Slashdot Mirror
Open-Destination Quantum Teleportation
Roland Piquepaille writes "An international team of physicists has entangled five photons for the first time in the world, reports Technology Research News in "Five photons linked." Why is this important? Because it's the minimum number of qubits needed for universal error correction in quantum computing. In other words, they found a way to check computational errors in future quantum computers. The physicists also demonstrated what they call 'open-destination teleportation,' a way to teleport quantum information within and between computers." "They teleported the unknown quantum state of a single photon onto a superposition of three photons. They were then able to read out this teleported state at any one of the three photons by performing a measurement on the other two photons," adds PhysicsWeb in "Entanglement breaks new record
". This will be used in about ten to twenty years to move information among quantum networks. You'll find more details and references in this overview."
What we don't know about quantum physics would float many battleships.
What we may be seeing is the physical evidence that space and time are not much at all like we think they are.
Entanglement seems to allow things far away from each other, that used to be close to each other, to react to each other like they are still close to each other.
Science fiction fans will understand that the most likely explanations for that kind of thing are also likely to be wrong.
I look forward to a better understanding of this kind of behavior because it will allow us to better manipulate and control the way our area of the universe works.
For those who think of this as star trek blek, try putting yourself in the place of someone 200 years ago who was told that someone who lives in England would be able to visit someone in the colonies by a trip of only 3 hours.
dzimmerm (who is at work and whose account does not seem to recognize his password and who does not have any way to pop his home email from work due to SPIT, filtering, and SPIT lotus notes)
In 1993 an international group of six scientists, including IBM Fellow Charles H. Bennett, confirmed the intuitions of the majority of science fiction writers by showing that perfect teleportation is indeed possible in principle, but only if the original is destroyed. In subsequent years, other scientists have demonstrated teleportation experimentally in a variety of systems, including single photons, coherent light fields, nuclear spins, and trapped ions. Teleportation promises to be quite useful as an information processing primitive, facilitating long range quantum communication (perhaps unltimately leading to a "quantum internet"), and making it much easier to build a working quantum computer. But science fiction fans will be disappointed to learn that no one expects to be able to teleport people or other macroscopic objects in the foreseeable future, for a variety of engineering reasons, even though it would not violate any fundamental law to do so.
In the past, the idea of teleportation was not taken very seriously by scientists, because it was thought to violate the uncertainty principle of quantum mechanics, which forbids any measuring or scanning process from extracting all the information in an atom or other object. According to the uncertainty principle, the more accurately an object is scanned, the more it is disturbed by the scanning process, until one reaches a point where the object's original state has been completely disrupted, still without having extracted enough information to make a perfect replica. This sounds like a solid argument against teleportation: if one cannot extract enough information from an object to make a perfect copy, it would seem that a perfect copy cannot be made. But the six scientists found a way to make an end run around this logic, using a celebrated and paradoxical feature of quantum mechanics known as the Einstein-Podolsky-Rosen effect.
Read just how this effect works, here.
And, the best part, we will see it in our lifetimes.
Maybe. This is the wrong time and political environment for these types of advances to be occuring, IMO. I could be wrong, but I see governmental control on this technology for the foreseeable future. There isn't more now because they really don't have anything that could be mass produced, but when we reach that point, get ready for the "terrorists could do xyz with this!" hyperbole and heavy legislation to control it.
I guess if they just limit it to universities and favored businesses we might still get to see some of the fruits of it. Let's hope I'm wrong. The faster we get quantum computing into the hands of as many people as possible, the faster our technology will advance.
Think for yourself, destroy your television.
As I understand it, the 'information' moves instantly (FTL), but the ability to read it doesn't, hence no faste-than-light violation.
"A language that doesn't affect the way you think about programming, is not worth knowing" - Alan Perlis
Charles Babbage came up with the concept of the Difference Engine in 1822. It took almost 114 years until Turing to come up with the formalism of computer science, which is the foundation of CS as we know it.
And today, we have half-decent computers - a good 182 years later. Even assuming that the technology is exponential, and the necessary developments in the other areas are made in the next 25 years -- it would atleast be another 34 years after that for QC to take off bigtime and for us to have the equivalet of today's computers (or better) in QC.
I'm not being pessimistic, just being honest about how I feel, as someone who works in this area.
I hate to be cynical, but who's funding this kind of research, directly or indirectly? Now think about this strategy:....
That's very true, but what I am talking about are the obvious patents, not the ones that require millions of dollars in legitimate investment in R&D. I'm talking about silly little patents that take someone a few hours of thinking and then they try to claim any use of quantum mechanics in some broad area of endeavor (like using qubits to optimize internet routings, or using entanglement to serve ads, or some such "add-a-q-to-any-ordinary-activity" type of patent).
