298th RQC Seminar

• 講演者

  Mr. Bora Basyildiz
  ( Caltech )

• 日程

  2026年7月28日(火), 11:00 - 12:00(11:00 a.m.-12:00 p.m.)

• 開催場所

  ハイブリッド（Zoom,
  W319-321 Meeting Room, 3F, Cooperation Center, Wako Campus / 和光地区 研究交流棟3階 会議室 (W319-321) (S41))

• 講演タイトル

  Speeding Up Entangling Gates: Expanding the Hilbert Space and Suppressing Diabatic Leakage
  

• お問合せ

  yasunobu.nakamura[at]riken.jp

講演概要
The speed of elementary quantum gates ultimately sets the limit on the speed at which quantum circuits can operate. Here we explore the possibilities of speeding up two-qubit gates by expanding our computational space outside the qubit space. We identify an optimal theoretical synthesis time for the iSWAP gate using two parametrically coupled superconducting transmons. By novelly leveraging the higher energy qutrit subspace, we can provably speed up the gate by 2-3 times using experimentally feasible control protocols. In addition to utilizing the high energy subspace to speed up two-qubit gates, we identify the time-optimal synthesis for the three-level or qutrit CZ gate. Our analysis focuses on a theoretical model for capacitively coupled superconducting transmons but can be extended to other systems. We empirically observe that the time to synthesize the two-qutrit CZ gate is identical to the two-qubit CZ gate. Lastly, extending past effective static coupling schemes, we develop techniques to generate high-fidelity fast adiabatic CZ gates in the tunable coupler architecture. Here we strongly drive the tunable coupler to quickly accumulate the total phase for the CZ gate. However, this induces diabatic leakage transitions. By analyzing these leakage channels, we can then apply optimized pulses at the leakage transition frequencies. We call this active driving, and it allows us to minimize the leakage error induced by strongly driving the tunable coupler and provides a pathway to improving the fidelity of adiabatic CZ gates beyond the industry standard of 99.9% at 20 ns or less.