Experimental realization of an intrinsically error-protected superconducting qubit

  1. Andras Gyenis,
  2. Pranav S. Mundada,
  3. Agustin Di Paolo,
  4. Thomas M. Hazard,
  5. Xinyuan You,
  6. David I. Schuster,
  7. Jens Koch,
  8. Alexandre Blais,
  9. and Andrew A. Houck
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 circuit-quantum-electrodynamics architecture, we experimentally realize a superconducting 0−π qubit, which hosts protected states suitable for quantum-information processing. 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 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 processor.
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