- #1
keen23
- 9
- 0
Hello all!
I try to follow the computation in my textbook (nielsen, quantum computation) and miss a step.
They say the following state
[tex]|p\rangle=\frac{1}{2}\big[a (|0\rangle+|1\rangle)(|00\rangle+|11\rangle)+b(|0\rangle-|1\rangle)(|10\rangle+|01\rangle)\big][/tex]
could be rearranged to
[tex]|p\rangle=\frac{1}{2}\big[|00\rangle(a|0\rangle+b |1\rangle)+|01\rangle(a|1\rangle+b|0\rangle)+|10\rangle(a|0\rangle-b|1\rangle)+|11\rangle(a|1\rangle-b|0\rangle)}\big]
[/tex].
But I don't see how.
(The start state comes from combining an arbitrary state a|0>+b|1> with an epr-pair in bell-state, then using CNOT for particles 1 and 2, then Hadamardgate on particle 1, well, I think that's not important for my question).
With normal expansion I get:
[tex]|p\rangle=\frac{1}{2}\big[a|0\rangle|00\rangle+a|0\rangle|11\rangle+a|1\rangle|00\rangle+a|1\rangle|11\rangle+b|0\rangle|10\rangle+b|0\rangle|01\rangle-b|1\rangle|10\rangle-b|1\rangle|01\rangle[/tex]
[tex]
=|00\rangle a(|0\rangle +|1\rangle )+|01\rangle b(|0\rangle -|1\rangle )+|10\rangle b(|0\rangle -|1\rangle )+|11\rangle a(|0\rangle +|1\rangle )
[/tex]
So "normal" expansion seems not to be the right way, but how shall I do it? Even if I think about the physical meaning I don't see what's wrong.
Maybe someone has more experience?
Thanks for your help!
I try to follow the computation in my textbook (nielsen, quantum computation) and miss a step.
Homework Statement
They say the following state
[tex]|p\rangle=\frac{1}{2}\big[a (|0\rangle+|1\rangle)(|00\rangle+|11\rangle)+b(|0\rangle-|1\rangle)(|10\rangle+|01\rangle)\big][/tex]
could be rearranged to
[tex]|p\rangle=\frac{1}{2}\big[|00\rangle(a|0\rangle+b |1\rangle)+|01\rangle(a|1\rangle+b|0\rangle)+|10\rangle(a|0\rangle-b|1\rangle)+|11\rangle(a|1\rangle-b|0\rangle)}\big]
[/tex].
But I don't see how.
(The start state comes from combining an arbitrary state a|0>+b|1> with an epr-pair in bell-state, then using CNOT for particles 1 and 2, then Hadamardgate on particle 1, well, I think that's not important for my question).
Homework Equations
The Attempt at a Solution
With normal expansion I get:
[tex]|p\rangle=\frac{1}{2}\big[a|0\rangle|00\rangle+a|0\rangle|11\rangle+a|1\rangle|00\rangle+a|1\rangle|11\rangle+b|0\rangle|10\rangle+b|0\rangle|01\rangle-b|1\rangle|10\rangle-b|1\rangle|01\rangle[/tex]
[tex]
=|00\rangle a(|0\rangle +|1\rangle )+|01\rangle b(|0\rangle -|1\rangle )+|10\rangle b(|0\rangle -|1\rangle )+|11\rangle a(|0\rangle +|1\rangle )
[/tex]
So "normal" expansion seems not to be the right way, but how shall I do it? Even if I think about the physical meaning I don't see what's wrong.
Maybe someone has more experience?
Thanks for your help!