Source-linked AI summary
Three Qubit Randomized Benchmarking
David C. McKay, Sarah Sheldon, John A. Smolin, Jerry M. Chow, Jay M. Gambetta
TL;DR
As quantum circuits grow, characterizing them becomes harder, and primitive-gate fidelities may not predict multiqubit algorithmic fidelity. The authors demonstrate three-qubit randomized benchmarking alongside subset simultaneous RB, finding 3Q EPCs of 0.106 for all-to-all connectivity and 0.207 for linear connectivity, while a calibration-related increase to 0.302 was not predicted by simultaneous RB.
Problem
Whether primitive-gate fidelities predict multiqubit algorithmic fidelity remains an open question, particularly given crosstalk and addressability errors.
Source: p. 1Method
The authors perform full three-qubit randomized benchmarking and subset simultaneous RB, including simultaneous two-qubit/one-qubit RB.
Source: pp. 1–2Results
3Q EPC was 0.106 for all-to-all connectivity and 0.207 for linear gate connectivity; a calibration-related increase to 0.302 was not predicted by a commensurate increase in simultaneous-RB primitive errors.
Source: p. 2Takeaways & Limitations
3Q RB measures fidelity not captured by one- and two-qubit gate metrics, providing a distinct multiqubit metric for algorithmic fidelity.
Source: p. 5The 3Q EPC prediction assumes uniform depolarizing probabilities across one-qubit gates and across two-qubit gates, and counts idle periods as one-qubit gates.
Source: p. 4
Abstract
from arXiv · showhide
As quantum circuits increase in size, it is critical to establish scalable multiqubit fidelity metrics. Here we investigate three-qubit randomized benchmarking (RB) with fixed-frequency transmon qubits coupled to a common bus with pairwise microwave-activated interactions (cross-resonance). We measure, for the first time, a three-qubit error per Clifford of 0.106 for all-to-all gate connectivity and 0.207 for linear gate connectivity. Furthermore, by introducing mixed dimensionality simultaneous RB --- simultaneous one- and two-qubit RB --- we show that the three-qubit errors can be predicted from the one- and two-qubit errors. However, by introducing certain coherent errors to the gates we can increase the three-qubit error to 0.302, an increase that is not predicted by a proportionate increase in the one- and two-qubit errors from simultaneous RB. This demonstrates three-qubit RB as a unique multiqubit metric.