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Experimental Demonstration of a Superconducting 0-π Qubit

Invited

Abstract

Encoding a qubit in logical quantum states with wavefunctions characterized by disjoint support and robust energies can offer simultaneous protection against relaxation and pure dephasing. Using a two-dimensional circuit-quantum-electrodynamics architecture, we experimentally realize a superconducting 0-π qubit, which hosts protected states suitable for quantum-information processing. Our multi-tone spectroscopy measurements reveal the energy level structure of the system, which can be precisely described by a simple two-mode Hamiltonian. We find that the circuit realizes an effective one-dimensional crystal with two sub-lattices, where the geometrical phase difference between Wannier states localized at adjacent phase unit cells leads to interference effects associated with tunneling of pairs of Cooper pairs. The parity symmetry of the qubit results in charge-insensitive levels connecting the protected states, allowing for logical operations. The measured relaxation (1.6 ms) and dephasing times (25 μs) demonstrate that our implementation of the 0-π circuit not only broadens the family of superconducting qubits but also represents a promising candidate for the building block of a fault-tolerant quantum computer.

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Presenters

  • Andras Gyenis

    Princeton University, Department of Electrical Engineering, Princeton University

Authors

  • Andras Gyenis

    Princeton University, Department of Electrical Engineering, Princeton University

  • Pranav Mundada

    Princeton University, Department of Electrical Engineering, Princeton University, Electrical Engineering, Princeton University

  • Agustin Di Paolo

    Institut quantique and Departement de Physique, Universite de Sherbrooke, Universite de Sherbrooke, Département de Physique, Université de Sherbrooke, Institut quantique & Département de Physique, Université de Sherbrooke, Institut Quantique and Departement de Physique, Universite de Sherbrooke, Sherbrooke, Canada, Institut quantique and Département de Physique, Universite de Sherbrooke

  • Thomas M Hazard

    Department of Electrical Engineering, Princeton University

  • Xinyuan You

    Northwestern University, Graduate Program in Applied Physics, Northwestern University

  • David I Schuster

    University of Chicago, Physics, University of Chicago, Department of Physics and the James Franck Institute, University of Chicago, The James Franck Institute and Department of Physics, University of Chicago, The James Franck Institute and Department of Physics, The University of Chicago

  • Jens Koch

    Northwestern University, Physics and Astronomy, Northwestern University, Department of Physics and Astronomy, Northwestern University, Physics, Northwestern University

  • Alexandre Blais

    Universite de Sherbrooke, Institut quantique and Departement de Physique, Universite de Sherbrooke, Institut Quantique, Universite de Sherbrooke, Département de Physique, Université de Sherbrooke, Institut quantique & Département de Physique, Université de Sherbrooke, Institut Quantique and Departement de Physique, Universite de Sherbrooke, Sherbrooke, Canada, Institut quantique and Département de Physique, Universite de Sherbrooke

  • Andrew Houck

    Princeton University, Electrical Engineering, Princeton University, Department of Electrical Engineering, Princeton University