Methods for Measuring Magnetic Flux Crosstalk between Tunable Transmons

To scale up the number of qubits in a quantum processor, it is important that each qubit, or pair of qubits, can be controlled individually. Flux crosstalk between frequency-tunable superconducting qubits means that assumptions about addressability may no longer be valid. In this study, the authors detail several methods for measuring flux crosstalk between transmon qubits. These crosstalk metrics can then be used to predict $s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}m\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}s$ performance of two-qubit gates, and thus employed as engineering milestones on the path to truly scalable quantum computers.