Only seven

How many atoms does it take to make a transistor? Apparently the latest answer is seven (www.science.unsw.edu.au/news/quantum-leap-world-s-smallest-transistor-built-with-just-7-atoms/). Strictly speaking, as the Australian team actually replaced silicon atoms with seven phosphorus atoms to produce a "quantum dot" Si transistor, the device contains more than seven atoms. Do any readers want to speculate on the theoretical minimum total number of atoms (host and dopant) needed to produce transistor behaviour? RTA congratulates Professor Michelle Simmons, it was certainly more than 7 years since we knew her at the Cavendish Laboratory, University of Cambridge.