Quantum Measurement: Teaching Two-State Systems with PhET Interactive Simulations

Take a tour of PhET's newly-released Quantum Measurement and Quantum Coin Toss simulations, appropriate for high school and introductory college students. This simulation supports students' conceptual understanding of quantum states, superposition, and measurement. The simulation introduces the idea of superposition of states and quantum thinking with a novel comparison of a classical coin with a biased probability and a "quantum" coin. The simulation then scaffolds and deepens student understanding of measurement in the context of two-state systems. It progresses to an exploration of the polarization states of photons with a beam splitter, and how spin-½ particles interact with the Stern-Gerlach experiment. Students can also explore a spin-½ state using a Bloch sphere representation to show spin-½ basis transformations. When a magnetic field is applied the students can visualize the precession of the quantum state on the Bloch Sphere as well as force a collapse of the spin -½ state by performing quantum measurements.