Quantum Weirdness and Communications

by Paul Gilster on March 20, 2007

‘Spooky action at a distance’ is still spooky no matter how you explain it. Einstein famously used the phrase to describe quantum entanglement, where two entangled particles appear to interact instantaneously even though separated in space. Now we’re talking about using the effect for communications, following the news that European scientists have proven that entanglement persists over a distance of 144 kilometers.

Fortunately for would be communicators, a pair of entangled photons can be created in a process called Spontaneous Parametric Down Conversion. Once entangled, the photons stay entangled until one of them interacts with a third particle. When that happens, the other photon changes its quantum state instantaneously. The beauty of entanglement for communications is that anyone trying to listen in on a message invariably disrupts the entangled system, a result that would be easily detectable.

The security potential is obvious in a world where so much banking information takes digital form, and where the security needs of military communications are greater than ever. But is entanglement a theoretical exercise or can it operate in real-world conditions? To find out, the researchers needed to learn not just how far the effect could travel but also how it might be affected by local conditions. Would it be possible for a ground station, for example, to communicate with an orbiting satellite? Or would the atmosphere destroy the entanglement effect?

To find out, the European team used the European Southern Observatory’s one-meter instrument on Tenerife (Canary Islands), situated 144 kilometers from an observatory on the nearby island of La Palma. The entangled pair was created on La Palma, with one photon sent toward Tenerife while the other remained at La Palma for comparison and study. The entanglement survived, implying that a ground-to-orbit connection is workable.

“We were sending the single-photon beam on a 144 kilometres path through the atmosphere, so this horizontal quantum link can be considered a ‘worst case scenario’ for a space to ground link,” says Josep Perdigues, ESA’s Study Manager. Up next: studying quantum entanglement at much greater distances, something that might be done by putting a quantum optical terminal on a dedicated satellite.

We’ll follow that mission concept as it develops. Meanwhile, theorists still have their work cut out for them. Just why does entanglement survive a journey through a medium in which it might be expected to interact with atmospheric molecules? We have much to learn about such bizarre effects, but the recent demonstration of a workable quantum computer from D-Wave Systems highlights how swiftly ‘spooky’ quantum properties are being harnessed for work in the macroscopic world around us.

Bob Mottram March 20, 2007 at 13:01

I’m not a physics expert, but I would expect that entanglement works over long distances because the message is not actually traveling *through* a medium, such as the atmosphere. More likely the entanglement is occurring in dimensions other than the usual three spatial ones which our senses normally observe.

Edg Duveyoung March 20, 2007 at 14:21

Action at a distance as it is “embodied” by quantum entanglement — since it is beyond conceptual grasping by today’s physics –it’s a miracle, right? Something “para,” right? A connection between two entities that is instantaneously responsive even though they are a hundred miles apart — it’s magic, right? What is it, I ask the physicists out there, that is NOT paraphysical about it? What can be measured “going on” to conceptually grasp the guts of “backstage doings behind the drama of entanglement?” So far, no instrumentation has been able to delve inside — it seems as impossible to grasp quantum entanglement operational dynamics as it is to figure out what’s going on inside a black hole. We’re so impotent that we don’t even have any idea if the concept “operational dynamics” applies to quantum entanglement. There may not be any operation of any sort whatsoever and yet the phenomenon is real.

The answer, the clarifying concept, for me is that the two entities are “merely one thought.” I mean this literally, physically — not merely analogously.

When we see this “thought” dynamic “at work” in any of our nightly dreams, it is completely acceptable to all of us. The dream character that I am identified with can travel to another planet — suddenly and instantly — and the dream character may not even “pause in wonder at the instantaneousness,” and we too, when we are “wakeful state minds,” understand that this is not strange, because the whole environment, the dream world, in which the instant travel was accomplished was all inside a mind — inside a personally programmed holodeck, if you will. Inside a dream, the speed of thought is, well, let’s use the word “infinite” — meaning at the very least that it is responsible for “things in a dream” going far faster than the speed of light. Right now at this moment, you can imagine being on Earth, and then, in your next thought, you can imagine being on the other side of the known universe. No problemo, right? We find no cognitive discomfort with these facts about thinking, because dream/imaginary phenomena are understood to have different “laws.” We are comfortable with the fact of “no limitations” in this “world of miracles.”

