Implementation of superconductor/ferromagnet/ superconductor -shifters in superconducting digital and quantum circuits

High operation speed and low energy consumption may allow the superconducting digital single-flux-quantum circuits to outperform traditional complementary metaloxidesemiconductor logic. The remaining major obstacle towards high element densities on-chip is a relatively large cell size necessary to hold a magnetic flux quantum 0. Inserting a -type Josephson junction in the cell is equivalent to applying flux 0/2 and thus makes it possible to solve this problem. Moreover, using -junctions in superconducting qubits may help to protect them from noise. Here we demonstrate the operation of three superconducting circuitstwo of them are classical and one quantumthat all utilize such -phase shifters realized using superconductor/ferromagnet/superconductor sandwich technology. The classical circuits are based on single-flux-quantum cells, which are shown to be scalable and compatible with conventional niobium-based superconducting electronics. The quantum circuit is a -biased phase qubit, for which we observe coherent Rabi oscillations. We find no degradation of the measured coherence time compared to that of a reference qubit without a -junction. ©2010

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