Search

With a growing interest in quantum technology globally, there is an increasing need for accessing relevant physical systems for education and research. In this paper we introduce a commercially available on-site quantum computer utilizing superconducting technology, offering insights into its fundamental hardware and software components. We show how this system can be used in education to teach quantum concepts and deepen understanding of quantum theory and quantum computing. It offers learning opportunities for future talent and contributes to technological progress. Additionally, we demonstrate its use in research by replicating some notable recent achievements. [ABSTRACT FROM AUTHOR]

Josephson junctions (JJs) in the presence of a magnetic field exhibit qualitatively different interference patterns depending on the spatial distribution of the supercurrent through the junction. In JJs based on two-dimensional topological insulators (2DTIs), the electrons/holes forming a Cooper pair (CP) can either propagate along the same edge or be split into the two edges. The former leads to a SQUID-like interference pattern, with the superconducting flux quantum ϕ 0 (where ϕ 0 = h / 2 e ) as a fundamental period. If CPs' splitting is additionally included, the resultant periodicity doubles. Since the edge states are typically considered to be strongly localized, the critical current does not decay as a function of the magnetic field. The present paper goes beyond this approach and inspects a topological JJ in the tunneling regime featuring extended edge states. It is here considered the possibility that the two electrons of a CP propagate and explore the junction independently over length scales comparable to the superconducting coherence length. As a consequence of the spatial extension, a decaying pattern with different possible periods is obtained. In particular, it is shown that, if crossed Andreev reflections (CARs) are dominant and the edge states overlap, the resulting interference pattern features oscillations whose periodicity approaches 2 ϕ 0 . [ABSTRACT FROM AUTHOR]

This study presents the first monolithically integrated full-duplex front-end for K/Ka satellite communication phased arrays. A 0.25 µm SiGe:C BiCMOS process was used to develop the integrated circuit. The receive and transmit channels are united into a common port through a novel duplexer. For each RF channel, the bias currents, the active channels and the power amplifier operation mode can be controlled through a serial bus. Amplitude and phase control are provided with fine granularity (65,536 states). In transmit mode, each channel provides 37.3 dB of gain with 12.9 dBm output power at 1-dB compression. In receive mode, 33.7 dB gain is measured with a noise figure of 3.2 dB. The amplitude/phase root-mean-square errors within the transmit (29.5-30.8 GHz) and receive (19.7-21 GHz) bands are below 0.7 dB/6.4° and 0.26 dB/1.1°, respectively. The chip occupies 1.64 × 3.5mm2 and it consumes 81 and 15.5 mW per transmit and receive channels, respectively. The use of a Doherty power amplifier with a novel dynamic adaptive bias circuit led to a 31% reduction of the total dc array power consumption. [ABSTRACT FROM AUTHOR]

A full set of measurements of the magnetic field has been carried out to define a different design of the TRASCO Intense Proton Source (TRIPS) magnetic system, based on permanent magnets, in order to increase the reliability of the source. The two coils of the source generate a maximum field of 150 mT and the optimum field was determined around 95 mT. The OPERA-3D package was used to simulate the magnetic field and a new magnetic system was designed as a combination of three rings of NdFeB magnets and soft iron. The high voltage insulation has been completely modified, in order to avoid any electronics at 80 kV voltage. The description of the magnetic measurements and the comparison with the simulations are presented, along with the mechanical design of the new version permanent magnet TRIPS (PM-TRIPS) and the new design of the extraction system. Finally the modification of the low energy beam transfer line (LEBT), which now includes a 30° bending magnet, will be outlined, with special regard to the accelerator availability improvement which can be obtained with the installation of two PM-TRIPS sources or more on the LEBT. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

An improved ac method to measure the thermal diffusivity in an extended temperature range is presented. The basic idea is to solder thermocouple wires directly on the sample, so that the sample itself acts as a thermocouple junction and the relaxation time for the temperature measurement becomes negligible. This new technique allows one to measure smaller samples and to increase the frequency of measurement so that the thermal losses could in principle be completely neglected. Finally, by the particular geometry a concurrent measurement of the electrical resistivity is obtained. [ABSTRACT FROM AUTHOR]

This paper describes an apparatus to measure the thermal diffusivity of high temperature superconductors in an extended range of temperature (10–300 K) and magnetic field (up to 8 T). Heat losses are taken into account by adopting an ac technique. Effects introduced by power dissipated on the heater and thermal contacts between thermocouples and sample are considered. In fact the presence of a thermocouple relaxation time not negligible in respect to the sample relaxation time causes an error in the thermal diffusivity evaluation (up to 13% in a sample with poor thermal contact). We have estimated that, also at the higher temperatures, frequencies over 0.03 Hz keep the thermal losses low enough; in this case the poor thermal contact of the thermocouples can be a major problem. All of the experiment is computer controlled. The accuracy of the measurement, mainly determined by evaluation of the sample length, is 10%, while the sensitivity to the relative variations is much higher (0.1%). [ABSTRACT FROM AUTHOR]

We discuss the resistivity, the Hall, the Seebeck and the Nerst effect in the mixed state taking the motion of Abrikosov and Josephson vortices into account. Measurements on a Bi(2223) tape point out how the contribution of Josephson vortices to the resistivity prevails at low temperatures while the thermomagnetic effects are, in a first approximation, due to the motion of Abrikosov vortices. [ABSTRACT FROM AUTHOR]

a.c. susceptibility measurements on a YBCO single crystal in an extended range of frequency and applied magnetic fields are presented. The dissipation phenomena shown by these measurements are interpreted inside the framework of the thermally activated flux motion theory developed for low-temperature superconductors in early '60. For this purpose the continuity equation for the magnetic field inside the sample is solved numerically, avoiding to use a priori the standard approximations of this theory: thermally activated flux creep and thermally assisted flux flow. The whole set of a.c. susceptibility measurements, performed in a wide range of the parameters, can be fitted with good agreement between the experimental and theoretical data. [ABSTRACT FROM AUTHOR]

Precise shaping of coherent electron sources allows the controlled creation of wavepackets into a one dimensional (1D) quantum conductor. Periodic trains of Lorentzian pulses have been shown to induce minimal excitations without creating additional electron–hole pairs in a single non-interacting 1D electron channel. The presence of electron–electron (e–e) interactions dramatically affects the non-equilibrium dynamics of a 1D system. Here, we consider the intrinsic spectral properties of a helical liquid, with a pair of counterpropagating interacting channels, in the presence of time-dependent Lorentzian voltage pulses. We show that peculiar asymmetries in the behavior of the spectral function are induced by interactions, depending on the sign of the injected charges. Moreover, we discuss the robustness of the concept of minimal excitations in the presence of interactions, where the link with excess noise is no more straightforward. Finally, we propose a scanning tunneling microscope setup to spectroscopically access and probe the non-equilibrium behavior induced by the voltage drive and e–e interactions. This allows a diagnosis of fractional charges in a correlated quantum spin Hall liquid in the presence of time-dependent drives. [ABSTRACT FROM AUTHOR]

This work presents the first example of monolithically integrated phase shifter based on a pass‐band filter architecture. The proposed configuration was realized mapping a classical quarter‐wave coupled filter circuit into its lumped element equivalent. Phase control is achieved by controlling the pass‐band through tunable tanks employing varactor diodes. A demonstrator was prototyped in the 24 GHz ISM band using a 0.25μm SiGe BiCMOS technology. Experimental results show 180° of phase range and maximum transmission losses of 8 dB. The main feature of this configuration is that it allows controlling the transmission losses by design and that its size is extremely compact. [ABSTRACT FROM AUTHOR]