Published online by Cambridge University Press: 21 March 2022
Correlations between the behavior of pairs of particles are generated in the following experimental situation. An on-line source emits a stream of two-particle systems, where each system is in one and the same quantum state. After emission, the particles – call then (I) and (II) – move off in opposite directions. Each particle then encounters one of several possible barriers that either it passes or doesn't. A short distance behind each barrier is a detector set to register the presence of the particle, should it get that far. Finally, the detectors are connected by a timed relay and counter that registers a “coincidence count” should the two detectors fire within a set, brief time interval. When the experiment is run with various different barriers, detection rates accumulate for each barrier singly, and coincidence rates (the correlations) for the various pairs of barriers.
Work on this project was supported, in part, by National Science Foundation Grant SES 79-25917. I owe thanks to many people whose responses and criticism have influenced the development of the themes of this essay (and probably to others whose devastating criticism I never received); groups at Indiana University, Stanford and Chicago Circle have been particularly helpful, flbner Shimony has been a powerful and useful critic, Paul Teller a ready, if skeptical, ear, and Dana Fine has been my mainstay as assistant and counselor. Thanks to you all! (You too, M.)