The most popular qubit for quantum computing—the superconducting transmon—operates at a frequency of several billion hertz (GHz), much like 5G cell phones. This frequency excites transitions between the qubit states that researchers use to control the qubit. Now Samuel Deléglise of Kastler Brossel Laboratory and the National Centre for Scientific Research (CNRS) in France and colleagues have demonstrated a low-frequency transmon alternative that operates at 1.8 million hertz (MHz)—the lowest frequency ever reported for a superconducting qubit [1]. Deléglise notes that a qubit that operates at this frequency could be directly coupled to mechanical resonators based on suspended membranes, which vibrate at a few MHz, to perform tests of macroscopic quantum phenomena.
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