Consider the phrase “God is doing the dreaming.” Isn’t that phrase’s concept analogous to what we see in quantum entanglement? — apparently there’s no time or space involved. No distance has been traversed; no time has passed that can be measured. Instant is instant. Is the virtual field conceptually identical to what is meant by the phrase “dreaming mind of God?” Is the real world virtual field equally described as “the mental space of God wherein creation happens?”

Quantum entangled objects have properties that are identical to the properties of dream objects. Do we really need two nomenclatures? On this one phenomenon, can’t philosophers and scientists just decide to use the same vocabulary?

Entanglement can’t involve radiation — that so slow dawdler. It has to be instant, and the way the mind works in a dream seems to offer an analog that resonates with the facts about quantum entanglement. There doesn’t seem to be any other analog that “is comfortable” with quantum entanglement, and dream-entangled objects have all the “rights and powers” that quantum entangled objects are assigned to have “in the real world.”

See, folks, here we are again having our heads banged into the paraphysical, and yet where are the funds for research into consciousness-as-tool, consciousness-as-a-reality-measuring-device, consciousness as Creator? Ask any top scientist about how “identificational processes impact science,” and you’ll get a blank look. Oh, we know that the observer counts in the processes, but who is researching the nature of the observer other than noting its presence? Answer: meditators around the globe are doing this type of research.

If I find that only a certain tool allows me to achieve a goal, no surprise if I’m interested in the tool itself.

But always the tool is being ignored and instead of “seeing what the mind adds,” erroneously the research focus is about “something out there,” instead of “everything’s inside my mind when I consider it, and so maybe I should see if my mind is tweaking ‘reality’ by it having a skewing nature” that bears looking into.

Everything must be modeled inside a brain — including time and space — and certainly it’s a profound question if we ask, “what about the nature of the brain/mind system defines time-space?” If we can see a thought forming from out of the quantum foam of our consciousness, maybe we can see if our waking thoughts, our non-meditating minds are obfuscating reality by a “coloring” that’s added to the thinking process by our “mind stuff.”

I may think that I can see a star, but what research can prove that the “I” who is seeing the star is awake and not actually merely a character inside a dream? If a dream character is told by another dream character that “you’re awake, this is real,” we know that that statement is suspect from our waking point of view, but the dream character has little chance of “doing science” to find out if he’s in a dream or not, and instinctively, dream characters validate all the phenomena in the dream as “ordinary and not suspicious” — even when waking world miracles are part of the dream, the character typically doesn’t start running around the dream like Chicken Little yelling about the “miracle.” This is blindness, yes? This is an ignorance, yes? Whatever “doesn’t work intellectually” almost never comes up as a “problem” for a dream character. We may be running away from a monster, it may have us emotionally spiking off the charts, but when we fly over the mountain to escape the monster, no sense of “something unusual” occurs to the dream character. This is the ability to selective ignore, yes?

What are we equally being selective about in our waking state minds?

As Einstein taught, we can devise no experiment to determine if acceleration or gravity is responsible for our “sticking to” the floor we are standing on. His “in space elevator constantly accelerating” mind-problem showed this equivalence, and no one has “explained it differently” yet. Gravity is acceleration. But how would we go about trying to convince a “very smart dream character” about gravity? We can easily imagine a dream-character-scientist performing absolutely screwball “experiments” that have no logic at all, and yet, there’s the scientist at the end declaring he’s discovered some truth and expecting a Nobel Prize. In the dream world, all things are provable as true — even the most untrue concept can be thought as “wise” by a dream character who is otherwise extraordinarily smarter than the other dream characters. Anything goes, anything is true, anything is possible.

