Search results for "Squid"

2008

ZnO doped with a few per cent (<10%) of magnetic ions such as Co exhibit room temperature (RT) ferromagnetism, transforming it into a very promising candidate for future spin electronic applications. We present x-ray magnetic circular dichroism (XMCD) spectroscopy, which has been used in total electron yield, total fluorescence yield, and reflection mode to investigate the origin of ferromagnetism in such diluted magnetic semiconductor materials in a surface, bulk and interface sensitive way, respectively. We investigated three different types of samples: ZnO doped with 5% Co, artificially layered films, and layered films with additional co-doping of 10% Li. These films are prepared by puls…

Resetting of a planar superconducting quantum memory

2009

We consider and analyze a scheme for the reset of a M × N planar array of inductively coupled Josephson flux qubits. We prove that it is possible to minimize the resetting time of an arbitrary chosen row of qubits by properly switching on and off the coupling between pairs of qubits belonging to the same column. In addition, the analysis of the time evolution of the array allows us to single out the class of generalized W states which can be successfully reset.

GENERATION OF ENTANGLED STATES OF TWO DISTANT CAVITY MODES VIA JOSEPHSON JUNCTION BASED DEVICES

2007

We present a simple scheme for the preparation of entangled states of the e.m. modes of two spatially separated microwave cavities exploiting their interaction with two superconducting SQUID rings embedded within them. The scheme requires that the two SQUID qubits are initially prepared in an entangled state and the possibility of controlling both the coupling strengths and the interaction times. We also briefly discuss the importance of such a theoretical scheme in view of possible applications in the context of quantum computing and its experimental feasibility.

Dynamic spin-triplet order induced by alternating electric fields in superconductor-ferromagnet-superconductor Josephson junctions

2021

Dynamic states offer extended possibilities to control the properties of quantum matter. Recent efforts are focused on studying the ordered states which appear exclusively under the time-dependent drives. Here we demonstrate a class of systems which feature dynamic spin-triplet superconducting order stimulated by the alternating electric field. The effect is based on the interplay of ferromagnetism, interfacial spin-orbital coupling (SOC) and the condensate motion driven by the field, which converts hidden static p-wave order, produced by the joint action of the ferromagnetism and the SOC, into dynamical s-wave equal-spin triplet correlations. We demonstrate that the critical current of Jos…

Operation of transition-edge sensors with excess thermal noise

2006

The superconducting transition-edge sensor (TES) is currently one of the most attractive choices for ultra-high resolution calorimetry in the keV x-ray band, and is being considered for future ESA and NASA missions. We have performed a study on the noise characteristics of Au/Ti bilayer TESs, at operating temperatures around ~100 mK, with the SQUID readout at 1.5 K. Experimental results indicate that without modifications the back-action noise from the SQUID chip degrades the noise characteristics significantly. We present a simple and effective solution to the problem: by installing an extra shunt resistor which absorbs the excess radiation from the SQUID input, we have reduced the excess …

Resonant effects in a SQUID qubit subjected to nonadiabatic changes

2013

By quickly modifying the shape of the effective potential of a double SQUID flux qubit from a single-well to a double-well condition, we experimentally observe an anomalous behavior, namely an alternance of resonance peaks, in the probability to find the qubit in a given flux state. The occurrence of Landau-Zener transitions as well as resonant tunneling between degenerate levels in the two wells may be invoked to partially justify the experimental results. A quantum simulation of the time evolution of the system indeed suggests that the observed anomalous behavior can be imputable to quantum coherence effects. The interplay among all these mechanisms has a practical implication for quantum…

Single and two-qubit dynamics in circuit QED architectures

2008

In this paper we overview our researches on the generation and the control of entangled states in the framework of circuit quantum electrodynamics. Applications in the context of quantum computing and quantum information theory are discussed.

Diindenoanthracene Diradicaloids Enable Rational, Incremental Tuning of Their Singlet-Triplet Energy Gaps

2020

Summary A fundamental understanding of the inherent electronic and magnetic properties of open-shell diradicaloids is essential so that these properties can be modified to create molecules that meet the potential needs of industry. However, there have been very few attempts to date to systematically accomplish this in diradicaloid compounds. Here, we present the synthetic, spectroscopic, and computational investigation of a series of molecules based on the diindeno[1,2-b:1′,2′-g]anthracene framework. Calculations suggest that by altering the transfer integral term, tab, we are able to manipulate the diradical character and, thus, ΔEST within this series of molecules. Experimentally determin…

Transition-edge microcalorimeters for X-ray space applications

2000

Abstract In an European Space Agency funded research project, our goal is to develop microbolometer technology for X-ray and far-infrared detection for ESA's future scientific missions. We report results on the X-ray calorimeter, which is based on the superconducting transition of the Ti/Au thermometer strip at about 200 mK. Incident X-rays heat up a Bi absorber, deposited on top of the 400 μm ×400 μm thermometer. The temperature rise of the absorber is measured as a change of the thermometer current with a SQUID operating at 1 K.

Josephson junctions and SQUIDs based on artificial grain boundaries in Bi 2 Sr 2 Ca 2 Cu 3 O 10 -thin films

1996

ABSTRACT High quality thin films of Bi2 Sr Ca2 Cu3 0 with critical temperatures of 95 K were used to prepare grainboundary josephson junctions on commercial 36.8° SrTiOg-bicrystal substrates. IR-products of 50 pV at 77 Kand 0.7 mV at 4.2 K have been reached. For temperatures higher than 50 K the current-voltage curves of thejunctions can be well described by the resistively shunted junction (RSJ) model and show no hysteresis. Fromthe hysteretic behavior at low temperature we estimate a junction capacitance of 2ljiF/cm2. The Fraunhoferpattern of the critical current in an external applied field shows, that the junctions are inhomogeneous on a pm scale. The SQUID modulation of a 30 x 40 pm2 w…