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Physicists Demonstrate Quantum Router

Soulskill posted more than 2 years ago | from the but-does-it-run-dd-wrt dept.

Network 81

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."

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It's okay... (-1)

Anonymous Coward | more than 2 years ago | (#40871415)

It's okay to screw my precious little snappyhole until there is absolutely zero snappyhole left to screw. It's okay. Everything's okay.

There is no hole!
There is no hole!
There is no hole!

Does This mean... (4, Funny)

sycodon (149926) | more than 2 years ago | (#40871483)

...I'll start getting at least half of the advertised speed from my AT&T DSL connection?

Re:Does This mean... (3, Funny)

zlives (2009072) | more than 2 years ago | (#40871559)

no you need the higgs field router for that

Re:Does This mean... (5, Funny)

bjoast (1310293) | more than 2 years ago | (#40872043)

He will have to make do with the standard model.

Re:Does This mean... (1)

sycodon (149926) | more than 2 years ago | (#40872123)

My electric bill would suck!

Re:Does This mean... (0)

Anonymous Coward | more than 2 years ago | (#40872163)

At least it explains the massive bill.

Re:Does This mean... (4, Funny)

dkleinsc (563838) | more than 2 years ago | (#40871655)

No, that's just the spin they're putting on it.

Re:Does This mean... (0)

Anonymous Coward | more than 2 years ago | (#40873057)

AT&T, what a bunch of quarks.

Re:Does This mean... (0)

Anonymous Coward | more than 2 years ago | (#40871725)

Only if you put open-wrt or dd-wrt on it.

Better hope it has 4 terabytes of flash ROM.

Re:Does This mean... (0)

Anonymous Coward | more than 2 years ago | (#40873691)

...I'll start getting at least half of the advertised speed from my AT&T DSL connection?

Well one version of you in one universe will. Unfortunately today is not your day. Neither is tomorrow.

Me chinese. Me play joke. (1)

Anonymous Coward | more than 2 years ago | (#40871521)

But what about the quantum backdoors implanted for the Chinese government?

Re:Me chinese. Me play joke. (2)

FatdogHaiku (978357) | more than 2 years ago | (#40872063)

But what about the quantum backdoors implanted for the Chinese government?

Quick, somebody lock down quantumbackdoors.com for use as a porn site.
When the Chinese government tries to use their secret backdoor they will encounter a black hole!

Re:Me chinese. Me play joke. (1)

AchilleTalon (540925) | more than 2 years ago | (#40875877)

Even not specified in the article, one of the photons of the entangled pair belongs to the Chinese government. That's what we call an entangled backdoor.

Professor Frink Reference (1)

mykepredko (40154) | more than 2 years ago | (#40871541)

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

Re:Professor Frink Reference (1)

P-niiice (1703362) | more than 2 years ago | (#40871585)

well, you take one 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." and then you have them encode information "in the polarization of photons, either horizontal or vertical". Two step process. Not too hard to understand.

Re:Professor Frink Reference (1)

Shavano (2541114) | more than 2 years ago | (#40871731)

All except the control part. What they can apparently do is MEASURE which way the photon WENT using the entangled partner.

Re:Professor Frink Reference (1)

mooingyak (720677) | more than 2 years ago | (#40871617)

Can anybody explain this using something simple, like stuffed bunnies?

You got this stuffed bunny, right? Then you rip him in half, but the halves still remember being part of the whole bunny, so they're half-bunnies, but they're still part of the whole bunny. And then you transmit info between the bunny pieces.

Re:Professor Frink Reference (1)

P-niiice (1703362) | more than 2 years ago | (#40871639)

If you can understand how sanrda lee bakes a cake, you can understand this.

SANDRA LEE [occasion] CAKE
1. Get one (1) cake
2. Add icing and cookies and decorations for [occasion] all over the cake.
3. Done.

Re:Professor Frink Reference (2)

mooingyak (720677) | more than 2 years ago | (#40871689)

But to comply with the OP's request, it would need to be a bunny cake.

Re:Professor Frink Reference (1)

Ichijo (607641) | more than 2 years ago | (#40871959)

Since every piece of matter in the Universe is in some way affected by every other piece of matter in the Universe, it is in theory possible to extrapolate the whole of creation - every Galaxy, every sun, every planet, their orbits, their composition, and their economic and social history from, say, one small piece of bunny cake. (Paraphrased from HHGTTG)

Re:Professor Frink Reference (1)

EdIII (1114411) | more than 2 years ago | (#40873519)

I like that.

Since "one small piece of bunny cake" is quite arbitrary, it could just as easily be anything else. Also consider the axiom that knowledge is power.

This leads to the inescapable conclusion, according to your theory, that my penis is all-knowing and all-powerful.

