Photon polarization states
A single photon with horizontal polarization gives a concrete example of a quantum state and its measurement prediction.
In a physics lab, Darius slowly turns a knob on the device that prepares his laser beam. The beam keeps hitting the same spot on the wall. So what about the light can change while its path stays the same?
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What you'll learn5 ideas
- Light arrives in tiny packets called photons, and a very dim laser sends them mostly one at a time, while special sources can send exactly one at a time.
- Even a single photon can have polarization, an orientation of its light, and the arrow drawn for it is only a marker, not a rod inside the photon.
- Against the lab's fixed reference, a left–right polarization is called horizontal polarization, and it describes how the light is oriented, not the direction the photon travels.
- A quantum state is a description that predicts measurement results, so a horizontal polarization state predicts an ideal horizontal test will confirm it every time.
- A polarization state says nothing about color, so a red photon and a blue photon can both have horizontal polarization.