98 research outputs found
Gaplessness and the Coulomb anomaly in the strongly disordered films of Molybdenum Carbide
Gaplessness was observed in the disordered films of MoC on approaching to the
superconductor to insulator transition by reducing the film thickness. The
gaplessness is attributed to the enhanced Coulomb interactions due to the loss
of screening in the presence of strong disorder in the films.Comment: 3 pages, 5 figure
Surpassing the resistance quantum with a geometric superinductor
The superconducting circuit community has recently discovered the promising
potential of superinductors. These circuit elements have a characteristic
impedance exceeding the resistance quantum which leads to a suppression of ground state charge
fluctuations. Applications include the realization of hardware protected qubits
for fault tolerant quantum computing, improved coupling to small dipole moment
objects and defining a new quantum metrology standard for the ampere. In this
work we refute the widespread notion that superinductors can only be
implemented based on kinetic inductance, i.e. using disordered superconductors
or Josephson junction arrays. We present modeling, fabrication and
characterization of 104 planar aluminum coil resonators with a characteristic
impedance up to 30.9 at 5.6 GHz and a capacitance down to
fF, with low-loss and a power handling reaching intra-cavity
photons. Geometric superinductors are free of uncontrolled tunneling events and
offer high reproducibility, linearity and the ability to couple magnetically -
properties that significantly broaden the scope of future quantum circuits.Comment: 8 pages, 5 figures, 1 tabl
Simulation Support for Optimizing the Design and Operation of a Large Open-Space Office Building
This paper deals with design and post-design operational optimization studies for a new head office of a bank in Prague. The building can be characterized as a large open space office building. During the design phase computational modeling and simulation was used to predict the performance of various design alternatives with respect to reducing the required cooling capacity, in order to verify the fan-coil capacity sizing and to optimize the ventilation system and strategy of the atriums. Since the design included exposed concrete ceilings, the design intent was to use the building thermal mass for cooling load reduction and to employ a strategy for low-energy operation of the building. The maximum cooling demand for the initial design was estimated at 3 MW for the whole building. Computational simulations showed a potential reduction to 81 % of this value. Additional simulations helped designers to optimize the thermal comfort in the open corridors in relation to the roof glazing and the shading devices of the atria. During the commissioning process the simulation based performance predictions were checked.
During the first year of operation, various building control strategies were tested and optimized. Smoke tests, thermal comfort and draft measurements were carried out to verify the indoor environment. During the commissioning process the field tests identified various important issues related to the design of large open space office buildings. These are also presented in the paper
Superconductivity from a melted insulator
Quantum phase transitions typically result in a broadened critical or
crossover region at nonzero temperature. Josephson arrays are a model of this
phenomenon, exhibiting a superconductor-insulator transition at a critical wave
impedance, and a well-understood insulating phase. Yet high-impedance arrays
used in quantum computing and metrology apparently evade this transition,
displaying superconducting behavior deep into the nominally insulating regime.
The absence of critical behavior in such devices is not well understood. Here
we show that, unlike the typical quantum-critical broadening scenario, in
Josephson arrays temperature dramatically shifts the critical region. This
shift leads to a regime of superconductivity at high temperature, arising from
the melted zero-temperature insulator. Our results quantitatively explain the
low-temperature onset of superconductivity in nominally insulating regimes, and
the transition to the strongly insulating phase. We further present, to our
knowledge, the first understanding of the onset of anomalous-metallic
resistance saturation. This work demonstrates a non-trivial interplay between
thermal effects and quantum criticality. A practical consequence is that,
counterintuitively, the coherence of high-impedance quantum circuits is
expected to be stabilized by thermal fluctuations.Comment: 8+18 pages, 4+15 figure
Observation of collapse and revival in a superconducting atomic frequency comb
Recent advancements in superconducting circuits have enabled the experimental
study of collective behavior of precisely controlled intermediate-scale
ensembles of qubits. In this work, we demonstrate an atomic frequency comb
formed by individual artificial atoms strongly coupled to a single resonator
mode. We observe periodic microwave pulses that originate from a single
coherent excitation dynamically interacting with the multi-qubit ensemble. We
show that this revival dynamics emerges as a consequence of the constructive
and periodic rephasing of the five superconducting qubits forming the vacuum
Rabi split comb. In the future, similar devices could be used as a memory with
in-situ tunable storage time or as an on-chip periodic pulse generator with
non-classical photon statistics
Disorder- and magnetic field-tuned fermionic superconductor-insulator transition in MoN thin films. Transport and STM studies
Superconductor-insulator transition (SIT) driven by disorder and transverse
magnetic field has been investigated in ultrathin MoN films by means of
transport measurements and scanning tunneling microscopy and spectroscopy. Upon
decreasing thickness, the homogeneously disordered films show increasing sheet
resistance Rs, shift of the superconducting transition Tc to lower temperatures
with the 3 nm MoN being the last superconducting film and thinner films already
insulating. Fermionic scenario of SIT is evidenced by applicability of the
Finkelsteins model, by the fact that Tc and the superconducting gap are coupled
with a constant ratio, and by the spatial homogeneity of the superconducting
and electronic characteristics. The logarithmic anomaly found in the tunneling
spectra of the non-superconducting films is further enhanced in increased
magnetic field due to the Zeeman spin effects driving the system deeper into
the insulating state and pointing also to fermionic SIT.Comment: Manuscript (6 Figures) including Supplemental Materials (7 Figures
Coyotes (\u3ci\u3eCanis latrans\u3c/i\u3e) are definitive hosts of \u3ci\u3eNeospora caninum\u3c/i\u3e
Four captive-raised coyote pups consumed tissues from Neospora caninum-infected calves. Feces were examined from 4 days before to 28 days after infection. One pup shed N. caninum-like oocysts, which tested positive for N. caninum and negative for Hammondia heydorni using PCR tests. Coyotes are the second discovered definitive host of N. caninum, after dogs. In North America, the expanding coyote ranges and population increase the probability of contact with domestic livestock. To reduce the risk of transmission of N. caninum to intensively farmed cattle, we recommend protection of feedstuffs using canid-proof fences, and careful disposal of dead stock
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