Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: melaniejs on 27/02/2020 15:59:22

Title: Is it possible to get 100% accurate results when testing quantum entanglement?
Post by: melaniejs on 27/02/2020 15:59:22

Izak asks:

Is it possible to get 100 percent accurate results when testing quantum entangled particles?

What do you think?

Title: Re: Is it possible to get 100% accurate results when testing quantum entanglement?
Post by: evan_au on 28/02/2020 07:49:14

No.

Current commercial "quantum factories" generate something like <1 entangled photon out of a million photons.
- You don't know which photon is entangled, because if you try to test it, it is no longer entangled!
- SO you can't screen out the non-entangled photons, in a sort of "quality control" process
- So producing entangled photons is a pretty inefficient process
- You have to test something 1000 million photons, and if you find slightly more than half pass the test, then you probably picked up a few entangled photons among the non-entangled photons.

Currently, the best method of transmitting entangled photons is through optical fiber:
- After 30 km, nearly all of your original photons will be lost (including most of your entangled photons)
- Some of the entangled photons which remain will have interacted with impurities in the fiber, and will no longer be entangled 
- And you still can't test which of the photons were the entangled ones.

Unlike digital bits (either 0 or 1), qubits can take on many intermediate states
- In this sense, quantum states are much more like analogue signals
- You can only measure them with a finite accuracy

So you can't get infinite precision - you have to use statistical techniques.
- But producing quantum factories with higher efficiency will certainly help.