Re:Professor Frink Reference (0)

Anonymous Coward | more than 2 years ago | (#40871715)

"It should be obvious to anyone with children (or plushy fetishes, but I don't want to hear about that), that information can be communicated in a stream of colored stuffed animals. By throwing blue or red stuffed bunnies past a window, with the color determining the data sent. Thanks to quantum stitching technology, a Chinese group has crated a single bunny that is in a supercoloration of both blue and red. They then convert this bunny into a pair of smaller supercolored bunnies with a rope connecting them. When observed, the bunny-pair becomes a single distinct color, so you can know what bunny you are waving in front of the window by looking at the one in your hand."

Yeah, not any simpler with bunnies.

HEY! You got stuffed bunny in my chocolate! (1)

Thud457 (234763) | more than 2 years ago | (#40871943)

BrundleBunny says : "keeeeelllllllllll meeeeeeeee...."

Re:Professor Frink Reference (0)

Anonymous Coward | more than 2 years ago | (#40871853)

Think of it like 2 fax machines. Machine A tells B to print a dot for a 1 and print nothing for a 0 Then you send a burst of 1111001011101010101010101111010101 From machine A to Machine B and Machine B produces and copy of the picture in Machine A.

Now to think of the Quantum Entanglement You can put Machine A with 1 particle of the pair anywhere in the universe. and Machine B with the other in your living room. And instead of sending a long burst of 1s and 0s you can now tell Machine A to flip from Vertical to Horizontal and Machine B to read the changes. they changes you make to A will occur to B at the same time. So we have a zero latency situation.

Though the speed will be directly related to how fast you can effect changes to the particle in Machine A and how fast Machine B can read those changes. Thinking of it as one bit per change if it takes 15 seconds to effect a change and you get an average speed of 4 bits per minute or 1 byte every 2 minutes in 2048 Minutes you can move 2 MB woot get me get me some of that now.

Re:Professor Frink Reference (1)

sexconker (1179573) | more than 2 years ago | (#40872919)

Think of it like 2 fax machines. Machine A tells B to print a dot for a 1 and print nothing for a 0 Then you send a burst of 1111001011101010101010101111010101 From machine A to Machine B and Machine B produces and copy of the picture in Machine A.

Now to think of the Quantum Entanglement You can put Machine A with 1 particle of the pair anywhere in the universe. and Machine B with the other in your living room. And instead of sending a long burst of 1s and 0s you can now tell Machine A to flip from Vertical to Horizontal and Machine B to read the changes. they changes you make to A will occur to B at the same time. So we have a zero latency situation.

Though the speed will be directly related to how fast you can effect changes to the particle in Machine A and how fast Machine B can read those changes. Thinking of it as one bit per change if it takes 15 seconds to effect a change and you get an average speed of 4 bits per minute or 1 byte every 2 minutes in 2048 Minutes you can move 2 MB woot get me get me some of that now.

No, it's not zero latency.
You still have to separate the entangled particles.

It's like you and your friend taking pictures of your naked crotches and putting them in 2 sealed envelopes, then traveling to opposite sides of the planet (each with 1 envelope, contents unknown), and then opening them for a furious masturbation session at an agreed upon time. The instant you start stuffing your cunt with a rancid tuber, you know your friend is doing the same and to which picture. The pictures didn't get there any sooner or quicker. You looking at yours collapses the probability space instantly, so you know what you friend is beating off to the instant you know what you're beating off to.

It's really no different than seeing a coin land heads up and then instantly knowing it landed tails down. Even if your coin was 1 lightyear thick and you viewed it from above, the tails down information doesn't travel from the tails side of the coin. The tails down information is implicit in the predetermined definition of the coin when combined with the tails up information.

Re:Professor Frink Reference (2)

Jane Q. Public (1010737) | more than 2 years ago | (#40873693)

Certainly.

Take two stuffed bunnies. Lay one on its side, and stand the other on its head. These are two "polarizations".

But with QUANTUM stuffed bunnies, it is possible to create a pair of stuffed bunnies that are actually in both positions at the same time... "superposition"... and "entangled", meaning the the positions of both are linked. (This has also led to the creation of a new illustrated book, the Quanta Sutra... but that's another story.)

So, you send these superposed stuffed bunnies down different pipes, and when they get to the end, one of them is knocked over the head with a laser, which causes them BOTH to resolve into one or the other position. Then by determining the position of that one you can determine the position of the other, even at a distance.

I am thinking about naming this the "stuff your bunny sideways" principle.

Re:Professor Frink Reference (1)

Darinbob (1142669) | more than 2 years ago | (#40876223)

You shine a light through some half mirrors, the beam of lights split and one is polarized one way and the other beam is polarized the other way. It's just like all that stuff you saw in undergrad physics labs except that you use words like quantum entanglement and superposition.

(ya it's more complex than this but that was my mental image when I read the summary and before I read the article)

v6? (0)

Anonymous Coward | more than 2 years ago | (#40871543)

Yes, but the really important question is: does it support IPv6?

Re:v6? (2)

RaceProUK (1137575) | more than 2 years ago | (#40871587)

Only if you measure it in the right way.

Re:v6? (1)

kiep (1821612) | more than 2 years ago | (#40876473)

It supports IPv6 and it doesn't support IPv6.

