Recent content by Ruik

The fact that I can always multiply a quantum state by ##e^{ix}## is very interesting and useful, thanks! I came to another solution, by taking the 3D-Koordinates of a point on the Bloch sphere ## \left(\begin{array}{c} sin(\theta)cos(\phi)\\ sin(\theta)sin(\phi)\\...

Hi :-) for my master thesis I'm working with qubits in the Bloch-sphere representation ##|q\rangle = cos(\frac{\theta}{2})|0\rangle + e^{i\phi}sin(\frac{\theta}{2})|1\rangle##. Side question: why is only the second amplitude complex? But let's move to my main question. I need to know how the...

Okay, thank you so far! @jk22: I cannot reconstruct the qubit after a measurement, that qould be a big almost. You say you know the probabilities, but if I perform a measurement I only get an idea of the probability, because of the outcome of my measurement. And if I measure ##|0\rangle## it's...

I'm currently working with several No-Go-Theorems in Quantum Mechanics for my master thesis and there are two, which are confusing me: The No-Deletion-Theorem and the No-Partial Erasure-Theorem. This is what I found out: The No-Deletion-Theorem shows that "there is no quantum deleting machine...

@kith: I meant, that after the measurement the qubit is definately in the state |+> an not in some kind of a superposition. But you are right, its absolutely possible to change the state again, so its not really fixed. What Strilanc wrote answers my question. I tought the entanglement would...

Hi :-) I'm working on my master thesis in the field of quantum theory; currently I investigante No-Go-Theorems like the No-Cloning, No-Deleting, No-Hiding, No-Communication-Theorems ans so on. There is a fundamental question which is somehow linked to the No-Communication-Theorem. Is it - in...