At recent quantum technical conferences it has been emphasized that qubit quality is a very important factor in creating a viable quantum computer. So kudos to IBM, Rigetti and IonQ for documenting the specifications of their respective chips. However, the companies are using different formats making it difficult to compare so we decided to put them into a common format. These parameters are shown below in the three tables below. Table 1 shows the qubit count, qubit connectivity, T1 and T2 or T2* times. Table 2 shows the single qubit gate fidelity, the two qubit gate fidelity and the readout fidelities. And Table 3 shows the sources of the data for the first two tables. Note that all of this data is for physical qubits without any error correction.
Although we don’t have complete data for Google’s implementations, they recently provided some information at the Adiabatic Quantum Computing Conference (AQC 2018) where they compared metrics from their 5 and 9 qubit test chips with IBM’s 20 qubit implementation. In the presentation Google indicated that their T1 times are roughly 24X worse than IBM’s, but that their single and two qubit gate fidelities are 210X better, and their measurement fidelities are roughly 10X better. They also gave their opinion that gate fidelities are a more realistic measure than coherence times and that they expect their forthcoming 72 qubit chip will show similar results as their 5 and 9 qubit chips. You can view Google’s complete presentation at AQC 2018 here. Also note that IonQ’s ion trap gate delays are about three orders of magnitude slower than those of the superconducting implementations. So this takes away a little of the advantage they may have in T1 and T2 decoherence times.
We encourage anyone else who has data on other implementations to contact us at info@quantumcomputingreport.com so we can include your data into these tables. Please see the notes at the end of this page that provides additional details of how these tables were generated.
Qubit Connectivity  T1 (µsec)  T2 (µsec)  
Computer  Qubit Count  Min  Max  Ave  Min  Max  Ave  Min  Max  Ave 
IBM Q5 Tenerife 
5 
2 
4 
2.4 
42.3 
57.7 
51.1 
10.6 
40.2 
25.9 
IBM Q16 Melbourne 
14 
2 
3 
2.71 
24.5 
110.0 
58.7 
17.0 
155.7 
71.5 
IBM Q20 Poughkeepsie 
20 
2 
6 
3.9 
39.4 
123.3 
73.2 
10.8 
123.6 
66.2 
IBM Q20 Tokyo 
20 
2 
6 
3.9 
42.2 
148.5 
84.3 
24.3 
78.4 
49.6 
IBM Q System One 
20 
2 
6 
3.9 
38.2 
132.9 
73.9 
39.2 
100.8 
69.1 
Rigetti 16Q Aspen1 
16 
2 
3 
2.25 
1.4 
14.4 
7.92 
4.8 
17.6 
11.33 
Rigetti 8Q Agave 
8 
2 
2 
2 
10.0 
15.5 
13.4 
9.2 
26.2 
15.1 
Rigetti 19Q Acorn 
19 
1 
3 
2.21 
8.2 
31.0 
20.3 
4.9 
26.8 
10.9 
IonQ 11 Qubit 
11 
11 
11 
11 
>10^{10} 
>10^{10} 
>10^{10} 
TBD 
TBD 
~3x10^{6} 
1Qubit Gate Fidelity  2Qubit Gate Fidelity  Readout Fidelity  
Computer  Min  Max  Ave  Min  Max  Ave  Min  Max  Ave 
IBM Q5 Tenerife 
99.66% 
99.93% 
99.84% 
94.24% 
97.76% 
95.98% 
91.80% 
96.80% 
94.46% 
IBM Q16 Melbourne 
99.11% 
99.87% 
99.68% 
69.86% 
96.81% 
92.84% 
81.87% 
97.41% 
93.02% 
IBM Q20 Poughkeepsie 
99.72% 
99.95% 
99.89% 
93.39% 
98.89% 
97.75% 
TBD 
TBD 
TBD 
IBM Q20 Tokyo 
99.39% 
99.94% 
99.80% 
92.88% 
98.53% 
97.16% 
N/A 
N/A 
91.72% 
IBM Q System One 
99.92% 
99.98% 
99.96% 
97.15% 
99.03% 
98.31% 
TBD 
TBD 
TBD 
Rigetti 16Q Aspen1 
94% 
99% 
97% 
67% 
97% 
91% 
83% 
97% 
93% 
Rigetti 8Q Agave 
93.20% 
98.20% 
96.15% 
67.00% 
93.00% 
87.00% 
67.80% 
94.30% 
83.84% 
Rigetti 19Q Acorn 
94.96% 
99.42% 
98.63% 
79.00% 
93.60% 
87.50% 
84.00% 
97.00% 
93.30% 
IonQ 11 Qubit 
99.18% 
99.64% 
99.46% 
95.1% 
98.9% 
97.5% 
N/A 
N/A 
99.3% 
Two Qubit Gate Delays  
Computer 
Min 
Max 
Average 
Rigetti 16Q Aspen1 
188 ns. 
