3 ms·
I'll make an attempt, though I am by no means a domain expert. As I said in another comment, Alice doesn't know which column is Bob's column, and Bob doesn't kn
by dooglius 7y ago
I'll make an attempt, though I am by no means a domain expert. As I said in another comment, Alice doesn't know which column is Bob's column, and Bob doesn't know which row is Alice's row. Bell-like inequalities allow something interesting to happen: Alice and Bob can measure a qubit at different "basis angles" such that the phase difference in their basis angles is reflected in the correlation of what outputs they observe from the qubit. You can't do this classically; what Alice does with a pre-shared bit and her row and what Bob does with the pre-shared bit and his column, form independent random variables.
It may help to point out that (someone correct me if I'm wrong here...) this only works if both Alice and Bob are able to use their hidden information to choose the bases they're using to measure the qubit; if they were stuck with measuring at pre-determined angles, this trick doesn't work.
- taneq 7y agoOK, so if I'm understanding this right - when you give them a pair of entangled particles, they can each do some stuff to their particle to determine what the other party is going to do. How is this not communication?
- caf 7y agoThey can determine what the other party is going to do, but can't influence it, so that's not communication.
- JadeNB 7y agoI think (but IANAP) the answer is in two parts: (1) you can’t intentionally send a message—it’s like asking whether ancient civilisations are communicating with archaeologists, to which the answer is surely “only metaphorically”; and (2) even if it is communication in some sense, it’s still surely surprising, no?
- taneq 7y agoPoint 1) matches my lay understanding of quantum entanglement; information is transferred somehow between the entangled particles but not in a way that we can use. So if this new thing IS communication via entanglement (and I can't see how it's not, given the description) then that's huge, and opens the door to all sorts of interesting things.
- dooglius 7y agoNot quite, you can do some stuff that affects the correlation between one output and the other, but that can't be used for communication as each output in isolation looks random.