# Notational question, |1>

1. Sep 5, 2010

### kweierstrass

What is meant when writing a "one-ket" like this |1> ?

2. Sep 5, 2010

That usually means the principle quantum number is 1.

3. Sep 5, 2010

### tom.stoer

It depends on the system; for the one-dim. harmonic oscillator it means the first excited state |1> above the ground state |0>.

4. Sep 5, 2010

### kweierstrass

Maybe I should have meantioned the whole context, I now realise that it means the eigenket coresponding to the eigenvalue 1 in my specific problem. Thanks anyway

5. Sep 9, 2010

### skynelson

My understanding is that it is often an abstract way of referring to the n=1 basis vector. This is similar to what someone wrote above.

The basis vectors must be implicitly defined, and then |n> refers to the nth basis vector. Unfortunately I am not clear on exactly where and how the |n> basis vectors are typically defined. I often see the notation |1> without it being clear what the ACTUAL eigenfunctions being referred to are. In that type of situation, I guess it is simply an abstraction; and index referring to a real function.

6. Sep 11, 2010