Characterization of a 5-Qubit Superconducting Device

Yi-Xiang Huang^1,2*, Zhen-Wei Hsu¹, Li-Chieh Hsiao¹, Teik-Hui Lee¹, Jyh-Yang Wang¹, Chin-Chia Chang¹, Yen-Chun Chen¹, Cheng-Cheng Huang¹, Yen-Yu Chiang¹, Chii-Dong Chen¹, Chiao-Hsuan Wang², Chung-Ting Ke¹

¹Department of Physics, Academia Sinica, Taipei, Taiwan
²Department of Physics, National Taiwan University, Taipei, Taiwan

* Presenter:Yi-Xiang Huang, email:r11222090@ntu.edu.tw

To realize a universal quantum computer, scaling up the number of qubits and comprehensively characterizing their properties are crucial. In this study, we systematically examined a five-qubit superconducting device of the transmon type, analyzing both single-qubit and two-qubit quantum gate properties.
First, we utilize multiplexed readout to observe the dispersive shift and the flux dependence of the five readout resonators simultaneously. We optimized the readout fidelity up to 90% without a low-temperature parametric amplifier. Next, we applied different qubit control pulses to observe Rabi oscillations and Ramsey chevrons resulting in a T₁ and T₂ decoherence times around 10 μs and 4 μs, respectively. The single qubit Clifford gate fidelity was found to exceed 99.3% through randomized benchmarking. In addition, we performed two-qubit operations including iSWAP and CZ gates to realize two-qubit gate operations between neighboring qubits.
In summary, we studied a 5-qubit chip by characterizing the single and two-qubit properties. In collaboration with the theoretical group, our future experiments will focus on implementing active reset, mitigating ZZ interactions, and evaluating entanglement among the five qubits.

Keywords: Quantum Computation, Transmon Qubit, Two-Qubit Gate