IBM had established a performance measure called Quantum Volume several years ago which characterizes the relative performance of a quantum processor based upon both the number of qubits and the number of qubit gate layers that could achieve reliably calculation. They have been steadily increasing been increasing their Quantum Volume processor performance for the past five years as shown below.

Chart Showing History of Quantum Volume Increases. Credit: IBM

Their latest improvement is with a processor they call Prague, which is a 27 qubit processor from the Falcon r10 family. This processor was measured to show a Quantum Volume performance of 256 meaning it successful ran a test circuit with 8 qubits and a gate depth of 8. IBM’s previously leader, named Montreal, had a Quantum Volume of 128 which was reached with a circuit of 7 qubits and a gate depth of 7.

Improvements in the Prague processor include implementation of a new design which incorporated faster, higher fidelity gates and a reduction of spectator errors (a disturbance of a qubit cause by gate operations on other nearby qubits). IBM also implemented improved two-qubit gate fidelity in this design with many qates approaching the 99.9% level. IBM has not yet listed all the technical parameters for this processor on their IBM Quantum services page. But when they do, we will add these details to our Qubit Quality page so that readers can compare the performance against processors from other vendors.

Additional details can be found in a recent blog posted located here on the IBM website.