Why can’t this be true in the waking world? In fact, is not our “waking world sense” impossibly unable to grasp quantum entanglement in the same way that a dream-scientist would be as unable to explain instant teleportation across the dreamscape’s universe? Perhaps our very best efforts to understand quantum entanglement will, even decades hence, come up as short as the theories of dream-scientists explaining the miracles of their world. Perhaps if I tell you that you’re real, my opinion is as unfounded as it is if you create a dream in which “a dream me” makes the same statement.

Maybe every law that science has ferreted out is just such an opinion — merely a thought, and having no causal connection to “the real cause of causes” — God’s aesthetic dream-making decision process. Perhaps the Pythagorean Theorem is only real because God dreams it so — for the nonce, not out of necessity. Can’t God dream? Can’t God imagine a universe where that theorem is untrue? Why not? You dream impossible dreams every night, but God can’t do it?

If we ever do understand quantum entanglement, it’ll be a spiritual moment in history, because this phenomenon is like having a peephole into God’s workshop from whence comes all ideation.

Edg

Eric James March 27, 2007 at 23:28

Edg,

Interesting philsophical considerations. However, I disagree with your assesment of Einstein’s general relativity equivalence principle. I’ve found that I can devise experiments the occupant can perform to detect whether he is being held fast to the floor by gravity, or acceleration.

Ronald March 29, 2007 at 9:34

Concerning speed: is anything known about speed (limits) of this quantum entanglement? I think I read something about no limits haven’t been found yet (the state ‘flip-over’ happening instantaneously). Fascinating thought: could this theoretically enable communication faster than light. I mean: suppose you have two machines, like QE mirror images, one on earth, one say on Mars (or Alpha Centauri planet b, or …). You could then flip the states in one machine and it would result in instant (?) state transitions through QE in the other machine, enabling a kind of binary way of communication.

Administrator March 29, 2007 at 13:51

As far as I know, quantum entanglement is instantaneous. Whether it can be used for communication seems problematic in the extreme, and I welcome the thoughts of readers who understand the phenomenon better than I do.

Edg Duveyoung March 30, 2007 at 8:38

Eric James,

I didn’t know that science had differentiated acceleration and gravitation. Er, have they? Or, do you mean that you personally have devised a repeatable, verifiable proof/method to do this?

While I’m at it, has science progressed to figure out how to solve the three-bodies-in-motion-prediction problem? I know we can get to Mars, but can we do it without course corrections? Last I heard the answer was “NO!” If you have a quick URL for these things, you’d save me a heap-O googling mebets. I haven’t heard about any geeks predicting the final state of a frictionless billiard table’s three balls — ever.

And, yeah, what about that there “three kinds of infinity” thingy — any more infinity types discovered since I read Gamow’s 1, 2, 3, Infinity?

Being out of date, I HATE IT!

Edg

Eric James March 31, 2007 at 1:02

Edg Duveyoung Says:
March 30th, 2007 at 8:38

I didn’t know that science had differentiated acceleration and gravitation. Er, have they? Or, do you mean that you personally have devised a repeatable, verifiable proof/method to do this?

Edg,

So you caught that after all, did you?

Actually, I meant that I personally have devised a repeatable, verifiable proof/method to do it. It’s real (more or less), but it doesn’t disprove Einstein or anything. It’s more an exercise in creative thinking than a scientific breakthrough. ;)

Care to make a wager on it?

Edg Duveyoung March 31, 2007 at 6:56

Eric James,

Ha! Like I know physics enough to take your “bar bet.”

My own theory about how to tell the difference would be that on a planet, all the mass is not in the center of the planet, but the math assumes it to be all “there.” But, in actuality, if one has, say, a big mountain right next to one, then that mountain will pull at you “sideways” just a bit, and in an elevator in space there’d be no such “side sucks by masses not quite in the center of things.” Haven’t a clue about how to set up equipment for such an experiment though — and I suspect very strongly that my concept above has been dealt with long ago by folks with brains so big they have to have levitation suspensor belt like Baron Vladimir Harkonnen in Dune. And they’ll be chuckling right now at my travail.

