowires.

Significant progress has been made in superconducting quantum circuits. However new quantum devices that have longer decoherence times at higher temperatures are urgently required for quantum technologies. Superconducting nanowires with quantum phase slips are promising candidates for use in novel quantum devices. Here, we demonstrate YBa2Cu3O7-x nanowires with phase-slip dynamics and study their switching-current statistics at temperatures below 20 K. We apply theoretical models developed for Josephson junctions and show that our results provide strong evidence for energy-level quantization in the nanowires. The crossover temperature to the quantum regime of 12-13 K and the lifetime in the excited state exceeding 20 ms at 5.4 K are superior to those in conventional Josephson junctions. We also show how the absorption of a single photon changes the phase-slip and quantum state of a nanowire, which is important for the development of single-photon detectors with high operating temperature and superior temporal resolution.

Quantum interference in heterogeneous superconducting-photonic circuits on a silicon chip.

Quantum information processing holds great promise for communicating and computing data efficiently. However, scaling current photonic implementation approaches to larger system size remains an outstanding challenge for realizing disruptive quantum technology. Two main ingredients of quantum information processors are quantum interference and single-photon detectors. Here we develop a hybrid superconducting-photonic circuit system to show how these elements can be combined in a scalable fashion on a silicon chip. We demonstrate the suitability of this approach for integrated quantum optics by interfering and detecting photon pairs directly on the chip with waveguide-coupled single-photon detectors. Using a directional coupler implemented with silicon nitride nanophotonic waveguides, we observe 97% interference visibility when measuring photon statistics with two monolithically integrated superconducting single-photon detectors. The photonic circuit and detector fabrication processes are compatible with standard semiconductor thin-film technology, making it possible to implement more complex and larger scale quantum photonic circuits on silicon chips.

High-speed and high-efficiency travelling wave single-photon detectors embedded in nanophotonic circuits.

Ultrafast, high-efficiency single-photon detectors are among the most sought-after elements in modern quantum optics and quantum communication. However, imperfect modal matching and finite photon absorption rates have usually limited their maximum attainable detection efficiency. Here we demonstrate superconducting nanowire detectors atop nanophotonic waveguides, which enable a drastic increase of the absorption length for incoming photons. This allows us to achieve high on-chip single-photon detection efficiency up to 91% at telecom wavelengths, repeatable across several fabricated chips. We also observe remarkably low dark count rates without significant compromise of the on-chip detection efficiency. The detectors are fully embedded in scalable silicon photonic circuits and provide ultrashort timing jitter of 18 ps. Exploiting this high temporal resolution, we demonstrate ballistic photon transport in silicon ring resonators. Our direct implementation of a high-performance single-photon detector on chip overcomes a major barrier in integrated quantum photonics.

Two-particle separation energy trends in the superdeformed well.

A measurement of the energy and spin of superdeformed states in 190Hg, obtained through the observation of transitions directly linking superdeformed and normal states, expands the number of isotopes in which binding energies at superdeformation are known. Comparison with neighboring nuclei shows that two-proton separation energies are higher in the superdeformed state than in the normal state, despite the lower Coulomb barrier and lower total binding energy. This unexpected result provides a critical test for nuclear models.

Bandwidth-tunable single-photon source in an ion-trap quantum network.

We report a tunable single-photon source based on a single trapped ion. Employing spontaneous Raman scattering and in-vacuum optics with large numerical aperture, single photons are efficiently created with controlled temporal shape and coherence time. These can be varied between 70 ns and 1.6 micros, as characterized by operating two sources simultaneously in two remote ion traps which reveals mutual and individual coherence through two-photon interference.

Linear polarization measurement of interband transitions in superdeformed 190hg: model-independent evidence for octupole vibrational structures.

The linear polarization of gamma rays between excited and yrast superdeformed (SD) states in 190Hg was measured using the four-element CLOVER detectors of the EUROBALL IV gamma-ray spectrometer. This measurement shows in a model-independent way that the interband transitions which compete with the highly collective in-band quadrupole transitions are largely enhanced electric dipoles. Not only do these results represent the first measurement of the multipolarity of transitions between different SD states, but they also provide strong evidence for the interpretation of the structures in the SD minimum of the A approximately 190 region in terms of octupole excitations.

Chloral hydrate sedation of children undergoing CT and MR imaging: safety as judged by American Academy of Pediatrics guidelines.

OBJECTIVE: The purpose of this prospective study was to determine the frequency of adverse events associated with supplemented and unsupplemented chloral hydrate sedation in a select group of children undergoing CT or MR imaging using the revised American Academy of Pediatrics (AAP) monitoring and management guidelines for pediatric sedation. The AAP guidelines do not recommend drug selection or dosages but define patient selection, discharge criteria, and monitoring standards for sedating children. SUBJECTS AND METHODS: This prospective study included 410 children 4 years of age or younger who were scheduled for CT and MR imaging as outpatients. Selected children were physical status 1 or 2 as determined by the American Society of Anesthesiologists physical status classification and had no contraindications to sedation per our institutional sedation policy. Children younger than 1 year old received only oral incremental doses of chloral hydrate. Children 1-4 years old received hydroxyzine plus incremental doses of chloral hydrate. Children between 2 and 4 years old who were not satisfactorily sedated 30 min after hydroxyzine plus incremental chloral hydrate were given 2 mg/kg meperidine intramuscularly, with a maximum dose of 50 mg. All children were monitored according to the revised guidelines recommended by the committee on drugs of the AAP. Vital signs and arterial hemoglobin oxygen saturation (SpO2) were monitored continuously by registered nurses trained in pediatric advanced life support from the time of sedative drug administration until the recommended discharge criteria were met. RESULTS: Mild hypoxia (SpO2, 90-95%) that resolved spontaneously without any therapeutic intervention was seen in 9% of the chloral hydrate group and in 5% of the chloral hydrate-hydroxyzine group. One child in the chloral hydrate group had severe hypoxia (SpO2, 85-89%), and one child in the chloral hydrate-hydroxyzine group had moderate hypoxia (SpO2, < 85%). Both required therapeutic intervention. In both cases, the severity of the underlying medical disease was underestimated at the time of presedation medical screening. The success rate of sedation was 100% for all the children having CT. For those having MR imaging, success was 100% for children 1-4 years old and 97% for children less than 1 year old. CONCLUSION: Use of supplemented and unsupplemented chloral hydrate sedation provides effective and safe sedation in children if the AAP guidelines for patient selection, monitoring, and management are followed. Careful medical screening and patient selection by knowledgeable medical personnel is important to exclude patients at high risk for life-threatening hypoxia. Monitoring with AAP guidelines is essential for prompt detection and management of life-threatening hypoxia.