Hi ATS denizens!
Time for a physics refresher so we can ponder the news that has been released in Thread's Title.
First is quantum mechanics (QM). It is different because at such a small distance, called Planck's constant, h
the world of the large,
everyday, matter we apprehend becomes strange and appears to follow a different set of rules.
The world of the "solar system atom" some us were taught was transformed into a world of "matter waves" where a formula called a "wave function"
describes where things like protons and neutrons and electrons can, and to the best of our knowledge, reside. The probabilities of where these atomic
pieces have been described and studied for over a hundred years.
A great read on QM is John Gribbin's, In Search of Schrodinger's Cat
Not too tough. There are various portions of an atom or a particle of light that can be described using QM. A particle can have a magnetic moment,
electron polarization, momentum, energy, etc.
The QM concept of "entanglement" gets thrown around (QE). You create an entangled state when you take, say a light particle, called a photon, and
split it in two. Now you have a photon that is described by the same wave function. If you shoot that wave function off to some other place, the
receiver can create another photon with the exact same wave function. That is called, "quantum teleportation" and has been in the news in the not
You can also use QE to perform the duties of encryption. The process is the same for QE but this time you make a set of particles, send them off, then
have the receiver perform measurements to verify that all the particles on one side is the same on the sending side. Since when you take a measurement
of entangled particle, you change the property. If you do not match up, somebody measured the wave function and you have re-send new QE pairs (quantum
I know that some people understand things better when explained by others, so for a different explanation see Swanne's ATS thread:
Physics We Can All Understand - Part 3: Quantum Entanglement
The problem with QM encryption is you have to do all this sending of keys around, QE starts to fall apart in a process called "decoherence".
What if you could send QE keys and the message all at once??
[If they can send the key, then they] can use the remaining photons to transmit data using the normal process of quantum communication, which is
And that’s exactly what Zhang and [Co.,] have done. [going] around a two-kilometer loop of optical fiber and carrying out the checks as quickly as
Of course, various improvements are needed to make this kind of system commercially viable. But the work is an important stepping stone toward
entirely quantum-based secure communication. Banks, governments, and military agencies will be watching eagerly.
MIT Technology Review,
Quantum Breakthrough Heralds
New Generation of Perfectly Secure Messaging
. (Warning: You have limited number of free viewing per month!)
From, arXiv.org - Experimental long-distance quantum secure direct communication
Using just ordinary fiber optics, like the stuff running under the ocean creating the internet, they sent both the message and quantum key around a 2
km. loop. They call it "Quantum Secure Direct Communication, (QSDC)", and it is a world's first.
The race will be to extend this method to all communications by increasing the distance.
This matters because when a universal quantum computer is built, other methods of sending secure transmission will be in the cross-hairs of being
broken. One of the first algorithms devised for a quantum computer was Shoar's algorithm which breaks the dominant RSA encryption used by the internet
so we can all buy and rent shows from Netflix and Amazon, pay our taxes, use a debit card, etc.
I know it is geeky tech stuff, but I like when something new arrives that proves, "yes, it can be done"!
edit on 1-11-2017 by TEOTWAWKIAIFF
because: add warning about technologyreview.com