Millisecond coherence in a superconducting qubit

  1. Aaron Somoroff,
  2. Quentin Ficheux,
  3. Raymond A. Mencia,
  4. Haonan Xiong,
  5. Roman V. Kuzmin,
  6. and Vladimir E. Manucharyan
Increasing the degree of control over physical qubits is a crucial component of quantum computing research. We report a superconducting qubit of fluxonium type with the Ramsey coherence time reaching T∗2=1.48±0.13 ms, which exceeds the state of the art value by an order of magnitude. As a result, the average single-qubit gate fidelity grew above 0.9999, surpassing, to our knowledge, any other solid-state quantum system. Furthermore, by measuring energy relaxation of the parity-forbidden transition to second excited state, we exclude the effect of out-of-equilibrium quasiparticles on coherence in our circuit. Combined with recent demonstrations of two-qubit gates on fluxoniums, our result paves the way for the next generation of quantum processors.
arxiv pdf

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