Magnifying quantum phase fluctuations with Cooper-pair pairing
- URL: http://arxiv.org/abs/2010.15488v2
- Date: Tue, 5 Apr 2022 12:59:46 GMT
- Title: Magnifying quantum phase fluctuations with Cooper-pair pairing
- Authors: W. C. Smith, M. Villiers, A. Marquet, J. Palomo, M. R. Delbecq, T.
Kontos, P. Campagne-Ibarcq, B. Dou\c{c}ot, Z. Leghtas
- Abstract summary: We fabricate a generalized Josephson element that can be tuned in situ between one- and two-Cooper-pair tunneling.
We measure a tenfold suppression of flux sensitivity of the first transition energy, implying a twofold increase in the vacuum phase fluctuations.
- Score: 0.0
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- 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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