ED1-3-INV
A two-qubit gate scheme robust to frequency collisions using fixed-frequency transmon qubits
10:45-11:15 Dec.3
*Shotaro Shirai1,2, Yuta Okubo2, Shinichi Inoue3, Rui Li1, Shuhei Tamate1, Kohei Matsuura3, Alto Osada2,4, Yasunobu Nakamura1,3 and Atsushi Noguchi1,2,5
RIKEN Center for Quantum Computing (RQC), Wako, Saitama 351-0198, Japan1
Komaba Institute for Science (KIS), The University of Tokyo, Meguro-ku, Tokyo, 153-8902, Japan2
Department of Applied Physics, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan3
PRESTO, Japan Science and Technology Agency, Kawaguchi-shi, Saitama4
Inamori Research Institute for Science (InaRIS), Kyoto-shi, Kyoto 600-8411, Japan5
In the development of quantum computers using superconducting qubits, fixed-frequency transmon qubits offer advantages for integration because they do not require a magnetic field and have excellent coherence properties. However, a limitation of these qubits is their inability to change frequency during gate operations, leading to potential frequency collisions caused by parameter fluctuations during fabrication. To fully leverage the advantages of fixed-frequency transmon qubits, it is essential to develop a scalable two-qubit gate scheme that is robust against qubit frequency variations. In this study, we experimentally demonstrated a two-qubit gate that addresses these challenges using a fixed-frequency transmon qubit as a coupler [1]. The gate operation is based on a microwave-induced parametric transition between an auxiliary level introduced by the fixed-frequency transmon coupler and a level within the computational subspace. Additionally, we found that the residual ZZ interaction could be suppressed without additional structures by carefully designing the capacitance network that includes the coupler. In this talk, I will present the theoretical and numerical modeling of this gate scheme, discuss the experimental results, and conclude with prospects.
[1] S. Shirai, Y. Okubo, K. Matsuura, A. Osada, Y. Nakamura, and A. Noguchi, “All-microwave manipulation of superconducting qubits with a fixed-frequency transmon coupler”, Phys. Rev. Lett. 130, 260601 (2023).
This work was partly supported by JST ERATO (Grant No. JPMJER1601), MEXT Q-LEAP (Grant No. JPMXS0118068682), and JSPS KAKENHI (Grant No. JP22J15257).
Figure 1. (a) Optical image of a fabricated superconducting circuit. Most of the structures are made from TiN electrodes (yellow) on a Si substrate (gray). (b) Equivalent circuit diagram of the coupled transmon system, where readout resonators, Purcell filters, and drive lines are omitted. Only the coupling capacitors connected to them are depicted.
Keywords: Superconducting qubit, Transmon, Frequency collision, Two-qubit gate