Macroscopic quantum phenomena in Josephson structures

Barone, A.; Lombardi, Floriana; Rotoli, G.; Tafuri, F.

doi:10.1063/1.3517171

Cited by 6 publications

(5 citation statements)

References 86 publications

(81 reference statements)

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“…Equation (24) was solved numerically for the input parameters shown in table (1) The results are consistent with the experimental findings for the YBCO class superconductors [35]. As we can see, the creep is slower when vortices possessing magnetic domain occurred in the system.…”

Section: Numerical Resultssupporting

confidence: 75%

“…Above a characteristic temperature T 0 in the thermal activation regime the decay rate is of the Arrhenius type Γ ∼ exp (−U 0 /k B T ). Below T 0 , the decay rate is assumed a priorito be essentially independent of temperature Γ ∼ exp (−S/h) and is interpreted as arising from the quantum tunneling of vortices through intrinsic pinning potential [20,21,22,24,23]. In the following we show a considerable change of tunneling rate and crossover temperature due to the SF phase formation in the vortex core.…”

Section: Macroscopic Quantum Tunnelling Through Intrinsic Pinning Bar...mentioning

confidence: 72%

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Quantum creep in layered antiferromagnetic superconductor

Krzysztoń

2013

Eur. Phys. J. B

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Abstract. In the mixed state of layered superconductor, the antiferromagnetic order of magnetic ions can create the spin-flop domains along the phase cores of the Josephson vortices, and this property impact upon the creep rate in the antiferromagnetic superconductor. The activation of the creep at constant temperature can be either thermal or quantum, depending on the intensity, or direction of the applied magnetic field. It is also shown that the action, and hence the activation energy, is rendered temperature dependent, when the damping and inertial mass of the vortex are included, so that the quantum tunnelling rate becomes temperature dependent below the crossover temperature.

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Section: Numerical Resultssupporting

confidence: 75%

Section: Macroscopic Quantum Tunnelling Through Intrinsic Pinning Bar...mentioning

confidence: 72%

Quantum creep in layered antiferromagnetic superconductor

Krzysztoń

2013

Eur. Phys. J. B

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“…The individual escape times can be directly measured in a variety of conditions [55,16], including high-Tc supercondutors [5,6]; in the case of underdamped JJ (a\1) when the system overcomes the energy barrier DU; it switches from the locked state to a finite voltage running state [4]:…”

Section: Physical Model Of a Jj Detectormentioning

confidence: 99%

Escape Time of Josephson Junctions for Signal Detection

Addesso

Филатрелла

Pierro

2012

Progress in Optical Science and Photonics

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In this Chapter we investigate with the methods of signal detection the response of a Josephson junction to a perturbation to decide if the perturbation contains a coherent oscillation embedded in the background noise. When a Josephson Junction is irradiated by an external noisy source, it eventually leaves the static state and reaches a steady voltage state. The appearance of a voltage step allows to measure the time spent in the metastable state before the transition to the running state, thus defining an escape time. The distribution of the escape times depends upon the characteristics of the noise and the Josephson junction. Moreover, the properties of the distribution depends on the features of the signal (amplitude, frequency and phase), which can be therefore inferred through the appropriate signal processing methods. Signal detection with JJ is interesting for practical purposes, inasmuch as the superconductive elements can be (in principle) cooled to the absolute zero and therefore can add (in practice) as little intrinsic noise as refrigeration allows. It is relevant that the escape times bear a hallmark of the noise itself. The spectrum of the fluctuations due to the intrinsic classical (owed to thermal or environmental disturbances) or quantum (due to the tunnel across the barrier) sources are different. Therefore, a careful analysis of the escape times could also assist to discriminate the nature of the noise.

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“…[9,10], a lot of experimental work has been performed on the role of noise in ac driven JJ to detect the phase of the applied signal [11], to study quantum computation [12] or ratchet effects [13]. Another remarkable topic is related to employ JJ as a threshold detector to characterize (up to higher order moments) weak fluctuations close to the quantum limit [14][15][16][17] (albeit there is also some controversial discussion about role of quantum noise in JJ [18]). In the ac driven quantum regime [19] the use of JJ is particularly appealing for signal detection since ways have been devised to minimize the environmental disturbances to the unavoidable quantum level [20].…”

Section: Introductionmentioning

confidence: 99%

Characterization of escape times of Josephson junctions for signal detection

Addesso¹,

Филатрелла

Pierro

2012

Phys. Rev. E

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The measurement of the escape time of a Josephson junction might be used to detect the presence of a sinusoidal signal embedded in noise when use of standard signal processing tools can be prohibitive due to the extreme weakness of the source or to the huge amount of data. In this paper we show that the prescriptions for the experimental setup and some physical behaviors depend on the detection strategy. More specifically, by exploitation of the sample mean of escape times to perform detection, two resonant regions are identified. At low frequencies there is a stochastic resonance or activation phenomenon, while near the plasma frequency a geometric resonance appears. Furthermore, detection performance in the geometric resonance region is maximized at the prescribed value of the bias current. The naive sample mean detector is outperformed, in terms of error probability, by the optimal likelihood ratio test. The latter exhibits only geometric resonance, showing monotonically increasing performance as the bias current approaches the junction critical current. In this regime the escape times are vanishingly small and therefore performance is essentially limited by measurement electronics. The behavior of the likelihood ratio and sample mean detector for different values of incoming signal to noise ratio is discussed, and a relationship with the error probability is found. Detectors based on the likelihood ratio test could be employed also to estimate unknown parameters in the applied input signal. As a prototypical example we study the phase estimation problem of a sinusoidal current, which is accomplished by using the filter bank approach. Finally we show that for a physically feasible detector the performances are found to be very close to the Cramer-Rao theoretical bound. Applications might be found, for example, in some astronomical detection problems (where the all-sky gravitational and/or radio wave search for pulsars requires the analysis of nearly sinusoidal long-lived waveforms at very low signal-to-noise ratio) or to analyze weak signals in the subterahertz range (where the traditional electronics counterpart is difficult to implement).

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Macroscopic quantum phenomena in Josephson structures

Cited by 6 publications

References 86 publications

Quantum creep in layered antiferromagnetic superconductor

Quantum creep in layered antiferromagnetic superconductor

Escape Time of Josephson Junctions for Signal Detection

Characterization of escape times of Josephson junctions for signal detection

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