Superconducting Coupler with Exponentially Large On:Off Ratio

Abstract

A significant challenge in the design of large-scale quantum processors is the presence of unwanted qubit-qubit crosstalk, which leads to uncontrollable accumulation of correlated errors. This work introduces a superconducting device that can controllably turn qubit-qubit interactions on and off. The design takes hints from noise-protected bosonic qubits to obtain $e\phantom{\rule{0}{0ex}}x\phantom{\rule{0}{0ex}}p\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l$ suppression of crosstalk in the off state. These results offer the possibility to keep crosstalk under control in large superconducting processors. Notably, this approach complements the recently introduced protected qubits; an architecture based on them and the proposed coupler would have built-in protection.