Yes... (2)

liquidpele (663430) | more than 2 years ago | (#40871557)

Yes.... I understand some of these words...

Very Nice (1)

KingPin27 (1290730) | more than 2 years ago | (#40871591)

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 take a dim view ... (0)

Anonymous Coward | more than 2 years ago | (#40871859)

... of your rather light-hearted banter.

On an unrelated note, they're should be more on this in two hours.

Re:Very Nice (2)

rts008 (812749) | more than 2 years ago | (#40873019)

Is it going to be light on the pocket book too when it comes out?

No.

It will create a black hole in your wallet that won't stop until you have lost your ass.

It's just simple consumerism, but you were mistaken that you are the consumer, instead of the consumed....

Re:Very Nice (1)

Farmer Tim (530755) | more than 2 years ago | (#40873923)

It will create a black hole in your wallet that won't stop until you have lost your ass.

That just leaves one question: how did a photograph of this phenomenon slip backwards in time to become the Goatse guy?

So... (2)

Dins (2538550) | more than 2 years ago | (#40871595)

How long until we have a working Ansible [wikipedia.org] ?

Re:So... (1)

Jamu (852752) | more than 2 years ago | (#40871739)

Never or yesterday.

Re:So... (2)

bluefoxlucid (723572) | more than 2 years ago | (#40871907)

Actually I was thinking more of something like that, but with store/drain, depending on how far entanglement goes and how long you can maintain it.

Think about 1 meter entanglement range. You entangle two particles, shift one a meter away. It takes time to move that particle, of course; but once it's entangled, flipping one flips the other instantly.

Bandwidth like this is infinite. If you have 1Gbit/s real bandwidth and can store 3000Gbit of entangled particles stably. and they're stable for 3000 seconds on average, you can eventually build up 3000Gbit of entanglement between two nodes.

Now space these nodes a meter apart down the wire, 1500Gbit on each end relaying, 2km. While there's less than 1Gbit/s in use, store entangled particles. At a point, you have 1500Gbit of bandwidth charge ... and then you can dump 1500Gbit of data straight on the link (if your computer is fast enough to send that to the hardware!) and your burst data rate is 1500Gbit INSTANTANEOUS. It's 1500Gbit in however many cycles it takes to move 1500Gbit from memory onto the output buffer--if it takes 10 cycles to get a bit from RAM onto the "wire" (that's 320 cycles per 32-bit word on a 32-bit bus, which is realistic--random RAM read can be 200-400 cycles to precharge, set RAS, CAS, etc, but sequential can be 10-20 cycles, plus overhead messing with the actual transmit hardware), at 1.5GHz CPU that's 150MHz or 10 seconds to transmit 1500Gbit. 3GHz that's 5 seconds, and with 3GHz quad core and a distributed architecture that's a little over a second--you've achieved nearly 1.5Tbit/s burst with near-zero latency over 2km!

By the time the technology is actually affordable for such use, the range will probably be in the km. That means repeaters entangled across miles and miles. You think we need 1500Gbit/s burst? Saturation will happen often enough to warrant bursting. It'd take 1500 seconds over a 1Gbit link running idle, like 2.5 hours. Probably 2-3 times capacity (2-3 Gbit) entangled store being used to artificially raise peak capacity (when off-peak, i.e. 50% utilization of 1Gbit/s over a few seconds means you can constantly burst, store up 3Gbit and then 3Gbit comes and you transmit it instantly instead of over 3 seconds). and decrease off-peak latency (50% saturation? Store for 50%, use for the other 50%, zero ping!).

All that untapped capacity of a 30% or 70% utilized network will ACTUALLY MAKE IT FASTER. Imagine!

Re:So... (1)

Anonymous Coward | more than 2 years ago | (#40872041)

but once it's entangled, flipping one flips the other instantly.

No it won't, that's not how entanglement works. It's more like you have two quarters, and if you flip both they will always land with the same face up. Mucking with the flipping (forcing it one way or the other) will break the pattern; the pattern only shows up when you flip them both and let them do their thing.

Re:So... (1)

Lithdren (605362) | more than 2 years ago | (#40872051)

I'm no expert in this, but I dont think you understand whats going on here at all. Flipping one doesn't instantly flip the other. You cant communicate information via entanglement.

Please, someone correct me if im wrong, but my understanding is its like having a red, and blue ball in seperate bags. You throw one ball (in its bag) across the room, then open the other bag. The open bag is blue, you now know the red one is across the room.

You've gained information but you haven't actually transfered any information. You cant do anything overly useful to the red ball with this information, only the blue one. The scheme you sugest above would allow you to determin what was sent over the wire, but the very nature of it would prevent you from sending anything useful over the wire, other than white noise.

All that said, I dont understand a word of the summary and how this can be used in a router, and frankly I hope my understanding is wrong. Sadly, i'm not so sure it is.

Re:So... (3, Interesting)

ByteSlicer (735276) | more than 2 years ago | (#40872629)

Please, someone correct me if im wrong, but my understanding is its like having a red, and blue ball in seperate bags. You throw one ball (in its bag) across the room, then open the other bag. The open bag is blue, you now know the red one is across the room.

