Thermodynamics, Statistical Physics, and Quantum Mechanics

To find the amplitude in state we operate on the above equation with
The probability P is found from the absolute-magnitude-squared of
this amplitude:

Let us quantize the spin states along the so that spin up and spin
down are denoted by

The eigenstates of are for pointing along the and for the

QUANTUM MECHANICS 275

5.29 Rotating Spin (Maryland, MIT)