464 ns. 
323 ns. 
Rigetti 8Q Agave 
119 ns. 
210 ns. 
169 ns. 
Rigetti 19Q Acorn 
122 ns. 
214 ns. 
172 ns. 
Computer  Reference  Date 
IBM Q5 Tenerife 
https://www.ibm.com/blogs/research/2019/03/powerquantumdevice/ 
3/4/2019 
IBM Q16 Melbourne 
https://quantumexperience.ng.bluemix.net/qx/devices 
10/8/2018 
IBM Q20 Poughkeepsie 
https://www.ibm.com/blogs/research/2019/03/powerquantumdevice/ 
3/4/2019 
IBM Q20 Tokyo 
https://www.ibm.com/blogs/research/2019/03/powerquantumdevice/ 
3/4/2019 
IBM Q System One 
https://www.ibm.com/blogs/research/2019/03/powerquantumdevice/ 
3/4/2019 
Rigetti 16Q Aspen1 
https://www.rigetti.com/qpu 
12/12/2018 
Rigetti 8Q Agave 
https://www.rigetti.com/qpu 
10/8/2018 
Rigetti 19Q Acorn 
https://www.rigetti.com/qpu 
12/18/2017 
IonQ 11 Qubit 
https://ionq.co/news/december112018#appendix

3/19/2018 
Notes
Besides this overview of the quality of IBM and Rigetti qubits, I believe adding overviews comparing different technology types (e.g. arXiv:1610.02208 or, a little older, arXiv:quantph/0607065 chapter 4.2.1) can be helpful to get a general understanding the prosandcons of different qubit types
We have also been looking for some good comparisons of the different implementation technologies. The best concise comparison we could find is an article published in Science Magazine written by Gabriel Popkin. It briefly summarizes the major technologies with the exception of photonics. You can find it at http://www.sciencemag.org/news/2016/12/scientistsareclosebuildingquantumcomputercanbeatconventionalone,
Hi,
I have seen various parameters but I am a little confused by the relations of them (coherence time/T1/T2, fidelity, connectivity, error rate)? Is error rate resulted by the other three parameters?)
Can I generally say:
Power of a quantum computer=Quality of qubits (connectivity x error rate) x Number of qubits = Number of logical qubits?
Thank you!
Eric
There is no simple agreed upon formula that fully describes the power of a quantum computer. All that can be said is that the higher the qubit count, quality level, and connectivity, the better. The number of logical qubits is a function of the specific error correction algorithm that is used with the physical qubits. It is not directly related to the qubit quality. However, the lower the qubit quality, the more error correction you may want to put in. Describing the details of the different error types can get a little complicated and I would refer you to a quantum computing textbook to get a more complete description.
Doug Finke
Managing Editor
It looks like the average and max columns are reversed for the one and twoqubit fidelities on the IonQ 11qubit device.
Thankyou for pointing this out. It is now corrected.
Doug Finke
Managing Editor
FYI: Rigetti just released a few new arXiv papers with updated figures of merit.
https://arxiv.org/abs/1901.08035
https://arxiv.org/abs/1901.08042
Thankyou for your comment. We did post a News article about Rigetti’s improved qubit quality metrics list week at https://quantumcomputingreport.com/news/rigettidisclosesimprovedqubitqualitymetricswiththeirnewarchitecture/. There are still some missing parameters including T2 times, single qubit fidelities, and readout fidelities. Once these are available we will add this new design to the tables on this page.
Doug Finke
Managing Editor