It's more like having two balls, both half-red half-blue, in separate bags. The balls contain a magnet that causes them to align: when one is red-up, the other is blue-up.

Then you shake the bags, open one, and pick out the ball. If it's red-up, you'll know the other ball will be blue-up, and vice versa.

At first glance this may look the same as your model with the full red or blue ball (a so called hidden variable model), but the statistics differ from real entanglement (which includes superposition of states).

In the first (classical) model FTL information transfer is impossible because nothing is actually transferred. The ball was blue or red to begin with, and opening the bag doesn't change that.

In the second (quantum) model FTL information transfer actually does occur (with entanglement, the magnet alignment in the model occurs slower than light obviously). But the observer can't choose what this information will be: picking a ball out of a bag will result in a random color. And the other bag will then contain a ball in the opposite but equally random color. You can't pick the color, so you can't choose the message/information.

Statistics from experiments have shown that the second model is the correct one, and that entanglement and the FTL state transfer are real.

Re:So... (0)

Anonymous Coward | more than 2 years ago | (#40873631)

Hidden variables has not been completely eliminated. Just one variant of it.
Entanglement is simply the "simplest" explanation.

If you prefer your simple involving magical spooky action at a distance.
http://en.wikipedia.org/wiki/Hidden_variable_theory#Non-local_hidden-variable_theory

Re:So... (1)

ByteSlicer (735276) | more than 2 years ago | (#40876665)

Lol. Non-locality is exactly what makes the "magical spooky action at a distance" possible.

Non-local hidden variables are a completely different beast, compared to classical (local) hidden variables. In fact, some theories are mathematical equivalent to entanglement.

Re:So... (0)

Anonymous Coward | more than 2 years ago | (#40877199)

Lemme rephrase.
Entanglement seems "magic"
non-local hidden variables is at least an explanation to me.
If I think about the universe as being a simulation running at plank time speeds (or any speed lower than our measuring), then updating variables in 2 locations is no big deal.

Entanglement feels "just so" and "spooky"

Obviously my feelings don't bear into the running of the universe...

Re:So... (0)

Anonymous Coward | more than 2 years ago | (#40887051)

I have read several years worth of quantum courses at the university level, worked on experiments at CERN and in general conveyed quantum models to "laymen" for years, and this was a brilliantly clear summary. Just wanted to say that :-) .

Re:So... (1)

TexVex (669445) | more than 2 years ago | (#40873107)

I'm no expert in this, but I dont think you understand whats going on here at all. Flipping one doesn't instantly flip the other. You cant communicate information via entanglement.

This is correct.

Please, someone correct me if im wrong, but my understanding is its like having a red, and blue ball in seperate bags. You throw one ball (in its bag) across the room, then open the other bag. The open bag is blue, you now know the red one is across the room.

This is not correct. What you are describing is classical information: the ball in each bag is either red or blue, you just don't know which ball is in which bag until you look.

To try to extend your analogy to how it really works, the balls would both be purple until you opened a bag and took the ball out. At that point, the ball would decide to be either red or blue, and the other ball would decide to be the opposite. But up until the bag is opened, each ball MUST be able to become red or blue when it is opened.

The reason has to do with how quantum observations are done. I'll use polarization of photons as an example. You cannot measure the exact angle of a photon's polarization. All you can do is pass that photon through a polarizing filter and see whether the photon passes through or not. If you don't know the state of the photon, then it passes through 50% of the time.

Once the photon passes through a polarizer set at a particular angle, it will thereafter always pass through a polarizer set at that exact angle. Its chance of passing through a polarizer at a different angle is the square of the cosine of the difference in angles. Suppose you have a stream of photons polarized at 0 degrees, then those photons have a 50% chance of passing through a filter set at 45 degrees and a 0% chance of passing through a filter set at 90 degrees. So far, this is all classical stuff that can be observed easily if you have a flashlight and a pair of polarized glass discs.

Now, at the quantum level, entanglement arises out of conservation laws. Each quantum interaction has to conserve energy and momentum and information and certain quantum properties of the objects that interacted like spin. So if you hit an atom with a photon, and that atom absorbs the photon, then releases the energy as two photons to return to its ground state, those two photons will be entangled. Each will carry away half of the energy (because each action must have an equal and opposite reaction)

Photons have spin. Spin is a conserved property. This means that when one quantum event creates two photons, those photons' spins must cancel each other out. Spin determines a photon's angle of polarization. So, the two newly created photons will have orthogonal polarizations. At the same time, it is not possible to know anything about the spin of the newly-emitted photons at the time of their creation. So, you've now got a pair of polarization-entangled photons. They have spin and their spins add to zero and you know nothing about their spins. (If you did something to generate photons with known spin values, those photons would not be spin-entangled. Entanglement and information are two sides of the same coin.)

