What is "transmon"

n. (context physics English) A particular form of superconducting qubit

In quantum computing, a transmon is a type of superconducting charge qubit that was designed to have reduced sensitivity to charge noise. The transmon was developed by scientists at Yale University in 2007. Its name is an abbreviation of the term transmission line shunted plasma oscillation qubit.

The transmon achieves its reduced sensitivity to charge noise by significantly increasing the ratio of the Josephson energy to the charging energy. This is accomplished through the use of a large shunting capacitor. The result is energy level spacings that are approximately independent of offset charge. Planar on-chip transmon qubits have T coherence times ~ 30 μs to 40 μs. By replacing the superconducting transmission line cavity with a three-dimensional superconducting cavity, recent work on transmon qubits has shown significantly improved T times, as long as 95 μs. These results demonstrate that previous T times were not limited by Josephson junction losses. Understanding the fundamental limits on the coherence time in superconducting qubits such as the transmon is an active area of research.