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Magnifying quantum phase fluctuations with Cooper-pair pairing

William C Smith 1, 2 Marius Villiers 1, 2 Antoine Marquet 3, 2 Jose Palomo 3 Matthieu Delbecq 1 Takis Kontos 1 Philippe Campagne-Ibarcq 1, 2 Benoît Douçot 4 Zaki Leghtas 5, 2, 1
1 Physique Mésoscopique
LPENS - Laboratoire de physique de l'ENS - ENS Paris
2 QUANTIC - QUANTum Information Circuits
MINES ParisTech - École nationale supérieure des mines de Paris, ENS Paris - École normale supérieure - Paris, SU - Sorbonne Université, Inria de Paris
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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https://hal.inria.fr/hal-03084684
Contributor : Mazyar Mirrahimi Connect in order to contact the contributor
Submitted on : Monday, December 21, 2020 - 12:05:18 PM
Last modification on : Tuesday, January 11, 2022 - 11:16:07 AM

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

Citation

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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