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Physicists Demonstrate Quantum Router
Diggester tips news that physicists from Tsinghua University in China have published "the first proof-of-principle demonstration of a genuine quantum router." The group's paper (PDF) is available at the arXiv. MIT's Technology Review describes it thus:
"In this new device, the information is encoded in the polarization of photons, either horizontal or vertical. The Chinese group begin by creating a single photon that is in a superposition of both horizontal and vertical polarization states. They then convert this single photon into a pair of lower energy photons that are entangled, a process called parametric down conversion. Both of these photons are also in a superposition of polarization states. The router works by using the polarization of one of these photons as the control signal to determine the route of the other, the data signal. The device is simple, little more than a collection of half mirrors for guiding photons and waveplates for rotating their polarization."
...I'll start getting at least half of the advertised speed from my AT&T DSL connection?
When Fascism comes to America, it will call itself Anti-Fascism, and tell you to give up your guns.
But what about the quantum backdoors implanted for the Chinese government?
It should be obvious to anyone with an advanced degree in polygonal quantum mechanics that you can encode information "in the polarization of photons, either horizontal or vertical" and using a Chinese group that began by "creating a single photon that is in a superposition of both horizontal and vertical polarization states. They then convert this single photon into a pair of lower energy photons that are entangled, a process called parametric down conversion. Both of these photons are also in a superposition of polarization states. The router works by using the polarization of one of these photons as the control signal to determine the route of the other, the data signal. The device is simple, little more than a collection of half mirrors for guiding photons and waveplates for rotating their polarization."
Can anybody explain this using something simple, like stuffed bunnies?
Thanx,
myke
Mimetics Inc. Twitter
Yes, but the really important question is: does it support IPv6?
Comment removed based on user account deletion
This router is very ...... enlightening..... I wonder how light it is... Is it going to be light on the pocket book too when it comes out?
"i lost my dignity on a slippery wiener"
How long until we have a working Ansible?
It sounds less like a router and more like a 1:2 demultiplexer.
In other words, coherence-preserving quantum comms have reached about the same point of capability that telegraphs did in the 1890's.
from the article:
"That's an interesting step forward but the new router has significant limitations. The most significant of these is that it can handle only one quantum bit or qubit at a time. And because the process of parametric down conversion cannot handle more qubits, it cannot be scaled to more qubits.
That's a significant drawback. It means that this is a proof-of-principle device but not one that will ever form the basis of a future quantum internet."
So interesting, but it won't directly lead to an awesome future internet where your illegal torrent downloads as fast as your HD can take it
Being from China, this has marginally more credibility than if it came out of North Korea.
I'd certainly love to see quantum entanglement become a usable means of communication, but all of the better minds than my own I've read say that due to uncertainty principles this would be impossible.
Simple really.
... of your rather light-hearted banter.
On an unrelated note, they're should be more on this in two hours.
BrundleBunny says : "keeeeelllllllllll meeeeeeeee...."
the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff
Right - what exactly is the point of this? This seems to be far inferior to standard approach.
From the title, I was hoping to be able to do some nano-scale woodworking.
The world is made by those who show up for the job.
What kind of VPN throughput am I looking at here? I need new technology to replace my aging Palo Alto gateway cluster. I've begged the emissary enough already for better throughput and removal of Pah-wraiths from my network. The Cisco has yet to respond.
Speaking of IPSEC VPN, can we get a portable configuration standard already? It's hard enough getting interoperability from devices from the same vendor (I'm looking vaguely in your direction Juniper)...
Quantum communication is supposed to be secure because you cannot read the message without altering it, and you get detected.
Now if I understand the article well, we can take one photon and make two entangled photons carrying the same information, and altering one of the two photons does not alter the other one. If we have multiple quantum routers, how can a receiver know that one of them was not a man in the middle that intercepted the message?
...Werner Heisenberg commented: your data may have been routed here.
I think you're confusing bandwidth and latency. Bandwidth will be limited by how many bits/second your hardware can process, latency is the part where transmission times factor in. Since each of your relays would still have to process the information to pass it on you maximum bandwidth wouldn't increase.
The way I pictured it was, assuming you could figure out how to keep the photons entangled indefinitely, you could send a stream of photons to Alpha Centauri while keeping their entangled pairs in some sort of holding pattern here on Earth (put them in orbit around a micro black hole or something if that's what it takes) . No information is encoded at that point. In 4.36 years, just before the first photons start arriving at the Alpha Centauri receiving station you can start feeding their entangled pairs into the router control to semi-deterministicly manipulate their polarization, and with it the polarization of their pairs reaching the receiving station. Now obviously there will be some alignment issues, but those should be easy to fix by initially encoding a stream of known data, say 1010101010.... and simply rotating the receiver until the proper pattern resolves. The other issue would be the high error rate due to the probabilistic nature of encoding - but a sufficiently redundant error-correcting code should easily be able to overcome that. I forget the exact theoretical limit, but I'm pretty sure a 1-in-3 error rate can be corrected for without too much difficulty, and it seems likely that they at least approache that in this experiment or they wouldn't have much to right about, after all completely turning of the routing control at the transmitter and crossing your fingers instead will still get you a 1-in-2 average error rate.
--- Most topics have many sides worth arguing, allow me to take one opposite you.