**PURPOSE: **Use properties of optical devices as analogs to illustrate quantum mechanical states and operators.

**DESCRIPTION: **Optical elements formed from polaroids, quarter and half wave plates, and combinations thereof, are analogous to spin up and spin down vectors and basis vectors formed from linear combinations of these vectors, the Pauli spin matrices, and the identity matrix. Place the blocks in the proper order and look through (or shine a light through) to observe zero, unity, or partial overlap of integrals. An accompanying document shows what is in the little cubes and how they work.

**SUGGESTIONS: **This is a good one for graduate students to argue about. It aids your understanding of both quantum mechanics and optics.

**REFERENCES: ** (PIRA unknown.)
See Demonstration Reference File for a number of papers dealing with these gizzits and for detailed instructiuons about how they are made.

**EQUIPMENT: **Ten optical elements.

**SETUP TIME: **None.