Personally, I am in favor of patents for non-trivial inventions. I wonder if part of the problem with the current patent system is that the examiners may not understand the state of the art well enough to judge which inventions were obvious and which inventions were hard. The point is that easy inventions don't need the encouragement created by a patent -- they will get invented and deployed anyway. Patents should reserved for inventions that could not have happened if the inventor did not think they had a chance of a patent.
It's a separate issue, entirely, whether the fruits of publicly funded research should be patented at all, but that's a different discussion.
Two wrongs don't make a right, but three lefts do.
The probability "amplitude" that represents a solution to say, Satisfiability, would, on average, be 2^-N. To distinguish a possible solution probabilistically from 0, 2^N trials would be needed. Or so says "A New Kind of Science" by Wolfram.
That's right. All your base.
No, that's the whole point of quantume entanglement.
Entangled particles are created in a process that conserves quantume properties, like spin. So if a particle is in the spin up state, the other has to be in the spin down state. When they are created, entangled couples are in a undetermined state. As soon as a measurement is made on one of the particles, the other collapse to the complementary state. This happens instantaneously, regardelss of the distance between the particles. However, since you cannot predict the result of the measurements, you cannot transfer information with this method. You can however use it to create secure keys fro criptography.
Your "understanding" of relativity is wrong. The speed of light is a constant for all observers and this causes all sorts of weirdness in the rest of physics. In particular it it makes it impossible to constistantly define whether two events at different places are "simultaneous". People moving in different directions or at different speeds will see a different order of events. Any method allowing FTL communication can be leveraged into sending a message into someone's past using people moving in oppostite directions fast enough.
Lets say we have a train driving past the earth at half the speed of light, from left to right. We have You standing still on earth with your Magic Instant Communication Device. At the (f)ront of the train we have Fred. At the (b)ack of the train we have Bob. In the exact (m)iddle of the train we have Milly. To make it easy lets assume the train is two light years long.
Now, as the train passes the earth, when it is exactly half way and you and Milly are at the same spot, you signal both Fred and Bob to turn on signalling lights "simultaneously". You will first see both of those signal lights simultaneously one year later, meaning Fred and Bob simultaneously turned them on 1 year ago. From YOUR point of view all is well and good, but that's only because we STARTED from your point of view in the first place.
Now lets look at YOUR view of what happens to MILLY, and then lets look at it from MILLY's point of view.
Milly has moved off to the right at half the speed of light. Fred's light has to pass Milly first, before it reaches you. In particular you'd say it would reach her 8 months after you hit your magic button. Also, by the time you see Bob's light from the back of the train Milly will he a half-light year off to the right. It will take a total of two years for Bob's light to catch up to Milly.
So according to you, Milly sees Fred's signal 16 months before Bob's signal.
Now lets go to Milly's point of view. As far as she is concerned her train isn't moving at all, it's YOU that is flying past at half the speed of light. Fred is motionless relative to her, one light year* in front of her. Bob is motionless relative to her, and one light year behind her. For her the speed of light is still one light year per year and it takes one year for a light to cross either half of the train to reach her. When she sees Fred's signal 8 months after you hit your button she knows Fred had to signal a year before that, or 4 months BEFORE you pressed your button. When she see's Bob's signal two years after you hit your button she knows Bob signaled a year AFTER you pressed your button. Milly can walk up and down the train and measure speeds and distances and all of the laws of physics, and the fact is that for her Fred signaled 16 months before Bob did, not simultaneuosly.
Now lets let Milly reach out and tap your Magic Instant Communication Device while you go zipping past them. She "simultaneously" tells Fred and Bob to turn on their signal lights. Fred's and Bob's signals zip down the train towards her at the speed of light, each singal covers the one-light year length in one year. Milly sees both signals simultaneously. Whoops! Your Magic Instant Communication Device is broken, it does something different depending on who presses the Magic Button.
If we add in a second train travelling in the opposite direction then no matter how you attempt to "fix" your Magic Instant Communication Device there will always be someone somewhere who can send a signal into the past and violate causality. Explaining how and proving it under General Relativity is the stuff of physics papers, not slashdot posts.
Nobody however says that wormholes would violate the laws of temporal causuality.
Flat-out false. Try Google, in particular search on Wormholes and Closed Time-like Loops. A "closed time-like loop" is a path you can fly along to get back to where you strated at the same time (or before) you left. You will find tons of refferen
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