An effect that demonstrates the physical reality of the electromagnetic potential in quantum mechanics. In 1959 Yakir Aharonov (1932– ) and David Bohm (1917–92) pointed out that in quantum theory electrically charged particles such as an electron can be affected by an electromagnetic field even if they are not in the region of space where the field exists. This occurs because of interaction between the electromagnetic potential and the phase of the wave function of the electron. The prediction was confirmed experimentally in 1960 using interference combined with a solenoid.