At the recent Q2B conference it was emphasized that qubit quality is a very important factor in creating a viable quantum computer. So kudos to IBM and Rigetti for documenting the specifications of their respective 20 qubit and 19 qubit chips. However, they 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. We encourage anyone else who has data on other implementations to contact us at email@example.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.
||1-Qubit Gate Fidelity
||2-Qubit Gate Fidelity
||Read Out Fidelity
- For most of the parameters we show the Min, Max, and Average values. Since both IBM and Rigetti publicize the individual values for every qubit, the Min shows the value for the worst of the qubits, the Max shows the value for the best of the qubits, and the Average shows the mean calculations for all of the qubits.
- The connectivity shows the number of connections from a qubit to a other qubits in the array for use in creating a CNOT gate. The higher the connectivity, the easier it would be to fit a quantum calculation into the structure. At this time, we do not differentiate on the flexibility of a connection. For example, if qubit 1 is connected to qubit 2, many implementation require one of the qubits to be the CONTROL and the other qubit to be the TARGET. Some implementations may be flexible enough so that either qubit can serve as the CONTROL and either qubit can serve as the TARGET. That implementation may have some configuration advantages, but for the purposes of the table we are still only counting it as one connection and not as two.
- The T1 measure is called the relaxation time and the T2 or T2* measure is called the decoherence time. For details of these definitions we refer you to this paper. Note that IBM only publishes the T2 times while Rigetti only publishes the T2* time. The measures are similar, but not exactly the same.
- The IBM reference link in Table 3 may require you to register for the IBM Q Experience. If you click on this link it may ask you for a logon and password to see in more detail the referenced data.
- Questions, suggestions, and any additions you may have to the data are welcomed. You can send them to firstname.lastname@example.org.