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>From a theoretical perspective, there’s nothing paradoxical about the idea of making a later measurement first and an earlier measurement second. One need only write down a factor of e^iHt/ℏ in between their two operators, where H is the system’s Hamiltonian, to represent the rewinding of time. (Forward-propagating time, in contrast, is represented by e^–iHt/ℏ.) Experimentally, it’s also possible, at least in principle, to turn back the clock on any quantum system. A quantum state has a unique backward trajectory in time, just as it has a unique forward trajectory, and an ably chosen combination of measurements can extract information about what that trajectory is. Despite their apparent oddity, OTO [out-of-time-order] commutators can make both mathematical and physical sense. @philipthrift -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/78d796c5-0413-4d2c-a19c-ca7056900b81%40googlegroups.com.
