Search results for "Josephson effect"
showing 10 items of 96 documents
Dissipative effects on a generation scheme of a W state in an array of coupled Josephson junctions
2011
The dynamics of an open quantum system, consisting of three superconducting qubits interacting with independent reservoirs, is investigated to elucidate the effects of the environment on a unitary generation scheme of W states (Migliore R et al 2006 Phys. Rev. B 74 104503). To this end a microscopic master equation is constructed and its exact resolution predicts the generation of a Werner-like state instead of the W state. A comparison between our model and a more intuitive phenomenological model is also considered, in order to find the limits of the latter approach in the case of structured reservoirs.
EFFECTS OF COLORED NOISE IN SHORT OVERDAMPED JOSEPHSON JUNCTION
2008
We investigate the transient dynamics of a short overdamped Josephson junction with a periodic driving signal in the presence of colored noise. We analyze noise induced henomena, specifically resonant activation and noise enhanced stability. We find that the positions both of the minimum of RA and maximum of NES depend on the value of the noise correlation time tau_c. Moreover, in the range where RA is observed, we find a non-monotonic behavior of the mean switching time as a function of the correlation time tau_c.
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.
Decoherence in circuits of small Josephson junctions
2001
We discuss dephasing by the dissipative electromagnetic environment and by measurement in circuits consisting of small Josephson junctions. We present quantitative estimates and determine in which case the circuit might qualify as a quantum bit. Specifically, we analyse a three junction Cooper pair pump and propose a measurement to determine the decoherence time $\tau_\phi$.
Geometric quantum computation with Josephson qubits
2001
The quest for large scale integrability and flexibility has stimulated an increasing interest in designing quantum computing devices. A proposal based on small-capacitance Josephson junctions in the charge regime in which quantum gates are implemented by means of adiabatic geometric phases was discussed. The proposed works, are in the charge regime where the qubit is realized by two nearly degenerate charge states of a single electron box.
Effects of Lévy noise on the dynamics of sine-Gordon solitons in long Josephson junctions
2015
We numerically investigate the generation of solitons in current-biased long Josephson junctions in relation to the superconducting lifetime and the voltage drop across the device. The dynamics of the junction is modelled with a sine-Gordon equation driven by an oscillating field and subject to an external non-Gaussian noise. A wide range of $\alpha$-stable L\'evy distributions is considered as noise source, with varying stability index $\alpha$ and asymmetry parameter $\beta$. In junctions longer than a critical length, the mean switching time (MST) from superconductive to the resistive state assumes a values independent of the device length. Here, we demonstrate that such a value is direc…
Generation of a DC Fiske current by coupling of Bloch and in-plane cyclotron oscillations in a semiconductor superlattice
2006
The coherent coupling between electron Bloch and in-plane cyclotron oscillations in semiconductor superlatices in tilted electric and magnetic fields induces a unidirectional quasi-DC current in analogy to the DC Fiske effect observed when a superconductor Josephson junction or a superfluid weak link is coupled to an electromagnetic respectively an acoustic resonator. In all cases, the coupling opens an elastic rectifying transport channel. We explore the effect for the case of a superlattice both experimentally and theoretically, and specifically address the influence of the coupling on the frequency of the magnetoBloch oscillations.
Suppression of timing errors in short overdamped Josephson junctions
2004
The influence of fluctuations and periodical driving on temporal characteristics of short overdamped Josephson junction is analyzed. We obtain the standard deviation of the switching time in the presence of a dichotomous driving force for arbitrary noise intensity and in the frequency range of practical interest. For sinusoidal driving the resonant activation effect has been observed. The mean switching time and its standard deviation have a minimum as a function of driving frequency. As a consequence the optimization of the system for fast operation will simultaneously lead to minimization of timing errors.
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…
Noise induced effects in overdamped Josephson junction in the presence of colored noise
2007
We analyze the role of the correlated fluctuations, with a correlation time τc, in the dynamics of an overdamped Josephson junction in the presence of a periodic driving signal.