# Quantum State Vector

1. Jan 8, 2015

### Quarlep

"Let’s begin by labeling the possible spin states along the three coordinate axes. If A is oriented along the z axis, the two possible states that can be prepared correspond to σz= ±1. Let’s call them up and down and denote them by ket-vectors |u> and |d> . Thus, when the apparatus is oriented along the z axis and registers +1, the state |u> has been prepared. " says in The Theoritical Minimum

what it means ? In particular "the state |u> has been prepared" Actually I am asking just this part

2. Jan 8, 2015

### Staff: Mentor

It means that the system is in state |u>,
$$| \psi \rangle = | \mathrm{u} \rangle$$

3. Jan 10, 2015

### jfizzix

By saying that the state $|u\rangle$ is prepared, one can assume that all subsequent measurements of that same system will be as though the system is in state $|u\rangle$.