US Department of Energy Releases Blueprint for a Domestic Quantum Internet

originally posted by: andy06shake
a reply to: Arbitrageur

What are the practical limitations they are encountering with distance?

It's explained in the link I posted earlier:

Quantum Communication Just Took a Great Leap Forward

entanglement falls victim to decoupling and the no cloning theorem. Decoupling is the tendency for entangled particles to become disentangled due to interaction with their surroundings, while the no cloning theorem states that quantum states cannot be copied.

This makes long distance communication difficult...

The article goes on to explain how they are trying to deal with that using quantum repeaters, and the problems with those.

Decoherence or losing the quantum states as they become entangled with the environment is a big problem in general for quantum technology. The reason why quantum computers need special cooling near absolute zero is to try to preserve the quantum states, which last longer at lower temperatures. I don't think that will be practical for the communication channels though.

a reply to: Arbitrageur

Cheers Arbitrageur.

If decoherence is the issue i dont see it being practical where communications are concerned nether.

Then again should they manage lick the problem its the perfect medium communication wise, which would be instantaneous, is that correct?

Be nice to somewhat negate distance if even only for communication purposes.

originally posted by: andy06shake
Then again should they manage lick the problem its the perfect medium communication wise, which would be instantaneous, is that correct?

The correlation of entangled particles has been measured to be at least 10,000 times faster than the speed of light (iirc) so instantaneous is not ruled out by that. But, remember the entangled particles we are talking about are photons, and photons only travel at the speed of light, so Bob still can't send photons to Alice any faster than light. So we have to wait for the speed of light for the photons to go from Bob to Alice, then instantaneously their measurements can correlate, but how do they know what each other measured? They don't at the instant the measurements are made, so they have to "compare notes" and what do they need to do that? Another communication channel called "classical" meaning light speed, so even though instantaneous quantum things happen, light speed is not circumvented and so far nobody has figured out how to defeat the "no communication theorem", though not for a lack of trying:

Quantum Field Theory Cannot Provide Faster-Than-Light Communication

I think most physicists believe this can't be circumvented, but there are other theories that might allow FTL communication, like maybe wormholes, but maybe not.

Skinny wormholes could send messages through time

“Does this mean we have the technology for building a wormhole?” asks Matt Visser at the Victoria University of Wellington in New Zealand. “The answer is still no.” Still, he is intrigued by Butcher’s work. “From a physics perspective, it may revitalise interest in wormholes.”