Stochastic resonance in an RF SQUID with shunted ScS junction

Abstract

Using a point (superconductor-constriction-superconductor, ScS) contact in a single-Josephson-junction superconducting quantum interference device (RF SQUID) provides stochastic resonance conditions at any arbitrary small value of loop inductance and contact critical current, unlike SQUIDs with more traditional tunnel (superconductorinsulator-superconductor, SIS) junctions. This is due to the unusual potential energy of the ScS RF SQUID which always has a barrier between two wells thus making the device bistable. This paper presents the results of a numerical simulation of the stochastic dynamics of the magnetic flux in an ScS RF SQUID loop affected by band-limited white Gaussian noise and low-frequency sine signals of small and moderate amplitudes. The difference in stochastic amplification of RF SQUID loops incorporating ScS and SIS junctions is discussed.

Experimental observation of induced stochastic transitions in a multiwall potential of an rf-SQUID loop

“…The numerical calculations 4,5,[7][8][9] show that the spectrum density of the internal flux in the SQUID loop at the useful signal frequency rapidly rises, peaks and then slowly decreases with the increase of the Gaussian noise intensity D, in accordance with the theory 12,13 . Fig.…”

“…in 5 ) predicted theoretically (see Refs. in 4,5,9 ) and numerical calculations 8,9 , it is necessary to optimize the SQUID parameters, particularly, use the interferometer with low β L ≥ 1 . For the high-T c RF SQUIDs in the area of strong fluctuations, the effective double-well potential and the best stochastic gain of a weak information signal should be observed at β L ≈ 4 .…”

“…Taking into account the smallness of C and R, we may neglect the second derivative in the flux motion equation 16 and reduce it to the form convenient for computations [7][8][9] :…”

“…This issue is the most severe for high-T c SQUIDs cooled down to the liquid nitrogen temperature level where the quantizing loop inductance and, correspondingly, the sensitivity to the magnetic field have to be considerably reduced. However, as shown in papers [4][5][6][7][8][9] , due to the same thermodynamic fluctuations and the external noise, the sensitivity of the magnetometers can be essentially enhanced by using the stochastic resonance (SR) effect.…”

Dynamical Properties of Nanostructured Josephson‐Junction Based on the Schwinger Quantum Action Analysis

“…Josephson junctions that join two superconductors became a class of the most realistic candidates for implementing modern technologies such as qubits, superconducting quantum interference devices (SQUIDs), and the rapid single flux quantum (RSFQ) logic circuits . Their mechanism is based on the Josephson effect that was developed from the quantum theory, while it cannot be explained by classical mechanics.…”