Yinqi Chen

Voltage Activated Parametric Entangling Gates on Gatemons

  1. Yinqi Chen,
  2. Konstantin N. Nesterov,
  3. Hugh Churchill,
  4. Javad Shabani,
  5. Vladimir E. Manucharyan,
  6. and Maxim G. Vavilov
We describe the generation of entangling gates on superconductor-semiconductor hybrid qubits by ac voltage modulation of the Josephson energy. Our numerical simulations demonstrate
that the unitary error can be below 10−5 in a variety of 75-ns-long two-qubit gates (CZ, iSWAP, and iSWAP‾‾‾‾‾‾‾√) implemented using parametric resonance. We analyze the conditional ZZ phase and demonstrate that the CZ gate needs no further phase correction steps, while the ZZ phase error in SWAP-type gates can be compensated by choosing pulse parameters. With decoherence considered, we estimate that qubit relaxation time needs to exceed 70μs to achieve the 99.9% fidelity threshold.
arxiv pdf

Fast Flux Entangling Gate for Fluxonium Circuits

  1. Yinqi Chen,
  2. Konstantin N. Nesterov,
  3. Vladimir E. Manucharyan,
  4. and Maxim G. Vavilov
We analyze a high-fidelity two-qubit gate using fast flux pulses on superconducting fluxonium qubits. The gate is realized by temporarily detuning magnetic flux through fluxonium loop
away from the half flux quantum sweet spot. We simulate dynamics of two capacitively coupled fluxoniums during the flux pulses and optimize the pulse parameters to obtain a highly accurate iswap‾‾‾‾‾‾√-like entangling gate. We also evaluate the effect of the flux noise and qubit relaxation on the gate fidelity. Our results demonstrate that the gate error remains below 10−4 for currently achievable magnitude of the flux noise and qubit relaxation time.
arxiv pdf