Abstract

Although the earliest tests of Bell's inequalities examined the spin correlations of two spatially separated particles, recent significant advances have led to the use of continuous variables, such as position and momentum or energy and time.¹ In all of these pioneering situations, the experiments relied on the production of two-particle states that were entangled with respect to only one type of observable. It is, however, possible to have two-particle states that are simultaneously entangled in more than one variable.

© 1995 Optical Society of America