One of the consequences of measuring pairs of polarization-entangled photons is that in order to conserve spin, the results of measuring their polarizations correlate. If photon A passes through a 0-degree filter, then photon B must never pass a 0-degree filter, because that would mean that their spins did not cancel. If A passes through a 0-degree filter, then B will pass through a 90-degree filter. This relationship holds true for any pair of angles you choose: if the angles are the same, then only one photon from each pair will pass the filter. If the angles are 90 degrees apart, then either both of them or neither of them will pass the filter (with an even chance of each outcome). They correlate, even though they are distant from each other.

And the rate of correlation depends on the difference between the angles of the detectors , which also are distant from each other.

So that is why finding a classical analogy is so difficult. To go back to the balls in the bags, when you open your bag you must first ask a question like "what color are you at 35 degrees?" then the balls in both bags must conspire to come up with a set of answers that follow the expected correlations no matter what question is asked before opening the other bag. Depending on the question you ask, both balls might be blue or both balls might be red, and the act of asking the question requires you to put some amount of red and blue paint into the bag so that the balls can change color while still making sure the total amount of red and blue in the universe does not change.

Re:So... (1)

bluefoxlucid (723572) | more than 2 years ago | (#40893545)

I'm no expert in this, but I dont think you understand whats going on here at all. Flipping one doesn't instantly flip the other. You cant communicate information via entanglement.

Well, I'm no expert in this, but you're wrong. You can't transfer information faster than light; what you can do is transfer an entangled particle at the speed of light, and then tap one particle and read the other to see what happened with it. Across 300 light years, if you manipulate particle A[0}, particle A[1] instantly reflects its new state; however it does take 300 years to get particles A[0] and A[1] 300 light years apart. You can't just wake up and decide to transmit 3 gigabytes of information without 3 gigabytes of entangled particles hanging out across the void already.

Viable FTL communications? (1)

Immerman (2627577) | more than 2 years ago | (#40884277)

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.

Re:Viable FTL communications? (1)

bluefoxlucid (723572) | more than 2 years ago | (#40893579)

You can only send 1 gigabit across a 1 gigabit link; but if your hardware is fast enough to process 1 terrabit/s, you could send that. We don't have 1Tb links, though there's 10GbE. Also entanglement isn't instant over distance; it's limited by the speed of light, i.e. two particles 1 light year apart take at a minimum a year to entangle. You can do this by entangling two particles together and then moving them apart, or if you find a magic way to entangle two particles that are far apart you can do that but it won't be any faster than speed-of-light.

If you want to cut latency, you have to pre-load entangled particles. If you want to pre-load entangled particles, you need more bandwidth than you're using (to set up; once you've got it, you can ride equillibrium by transmitting newly entangled particles while transmitting data across the entangled ones). If you've got that, though, you can fill an even bigger bucket and then drain it by transmitting at a burst rate higher than the physical link can carry. So a 1Gbit link can store up 10Gbit over 10 seconds, and then burst down 10Gbit in precisely as much time as it takes the processor to shove it down the link--ignoring physical link speed entirely.

It's a little like using a metalmind.

Re:Viable FTL communications? (1)

Immerman (2627577) | more than 2 years ago | (#40894973)

You're referring to relativistic quantum field theory, which as far as I'm aware has yet to get supporting evidence - it's simply a reasonable prediction based on the assumption that Special Relativity holds in the quantum domain, which may not be the case. SR is based on an understanding of the universe in which matter possesses locality - i.e. you can point at it an say "this thing is here", whereas one of the underlying principles of QM is that all waveforms exist at all points in the universe, albeit with very low probability at most points. (Particles don't even factor in to QM until we try to make sense of our measurements - under the many-world hypothesis they're actually redundant).

This is the first real-world experiment I've heard of that successfully manipulates remote particles in a controlled fashion - as such it would be a shoe-in for actually testing the theory - once we manage to separate entangled photons sufficiently for our instruments to measure relativistic delays. It may be that, just like every theory before it, Special Relativity possesses some fundamental flaws.

All right, I get what you're saying now, interesting thought. My impression though is that typically it's the hardware at the endpoints that limits the bandwidth, not the channel itself. Whether radio, wire, or fiber optic cable, we could transmit far more information than currently used - we just don't have the hardware to keep the signal clean while doing so. Eventually though, when we're encoding information in individual photons and packing the fiber to capacity... like I said an interesting thought.

Re:Viable FTL communications? (1)

bluefoxlucid (723572) | more than 2 years ago | (#40895263)

It's very hard to switch light on and off quite that fast without the pulses degrading. You have a switch that can run 32 of these ports, it can do 32 times as much bandwidth as 1 port. Simple?

Instantaneous sub-space communications over infinite distance would be freakishly strange given our current understanding of physics. It would imply that information can travel over great distances with no energy.

Re:Viable FTL communications? (1)

Immerman (2627577) | more than 2 years ago | (#40896821)

If we're sending information as single photons then pulse degradation is no longer an issue, as that's a phenomena associated with statistical wavefronts, not individual photons.

