Partial Measurement / Teleportation

msumm21

What is meant by a "partial measurement" or "partial measurement in the Bell basis?"

More specifically, I'm trying to read the Wikipedia article on quantum teleportation, but I don't know what is meant when they say Alice performs a partial measurement on her qubits.

ruleva1983

Hi

i do not know what does it mean partial measurement...

up to my knowledge, Alice simply makes a measurement on her qbits in order to find out in what of the 4 Bell states they are. Then I think the protocol contoinues as wikipedia says. So Alice and Bob comunicate through a classical channel and Alice tells Bob the result of her measurement. With these information Bob can recover the initial state and thus the teleportation is accomplished.

Bye

xepma

Assuming we have a particle which is in some (spin) entangled state with 1 or more other spin particles. My guess is then that with a partial measurement you only measure the spin component of 1 particle. The measurement causes a "collapse". Normally, you would expect the "collapsed state" to be some unique state. But it's possible in the case of entangled states that the "collapsed state" is itself an entangled state as well, only now of the two remaning particles.

So, a partial measurement causes in some sense a partial collapse. The resulting wavefunction is still in some superposition.