quantum teleportation - current developments

[jefferiestubes8]

A team of scientists at the University of Science and Technology of China and the premier Tsinghua University in Beijing successfully streamed quantum information between photons over 16 km, much farther than the earlier record of a few hundred meters, the researchers claimed in their report, published last week.

Although peer scientists state emphatically that a Star Trek-inspired teleportation of objects and persons remains firmly in the realm of fantasy, they acknowledge the significance of the latest development as a “giant leap” in quantum teleportation.

The fact that the quantum information between photons was teleported over a distance of 16 km, which is greater than the effective ‘thickness’ of the aerosphere, means that the results could be invoked to facilitate experiments between, for instance, a ground station and a satellite.


In their report on the findings of the project, supervised by Peng Cheng-Zhi and Pan Jian-Wei, the scientists said, “Our result confirms the feasibility of space-based experiments, and is an important step towards quantum-communication applications on a global scale.”

Although it’s called “quantum teleportation”, scientists say there is no physical teleportation of any object: what happens, instead, is that two photons or ions are ‘entangled’ — that is, connected by an invisible ‘umbilical cord’ — in such a way that when the quantum state of one is altered, the state of the other (which is physically separate) is also altered.
Thus, information is “teleported” between the two without using signals or networks.

Quantum teleportation was first postulated in 1993 by Charles Bennet, an IBM researcher. But it was “brought to life’ by Nicolas Gisin, at the University of Geneva, who demonstrated teleportation. The unearthly application potential of this technology —as envisioned by science fiction fantasists — has led it to be branded a kind of ‘voodoo’ experiment — or an optical illusion worthy of PC Sorcar.

Will Star Trek-style beam-up become reality from sci-fi?

In layman's terms how does this make communication faster? Fiber Optics and optical routing & switching already are the fastest thing on Earth for transmission of communcations.

 

[Lindley]

My understanding is that it doesn't so much make communication faster, as it enables absolutely secure communications.

 

[jefferiestubes8]

it enables absolutely secure communications.

Are you saying it is better than using multiple types of heavy encryption? What is the real goal of this research to come in the future from the article:

“Our result confirms the feasibility of space-based experiments, and is an important step towards quantum-communication applications on a global scale.”

What kind of application? Is this for a spy satellite or what?

 

[Lindley]

At this point I think it's pure research. It's not yet practical enough to start talking about goals, only possibilities.

 

[FlyingLemons]

The field of quantum information is developing quite fast, and this is effectively just a "highlight" of current research that doesn't really reflect what the field's about - it ranges from things like applied quantum computation to more abstract areas such as tackling cosmological questions such as the Big Bang model from a computational perspective.

The "star trek style beamup" angle is pure fantasy, and it's more likely to make its way into encryption technologies than anything else. Quite interesting to read about, anyway.

 

[Zachary Smith]

Does quantum teleportation happen at the speed of light or is it, in fact instantaneous. If it is instantaneous, by what mechanism is it thought to use to get around the speed of light?

 

[Lindley]

The effects are instantaneous, but due to some Heisenberg-related weirdness, there is no information transfer at FTL speeds. Or something.

 

[Snaploud]

it enables absolutely secure communications.

Are you saying it is better than using multiple types of heavy encryption?

I assume the answer would be yes (as there would be nothing to intercept between the point of origin and the end-user). You should still use encryption to prevent hacking at either the end user point or the point of origin, but the communication (the transfer of information) itself would be secure.

Edit: There would also no longer be a method of "blocking" communications (either intentionally via a human intervention or unintentionally via natural interference).

 

[Zachary Smith]

The effects are instantaneous, but due to some Heisenberg-related weirdness, there is no information transfer at FTL speeds. Or something.

There must be SOME kind of information transfer at FTL speeds for the effect to be instantaneous. If not, one photo would never "know" the state of its entangled partner. At the very least the information concerning the state of one photo relative to the other MUST transfer at FTL speed, right?

 

[Lindley]

http://en.wikipedia.org/wiki/Quantum_teleportation

In particular:

The teleportation scheme combines the resources of two separately impossible procedures. If we remove the shared entangled state from Alice and Bob, the scheme becomes classical teleportation, which is impossible as mentioned before. On the other hand, if the classical channel is removed, then it becomes an attempt to achieve superluminal communication, again impossible.

 

[ProtoAvatar]

The effects are instantaneous, but due to some Heisenberg-related weirdness, there is no information transfer at FTL speeds. Or something.

There must be SOME kind of information transfer at FTL speeds for the effect to be instantaneous. If not, one photo would never "know" the state of its entangled partner. At the very least the information concerning the state of one photo relative to the other MUST transfer at FTL speed, right?

Information IS transmitted instantaneously from one entangled particle to the other.
It's just that you can't decide/control what information is transmitted (this information is random) - as such, it is more correct to say that NOISE is transmitted instantaneously (meaning you can't actually comunicate).

The classical channel is needed in order to know if this noise is actually transmitted from the sender-particle and not only generated when scanning the receiver-particle.

All physicists will tell you that transmitting anything faster than light is impossible - that being a fundament of special relativity (if one can transmit information faster than light one can identify a preferential frame of reference and that shoudn't be allowed).
However, entanglement, while not practically violating this interdiction (useful information is not transmitted), does violate it from a philosophical point of view (noise IS transmitted instantaneously).

 

[Zachary Smith]

^^

Sounds like some scientists want to have it both ways. If even "noise" is transmitted instantaneously--then SOMETHING is traveling faster than the speed of light. To try to disqualify it because it is disorganized or "uncontrolled" sounds like trying to say lightning is not really electricity because it didn't come from a man-made generator.

 

[ProtoAvatar]

Special relativity has been a fundament of science for a century.
It is backed by sufficient experimental evidence (though not all its predictions are experimentally verified).
It is what the current - and not only - generation of scientists were taught - the 'orthodoxy', so to speak.
And it ABSOLUTELY REQUIRES for the speed of light to be the top speed at which anything travels.

In order to disprove this theory, one needs a LOT more than just something that philosophically contradicts it. One needs someting that negates it in practice.


My problem with special relativity is that it only says that time dilates, space contracts, mass increases (all this, contradictory in two different POVs - which is why 'god's point of view', which would take into account both POVs simultaneously, generates contradictorial non-sense), simultaneity is different in two POVs, but it doesn't explain HOW these happen.
What is the CAUSE - by what mechanism do time, space and mass behave like this? It only gives a disconnected 'why' as a distant reason - so that light can have the same speed in all reference systems - but it doesn't say how this is accomplished, that's essentially 'by magic'.

 

[FlyingLemons]

The reason why we have space contraction and time dilation is due to the Lorentz factor present in the transformations between frames - different speeds give different ratios of v/c - v being the velocity, c being the absolute speed of light. The higher speed you go, the more the Lorentz factor comes into play, causing the phenomenon of time dilation between two observers, and so on.

Special relativity violations would be an interesting phenomenon as they might provide an insight into physics at higher energies, but none have been detected so far.

 

[ProtoAvatar]

In other words - the space/time distorsions appear because light must have the same speed c in all inertial POVs (with different speeds v) - and this gives the Lorentz factor.

As I said - this only gives a distant 'why'.
What it doesn't give is the 'how'. What causes the time to dilate, the space to contract, etc? By what mechanism is the fabric of time and space altered?

 

[CuttingEdge100]

Is the result of time dilation at speeds close to that of light due to the fact that mass increases as you approach the speed of light? I remember hearing that gravity causes time to slow down...