Flux-Quantum Transitions in a Three-Junction SQUID Controlled by Two RF Signals(<特集>Special Issue on Superconductive Electronics)

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We present analytical and numerical results on the flux-quantum transitions in a three-junction superconducting quantum interference device (3J-SQUID) controlled by two RF signals. The 3J-SQUID has two superconducting loops, and the RF signals are magnetically coupled to the loops. Flux-quantum transitions in the 3J-SQUID loops can be controlled by utilizing the phase difference of the two RF signals. Under proper conditions, we can obtain a situation where one flux quantum passes through the 3J-SQUID per one cycle of the RF signals without DC current biasing, which results in a zero-crossing step on the current-voltage characteristics. In this paper, we first explain the operation principle by using a quantum state diagram of a 3J- SQUID. Next, we numerically simulate RF-induced transitions of the quantum states. A zero-crossing step on the current-voltage characteristics is demonstrated. We also investigate dependence of zero-crossing steps upon parameters of the 3J-SQUID and RF signals.
社団法人電子情報通信学会の論文
2002-03-01