Every time a photon reaches Earth from a distant galaxy information (that the photon was created, if nothing else) travels vast distances with no more energy than it would take to cross the room. Obviously transmitting individual photons would be immensely more efficient than a beam of light, since that pesky inverse-square law wouldn't factor in, but that has nothing to do with entanglement.

All my proposed test would really do would be to leave some of the information carried by each photon unresolved until just before it reaches it's destination. If it turns out that the polarization information is indeed shared* instantly by the two photons then that would indeed upset our understanding of the universe - at a minimum the ability to synchronize clocks in different reference frames would call much of our understanding of Special Relativity into question. Personally I don't see how it would effect causality - all the causality-breaking examples I've seen for FTL information are restricted to perceived causality - "I can know the effect before I know the cause" rather than the far more problematic "I can *change* the cause after seeing the effect" variety

* note I say shared, not transmitted - transmission implies the photons exists as separate discrete objects, which is precisely the distinction that entanglement removes.

Hmm, just occurred to me - your "photon buffers" would work just as well for interstellar communication - pack 'em full of as many entangled photon half-pairs as they will hold and put one of them on your ship while leaving the other on Earth, then occasionally read just a tiny trickle of them in some sort of handshake protocol to check for pending messages. Of course your bits are far more precious than if you have an ongoing supply of new ones, but you don't have to worry about interference or interception because the information being transmitted never leaves the sender/buffer-pair/reader system. Come to think of it, even if entanglement information does travel at c, that could still have immense strategic value for Earth-bound uses as well, both of the military/espionage variety and in communicating with things like submarines or burrowing vehicles where maintaining a data-link through the dense intervening matter is problematic

Hmm, it also highlights that in my original example the Centauri station wouldn't need to generate it's own stream of photon half-pairs to enable bi-direction communication - given a suitable handshake protocol they could just as easily be the ones who impose a polarization on the incoming photons, thus routing the Earth-bound pairs. Or to hybridize the ideas - both Earth and Centauri have entangled buffers, with Centauri's being refilled by the stream from Earth. There would be a 4.4 year lag in refilling so Earth's buffer would need to be considerably larger to hold the pairs for all those in-transit photons in addition to the shared buffer, but that's simply a logistics issue.

Re:Viable FTL communications? (1)

bluefoxlucid (723572) | more than 2 years ago | (#40898735)

You can always send more particles by beaming light there. Though outages are amusing. "Alpha-Centauri station? Yeah, our trasnciever is down. In 379 years there's going to be a service interruption from us, guess we'll have to work from the stock of supplied particles you're sending now, so for a little while half as much data. We'll let you know when it's back up so you know how long the outage is gonna last."

It takes no more energy to move a photon lightyears, but it takes YEARS to move it. If we postulate that there must be a way to make an entanglement occur over 10 lightyears in an instant, rather than moving a photon for 10 years to create that gap; then we would assume that it takes somewhat more energy to make that instant entanglement across 10 lightyears than it does to make it across 10 meters. If we find out this is not true, then something about the way space physically works is VERY different from our understanding, and we could just teleport physical matter with little to no power usage. A discovery like that would obsolete weird entanglement communications.

And really, if you can make it to Alpha-Centauri in any appreciable time (that is, in any amount of time where technology doesn't outpace your transit and send a faster vessel to beat you there), then you're better off sending gap courier drones instead of bothering with the complexities of entangled particles. Realize the entanglement has to be maintained for the long years across the long distances it takes to get a particle from point A to point B; if you can just put a message in a bottle and pop it over there in short order, that's probably better. Be mindful that a 400 year space trip is likely untenable.

Re:Viable FTL communications? (1)

Immerman (2627577) | more than 2 years ago | (#40900705)

Who says we can create entanglement over a 10ly distance in an instant? We create the entanglement on Earth, then wait 4.4y for half the pair to reach Alpha Centauri. The information transfer might occur in an instant, but that's a completely separate issue from creating the entanglement. Now if someone can figure out how to convert 1 remotely entangled pair into 2 (or more) that would certainly improve the picture, but I don't see that there should be any assumption that it would require more energy, what are you basing your claim on?

As for physical transportation, it seems to me that's a completely different question. I don't see how the existence of instantaneous quantum entanglement over vast distances would have any direct bearing on it. It *might* imply the possibility of instantaneous *quantum* "teleportation" but that would, at best, be a matter of making an "exact" nonquantum-duplicate via some other means and then employing quantum "teleportation" to transfer the quantum states from the original to the duplicate; however, for information transfer that would likely be terribly inefficient - if you can communicate, on average, even a sizable fraction of 1 bit per entangled pair, then instead transferring all the quantum information for the particles in say a hard drive would fall woefully short, how many millions (billions? trillions?) of atoms are there in a hard drive per bit of information?

As to other physical processes that might be discovered as a consequence of quantum instaneity... well I think it's just a *tiny* bit premature to make any conjectures on those.

