Non-Poissonian Quantum Jumps of a Fluxonium Qubit due to Quasiparticle Excitations

Vool, U.; Sliwa, K.; Catelani, G.; Schoelkopf, R. J.; Shankar, S.; Pop, I. M.; Devoret, M. H.; Glazman, L. I.; Wang, C.; Gao, Y. Y.; Mirrahimi, M.; Abdo, B.; Brecht, T.; Hatridge, M.; Frunzio, L.

doi:10.1103/PhysRevLett.113.247001

Journal Article

FZJ-2014-07008

Non-Poissonian Quantum Jumps of a Fluxonium Qubit due to Quasiparticle Excitations

Vool, U. (Corresponding Author) ; Pop, I. M. ; Sliwa, K. ; Abdo, B. ; Wang, C. ; Brecht, T. ; Gao, Y. Y. ; Shankar, S. ; Hatridge, M. ; Catelani, G.FZJ* ; Mirrahimi, M. ; Frunzio, L. ; Schoelkopf, R. J. ; Glazman, L. I. ; Devoret, M. H.

2014
APS College Park, Md.

Physical review letters 113(24), 247001 (2014) [10.1103/PhysRevLett.113.247001]

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Please use a persistent id in citations: http://hdl.handle.net/2128/8177 doi:10.1103/PhysRevLett.113.247001

Abstract: As the energy relaxation time of superconducting qubits steadily improves, nonequilibrium quasiparticle excitations above the superconducting gap emerge as an increasingly relevant limit for qubit coherence. We measure fluctuations in the number of quasiparticle excitations by continuously monitoring the spontaneous quantum jumps between the states of a fluxonium qubit, in conditions where relaxation is dominated by quasiparticle loss. Resolution on the scale of a single quasiparticle is obtained by performing quantum nondemolition projective measurements within a time interval much shorter than T1, using a quantum-limited amplifier (Josephson parametric converter). The quantum jump statistics switches between the expected Poisson distribution and a non-Poissonian one, indicating large relative fluctuations in the quasiparticle population, on time scales varying from seconds to hours. This dynamics can be modified controllably by injecting quasiparticles or by seeding quasiparticle-trapping vortices by cooling down in a magnetic field.

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