arXiv:1506.00953

Stochastic amplification of weak signals in an RF SQUID with ScS contact

Oleg G. Turutanov, V. Yu. Lyakhno, V. I. Shnyrkov

Published Jun 2, 2015• 0 citations

Abstract

The paper presents results of a numerical simulation of the stochastic dynamics of magnetic flux in an RF SQUID loop with a Josephson point (ScS) contact driven by a mix of band-limited Gaussian noise and low-frequency small-amplitude sine signal, at finite temperatures $0

DOI: 10.48550/arxiv.1506.00953

Related papers

Controlled Stochastic Amplification of a Weak Signal in a Superconducting Quantum Interferometer

Oleg G. Turutanov, V. Yu. Lyakhno, M. E. Pivovar +1 more

In a single-junction niobium superconducting quantum interferometer (RF SQUID loop), a weak low-frequency harmonic signal is amplified when quasi-white Gaussian noise magnetic flux is applied to the loop; such amplification is due to stochastic resonance (SR). We have experimentally shown that if the suboptimal flux noise intensity is insufficient for SR, the mean rate of transitions between the metastable states of the loop, and thus the signal gain, can be controlled by an additional deterministic alternating magnetic flux with frequency being much higher than that of the useful signal to provide the maximal possible gain. The frequency characteristics of a multi-tone composite signal amplification in the cases of controlled stochastic amplification and “pure” SR are compared to each other.

Low Temperature PhysicsJan 1, 20193 citations

Stochastic-parametric amplification of narrow-band signals in a single-junction SQUID interferometer

Oleg G. Turutanov, V. I. Shnyrkov, A. M. Glukhov

The features of the response of a single-junction superconducting quantum interferometer to a low-frequency harmonic signal in the presence of noise and a high-frequency electromagnetic field are investigated through numerical solution of the equations of motion. It is shown that in this situation a system described by a double-well potential will display stochastic-parametric amplification of weak harmonic signals owing to the cooperative effects of noise and the high-frequency field. The gain is a nonmonotonic function of the amplitude of the high-frequency field and the variance of the noise flux and passes through a maximum. A detailed numerical analysis of the dependence of the gain on the noise intensity and on the frequency and amplitude of the high-frequency field is carried out in the stochastic, parametric, and stochastic-parametric amplification regimes. It is shown that at optimal amplitude of the high-frequency field the gain for a weak harmonic signal reaches rather high values (10–30). The specific properties of stochastic-parametric amplification are discussed, and the possible applications of this effect for constructing input circuits of detectors based on SQUIDs with registration of weak narrow-band information signals are considered.

Low Temperature PhysicsJan 1, 20081 citation

Low-frequency excess noise in SQUIDS with YBa2Cu3O7step-edge junctions

V. N. Glyantsev, M. Siegel, Jürgen Schubert +2 more

We have fabricated RF and DC SQUIDS with step-edge Josephson junctions (SEJ) and YBa 2 Cu 3 O 7 thin films. The low-frequency noise of these SQUIDS has been investigated as a function of temperature, bias current and magnetic field. Typically, the energy resolution in the white noise region of the DC SQUIDS with an inductance of 45 pH was 3*10 -30 J Hz -1 at 77.5 K. Depending on the bias current, the low-frequency spectrum could be of either 1/f type or Lorentzian type. The Lorentzian spectrum was generated by random telegraph signals (RTSS). An Arrhenius plot was obtained from the temperature dependence of the switching time of these RTSS. We have determined two barrier lengths of 0.23 eV and 1 eV of the two-level fluctuator (TLF) generating this RTS noise. From the magnetic-field dependence of the low-frequency noise we have found that the noise is periodic with the flux corresponding to the area of the SEJ. The results were discussed in terms of a model treating the SEJ as a multi-junction interferometer which forms a two-level fluctuator when the junction is placed inside a SQUID loop. The noise is generated by thermally activated switching of the SQUID between the two different states of the SQUID.

Superconductor Science and TechnologyMay 1, 199411 citations

Noise in the RF SQUID

L. D. Jackel, Robert A. Buhrman

This paper presents the results of an extensive study of the sensitivity-limiting noise sources in rf-biased SQUID flux detectors. Our investigation has included both experiments with point contact and thin-film SQUIDs and digital computer simulations. The paper begins with a discussion of rf SQUID operation, with special emphasis on those aspects that determine flux detector sensitivity. We then discuss the origin and consequences of intrinsic device noise in rf SQUID systems. We describe a straightforward technique for determining intrinsic noise amplitude directly from SQUID rf I–V characteristics. Deviations in the measured intrinsic noise of many devices from the Kurkijarvi-Webb prediction are attributed to departures from the ideal Josephson sinusoidal current-phase relation in the SQUID weak link. Kurkijarvf's SQUID tank circuit noise analysis is reviewed and we show how SQUID sensitivity can be maximized by an optimal coupling between SQUID ring and tank circuit. This optimal coupling depends upon circuit parameters, ring inductance, and weak-link properties. The analysis reveals that variations in the current-phase relation can result in a difference of as much as a factor of ten in the attainable sensitivity of two otherwise identical SQUID systems. We also suggest efforts in circuit design that are most likely to lead to further improvements in flux detector sensitivity. Finally, other factors, including external magnetic noise and underdamping of the SQUID ring, are discussed.

STINOct 1, 19740 citations

Numerical investigation for the frequency dependence of Shapiro steps in an RF-field-driven SQUID

Yoshinao Mizugaki

Shapiro steps in an RF-field-driven dc-SQUID (RFDS), where an RF signal is coupled to the SQUID loop magnetically, are numerically investigated. We calculate the current–voltage characteristics of RFDSs under no dc offset flux, which show the enhancement of the even-order Shapiro steps. First, the maximum second (the lowest even-order) step height is evaluated as a function of the normalized frequency Ω. In the case of the inductance parameter βL ≥ 1.0, the maximum second step height is maintained at a certain value in the low frequency region. In the case of βL < 1.0, on the other hand, the maximum step height decreases in the low frequency region of Ω < 0.10. The dependence of the current positions of the step upon the RF signal amplitude shows that the voltage transition at the non-superconductive area between the superconducting interference lobes limits the upper current position of the step.

Superconductor Science and TechnologyNov 5, 20032 citations

Noise properties of SQUIDs with step-edge Josephson junctions

V. N. Glyantsev, M. Siegel, Jürgen Schubert +5 more

The authors investigated low-frequency noise in RF and DC superconducting quantum interference devices (SQUIDs) with step-edge Josephson junctions (SEJs). The noise properties have been measured as a function of frequency, temperature, bias current, and magnetic field. The low-frequency noise has a telegraph-like character in certain conditions and depends quasi-periodically on flux and temperature. This telegraph noise was also observed in single step-edge junctions. The experimental results were explained by a model of such a junction in which an array of parallel and series connected weak links acts like a two-level fluctuator. This fluctuator arises from the quantum states of a multijunction SQUID with spatially inhomogeneous SEJs resembling a multijunction array.>

IEEE Transactions on Applied SuperconductivityMar 1, 199320 citations