Edg

Eric James March 31, 2007 at 16:15

Edg,

The wisest men of all, are those that know their own limitations. Besides, these mega-brain support systems aren’t very comfortable. ;)

Eric

ljk April 9, 2007 at 10:03

SEGMENT OF A “QUANTUM REPEATER” DEMONSTRATED (PHYSICS)

Physicists have demonstrated a way to create a segment of a channel
that can distribute quantum entanglement over distances. The
division into segments and storage of entanglement in material
systems is necessary for long-distance quantum communications to
take place, and could lead to long-distance quantum communications,
scalable quantum networks, and even a quantum internet.

Details: http://mr.caltech.edu/media/Press_Releases/PR12969.html

ljk May 4, 2007 at 14:06

Entanglement dies a sudden death (May 1)

http://physicsweb.org/article/news/11/5/1

A strange quantum phenomenon that could be a stumbling block to building
quantum computers has been observed for the first time by physicists in
Brazil. Known as entanglement sudden death (ESD), it involves the rapid
decay of the “entangled” pairs of particles that will be central to the
operation of quantum computers. Since the particles decay so quickly,
the physicists claim that the decay cannot be reversed using the
error-correction schemes that have been proposed to increase the
lifetimes of entangled particles (Science 316 579).

ljk June 5, 2007 at 10:39

New distance record for quantum communication

NewScientist.com news service June 4, 2007

*************************

A quantum communication has been
sent across a record 144 kilometers
(90 miles) using a process that may
one day be used to send secret
messages across space via a network
of…

http://www.kurzweilai.net/email/newsRedirect.html?newsID=6873&m=25748

ljk January 31, 2008 at 9:51

Researchers Demonstrate Quantum
Teleportation and Memory in Tandem

PhysOrg.com Jan. 30, 2008

*************************

An international team of
researchers created an experiment in
which a quantum bit of information
was transported across a distance of
seven meters and briefly stored in
memory, the first time that both
quantum memory and teleportation
have been demonstrated in a single
experiment….

http://www.kurzweilai.net/email/newsRedirect.html?newsID=7899&m=25748

ljk March 4, 2008 at 10:59

When humans become entangled

March 3rd, 2008 by KFC

Something curious is happening at Nicolas Gisin’s lab at the University of Geneva. Gisin is a world expert in entanglement, the ghostly quantum phenomenon in which two or more particles become so deeply linked that they share the same existence, even when far apart.

Entanglement is now a routine resource in many labs: it can be generated, studied and even passed from one particle to another. It is usually measured using two detectors–Alice and Bob in the lingo of quantum physicists–which analyse pairs of incoming photons to see whether there is any spooky-action-at-a-distance, as a Einstein called it. In these so-called “Bell experiments”, spooky action rules.

Given the amazing properties of entangled photons, it was never going to be long before curious postdocs pointed these photons on themselves, in the manner of Nobel Prize winning Barry Marshall who famously swallowed H Pylori bacteria to see if it gave him ulcers, or more fittingly like Jeff Goldblum in The Fly.

What would happen if two humans–let’s call them Alf and Bess–replaced the lifeless Alice and Bob?

I guess most physicists would say that the process of observation in the eye is macroscopic, it involves large numbers of photons, and so any quantum effects would be drowned out.

Not so, reckons Gisin. It has long been known that the eye is sensitive enough to detect a mere handful of photons. He and a couple of pals, Nicolas Brunner and Cyril Branciard, have calculated that, were the eye a lifeless detector, it could be used to carry out the kind of Bell experiments described above.

“Thus entanglement could in principle be seen,” conclude the group.

Full article, plus link to the paper here:

http://arxivblog.com/?p=294

ljk March 6, 2008 at 10:29

PHYSICISTS TRANSCRIBE ENTANGLEMENT INTO AND OUT
OF A QUANTUM MEMORY (PHYSICS)

Caltech scientists have laid the groundwork for a crucial step in
quantum information science. They show how entanglement, an
essential property of quantum mechanics, can be generated between
beams of light, stored in a quantum memory, and mapped back into
light with the push of a button.

