PT Journal
AU Feofanov, AK
   Oboznov, VA
   Bol'Ginov, VV
   Lisenfeld, J
   Poletto, S
   Ryazanov, VV
   Rossolenko, AN
   Khabipov, M
   Balashov, D
   Zorin, AB
   Dmitriev, PN
   Koshelets, VP
   Ustinov, AV
TI Implementation of superconductor/ferromagnet/ superconductor
SO Nature Physics
JI Nat. Phys.
PY 2010
BP 593
EP 597
VL 6
IS 8
DE fromIPMRAS
AB High operation speed and low energy consumption may allow the superconducting digital single-flux-quantum circuits to outperform traditional complementary metal-oxide-semiconductor logic. The remaining major obstacle towards high element densities on-chip is a relatively large cell size necessary to hold a magnetic flux quantum Φ0. Inserting a π-type Josephson junction in the cell is equivalent to applying flux Φ0/2 and thus makes it possible to solve this problem. Moreover, using π-junctions in superconducting qubits may help to protect them from noise. Here we demonstrate the operation of three superconducting circuits-two of them are classical and one quantum-that all utilize such π-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 π-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 π-junction.
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