Marketing

Quantum mechanics

Algorithm

Quantum gate

Curse of dimensionality

Benchmarking

Economics

Computer science

Controlled NOT gate

Business

Physics

Database

Mathematics

Transmon

Operations management

Artificial intelligence

Quantum

Measure (data warehouse)

Combinatorics

Qubit

Metric (unit)

Topology (electrical circuits)

Machine learning

Physical Review Letters

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.

Three-Qubit Randomized Benchmarking