- #1

fog37

- 1,568

- 108

My understanding is that a two-quantum state system is simply a system that can only be in two states. That is equivalent to say that the observable of interest that is being considered can only have possible values. Is that the case?

If so, a classical bit can have two values (either 1 or 0) while a quantum bit can have value 1, 0 or a superposition of both. The state with eigenvalue 1 is indicated by ##|1>## while the state with eigenvalue 0 by ##|0>##. The superposition state is give by $$|\Psi=c_1 |1> +c_2 |0>$$

This two state system could be achieved using the spin (which has values 1/2 and -1/2) or even the energy observable if there are only two energy states available, correct? The system could be in a superposition of the two energy eigenstates...

What is a system of two qubits? Is it a physical system with two particles? In the case of two qubits, what would the notation ##|11>## or ##|10>## indicate? Does ##|10>## indicate the one particle is in state 1 while the other is in state 0?

The superposition state for 2 qubits appears to be

$$|\Psi> = c_{11} |11> + c_{10} |10> + c_{01} |01> +c_{00} |00> $$