The image above gives the electron probability density in the classic two slit interference experiment. A nearly parallel beam of electrons impinges on the observation region from the top. The black rectangular features are "photographic plates" with perfectly absorbing boundary conditions.

Note the hyperbolic nodes in the probability density and the classic intereference pattern impingent on the lower photographic plate.

Click below to see what happens when the aparatus determines through which slit the electrons pass.

A code developed with Amir Farbin (MIT Phys '97) carried out the calculations. The algorithm uses a Feynman sum/Green's function method and a simple finite difference representation of the kinetic energy operator. Some artifacts of the finite difference approximation are evident in the figure.

A. Farbin is developing an interactive 2d solver based on the same algorithm. The generosity of the MIT UROP office supports his work.