Quantum Mechanics
H. Dieter Zeh
Discovered decoherence: how the environment makes quantum systems look classical.
1932 Braunschweig – 2018 Heidelberg · Germany
Who they were
A theoretical physicist at Heidelberg who worked on quantum foundations from the 1960s, often without much support.
What they found or built
In a 1970 paper he showed that a quantum system is never truly isolated. Its interaction with the surrounding air, light and heat entangles it with the environment, and the interference between possibilities spreads out into that environment where it can no longer be recovered. To anyone looking only at the system, it appears to have chosen one outcome.
Why it mattered
Decoherence explains why you do not see cats in two states. It does not by itself say why one outcome occurs, so it is invoked by Everettians, Bohmians and Copenhagen alike. It is also the main enemy of quantum computers, which must fight it constantly.
Equations and key ideas
- Decoherence
- Environment-induced classicality