Delayed Choice Quantum Eraser
Delayed choice quantum eraser (an experiment of Marlan Scully) is a version of the EPR paradox in which the observation or not of interference after the passage of a photon through a double slit experiment depends on the conditions of observation of a second photon entangled with the first. The characteristic of this experiment is that the observation of the second photon can take place at a later time than the observation of the first photon, which may give the impression that the measurement of the later photons "retroactively" determines whether the earlier photons show interference or not, although the interference pattern can only be seen by correlating the measurements of both members of every pair and so it can't be observed until both photons have been measured, ensuring that an experimenter watching only the photons going through the slit does not obtain information about the other photons in an FTL or backwards-in-time manner.
Read more about this topic: Faster-than-light, FTL Travel of Non-information, Quantum Mechanics
Famous quotes containing the words delayed, choice and/or quantum:
“When the people saw that Moses delayed to come down from the mountain, the people gathered around Aaron, and said to him, “Come, make gods for us, who shall go before us; as for this Moses, the man who brought us up out of the land of Egypt, we do not know what has become of him.””
—Bible: Hebrew, Exodus 32:1.
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—Clara (Marquise)
“A personality is an indefinite quantum of traits which is subject to constant flux, change, and growth from the birth of the individual in the world to his death. A character, on the other hand, is a fixed and definite quantum of traits which, though it may be interpreted with slight differences from age to age and actor to actor, is nevertheless in its essentials forever fixed.”
—Hubert C. Heffner (1901–1985)