Zuchongzhi 2.1

Zuchongzhi 2.1 is a superconducting circuits quantum computer operated by USTC in China. It has 66 physical qubits. It ranks 32 of 74 superconducting machines in this table by physical qubit count. 8 sourced specs are in the spec sheet. 3 published benchmark or milestone records are listed below, each marked by who measured it.

Also known as USTC 66-qubit superconducting processor

USTC's 66-qubit programmable superconducting machine, led by Pan Jianwei's group and used for random circuit sampling on up to 60 qubits and 24 cycles; the authors estimate about 4.2 hours on the device against roughly 4.8e4 years on a leading supercomputer. The paper reports 99.84 percent average single-qubit, 99.40 percent two-qubit (an iSWAP-like gate of about 24 ns, down from about 32 ns on Zuchongzhi 2.0) and 97.74 percent readout fidelity; one of the 110 couplers is faulty and acts as a fixed coupler. A March 2023 China Daily piece (reposted by USTC) says it was running in a Hefei lab and that a replica was planned to link to a cloud platform, so access is recorded as internal. Press speedup claims vary (10 million times a supercomputer versus about 1 million times Google's 2019 Sycamore). The successors are zuchongzhi-3-0 and zuchongzhi-3-2.

Spec sheet

Technical details as the builder or a paper states them, each with its own source. A blank is a fact we could not source, not a zero. Fidelity and coherence figures are in the benchmark table below.

Spec	Value	Basis	Note	Source
Processor	66-qubit transmon processor on two flip-chip-bonded sapphire chips	Vendor reported	Qubit chip carries 66 qubits and 110 couplers; second chip carries control lines.	ar5iv.labs.arxiv.org arxiv.org
Qubit type	transmon	Vendor reported		ar5iv.labs.arxiv.org arxiv.org
Topology	11 by 6 two-dimensional rectangular array with tunable couplers	Vendor reported		ar5iv.labs.arxiv.org arxiv.org
Couplers	110	Peer reviewed	110 couplers on the qubit chip; one is faulty and gives only fixed coupling.	ar5iv.labs.arxiv.org
Native gates	iSWAP-like two-qubit gate with single-qubit rotations	Vendor reported	The paper uses an iSWAP-like gate, not CZ.	ar5iv.labs.arxiv.org
Two-qubit gate time	24 ns	Peer reviewed	iSWAP-like gate duration of about 24 ns, down from about 32 ns on Zuchongzhi 2.0.	ar5iv.labs.arxiv.org
Fabrication	Indium-bump flip-chip bonding of two sapphire chips	Vendor reported		ar5iv.labs.arxiv.org arxiv.org
Access and pricing	Lab system at USTC in Hefei; a replica was planned for cloud access	Vendor reported	From a March 2023 China Daily article reposted by USTC.	en.ustc.edu.cn

Published benchmark figures

These are numbers the builder or a paper reports for this machine, not results from a common test. The basis column says who measured them. What the metrics mean and why they are not comparable across technologies.

Metric	Value	Measured	Basis	Note	Source
Readout fidelity	97.74%	2021-09	Peer reviewed	Average readout fidelity stated in the abstract.	arxiv.org ar5iv.labs.arxiv.org
Single-qubit gate fidelity	99.84%	2021-09	Peer reviewed	Average single-qubit gate fidelity reported in the PRL paper.	ar5iv.labs.arxiv.org arxiv.org
Two-qubit gate fidelity	99.4%	2021-09	Peer reviewed	Average iSWAP-like gate fidelity.	ar5iv.labs.arxiv.org arxiv.org

Timeline

2021-09: Announced
2021: First operational
2023-03-09: Status checked: operational

Comparable superconducting machines

Closest in physical qubit count within the same technology. Counts of different qubit types are not interchangeable across technologies.

Machine	Operator	Qubits	Status
G-QuAT System F	AIST	64	operational
Osaka University 64-Qubit System	Osaka University	64	operational
RIKEN 64-Qubit System	RIKEN	64	operational
RIKEN-Fujitsu 64-Qubit System	RIKEN	64	operational
Origin Wukong	Origin Quantum	72	operational
Euro-Q-Exa	LRZ	54	operational