The quantum internet has arrived (and it hasn’t)
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Re: The quantum internet has arrived (and it hasn’t)
#2Ugh. Images like this are why no one should ever pay attention to fluff magazine articles about quantum anything:
https://media.nature.com/w800/magazine-assets/d41586-018-018...
The person who created that picture had no clue what the diagram is supposed to represent. They obviously created the infographic based on a conversation with someone who probably also doesn’t completely understand what their talking about.
Why articles like this must be written at all is what gets me. Someone out there wants this topic to have an article published, and they just don’t really care if the information it presents lacks accuracy.
Re: The quantum internet has arrived (and it hasn’t)
#3Stephanie Wehner also taught a great course on quantum cryptography.
Re: The quantum internet has arrived (and it hasn’t)
#4No, it hasn't.
Also, re: this image[0], I thought entanglement couldn't be used to send information? Isn't this complete nonsense?
[0] https://media.nature.com/w800/magazine-assets/d41586-018-018...
Re: The quantum internet has arrived (and it hasn’t)
#5I'm a bit confused by the process of entangling photons emitted by two distinct qubits, wouldn't entangling those photons affect the state of the two original distinct qubits? Or is that simply how entanglement works?
Re: The quantum internet has arrived (and it hasn’t)
#6No, it hasn't. Also, re: this image[0], I thought entanglement couldn't be used to send information? Isn't this complete nonsense? [0] https://media.nature.com/w800/magazine-assets/d41586-018-018...
The image is correct. The information is sent over a classical channel, not using entanglement.
Re: The quantum internet has arrived (and it hasn’t)
#7No, it hasn't. Also, re: this image[0], I thought entanglement couldn't be used to send information? Isn't this complete nonsense? [0] https://media.nature.com/w800/magazine-assets/d41586-018-018...
The last section tells that you need to transmit classical information to make sense of entangled particle measurement. Entanglement serves as a secure channel.
If you have two entangled coins, you know that the second coin came up heads, if your coin came up tails. You can't transmit information that way, because if you'll force your coin to land heads, you'll break entanglement. But you can use the results of coin flips as a cipher.
Re: The quantum internet has arrived (and it hasn’t)
#8I'm a bit confused by the process of entangling photons emitted by two distinct qubits, wouldn't entangling those photons affect the state of the two original distinct qubits? Or is that simply how entanglement works?
Very naively, the following happens: Qubit A is entangled with Photon A. Qubit B is entangled with Photon B. Photon A and Photon B are measured together in way that does not permit distinguishing the two photons (this is where the magic happens) and destroyed. This results in Qubit A and Qubit B now being entangled.
Re: The quantum internet has arrived (and it hasn’t)
#9> quantum particles [...] has been used for years to enhance data encryption.
As an entropy source or more?
Re: The quantum internet has arrived (and it hasn’t)
#10No, it hasn't. Also, re: this image[0], I thought entanglement couldn't be used to send information? Isn't this complete nonsense? [0] https://media.nature.com/w800/magazine-assets/d41586-018-018...
The image is correct. The information is sent over a classical channel, not using entanglement.
While the image is correct, your statement would be a bit misleading to novices:
You can not transfer the state of the qubit over a classical channel. You need both a classical channel and entanglement. Or in other words: a bit can be send over a classical communication channel (by copying it), but to transmit a qubit (which can not be copied due to its quantum nature), you either need to carry the physical qubit over, or use entanglement together with classical communication.