Abstract 13 February 2015

Coherent supression of quasiparticle dissipation

Ion Pop (Yale)

We demonstrate immunity to quasiparticle dissipation for the central Josephson junction of a superconducting artificial atom. At the foundation of this protection rests a prediction by Brian Josephson from fifty years ago: the particle-hole interference of superconducting quasiparticles when tunneling across a Josephson junction [1]. The junction under study is the central element of a fluxonium artificial atom, which we place in an extremely low loss environment and measure using radio-frequency dispersive techniques [2]. Furthermore, by using a quantum limited amplifier (a Josephson Parametric Converter) we can observe quantum jumps between the 0 and 1 states of the qubit in thermal equilibrium with the environment. The distribution of the times in-between the quantum jumps reveals quantitative information about the population and dynamics of quasiparticles [3]. The data is entirely consistent with the hypothesis that our system is sensitive to single quasiparticle excitations, which opens new perspectives for ultrasensitive detection and quasiparticle suppression in low temperature devices. 

[1] B. D. Josephson, Physics Letters 1, 251 (1962)

[2] I. M. Pop et al., Nature 508 (2014)

[3] U. Vool, I. M. Pop et al., PRL 113 (2014)



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