# Tag Info

Accepted

### Swap test vs measurement in a specific basis

Probably the most important difference between the swap test and the projective measurement technique is that performing the swap test does not require knowledge of its inputs. When applying the swap ...
• 4,952

### Given a state $\rho$ and operator $0\le \Lambda\le I$, what does $\sqrt\Lambda \rho \sqrt\Lambda$ represent?

TL;DR: Yes, we can give meaning to $\sqrt{\Lambda}\rho\sqrt{\Lambda}$: it is the post-measurement state up to an unknown change of basis (the correct basis being exactly the piece of information that ...
• 14.4k
Accepted

### How does interference help to bias the measurement of a qubit towards a desired state?

Maybe a simple example (modified from https://quantumcomputing.stackexchange.com/a/16701/14597) can help answer your question. Let us take a single qubit and see how interference can lead to a bias of ...

### How does interference help to bias the measurement of a qubit towards a desired state?

Generally speaking: Each entry of a quantum statevector is a probability amplitude of a basis state. The probability to measure each basis state equals to the squared magnitude of the probability ...
• 600