Details: http://mr.caltech.edu/media/Press_Releases/PR13115.html

ljk March 23, 2008 at 19:38

Quantum entanglement

Quantum entanglement is a strange telepathic link which allows
particles to influence each other’s properties. Some have suggested
the power travels at millions of times the speed of light. The notion
defies our idea of common sense. Einstein dismissed the theory
as too spooky to be real. But entanglement is more than just a
product of the equations of quantum theory. It exists and plays a
part in the real world. It is at the forefront of a technological revolution.
It can be used in encrypting information. It is unbreakable.

The race is on to bring quantum cryptography to a worldwide
market. It will be used to protect financial transactions and
information flow. It will be used to drive quantum computers.
Michael Brooks’s book, Entanglement is a thriller based on the
power of entanglement falling into the wrong hands.

Full transcript here:

http://www.abc.net.au/rn/scienceshow/stories/2008/2190074.htm

ljk June 3, 2008 at 11:00

Scientists find new ‘quasiparticles’

PhysOrg.com June 2, 2008

Weizmann Institute physicists have
demonstrated, for the first time,
the existence of “quasiparticles”
with one quarter the charge of an
electron. This finding could be a
first step toward creating exotic
types of quantum computers that
might be powerful, yet highly
stable. Quarter-charge
quasiparticles have been sought as
the basis of the…

http://www.kurzweilai.net/email/newsRedirect.html?newsID=8799&m=25748

ljk June 9, 2008 at 16:39

Space-QUEST: Experiments with quantum entanglement in space

Authors: Rupert Ursin, Thomas Jennewein, Johannes Kofler, Josep M. Perdigues, Luigi Cacciapuoti, Clovis J. de Matos, Markus Aspelmeyer, Alejandra Valencia, Thomas Scheidl, Alessandro Fedrizzi, Antonio Acin, Cesare Barbieri, Giuseppe Bianco, Caslav Brukner, Jose Capmany, Sergio Cova, Dirk Giggenbach, Walter Leeb, Robert H. Hadfield, Raymond Laflamme, Norbert Lutkenhaus, Gerard Milburn, Momtchil Peev, Timothy Ralph, John Rarity, Renato Renner, Etienne Samain, Nikolaos Solomos, Wolfgang Tittel, Juan P. Torres, Morio Toyoshima, Arturo Ortigosa-Blanch, Valerio Pruneri, Paolo Villoresi, Ian Walmsley, Gregor Weihs, Harald Weinfurter, Marek Zukowski, Anton Zeilinger

(Submitted on 5 Jun 2008)

Abstract: The European Space Agency (ESA) has supported a range of studies in the field of quantum physics and quantum information science in space for several years, and consequently we have submitted the mission proposal Space-QUEST (Quantum Entanglement for Space Experiments) to the European Life and Physical Sciences in Space Program.

We propose to perform space-to-ground quantum communication tests from the International Space Station (ISS). We present the proposed experiments in space as well as the design of a space based quantum communication payload.

Comments: 4 pages, 1 figure, accepted for the 59th International Astronautical Congress (IAC) 2008

Subjects: Quantum Physics (quant-ph)

Cite as: arXiv:0806.0945v1 [quant-ph]

Submission history

From: Johannes Kofler [view email]

[v1] Thu, 5 Jun 2008 15:33:47 GMT (39kb,D)

http://arxiv.org/abs/0806.0945

ljk June 17, 2008 at 9:51

World’s Largest Quantum Bell Test Spans Three Swiss Towns

PhysOrg.com June 16, 2008

In an attempt to test quantum
nonlocality — the “spooky
interaction at a distance” that
occurs between two entangled
particles, physicists from the
University of Geneva have sent two
entangled photons traveling to
different towns located 18 km apart
–the longest distance for this type
of quantum measurement. (D. Salart,
et al.) By…

http://www.kurzweilai.net/email/newsRedirect.html?newsID=8895&m=25748

James M. Essig June 17, 2008 at 21:06

Hi ljk;

Great find by the way of the above article!

The testing of quantum entanglement between two locations 18 km apart is fantastic.

