All-microwave leakage reduction units for quantum error correction with superconducting transmon qubits

  1. J. F. Marques,
  2. H. Ali,
  3. B. M. Varbanov,
  4. M. Finkel,
  5. H. M. Veen,
  6. S. L. M. van der Meer,
  7. S. Valles-Sanclemente,
  8. N. Muthusubramanian,
  9. M. Beekman,
  10. N. Haider,
  11. B. M. Terhal,
  12. and L. DiCarlo
Minimizing leakage from computational states is a challenge when using many-level systems like superconducting quantum circuits as qubits. We realize and extend the quantum-hardware-efficient, all-microwave leakage reduction unit (LRU) for transmons in a circuit QED architecture proposed by Battistel et al. This LRU effectively reduces leakage in the second- and third-excited transmon states with up to 99% efficacy in 220 ns, with minimum impact on the qubit subspace. As a first application in the context of quantum error correction, we demonstrate the ability of multiple simultaneous LRUs to reduce the error detection rate and to suppress leakage buildup within 1% in data and ancilla qubits over 50 cycles of a weight-2 parity measurement.
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