APS/Matthias Steffen

Figure 1: Representative evolution of $T2$ coherence times since the first demonstration of a superconducting qubit in 1999 [3]. While the best coherence times (circles, light blue) are longer than those that are reproducible (circles, dark blue), the overall progress has been remarkable as indicated by the dashed black trend line. The most recent 3D work [1] puts another data point right at the top of the list. The dotted green line indicates the coherence time necessary for fault-tolerant quantum computing, assuming the use of quantum error correcting surface codes and a $30ns$ two-qubit gate.