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Magnifying quantum phase fluctuations with Cooper-pair pairing

Abstract : Remarkably, complex assemblies of superconducting wires, electrodes, and Josephson junctions are compactly described by a handful of collective phase degrees of freedom that behave like quantum particles in a potential. The inductive wires contribute a parabolic confinement, while the tunnel junctions add a cosinusoidal corrugation. Usually, the ground state wavefunction is localized within a single potential well -- that is, quantum phase fluctuations are small -- although entering the regime of delocalization holds promise for metrology and qubit protection. A direct route is to loosen the inductive confinement and let the ground state phase spread over multiple Josephson periods, but this requires a circuit impedance vastly exceeding the resistance quantum and constitutes an ongoing experimental challenge. Here we take a complementary approach and fabricate a generalized Josephson element that can be tuned in situ between one- and two-Cooper-pair tunneling, doubling the frequency of the corrugation and thereby magnifying the number of wells probed by the ground state. We measure a tenfold suppression of flux sensitivity of the first transition energy, implying a twofold increase in the vacuum phase fluctuations.
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Preprints, Working Papers, ...
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Contributor : Mazyar Mirrahimi <>
Submitted on : Monday, December 21, 2020 - 12:05:18 PM
Last modification on : Friday, January 8, 2021 - 3:39:17 AM

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  • HAL Id : hal-03084684, version 1
  • ARXIV : 2010.15488


William C Smith, Marius Villiers, Antoine Marquet, Jose Palomo, Matthieu Delbecq, et al.. Magnifying quantum phase fluctuations with Cooper-pair pairing. 2020. ⟨hal-03084684⟩



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