I have often wondered if at some level, all of the mattergy within the universe is somehow entangled such as entanglement that could have resulted in the very instant of creation, perhaps as a result of the common origin of all mattergy within the original scalar field fluctuation that lead to the big bang according to the theory of chaotic inflation. Such entanglement would seem to require some sort of deep level hidden quantum variables, a taboo for much of the quantum physics community.

If such quantum entanglement exist along with any associated hidden variables, perhaps the phenomenon as such could be controlled so as to induce macroscopic influence between different regions of space containing mattergy over very large distances of separation simultaneously. Obviously if such is possible, then perhaps arbitrary quantum teleportation may become possible even for systems that are not entangled in the traditional or current laboratory produced fashion.

Now if such entanglement exists, somehow beneath the level of all of the acts of quantum wave-function collapses and quantum background noise, perhaps regions of space time devoid of any real mattergy can be and/or are quantum entangled also. Quantum entanglement of space time regions or the space time analogue of quantum entanglement might be used to teleport space time information such as degree of space time warpage or curvature, space-time dimensionality, zero point vacuum field characteristics, and even perhaps mouths of wormholes.

Thanks;

Jim

James M. Essig July 3, 2008 at 14:49

Hi Folks;

With all of the recent talk of quantum computers, I thought I would bring up the following concept.

We have all heard of the qubit, essentially an atom or other particle that can be in either a spin-up, spin down, or both spin up and spin down state simultaneously. Accordingly, a quantum computer utilizing 200 entangled particles or qubits could have a total of 2 EXP 200 possible states.

Now a rather bazaar idea occurred to me yesterday as I was reading a web-based document on qubits. The idea involves the concept of a single atom, somehow being in state or simultaneous states selected from the set {spin up, spin down, or both spin up and spin down, {all three of spin up, spin down, and both spin up and spin down simultaneously}, {both spin up and the set {all three of spin up, spin down, and both spin up and spin down simultaneously}, simultaneously}, {both spin down and {all three of spin up, spin down, and both spin up and spin down simultaneously} simultaneously}, {both {spin up and spin down } and {all three of spin up, spin down, and spin up and spin down simultaneously} simultaneously}, … and the proposed set is infinite.

Now perhaps quantum theory mathematics limits a qubit to being on, off, or on and off simultaneously and that all of the other terms of the proposed infinite set have no meaning or are mathematically degenerate, but in the case where such infinite sets have real meaning and actual existence, perhaps they could be harnessed for even more exotic forms of quantum computers and even more exotic physics based technologies in general.

Note that I am not an expert in quantum computing and so I apologize to expert quantum computationalists if the above conjecture is nonsense, however, I just thought I would throw the concept.

One further concept I wanted to touch on is the concept that quantum computers could somehow be used to look inside parallel worlds as in the many worlds interpretation of quantum mechanics. Some theorists propose that quantum computers would imply the existence of such parallel histories or worlds. Perhaps the interface of a stack of qubits with parallel worlds can be a window for indirect observation of such worlds.

Thanks;

Jim

James M. Essig July 3, 2008 at 19:07

Hi Folks;

I read an excellent article on quantum computer research yesterday. This is also an interesting subject for me. Although quantum computers supposedly will offer very little improvement over conventional computers for many types of calculations, the jury is still out about how effective they could be on these very same types of calculations. If quantum computers could efficiently do lattice QCD, our understanding of applied strong nuclear force physics might make tremendous advances very quickly.

It just occurred to me the great ramifications of developing a technology wherein each atom within the composition of an interstellar space craft and its crew members’ bodies could be made to accelerate with a force that would act on each such atom as such with the same intensity that nucleons within a stable atomic nucleus are bound to each other. Such a space craft would reach a velocity of 86 % of C in roughly 10 EXP – 24 of a second. That is a trillionth of a trillionth of a second!

Perhaps the production of tailor made forces will enable us to produce such space craft propulsion systems, but I think it will be quite a long time before any of this could be realized. Computational Lattice QCD however might point us in the right direction.

