monique morrow Mar 11, 2009

Maria,

Great input to this journey of impossibilities!

Note that teleporting matter whilst embryonic in research, will certainly not happen overnight -and uhmm—who knows right?

Holograms as 3d Telepresence ?  Absolutely!

I appreciate your comments!
Monique

Santanu Ganguly Mar 13, 2009

VERY SORRY Monique about the length of this post. Its just one of my favourite subjects.  Don’t bother to read it or even better just delete it if you wish…its not worth your time OK , you got me started .I hope there are no “number of character” limits to this blog…..

Holograms as modes to store information:

The first ever research projects that I ever particpated in ( undergrad summer student) was Holography as a form of optical storage. One of the most important issues of Hologram related developments in order to store information is the efficiency of the Holograms involved. Two major type of Holograms are Refelection and Transmission. whereas Transmission holograms have been known to be of very high efficiencies ( 96% and higher) reflection holograms are usually of fairly low ones. Added to this is the factor that most holographic plates for most techniques, for maximum efficiency, requires a developmental procedure similar to the plain-old-film photographs before the digital poto revolution. Added also to this, most holograms are vibration sensitive. Longer the exposure time of the holograms, more chances you have for a corrupted efficiency, hence information loss. I worked in the underground lab of COPL ( Centre d’optique, photonique et laser: Université Laval, Quebec, Canada) and used DCPVA ( DiChromated PolyVinyl Achohol) as emulsion and tried to get as much efficiency as possible for a real-time ( in other words, polaroid mode—>no post exposure development process) in Refelction mode. Goal of the project was to see if we could come up with something whoich gives high efficiency and gets rid of the processing part. Vibration caused by people walking around 50m away would ruin my holograms in day time. I tried everything including beam-stabilisers so that the lasers would stay locked on the diffraction pattern. So I started going in my lab after 10 PM ( so no people bugging me) and worked to hit the Bragg angle for difraction to get maximum efficiency. Took me a good part of 3 months to hit 76%. That was as much as could get out of it. The fragile general nature of the holograms and the
complexity involved in generating them with associated information loss ( lack of efficiency ), in my humble opinion, are two of the main reasons why people started to drift off holograms as a mode of information storage or exchange ( optical memory). The fundamental ideas are fantastic: realistic, 3-D and fast. It was just not practically feasible. BUT these days there are computer generated holograms as well. Some realistic work that area might actually give us a practical break through.

Teleportation:

Basically there are two communication protocols, which, as is known so far, can be implemented using quantum mechanics:
super-dense coding and quantum teleportaion. The basic idea behind Quantum Teleportation is the following: Let’s say Alice has particle 1 in a certain quantum state, a qubit A ( I am refraining from throwing in mathematical representations as that is not easy to do here) which has two orthogonal states { |0> and |1> } with complex amplitudes. She wishes to deliver this state to Bob but cannot do so directly ( let’s say). Now, according to the posptulates of QM ( quantum mecahnics) any measurement performed by Alice on her
particle will destroy the quantum state at hand without giving Bob all the necessary info required in order to reconstruct the quantum state. Then how do they communicate? The way around is to use an ancilliary pair of “ENTANGLED” particles, say, X and Y ( the EPR pair, Eisntein, Podolsky & Rosen, Physics Review, 1935, 47, 777-780), where Alice has particle X and Bob particle Y. The EPR pair is also knows as the Bell state. Such a state, for sake of intuitive experimentation, would have to be created ahead of time, when the qubits are in a lab together and can be made to interact in a way which will give rise to the entanglement between them. After the
state is created, Alice and Bob each take one of the two qubits away with them. Alternatively, a third party could create the EPR pair and give one particle to Alice and the other to Bob. If they are careful not to let them interact with the environment, or any other quantum system, Alice and Bob’s joint state will remain entangled. This entanglement becomes a resource which Alice and Bob can use to achieve protocols such as super-dense coding and teleporation.

For quantum teleportation, the scenario is that Alice wishes to communicate the state of a qubit to Bob. Suppose Alice only has a
classical channel linking her to Bob. To send the state of a qubit exactly, it would seem that Alice would either have to send the physical qubit itself, or she would have to communicate the two complex amplitudes with infinite precision. However, if Alice and Bob possess an entangled state this intuition is wrong, and a quantum state can be sent exactly over a classical channel. Teleportation is a protocol which allows Alice to communicate the state of a qubit exactly to Bob, sending only two bits of classical information to him.Technical implementation of many qubit systems has been, so far, a challenge especially the necessity to have a shared EPR pair for every qubit ( or electron, photon, nucleon) whose state is to be teleported. Single qubit states have been successfully teleported in more than one laboratory using optical and NMR techniques ( please see references 1 and 2).

THAT leads us to Quantum non-locality of EPR pairs which is so impressive and difficult to accept that it does appear to be on the verge of the mystical as it seems to demonstrate existence of superluminal effects, in other words, exchange of signalling at a speed faster than light . Efforts to clarify non-locality using the transactional interpretation of quantum mechanics ( EPR experiments), and the possibility of superluminal effects (e.g., faster-than-light communication) from nonlocality and non-linear quantum mechanics is still under investigation ( Prof. J. Cramer’s group at University of Washington for e.g.).

Excited atoms often produce two photons in a process called a “cascade” involving two successive quantum jumps. Because of angular momentum conservation, if the atom begins and ends with no net angular momentum, the two photons must have correlated polarizations. When such photons travel in opposite directions, angular momentum conservation requires that if one of the photons is measured to have some definite polarization state, the other photon is required by quantum mechanics to have exactly the same polarization state, no matter what measurement is made.Such correlated photon pairs are in an “entangled” quantum states.
Experimental tests of Bell’s theorem, i.e, the “EPR experiments”, usually use entangled photons from such an atomic cascade.

