Simultaneous tracking of spin angle and amplitude beyond classical limits Nature 543, 525–528 (23 March 2017) www.nature.com/nature/journal/v543/n7646/abs/nature21434.html The authors remark that "because spins obey non-Heisenberg uncertainty relations, enables simultaneous precise knowledge of spin angle and spin amplitude." What are “non-Heisenberg uncertainty relations” and what other quantum observables obey them? (There were two references about measuring spins. But they were of no help. Ref. 9 was not available on the Web. Ref. 10 was about measuring spins. However, there was no mention of a “simultaneous precise knowledge of spin angle and spin amplitude.”) Can someone please answer my questions in a way that a layman can understand?