Daniel Cohen

Cavity-mediated cross-cross-resonance gate

  1. Alexey V. Gorshkov,
  2. Daniel Cohen,
  3. Arbel Haim,
  4. Amit Rotem,
  5. Or Golan,
  6. Gihwan Kim,
  7. Andreas Butler,
  8. Connor T. Hann,
  9. Oskar Painter,
  10. Fernando G.S.L. Brandão,
  11. and Alex Retzker
We propose a cavity-mediated gate between two transmon qubits or other nonlinear superconducting elements. The gate is realized by driving both qubits at a frequency that is near-resonant
with the frequency of the cavity. Since both qubits are subject to a cross-resonant drive, we call this gate a cross-cross-resonance gate. In close analogy with gates between trapped-ion qubits, in phase space, the state of the cavity makes a circle whose area depends on the state of the two qubits, realizing a controlled-phase gate. We propose two schemes for canceling the dominant error, which is the dispersive coupling. We also show that this cross-cross-resonance gate allows one to realize simultaneous gates between multiple pairs of qubits coupled via the same metamaterial composed of an array of coupled cavities or other linear mediators.
arxiv pdf

Robust gates with spin-locked superconducting qubits

  1. Ido Zuk,
  2. Daniel Cohen,
  3. Alexey V. Gorshkov,
  4. and Alex Retzker
Dynamical decoupling has been shown to be effective in reducing gate errors in most quantum computation platforms and is therefore projected to play an essential role in future fault-tolerant
constructions. In superconducting circuits, however, it has proven difficult to utilize the benefits of dynamical decoupling. In this work, we present a theoretical proposal that incorporates a continuous version of dynamical decoupling, namely spin locking, with a coupler-based CZ gate for transmons and provide analytical and numerical results that demonstrate its effectiveness.
arxiv pdf