The EPR paradox

Week 2: reality · quantum

The EPR paradox

Reconstruct Einstein, Podolsky, and Rosen's argument that quantum mechanics is incomplete.

In this lesson

  1. Read the core idea (2 min).
  2. Walk through one worked example.
  3. Take the 4-question quiz; pass with 4/4 or better.

Hook

In 1935 Einstein, Podolsky, and Rosen published a four-page paper with one of the most provocative titles in physics: 'Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?' Their answer was no. They did not claim quantum mechanics was wrong; they claimed it was missing something — that there had to be more to reality than the wave function, even if we did not yet know what.

The argument is short, sharp, and depends on three premises that look perfectly innocent until they collide.