Re:Viable FTL communications? (1)

bluefoxlucid (723572) | more than 2 years ago | (#40904055)

Damn, it's only 4.4LY? I thought the closest thing out there was 60-ish ... or is that the closest we can get to a nova without our planet being stripped of life?

It will always require as much energy to move information across space as it takes to move information across space. If it suddenly takes very little, a lot of interesting stuff happens. It's like how you have to apply a megajoule of energy to a block of steel to make it liquid molten steel; then someone says by a cheap trick of physics they can tap on the steel gently and it's suddenly 1700 degrees and glowing red and flowing. Something very interesting just happened, to say the least; where the fuck did all this energy come from?

Instantaneous entanglement across any distance is akin to snapping your fingers and having magical shit happen. If it's possible, you're going to need a hell of a lot of energy.

Re:Viable FTL communications? (1)

Immerman (2627577) | more than 2 years ago | (#40906175)

Yeah, A.C.'s only 4.4ly away, there's quite a few stars within 60ly. That might be the minimum safe nova distance, but seems really close for that - but maybe I'm thinking supernova.

Sure, heating a block of steel requires a certain minimum amount of energy, because a pool of molten steel contains considerably more energy than the block, and that energy has to come from somewhere.

My understanding though is that the whole energy-versus-information conversion factor is still very much in debate, is there even any consensus as to whether a theoretical minimum amount of energy required to store or transmit one bit of information even exists?

As for long-distance transmission, again, as far as I know there is no inherent increase in energy. Yes it normally takes more *time*, but that's a completely unrelated concept. If you were trying to move a ball from A to B in time X then yes - you have to accelerate and then decelerate it, and at it's fastest the increased kinetic energy has to come from somewhere, and since it increases with the square of the speed it will increase quite dramatically as you shorten the time taken. Though it's worth noting that the acceleration and deceleration energies are equal and opposite, in the absence of friction regenerative braking could theoretically recapture 100% of the acceleration energy when decelerating, allowing for example a vacuum tube maglev train to wisk you halfway around the world in an hour with no net energy consumption.

Moreover even the peak energy rules only apply to moving matter through normal space - if you had a stabilized wormhole or hyperdrive or something that didn't require you to pass through the intervening space then you can ignore all the normal requirements because they simply don't apply - you're not accelerating through normal space, you might travel a thousand light years in a few minutes without ever moving faster than a walk. Similar principles may well apply to quantum entanglement - so far as I know there's no evidence that any information passes through the space between entangled particles, they simply "know" what happens to their partner. In fact I don't believe there's even any theoretical mechanism for any such a transmission to occur, it would certainly require a something much more complicated than the generally accepted QM theory.

Re:Viable FTL communications? (1)

bluefoxlucid (723572) | more than 2 years ago | (#40907539)

Regenerative braking cannot produce 100% of the energy used to accelerate. It's physically impossible. If you have a little angry demon with a molecular gate allowing hot molecules through a little door and closing it to block cold molecules, you don't get a thing with one side very hot with no energy input; the little demon must do work, and so expends energy in the process. Regenerative braking involves doing work, and so will expend energy in the process.

Re:Viable FTL communications? (1)

Immerman (2627577) | more than 2 years ago | (#40908089)

Maxwell's demon is an unrelated concept - basically he's trying to reverse entropy by converting two equal-temperature reservoirs into a hot and cold reservoir, from which work could then be extracted. And yes - it's not possible to do, manning the gate (or more precisely, measuring the velocity of the particles) generates more entropy than would be reversed, at least using classical physics. There was an article just the other day about some research suggesting that if the particles were entangled so that one measurement gets information about more than one particle, then at the very least the nature of the question changes (the altered question itself is still completely undecided)

Regenerative braking on the other hand is a completely different question - let's say you're using an electric motor for propulsion and some sort of ultra-capacitor for energy storage (to remove battery chemistry from the discussion). There is no theoretical limit to the efficiency of either electric motors or capacitors, as they are converting energy from one "high quality" form to another, efficiencies well upwards of 90% have already been achieved in the real world, and while the laws of thermodynamics insist that there always be *some* loss, they put no lower bound on it, so efficiencies could reach 99%, or 99.99%, or anything short of actual 100%.

The trick is that "work" is actually a signed quantity, the dot-product of force and distance. If force and distance are in the same direction (as when accelerating) then work is positive and you are putting energy into the system, but if they are in opposite directions (as when decelerating) then work is negative, meaning you are extracting energy from the system, and can potentially recapture it. So long as you're converting between energy forms of the same "quality" (mechanical and electric are both high-quality, thermal is the lowest-quality) there's no inherent losses to entropy.

To make it even clearer imagine our train stores energy in flywheels - when accelerating or decelerating it's simply transferring kinetic energy from one area (train movement) to another (flywheel velocity), and just like billiard balls colliding in space there is no inherent energy loss. In the real world you'll lose a little energy to friction, resistance, etc, but that comes down to implementation details, and is not subject to any sort of theoretical limit

Re:So... (1)

wierd_w (1375923) | more than 2 years ago | (#40872135)

From this? Never.

