This title appears in the Scientific Report : 2014 

Coherent suppression of electromagnetic dissipation due to superconducting quasiparticles
Pop, Ioan M. (Corresponding Author)
Geerlings, Kurtis / Catelani, Gianluigi / Schoelkopf, Robert J. / Glazman, Leonid I. / Devoret, Michel H.
Theoretische Nanoelektronik; PGI-2
Nature , 508 (2014) 7496, S. 369 - 372
London [u.a.] Nature Publising Group78092 2014
10.1038/nature13017
24740067
Journal Article
Spin-based and quantum information
Please use the identifier: http://dx.doi.org/10.1038/nature13017 in citations.
Owing to the low-loss propagation of electromagnetic signals in superconductors, Josephson junctions constitute ideal building blocks for quantum memories, amplifiers, detectors and high-speed processing units, operating over a wide band of microwave frequencies. Nevertheless, although transport in superconducting wires is perfectly lossless for direct current, transport of radio-frequency signals can be dissipative in the presence of quasiparticle excitations above the superconducting gap1. Moreover, the exact mechanism of this dissipation in Josephson junctions has never been fully resolved experimentally. In particular, Josephson’s key theoretical prediction that quasiparticle dissipation should vanish in transport through a junction when the phase difference across the junction is π (ref. 2) has never been observed3. This subtle effect can be understood as resulting from the destructive interference of two separate dissipative channels involving electron-like and hole-like quasiparticles. Here we report the experimental observation of this quantum coherent suppression of quasiparticle dissipation across a Josephson junction. As the average phase bias across the junction is swept through π, we measure an increase of more than one order of magnitude in the energy relaxation time of a superconducting artificial atom. This striking suppression of dissipation, despite the presence of lossy quasiparticle excitations above the superconducting gap, provides a powerful tool for minimizing decoherence in quantum electronic systems and could be directly exploited in quantum information experiments with superconducting quantum bits.