Universal flux-based control of a π-SQUID

  1. J. Wilson Staples,
  2. Thomas B. Smith,
  3. and Andrew C. Doherty
We describe a protocol for the universal control of non-ideal π-periodic superconducting qubits. Our proposal relies on a π-SQUID: a superconducting loop formed by two π-periodic circuit elements, with an external magnetic flux threading the circuit. The system exhibits an extensive sweet spot around half-flux where residual 2π-periodic Cooper pair tunneling is highly suppressed. We demonstrate that universal single-qubit operations can be realised by tuning the flux adiabatically and diabatically within this broad sweet spot. We also assess how residual 2π-periodicity in π-SQUIDs impacts holonomic phase gates.
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