Quantum transitions and zero-crossing current steps in a SQUID controlled by multi-phase RF fields

摘要

We numerically demonstrate zero-crossing current steps on current-voltage characteristics (IVC) of a three-junction superconducting quantum interference device (SQUID) activated by multi-phase RF magnetic flux. First, we analyze how the quantum state of the SQUID can be controlled by two RF magnetic signals with phase difference of π/2. It is shown on the quantum diagram that one flux quantum can pass through the SQUID per one cycle of the RF signals without DC biasing current, which results in a zero-crossing step on its IVC. Next, we numerically demonstrate IVC of the SQUID and zero-crossing steps on them. We also investigate the dependence of zero-crossing steps upon the DC offset flux. The results show that the voltage position of zero-crossing steps can be set at one of three values (―Φ_0f, 0, and Φ_0f) by tuning the DC offset flux.