130_notes.dvi

Flux is observed to be quantized but the charge of the particle seenis 2e.

Φ =

2 nπ ̄hc

2 e

This is due to the pairing of electrons inside a superconductor.

TheAharanov B ̈ohm Effectbrings us back to the two slit diffraction experiment but adds mag-
netic fields.

electron 






flux

screen

gun

The electron beams travel through two slits in field free regions butwe have the ability to vary a
magnetic field enclosed by the path of the electrons. At the screen, the amplitudes from the two