A. Miano

Real-time quantum error correction beyond break-even

  1. V. V. Sivak,
  2. A. Eickbusch,
  3. B. Royer,
  4. S. Singh,
  5. I. Tsioutsios,
  6. S. Ganjam,
  7. A. Miano,
  8. B. L. Brock,
  9. A. Z. Ding,
  10. L. Frunzio,
  11. S. M. Girvin,
  12. R. J. Schoelkopf,
  13. and M. H. Devoret
The ambition of harnessing the quantum for computation is at odds with the fundamental phenomenon of decoherence. The purpose of quantum error correction (QEC) is to counteract the
natural tendency of a complex system to decohere. This cooperative process, which requires participation of multiple quantum and classical components, creates a special type of dissipation that removes the entropy caused by the errors faster than the rate at which these errors corrupt the stored quantum information. Previous experimental attempts to engineer such a process faced an excessive generation of errors that overwhelmed the error-correcting capability of the process itself. Whether it is practically possible to utilize QEC for extending quantum coherence thus remains an open question. We answer it by demonstrating a fully stabilized and error-corrected logical qubit whose quantum coherence is significantly longer than that of all the imperfect quantum components involved in the QEC process, beating the best of them with a coherence gain of G=2.27±0.07. We achieve this performance by combining innovations in several domains including the fabrication of superconducting quantum circuits and model-free reinforcement learning.
arxiv pdf

Frequency-tunable Kerr-free three-wave mixing with a gradiometric SNAIL

  1. A. Miano,
  2. G. Liu,
  3. V. V. Sivak,
  4. N. E. Frattini,
  5. V. R. Joshi,
  6. W. Dai,
  7. L. Frunzio,
  8. and M. H. Devoret
Three-wave mixing is a key process in superconducting quantum information processing, being involved in quantum-limited amplification and parametric coupling between superconducting
cavities. These operations can be implemented by SNAIL-based devices that present a Kerr-free flux-bias point where unwanted parasitic effects such as Stark shift are suppressed. However, with a single flux-bias parameter, these circuits can only host one Kerr-free point, limiting the range of their applications. In this Letter, we demonstrate how to overcome this constraint with a gradiometric SNAIL, a doubly-flux biased superconducting circuit for which both effective inductance and Kerr coefficient can be independently tuned. Experimental data show the capability of the gradiometric SNAIL to suppress Kerr effect in a three-wave mixing parametric amplifier over a continuum of flux bias points corresponding to a 1.7 GHz range of operating frequencies.
arxiv pdf