An ansible needs to transmit information to outside its light cone.

You can only do that in a godel spacetime, or similar spacetime. Our universe does not appear to support that.

Also, if you create an ansible, wave goodbye to both self-determinism as a rational belief, and to causality as you know it.

Re:So... (0)

Anonymous Coward | more than 2 years ago | (#40872899)

From this? Never.

An ansible needs to transmit information to outside its light cone.

You can only do that in a godel spacetime, or similar spacetime. Our universe does not appear to support that.

Also, if you create an ansible, wave goodbye to both self-determinism as a rational belief, and to causality as you know it.

Self-determinism requires dualism (physics only allows deterministic and random events, self determinism requires a "self" capable to non-deterministic, non-random events). So it's pretty much already gone if you subscribe to a materialist view of the universe (largely required for science to matter).

As for causality (also largely required for science to matter), you only need to give up causality if you aren't willing to give up Relativity. A causal universe with FTL travel can exist if Relativity is somehow wrong.

Re:So... (0)

Anonymous Coward | more than 2 years ago | (#40875607)

Is it really random, or does it only appear random because we can't see all the hidden variables of the deterministic universe?

Demux (0)

Anonymous Coward | more than 2 years ago | (#40871609)

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.

Not as exciting as they make it out to be (0)

Anonymous Coward | more than 2 years ago | (#40871679)

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

Re:Not as exciting as they make it out to be (1)

subanark (937286) | more than 2 years ago | (#40871773)

Well, I don't think something like this would affect speed so much as latency. Besides I don't think you can just pair up any two routers, you would have to send someone the part in anticipation of sending them data on said part.

Now if someone could figure out a way of doing broadcast where you can record information in a device and have multiple devices that all "hear" what that device hears then you could push a lot of data to a lot of people easily.

Dubious... (0)

Vrallis (33290) | more than 2 years ago | (#40871701)

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.

Re:Dubious... (-1)

Anonymous Coward | more than 2 years ago | (#40871831)

You're also a mongoloid who was conceived by incestuous rape. No one cares what you think.

Re:Dubious... (1, Insightful)

MobyDisk (75490) | more than 2 years ago | (#40871837)

Wow, that's just plain racist. I'll let MIT's Technology Review tell me if they have reason to think the is not legitimate. Comparing Chinese research to North Korea's research is absurd. China is a modern nation with a top-tier space program.

Re:Dubious... (1)

Targon (17348) | more than 2 years ago | (#40872931)

I think you mistake a distrust of CHINA as a country with racism. The issue isn't that a Chinese person or team may have come up with it, and is more about not having much faith in press releases from certain nations. China(not Chinese people) along with North Korea are known for trying to impress those in other countries with this sort of press release when nothing exciting has happened or been discovered. That is what it all comes down to, and it does remain to be seen if this is REAL, or if it is the sort of thing such as "we have a way to XXXXX" without there being any evidence to support it(has not been verified by others).

Re:Dubious... (0)

Anonymous Coward | more than 2 years ago | (#40873097)

Why people never read the papers before talking S**t, this was a research made in collaboration with USA, SO if you distrust China, you should also DISTRUST THE USA.

Re:Dubious... (1)

postbigbang (761081) | more than 2 years ago | (#40871875)

Sure. No one misleads anyone in science in the US. Please dismiss the report.

The better minds that you have read claiming to dismiss quantum communications often dismiss *everything* because of uncertainty principles. I have an old, breadboard-based 8080 computer; I can sometimes calculate numbers in my head faster than it can provide the correct answer. Quantum communications is at level approximating the mid-1970s in personal computing. Be patient.

Re:Dubious... (0)

Anonymous Coward | more than 2 years ago | (#40872045)

Actually, the last author on this paper is a highly respected physicist in the field of quantum information and he has been a professor at the U of Michigan for many years now.

Makes Sense... (1)

DarthVain (724186) | more than 2 years ago | (#40871727)

Simple really.

TFA says "Quantum Louter" (-1)

Anonymous Coward | more than 2 years ago | (#40871919)

Please to fix headline.

What problem does this exactly solve? (0)

Anonymous Coward | more than 2 years ago | (#40872449)

Right - what exactly is the point of this? This seems to be far inferior to standard approach.

Re:What problem does this exactly solve? (1)

sexconker (1179573) | more than 2 years ago | (#40872947)

Right - what exactly is the point of this? This seems to be far inferior to standard approach.

None. You have to send the particles away via normal methods anyway.

I had high hopes (1)

jbeaupre (752124) | more than 2 years ago | (#40872755)

From the title, I was hoping to be able to do some nano-scale woodworking.

IPSEC? (1)

aaronb1138 (2035478) | more than 2 years ago | (#40873613)

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)...

Man in the middle? (1)

manu0601 (2221348) | more than 2 years ago | (#40875257)

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?

In a related news... (1)

ctrl-alt-canc (977108) | more than 2 years ago | (#40875909)

...Werner Heisenberg commented: your data may have been routed here.
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