A quantum of play - [Past Forward_by Allison Marsh]

Quantum mechanics is hard. Can a toy make the subject any easier? Costas Papaliolios thought so. As a graduate student at Harvard in the early 1960s, he created these aluminum blocks marked with variations of Paul Dirac's bra-ket notation for describing quantum states. He made 4-inch blocks and 1-inch blocks. (The upper photos are enlargements of the 1-inch, or 2.54-centimeter, blocks.) A polarized filter fit inside each open-ended block. Shining a light through a block, or a series of blocks, yielded one of two results: The light passed through or it didn't. Papaliolios hoped his toys would help students grasp abstract concepts like linear operators and matrix representation. For most people, though, quantum mechanics remains as puzzling as ever.