Comments about the article in Nature: The entangled Web

Following is a discussion about this News & Views in Nature Vol 554 15 February 2018, "The entangled Web" by Davide Castelvececchi
To read the article select: In the last paragraph I explain my own opinion.


The ability of quantum particles to live in undefined states - like Schrodinger's proverbial cat, both alive and dead - has been used for years to enhance data encryption.
This sentence is too simple.
Many technical details still need to be sorted out, and some researchers caution that it is too early to say exactly how much a quantum internet might deliver.
Completely correct. It is too early to decide.

Quantum Keys

Stephan Wiesner, then a young physicist at Columbia University in New York City, saw potential in one of the most basic principles of quantum mechanics: that it is impossible to measure a property of a system without changing it.
Any measurement at particle level causes a change in the particle level.
In certain processes two particles are created. In some cases when you measure both particles the measurements indicate a correlation. The important physical implication is that the two particles are entangled after creation.
Wiesner suggested that information could be encoded in the states of objects such as isolated atoms, whose 'spins' can point up or down like the 0 and 1 of classical bits - but can also be in both states simulataneously.
This requires a very precise definition of the concept simultaneously within the context of an individual isolated atom.
A different problem is how to test that an atom is in superposition.
Wiesner pointed out that because the properties of a qubit can't be measured without changing its state , it is also impossible to make exact copies or 'clones' of one.
The first part of the sentence more or less answers the question: How do you know that a particle is in superposition? IMO you cannot. A whole different issue is when two particles (Qubits) are involved. Those two particles can be entangled. This can easily be tested because the state of each can be tested. (Implying that neither one is in superposition?)

The fact if you can or can not copy a qubit requires a physical description of exactly what a qubit is. More physical detail is required.

Otherwise, some one could extract information about the state of the original qubit without affecting it, simply by measuring its clone.
This also depents how much information or energy is extracted from the original qubit.
Using a variant of Bennett and Brassard's protocol, the space craft created two keys, then sent one to a ground station in Beiing and another to Vienna as it passed overhead.
This is step 1. See Reflection 1 - China's Micius satellite
An on-board computer then combined the two secret keys to create a new one, which it beamed down classically.
This is step 2
Armed with their private keys, the Vienna and Beiing teams could unscramble that combined key by essentially subtracting their own, and so learn the other's secret key.
This is done in step 3

Quantum Connections

A true quantum network would be able to harness entanglement and teleportation to transmit quantum information over long distances, without the need for vulnerable trusted nodes.
See See Reflection 2 - Computer security
"the extra cool thing is " says Ronald Hanson, an experimental physicist at Delft. "People at the server"

Spooky Security

Link and repeat

Box 1: Creating A Quantum Internet

To create a link, Alice can emit a photon towards Bob from her qubit. Bob does the same towards Alice. Because the photons are entangled with their original qubits, when they interact, Alice's and Bob's qubits become entangled, too.
The word Because is in appropiate with out a much more laborate explanation.
Let us call the photon that Alice emits towards Bob A1 and the photon that Bob towards Alice B1. The stay at home electrons are called A2 and B2
What you need is a test which demonstrates that both A1 and B1 when they meet are entangled. What you also need is test which demonstrates that the two electron's are entangled

These tests are very tricky.

Reflection 1 - China's Micius satellite

Reflection 2 - Computer security

The biggest problem in communication is not so much if the Internet is reliable, but the content of the communication.

The whole issue is will the "Entangled web" concept, make my PC more secure. I doubt that because my PC security depents very much what Microsoft has to offer. The general attitude is the question: Do you trust the content that is received? When the answer is: Yes all will be loaded and excuted. This is the wrong approach.


Created: 16 February 2018

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