The old textbooks might make handy paperweights...
(Phys.org)—In quantum mechanics, it's impossible to precisely and simultaneously measure the complementary properties (such as the position and momentum) of a quantum state. Now in a new study, physicists have cloned quantum states and demonstrated that, because the clones are entangled, it's possible to precisely and simultaneously measure the complementary properties of the clones. These measurements, in turn, reveal the state of the input quantum system.
More information: G. S. Thekkadath, R. Y. Saaltink, L. Giner, and J. S. Lundeen. "Determining Complementary Properties with Quantum Clones." Physical Review Letters. DOI: 10.1103/PhysRevLett.119.050405, Also at arXiv:1701.04095 [quant-ph]