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Charge quantum interference device on superconducting nano-wires
Oleg Astafiev (Royal Holloway, University of London)
The Coherent Quantum Phase Slip (CQPS) effect in superconducting nanowires is exactly dual to the Josephson effect – tunneling of Cooper pairs through a thin dielectric layer. CQPS has been experimentally demonstrated for the first time in Ref.  and since then reproduced in different materials [2, 3]. CQPS is interesting from the fundamental point of view as well as for practical applications, particularly, for quantum metrology as it promises to build quantum current standards dual to voltage standards on the Josephson effect. An important milestone in this direction is demonstration of interference of a pair of flux tunneling amplitudes similarly to charge tunneling amplitudes in SQUIDs. We demonstrate a device exactly dual to SQUIDs, consisting of a superconducting island with two nanowires. This represents a charge quantum interference device (CQUID). The two tunneling amplitudes interfere and the effective tunneling energy depends on the gate induced charge on the island. In our experiment, the CQUID is incorporated into a superconducting loop, forming a phase-slip qubit with tunable energy. Such a circuit allows to measure the CQPS energy and is exactly dual to the charge qubit with a SQUID, where the effective Josephson energy is tuned.
 O. V. Astafiev, L. B. Ioffe, S. Kafanov, Yu. A. Pashkin, K. Yu. Arutyunov, D. Shahar, O. Cohen, J. S. Tsai. Nature 484, 355 (2012).
 J. T. Peltonen, O. V. Astafiev, Y. P. Korneeva, B. M. Voronov,A. A. Korneev, I. M. Charaev, A. V. Semenov, G. N. Gol’tsman, L. B. Ioffe, T. M. Klapwijk, J. S. Tsai. Phys. Rev. B 88, 220506 (2013).
 J. T. Peltonen, Z. H. Peng, Yu. P. Korneeva, B. M. Voronov, A. A. Korneev, A. V. Semenov, G. N. Gol’tsman, J. S. Tsai, and O. V. Astafiev. Phys. Rev. B 94, 180508® (2016).
Contact : Oleg Astafiev
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