Pinch resonances in a radio-frequency-driven superconducting-quantum-interference-device ring-resonator system (original) (raw)
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Pinch Resonances in a Radio Frequency Driven SQUID Ring-Resonator System
Physical Review E, 2004
In this paper we present experimental data on the frequency domain response of a SQUID ring (a Josephson weak link enclosed by a thick superconducting ring) coupled to a radio frequency (rf) tank circuit resonator. We show that with the ring weakly hysteretic the resonance lineshape of this coupled system can display opposed fold bifurcations that appear to touch (pinch off). We demonstrate that for appropriate circuit parameters these pinch off lineshapes exist as solutions of the non-linear equations of motion for the system.
Self-oscillations in a superconducting stripline resonator integrated with a DC-SQUID
Eprint Arxiv 0907 3267, 2009
We study self-sustained oscillations (SO) in a Nb superconducting stripline resonators (SSR) integrated with a DC superconducting quantum interface devices (SQUID). We find that both the power threshold where these oscillations start and the oscillations frequency are periodic in the applied magnetic flux threading the SQUID loop. A theoretical model which attributes the SO to a thermal instability in the DC-SQUID yields a good agreement with the experimental results. This flux dependant nonlinearity may be used for quantum state reading of a qubit-SSR integrated device.
Physical Review B, 2011
We study the metastable response of a highly hysteretic DC-SQUID made of a Niobium loop interrupted by two nano-bridges. We excite the SQUID with an alternating current and with direct magnetic flux, and find different stability zones forming diamond-like structures in the measured voltage across the SQUID. When such a SQUID is embedded in a transmission line resonator similar diamond structures are observed in the reflection pattern of the resonator. We have calculated the DC-SQUID stability diagram in the plane of the exciting control parameters, both analytically and numerically. In addition, we have obtained numerical simulations of the SQUID equations of motion, taking into account temperature variations and non-sinusoidal current-phase relation of the nano-bridges. Good agreement is found between experimental and theoretical results.
Applied Physics Letters, 2009
We study self-sustained oscillations in a Nb superconducting stripline resonator integrated with a dc superconducting quantum interference device ͑SQUID͒. We find that both the power threshold where these oscillations start and the oscillation frequency are periodic in the applied magnetic flux threading the SQUID loop. A theoretical model which attributes the self-sustained oscillations to a thermal instability in the dc-SQUID yields a good agreement with the experimental results. This flux dependant nonlinearity may be used for quantum state reading of a qubit-superconducting resonator integrated device.
Quantum State Engineering With the Rf-SQUID: A Brief Introduction
Arxiv preprint quant-ph/0307101, 2003
The SQUID, or superconducting quantum interference device, is a highly sensitive instrument employed for the nondestructive measurement of magnetic fields, with a host of applications in both biophysics and materials technology. It is composed of a cooled superconductive metal ring separated by a thin insulating barrier of non-superconducting metal. Electrons tunnel across the barrier to form a Josephson junction; an rf SQUID is essentially a Josephson junction with tunable current and energy. Quantum computers take advantage of the superpositional logic of quantum mechanics to allow for dramatic increases in computational efficiency. rf SQUIDs show potential for quantum computing applications by forming the qubit component of a quantum computer, through simply treating the direction of current, clockwise or counterclockwise, as the value of the bit.
Journal of Applied Physics, 2000
We measured the amplitude-frequency characteristics of radio frequency superconducting quantum interference devices ͑rf SQUIDs͒ over a temperature range between 65 and 79 K. Using the expressions derived from the recently developed rf SQUID theory, valid also at large thermal fluctuations, we determined from these data the basic parameters of high-transition-temperature superconductor ͑HTS͒ rf SQUIDs. These parameters were: ͑a͒ the high-frequency coupling coefficient between the rf SQUID and the tank circuit resonator, k, ͑b͒ the SQUIDs hysteretic parameter, , ͑c͒ the critical current of the Josephson junction, I c , ͑d͒ its normal resistance, R n , and ͑e͒ its noise parameter, ⌫. We found a good agreement with the values of (I c) and R n determined directly after destructively opening the SQUID loop. In accordance with the theoretical predictions, our experimental results show that at large thermal fluctuation levels (TХ77 K), rf SQUIDs with large loop inductance operate in nonhysteretic mode up to  values exceeding 3. Furthermore, we have shown that the optimal energy sensitivity is attained in the nonhysteretic mode at a value of  distinctly higher than 1. A quantitative comparison of white noise predicted by the theory with that obtained from the experiment showed a reasonable agreement. We also discussed the contribution of the phase information to the SQUID's signal and noise at optimum operation conditions, when a mixer was used as a signal detector.
Zero-dispersion stochastic resonance in a model for a superconducting quantum interference device
Physical Review E, 1998
It is demonstrated that the signal-to-noise ratio for a weak periodic signal in a superconductive loop with a Josephson junction ͑a superconducting quantum interference device, or SQUID͒ can be substantially enhanced, over a wide range of frequencies, by the addition of noise. This manifestation of zero-dispersion stochastic resonance ͑ZDSR͒ is shown to occur for a wide variety of loop parameters and signal frequencies. Unlike most earlier examples of stochastic resonance, ZDSR does not depend on fluctuational transitions between coexisting stable states. Rather, it exploits the noise-enhanced susceptibility that arises in underdamped nonlinear oscillators for which the oscillation eigenfrequency possesses one or more extrema as a function of energy. The phenomenon is investigated theoretically, and by means of analog and digital simulations. It is suggested that ZDSR could be used to enhance the sensitivity of radio-frequency SQUIDs and other SQUID-based devices. In the course of the work, two additional useful results were obtained: ͑a͒ an asymptotic expression describing ZDSR for the general case in the limit of weak dissipation; ͑b͒ a method for the numerical calculation of fluctuation spectra in bistable or multistable underdamped systems. ͓S1063-651X͑97͒08112-9͔
Physical review, 2022
Strong nonlinearity of a self-resonant radio frequency superconducting quantum interference device (rf-SQUID) meta-atom is explored via intermodulation (IM) measurements. Previous work in zero dc magnetic flux showed a sharp onset of IM response as the frequency sweeps through the resonance. A second onset at higher frequency was also observed, creating a prominent gap in the IM response. By extending those measurements to nonzero dc flux, new dynamics are revealed, including: dc flux tunabililty of the aforementioned gaps, and enhanced IM response near geometric resonance of the rf-SQUID. These features observed experimentally are understood and analyzed theoretically through a combination of a steady state analytical modeling, and a full numerical treatment of the rf SQUID dynamics. The latter, in addition, predicts the presence of chaos in narrow parameter regimes. The understanding of intermodulation in rf-SQUID metamaterials is important for producing low-noise amplification of microwave signals and tunable filters.