It just so happens that quantum mechanics and Bell’s Theorem make qualitatively different predictions about EPR measurements. In other words, the intrinsic nonlocality of quantum mechanics has been demonstrated by the experimental tests of Bell’s theorem. It has been experimentally demonstrated that nature arranges the correlations between the polarization of the two photons by some faster-than-light mechanism that violates Einstein’s intuitions about the intrinsic locality of all natural processes. What Einstein called “spooky actions at a distance” are an important part of the way nature works at the quantum level. Einstein’s faster-than-light spooks cannot be ignored.

Question: Can quantum nonlocality be used for faster-than-light or backward-in-time communication? Perhaps, for example, a message could be telegraphed from one measurement site of the EPR experiment to the other through a judicious choice of which measurement was performed. The simple answer to this question is “No!” Briefly, the quantum operators characterizing the separated measurements always commute, no matter which measurement is chosen, so non-local information transfer is impossible.

HOWEVER, this prohibition against superluminal communication, as stated above, is a part of standard quantum mechanics. This is broken if quantum mechanics is allowed to be slightly “non-linear”, a technical term meaning that when quantum waves are superimposed they may generate a small cross-term not present in the standard formalism. The onset of non-linear behavior is seen in other areas of physics, e.g. laser light in certain media, and, it is suggested by Nobel Laureate Steven Weinberg that this might also be
present but unnoticed in quantum mechanics. Weinberg’s non-linear QM subtly alters certain properties of the standard theory,
producing new physical effects that can be detected through precise measurements.

So, the answer to the query of “Theoretical Possibility” of teleportation (and Beam-me-up Scotty type transport) as it stands today would be an emphatical “YES”. Practically, it has not been proven to be so YET. But that does not mean quantum non-locality or entanglement cannot be faster than light in vacuum. It just means that we have, so far, been unable to prove it to be so.

A solid step towards a Quantum Internet has been taken by Prof. Seth Lloyd of MIT and Prof. Prem Kumar of NW University by establishing quantum logic gates by using “entangled” photons. Please see the link from MIT Tech Review and UoW. The rest should be history in the making

Links:
http://faculty.washington.edu/jcramer/NLS/NL_signal.htm

MIT Tech Review:

http://www.technologyreview.com/Infotech/20565/?a=f

References:

1) A. Galindo and M.A. Martin-Delgado: Infomration and Computation: Classical and Quantum Aspects, 74:347-423, 2002

2) Michael A. Nielsen and I. L. Chuang, Quantum Information and Communication. Cambridge University Press, 2001

In my very humble personal opinion, the work in stuff like quantum teleportation (QTP) and quantum non-locality is not really as far away as it seems, especially if the tech-sector biggies ( Cisco for example ) decide to invest in the research of the same. I think development in this area has suffered because most students of Physics lack a bridge to the real world of telecommunication and most
telecom engineers lack a thorough insight into Quantum Mecahnics and hence the inspiration to go ahead dissappears quickly. Many people who are interested in QTP hack “sh mpls tag-switching ip” for a living. At the end of a two week bsuiness trip or technical project, the code that we though of in C++ as the next step to Quantum Crptography stays unresolved. By the time we get up and start again, the next project is there and professional responsibility takes precedence. Like many things in life it is a difficult balance.

Since you quoted Albert Einstein in your blog about quantum mecahnics and also asked “WHERE are you in this journey of
impossibilities?”, I shall attempt to answer in terms of the MAN or rather The God ( Einstein of course!) and quantum mechanics: I am currently at rest and any particle which is REALLY at rest ( rest mass zero), i.e., if it knows that it has precisely Zero velocity - then according to the Uncertainty Principle, it should have NO IDEA whatsoever about where in the world it is resting ! 

Hence, I am truly lost at this particular instant

With RESPECTS

santanu

monique morrow Mar 13, 2009

Dear Santanu,

I thank you for your response and no apologies are required!
I touched on several subjects that you are passionate about and appreciate you feedback. 

To holograms, you do concur that even in computer generated holograms, that we may see interesting 3D collaborative possibilities moving forward.

As to teleportation, we could imagine phases in terms of its development and evolution—

And u are everywhere!

Thanks again and keep these comments coming!

Best always,

Monique

Santanu Ganguly Mar 13, 2009

Monique!

You are way too kind as always.

Yes, I do think that holograms may have a future in information storage and exchange in 3-D industry IF enough money is invested behind development of the technology. For example, retention of information in holographic media is often directly and heavily influenced by the immediate environment. We need to cross that barrier from the point of view of technical implementation. Often things like even a small clean-room facilty will involve money in terms of millions of dollars. This, in pure academic research environment, is a hefty blow on pocket. However, a healthy collaboration with industry will make that a far easily reached horizon.

I think ( probably stupidly and stubbornly so ) that the same philosophy applies to quantum information exchange. There is too little money in research in this field probably due to scepticism among other reasons. This is a science that, if successfully implemented, will break all known barriers of technology. But very little industrial interest is openly exhibited at present time. Physics of stuff like quantum cryptography offers not a quantum algorithm or a “quantum software” but a solution based on the quantum system themselves. Technology connected directly to mother nature…

Have a great weekend!:-)

Respects

santanu

monique morrow Mar 13, 2009

Santanu my friend -YOU have a super weekend—let’s chat about DNA computing next….

Best/Monique

Santanu Ganguly Apr 26, 2009

Hi Monique,

Take a look if you already have not seen it

http://www.musion.co.uk/Cisco_TelePresence.html

Respects

santanu

monique morrow Apr 27, 2009

Hi Santanu,

Indeed I have seen this and am very aware of the work!

It is sooo great that you are following this topic closely.

Thanks always for your comments!