2 - States, Observables, And Measurements Flashcards Preview

PHYS2012 Quantum Physics > 2 - States, Observables, And Measurements > Flashcards

Flashcards in 2 - States, Observables, And Measurements Deck (7)
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1

What is |e^(i*phi)|^2 equal to?

1

2

What are the eigenvalues of operators?

Typically +- hbar/2

3

What are expectation values?

The average value of repeated experiments. It is calculated by:

=Sigma (probability)*(outcome)
=P_+(+hbar/2)+P_-(-hbar/2)
=hbar/2(|a|^2-|b|^2)

OR

=(a*,b*)hbar/2(1 0;0 -1)(a;b)
=hbar/2(|a|^2-|b|^2)

4

What is an observable?

An observable is simply a measurable quantity. Mathematically, the observable is the operator used. However, observables have the property wherein if you repeat the measurement without the system change in between, then you get the same result.

5

What is Hilbert Space?

A Hilbert Space, after David Hilbert, is a complex vector space with an infinite-dimensional inner product having the product that it is complete or closed.

6

What is a spin operator?

A mathematical object that acts or operates on a ket and transforms it into a new ket for example;

A|psi>=|phi>

7

What are the spin operators for the three cartesian axes?

S_z = hbar/2(1 0;0 1)

S_y = hbar/2(0 -i;i 0)

S_z = hbar/2(0 1;1 0)