Today I Learned: August 9, 2019
The No-Cloning Theorem. Animal magnetism. As low as a one in three chance.
1) The No-Cloning Theorem
The no-cloning theorem is a theorem of quantum mechanics that says you can’t make a perfect duplicate of a quantum state. Specifically, you can’t make a duplicate of a quantum state without modifying the original state. This is, in a way, a formalization of the idea that you can’t observe a system without modifying it.
Like many important scientific ideas, the no-cloning theorem was almost completely unknown in physics for many years after its discovery, until another set of authors independently derived and published it with better publicity.
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Related: The no-teleportation theorem states that a quantum state cannot be perfectly converted into a series of classical bits. This means that any kind of exact “quantum teleportation” can’t rely on measuring a state, digitizing it, sending the digitization as a message, and reproducing it on the other end. The information teleported would have to somehow “stay quantum” throughout the entire process.
2) Animal magnetism
The term “animal magnetism” wasn’t, originally, supposed to be metaphorical — it was the brainchild of one Franz Mesmer (yes, the Mesmer responsible for the word “mesmerizing”), who believed that all animals produce a special sort of magneticish force field. Disturbances to this force field were supposed to be responsible for all aspects of health, and the manipulation of them by, for example, fancy stage theatrics, could cure virtually any ailment.
3) “As low as a one in three chance”
The executive branch of the United States knew that we probably weren’t winning the Vietnam War from quite early on. In 1965, just after the US committed its first serious forces to Vietnam (and just before ramping up troop deployment roughly another 10-fold), Robert McNamara estimated that the US had as low as a one in three chance of winning the war.
