Decoherence in Josephson Qubits from Dielectric Loss

Martinis, John M.; Cooper, Ken B.; McDermott, Robert; Steffen, Matthias; Ansmann, M.; Osborn, Kevin; Cicak, Katarina; Oh, Seongshik; Pappas, David P.; Simmonds, Raymond W.; Yu, Clare C.

doi:10.1103/physrevlett.95.210503

Cited by 712 publications

(806 citation statements)

References 24 publications

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“…For example, a key limitation in solid-state based quantum processing of information is the decoherence due to fluctuating TLSs in the dielectric layers fabricated on-chip [26][27][28] . We anticipate, resting on the motional narrowing phenomenon, that the dephasing times of the existing superconducting qubits may be dramatically improved if one is able to accelerate the dynamics of the longitudinally coupled TLSs.…”

Section: Discussionmentioning

confidence: 99%

Motional averaging in a superconducting qubit

et al. 2013

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Superconducting circuits with Josephson junctions are promising candidates for developing future quantum technologies. Of particular interest is to use these circuits to study effects that typically occur in complex condensed-matter systems. Here we employ a superconducting quantum bit-a transmon-to perform an analogue simulation of motional averaging, a phenomenon initially observed in nuclear magnetic resonance spectroscopy. By modulating the flux bias of a transmon with controllable pseudo-random telegraph noise we create a stochastic jump of its energy level separation between two discrete values. When the jumping is faster than a dynamical threshold set by the frequency displacement of the levels, the initially separate spectral lines merge into a single, narrow, motional-averaged line. With sinusoidal modulation a complex pattern of additional sidebands is observed. We show that the modulated system remains quantum coherent, with modified transition frequencies, Rabi couplings, and dephasing rates. These results represent the first steps towards more advanced quantum simulations using artificial atoms.

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Section: Discussionmentioning

confidence: 99%

Motional averaging in a superconducting qubit

et al. 2013

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“…One may view a number of mechanisms causing energy or phase relaxation as extrinsic ones. These involve, e.g., imperfections in the tunnel barriers comprising junctions 7 , charge trapping 8 , and interaction with stray photons 9,10 . Along with them, there are intrinsic mechanisms associated with the kinetics of quasiparticles in the superconductors [11][12][13] .…”

Section: Pacs Numbersmentioning

confidence: 99%

Frequency-dependent admittance of a short superconducting weak link

2013

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We consider the linear and non-linear electromagnetic responses of a nanowire connecting two bulk superconductors. Andreev states appearing at a finite phase bias substantially affect the finite-frequency admittance of such a wire junction. Electron transitions involving Andreev levels are easily saturated, leading to the nonlinear effects in photon absorption for the sub-gap photon energies. We evaluate the complex admittance analytically at arbitrary frequency and arbitrary, possibly non-equilibrium, occupation of Andreev levels. Special care is given to the limits of a single-channel contact and a disordered metallic weak link. We also evaluate the quasi-static fluctuations of admittance induced by fluctuations of the occupation factors of Andreev levels. In view of possible qubit applications, we compare properties of a weak link with those of a tunnel Josephson junction. Compared to the latter, a weak link has smaller low-frequency dissipation. However, because of the deeper Andreev levels, the low-temperature quasi-static fluctuations of the inductance of a weak link are exponentially larger than of a tunnel junction. These fluctuations limit the applicability of nanowire junctions in superconducting qubits

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“…[7][8][9][10][11][12] These anticrossings indicate intrinsic, microscopic TLSs being coupled coherently to the qubit circuit. In general, ensembles of two-level microscopic defects are believed to be responsible for loss in a wide variety of systems, including phase-and flux-based superconducting qubits and even nanomechanical oscillators, 13,14 as well as more general effects in amorphous and spin-glass systems.…”

Section: Introductionmentioning

confidence: 99%

Multiphoton spectroscopy of a hybrid quantum system

et al. 2010

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We report on experimental multiphoton spectroscopy of a hybrid quantum system consisting of a superconducting phase qubit coherently coupled to an intrinsic two-level system ͑TLS͒. We directly probe hybridized states of the combined qubit-TLS system in the strongly interacting regime, where both the qubit-TLS coupling and the driving cannot be considered as weak perturbations. This regime is described by a theoretical model which incorporates anharmonic corrections, multiphoton processes and decoherence. We present a detailed comparison between experiment and theory and find excellent agreement over a wide range of parameters.

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Decoherence in Josephson Qubits from Dielectric Loss

Cited by 712 publications

References 24 publications

Motional averaging in a superconducting qubit

Motional averaging in a superconducting qubit

Frequency-dependent admittance of a short superconducting weak link

Multiphoton spectroscopy of a hybrid quantum system

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