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Flux-Quantum Transitions in a Three-Junction SQUID Controlled by Two RF Signals

Yoshinao Mizugaki

IEICE Transactions on ElectronicsMar 1, 20022 citations

Large RF-controlled voltage steps in DC SQUIDs applicable to voltage standards and sources

G.S. Lee, H.L. Ho, Rich Ruby +1 more

The current height of RF-induced voltage steps in nonhysteretic single Josephson junctions is usually a small fraction of the critical current. It is demonstrated that when a resistively shunted DC superconducting quantum interference device (SQUID) is subjected to an RF magnetic flux, a voltage step with a large current height is obtained. In contrast to weak selection rules for single Josephson junctions, strong selection of the step harmonic number occurs in a shunted DC SQUID for appropriate choice of RF amplitude and DC flux offset, with odd harmonic numbers selected by half-integer flux quantum offsets and even harmonic numbers by integer flux quantum offsets. This pronounced effect has immediate implications for voltage standards and fast, high-precision digital-to-analog converters.>The current height of RF-induced voltage steps in nonhysteretic single Josephson junctions is usually a small fraction of the critical current. It is demonstrated that when a resistively shunted DC superconducting quantum interference device (SQUID) is subjected to an RF magnetic flux, a voltage step with a large current height is obtained. In contrast to weak selection rules for single Josephson junctions, strong selection of the step harmonic number occurs in a shunted DC SQUID for appropriate choice of RF amplitude and DC flux offset, with odd harmonic numbers selected by half-integer flux quantum offsets and even harmonic numbers by integer flux quantum offsets. This pronounced effect has immediate implications for voltage standards and fast, high-precision digital-to-analog converters.>

IEEE Transactions on Applied SuperconductivityMar 1, 199316 citations

RF responses of double-junction SQUID models

Yoshinao Mizugaki, J Chen, Kensuke Nakajima +1 more

We present numerical investigation of the RF properties of a double-junction SQUID model, which is referred to as an RF-field-driven double-junction SQUID (RFDS). The RFDS generates large current steps, the order of which can be controlled by external dc field. We simulate the current-voltage characteristics of the RFDS in the normalized frequency range from 0.065 to 5.0. In comparison with the results for a single junction, the step heights of the RFDS are much larger for the low frequency region; e.g. the first step of the RFDS becomes nine times larger than that of a single junction when a dc flux of 0.5 0 is applied ( 0 is a flux quantum). For the high frequency region, the step height of the RFDS is comparable to that of a single junction. The results suggest that the RFDS should be applicable as a wide-band RF detector.We present numerical investigation of the RF properties of a double-junction SQUID model, which is referred to as an RF-field-driven double-junction SQUID (RFDS). The RFDS generates large current steps, the order of which can be controlled by external dc field. We simulate the current-voltage characteristics of the RFDS in the normalized frequency range from 0.065 to 5.0. In comparison with the results for a single junction, the step heights of the RFDS are much larger for the low frequency region; e.g. the first step of the RFDS becomes nine times larger than that of a single junction when a dc flux of 0.5 0 is applied ( 0 is a flux quantum). For the high frequency region, the step height of the RFDS is comparable to that of a single junction. The results suggest that the RFDS should be applicable as a wide-band RF detector.

Superconductor Science and TechnologyNov 1, 19993 citations

A tunable rf SQUID manipulated as flux and phase qubits

Stefano Poletto, CHIARELLO F., CASTELLANO M. G. +4 more

Jan 1, 20090 citations

Double-barrier junction based dc SQUID

Elena Bartolomé, Alexander Brinkman, Jakob Flokstra +2 more

Physica C SuperconductivityDec 1, 20008 citations

Zero-crossing shapiro step in a three-junction SQUID magnetically coupled with two phase-shifted RF signals

Yoshinao Mizugaki, Jian Chen, S. Nishikata +3 more

We demonstrate a zero-crossing Shapiro step in a three-junction SQUID (3J-SQUID) coupled with two phase-shifted RF signals. The operation is based on periodic flux quantum transitions in the 3J-SQUID under the zero- and negatively-biasing conditions. A test circuit is fabricated using a Nb/AlO/sub x//Nb junction technology. When we feed RF signals up to 10.5 GHz, we observe a Shapiro step crossing the zero-current axis at the voltage position of the 1st order. The experimental current-voltage characteristics are quantitatively reproduced by simulation. Zero-crossing conditions for the DC offset flux and the RF power are obtained experimentally, which is also confirmed by simulation. A programmable Josephson voltage standard is discussed as one of the possible applications.We demonstrate a zero-crossing Shapiro step in a three-junction SQUID (3J-SQUID) coupled with two phase-shifted RF signals. The operation is based on periodic flux quantum transitions in the 3J-SQUID under the zero- and negatively-biasing conditions. A test circuit is fabricated using a Nb/AlO/sub x//Nb junction technology. When we feed RF signals up to 10.5 GHz, we observe a Shapiro step crossing the zero-current axis at the voltage position of the 1st order. The experimental current-voltage characteristics are quantitatively reproduced by simulation. Zero-crossing conditions for the DC offset flux and the RF power are obtained experimentally, which is also confirmed by simulation. A programmable Josephson voltage standard is discussed as one of the possible applications.

IEEE Transactions on Applied SuperconductivityJun 1, 20033 citations

Two-Junction SQUID Controlled by Both DC and RF Magnetic Flux

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