Perhaps computational electro weak methods could be developed which could bridge the gap between the electro weak unification with that of any valid Grand Unification Theories or G.U.T.s wherein computational methods for strong nuclear force analysis could serve the above purposes.

I can imagine developing a hybrid force that acts over a long range wherein the intensity of interaction actually increases with separation distance as sort of an inverse effect for the strong nuclear force wherein at short distances the binding force between quarks is minimal but quickly increases as the quarks are pulled away from each other to reach a maximum force in a manner analogous to that of a elastic band. If a force with the intensity of the strong nuclear force could act in a repulsive manner similar to that of the strong nuclear force but over interstellar and even intergalactic distances, we could have one heck of a transport system. Perhaps reactive effects with respect to the zero point fields could be of benefit here.

Thanks;

Jim

ljk July 10, 2008 at 11:38

Entanglement and intra-molecular cooling in biological systems? – A quantum thermodynamic perspective

Authors: Hans J. Briegel, Sandu Popescu

(Submitted on 27 Jun 2008)

Abstract: We discuss the possibility of existence of entanglement in biological systems. Our arguments centre on the fact that biological systems are thermodynamic open driven systems far from equilibrium. In such systems error correction can occur which may maintain entanglement despite high levels of de-coherence. We also discuss the possibility of cooling (classical or quantum) at molecular level.

Comments: 17 pages, 6 figures

Subjects: Quantum Physics (quant-ph); Biomolecules (q-bio.BM)

Cite as: arXiv:0806.4552v1 [quant-ph]

Submission history

From: Hans Briegel [view email]

[v1] Fri, 27 Jun 2008 19:39:09 GMT (690kb,D)

http://arxiv.org/abs/0806.4552

ljk August 14, 2008 at 22:31

Entanglement remains a mystery

Swiss experiment implies information would have to travel thousands of times
faster than light to explain quantum entanglement

http://physicsworld.com/cws/article/news/35404

ljk May 28, 2009 at 9:54

http://www.technologyreview.com/blog/arxiv/23581/

First evidence of entanglement in photosynthesis

Room temperature entanglement seems to be a by-product of the process of harvesting light

Thursday, May 28, 2009

Physicists are fascinated with entanglement, the strange quantum phenomenon in which distinct objects share the same existence, regardless of the distance between them. But in their quest to study and exploit entanglement for information processing, physicists have found it fragile and easily destroyed. This fragility seems to severely limits how entanglement might ever be used.

But a new, more robust face of entanglement is beginning to emerge from other types of experiment. For example, physicists have recently found the signature of entanglement in the thermal states of bulk materials at low temperatures. This has huge implications for biological systems: if entanglement is more robust than we thought, what role might it play in living things?

Now we’re beginning to find out. In the first rigorous quantification of entanglement in a biological system, an answer is beginning to emerge. Researchers from various institutions in Berkeley California have show that molecules taking part in photosynthesis can remain entangled even at ordinary atmospheric temperatures.

The evidence comes from detailed study of light sensitive molecules called chromophore that harvest light in photosynthesis.

Various studies have shown that in light harvesting complexes, chromophores can share coherently delocalised electronic states. K. Birgitta Whaley at the Berkeley Center for Quantum Information and Computation and pals say this can only happen if the chromophores are entangled.

They point out that these molecules do not seem to exploit entanglement. Instead, its presence is just a consequence of the electronic coherence.

This is a big claim that relies somewhat on circumstantial evidence. It’ll be important to get confirmation of these idea before they can become mainstream.

Nevertheless, if correct, the discovery has huge implications. For a start, biologists could tap into this entanglement to make much more accurate measurement of what goes on inside molecules during photosynthesis using to the various techniques of quantum metrology that physicists have developed.

More exciting still, is the possibility that these molecules could be used for quantum information processing at room temperature. Imagine photosynthetic quantum computers!

And beyond that is the question that Whaley and co avoid altogether. If entanglement plays a role in photosynthesis, then why not in other important biological organs too? Anybody think of an organ where entanglement might be useful?

Ref: arxiv.org/abs/0905.3787: Quantum Entanglement in Photosynthetic Light Harvesting Complexes

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