ABSTRACT
The density of quasiparticles typically observed in superconducting qubits exceeds the value expected in equilibrium by many orders of magnitude. Can this out-of-equilibrium quasiparticle density still possess an energy distribution in equilibrium with the phonon bath? Here, we answer this question affirmatively by measuring the thermal activation of charge-parity switching in a transmon qubit with a difference in superconducting gap on the two sides of the Josephson junction. We then demonstrate how the gap asymmetry of the device can be exploited to manipulate its parity.
ABSTRACT
We study the electrodynamics of spin triplet superconductors including dipolar interactions, which give rise to an interplay between the collective spin dynamics of the condensate and orbital Meissner screening currents. Within this theory, we identify a class of spin waves that originate from the coupled dynamics of the spin-symmetry breaking triplet order parameter and the electromagnetic field. In particular, we study magnetostatic spin wave modes that are localized to the sample surface. We show that these surface modes can be excited and detected using experimental techniques such as microwave spin wave resonance spectroscopy or nitrogen-vacancy magnetometry, and propose that the detection of these modes offers a means for the identification of spin triplet superconductivity.
ABSTRACT
At non-zero temperatures, superconductors contain excitations known as Bogoliubov quasiparticles (QPs). The mesoscopic dynamics of QPs inform the design of quantum information processors, among other devices. Knowledge of these dynamics stems from experiments in which QPs are injected in a controlled fashion, typically at energies comparable to the pairing energy1-5. Here we perform tunnel spectroscopy of a mesoscopic superconductor under high electric fields. We observe QP injection due to field-emitted electrons with 106 times the pairing energy, an unexplored regime of QP dynamics. Upon application of a gate voltage, the QP injection decreases the critical current and, at sufficiently high electric field, a field-emission current (<0.1 nA in our device) switches the mesoscopic superconductor into the normal state, consistent with earlier observations6. We expect that high-energy injection will be useful for developing QP-tolerant quantum information processors, will allow rapid control of resonator quality factors and will enable the design of electric-field-controlled superconducting devices with new functionality.
ABSTRACT
INTRODUCTION: This study evaluated the incidence of inappropriate use of bed days in Danish medical wards using the European Appropriateness Evaluation Protocol (AEP). Several European countries have used the AEP to assess the appropriateness of hospitalisation days. MATERIALS AND METHODS: The study was carried out in four Danish medical wards from October 2004 to January 2005. On pre-selected days a doctor and nurse performed case record analyses of all hospitalised patients with registration of the AEP criteria. To assess activities during the entire day, the screening comprised activities from the previous day. RESULTS: Altogether, 738 patients were reviewed. On average, 32.1% of hospitalisation days on the four wards were assessed as inappropriate (range 19.2-39.2%). Lack of alternative facilities (different outpatient services, rehabilitation, home nursing, etc.) and internal waiting time for diagnostic tests were the most common causes of inappropriate bed use. 6.4% of bed days were considered appropriate from a clinical point of view even though no AEP criteria were met. CONCLUSION: In order to reduce the number of inappropriate hospital days, it is necessary to optimise the cooperation with the primary health care sector and ensure immediate availability of diagnostic tests.
