Teleportation

TELEPORTATION SEMINAR REPORT, 2009

TELEPORTATIONA seminar report submitted in partial fulfillment of the requirements for the award

of B-Tech degree in

Electronics & Instrumentation Engineering

Of

Cochin University of Science and Technology, Kochi-22

By

LIJO VARGHESE

Under the guidance of

Mr. SHAMMY ARUN MATHEW

April 2009

DEPARTMENT OF ELECTRONICS & INSTRUMENTATION ENGINEERING

Thangal Kunju Musaliar Institute of Technology

DEPT. OF ELECTRONICS AND INSTRUMENTATION, TKMIT Page 1


Musaliar hills, Karuvelil P.O, Kollam-691505

DEPARTMENT OF ELECTRONICS & INSTRUMENTATION

ENGINEERING

Thangal Kunju Musaliar Institute of Technology

Musaliar hills, Karuvelil P.O, Kollam-691505

CERTIFICATE

This is to certify that the seminar report entitled

TELEPORTATION

Being submitted by

LIJO VARGHESE

For the award of the Degree of Bachelor of Technology in Electronics & Instrumentation Engineering of Cochin University of Science And Technology

is a bona fide account of the work carried out by him in this department during the academic year 2009 under our supervision.

Seminar Guide Seminar CoordinatorMr. SHAMMY ARUN MATHEW Mr.TOM GEORGE

Lecturer, EI Dept Lecturer, EI Dept

Mr. SARATH RAJ



Head of the Department, EI Dept

ACKNOWLEDGEMENT

First and foremost I concede the surviving presence and the flourishing refinement of

The Almighty God for his concealed hand yet substantial supervision all through the seminar.

I extend my sincere gratitude to Dr.M.C.Philipose, The Principal, TKM Institute of

Technology, for his countenance towards the successful accomplishment of my seminar.

I express my deep sense of gratitude to Mr. Sarath Raj, Head of the Department of

Electronics & Instrumentation Engineering, for his valuable advice.

I express my sincere gratitude to Mr. Shammy Arun Mathew, Lecturer, Department

of Electronics & Instrumentation Engineering, for his valuable suggestions, advice and

generous help and encouragement right from the point of selection of the topic, up to the

successful completion of it.

I also express my sincere thanks to my seminar Co-coordinator

Mr. Tom George, Lecturer, Department of Electronics & Instrumentation Engineering for

his guidance and support.

I sincerely thank all the staffs of the Electronics & Instrumentation Engineering

Department for providing their valuable guidance and support.

Above all I express my gratitude to my parents and friends who had gifted me the

necessary driving force and the boost to remain positive always with high spirits.



ABSTRACT

Teleportation is the name given by science fiction writers to the feat of making an

object or a person disintegrate in one place while a perfect replica appears some where else. A

teleportation machine would be like fax machine except that it would work on three dimensional

objects as well as documents, it would produce an exact copy rather than an approximate

facsimile, and it would destroy the original in the process of scanning it. What this means is that

time and space could be eliminated from travel – we could be transported to any location

instantly, without actually crossing a physical distance. Most of us were introduced to the idea of

teleportation, and other futuristic technologies, by the short-lived star Trek television series

(1966-69) based on tales written by Gene Roddenberry. Teleportation was not taken 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. In 1993, the idea of teleportation moved out of the realm of science fiction and

into the world of theoretical possibility. It was then that physicist Charles Bennett and a team of

researchers at IBM confirmed that quantum teleportation was possible, but only if the original

object being teleported was destroyed. Scientists found a way to make and end-run around this

logic, using a celebrated and paradoxical feature of quantum mechanics known as the Einstein-

Podolsky-Rosen effect.

Today, far from being a science fiction dream, teleportation happens routinely in

laboratories all around the world in the form of quantum teleportation. This is restricted at

present to tiny particles, such as individual photons, or to quantum properties of atoms; although

in January 2009 scientists announced that for the first time they had managed to teleport a single

ion of the element ytterbium. The future is promising that we can even teleport man. But the

question naturally arises as to whether it will ever be possible to teleport larger objects and even

human beings.



CONTENTS

1. Introduction…………………………………………………………………………..1

2. Mechanism of Quantum Teleportation…………………………………………….....3

3. Teleportation of Light………………………………………………………………..4

4. Quantum Entanglement(EPR Effect)………………………………………………...6

5. Generation of Entangled Photons…………………………………………………….9

6. Putting Entangled Photons to Work………………………………………………....10

6.1 Circumventing Heisenberg……………………………………………………..13

7. Quantum Teleportation……………………………………………………………...15

8. The INNSBRUCK Experiment……………………………………………………..18

8.1 Building a Teleporter………………………………………………………...…18

9. BELL State Measurements………………………………………………………….22

10. Photon Experiments…………………………………………………………………27

11. Future Possibilities of Teleportation………………………………………………...29

11.1 Human Teleportation…………………………………………………………..2911.2 Communication…………………………………………………………….…..3011.3 Quantum Cryptography………………………………………………………..3111.4 Quantum Computers…………………………………………………………...3211.5 Time Travel…………………………………………………………………….3311.6 Latest News in Teleportation…………………………………………………..34



12. Conclusion…………………………………………………………………………...35

References…………………………………………………………………………...36

1. INTRODUCTION

Teleportation involves dematerializing an object at one point and sending the details of

that object’s precise atomic configuration to another location, where it will be reconstructed. It is

the transfer of matter from one point to another, more or less instantaneously, either by

paranormal means or through technological means. Teleportation has been widely utilized in

works of science fiction.

The word was coined in 1931 by American writer Charles Fort to describe the strange

disappearances and appearances of anomalies, which he suggested may be connected. He joined

the Greek prefix tele- (meaning "distant") to the Latin verb portare (meaning "to carry"). Fort's

first formal use of the word was in the second chapter of his 1931 book, Lo! "Mostly in this book

I shall specialize upon indications that there exists a transportory force that I shall call

Teleportation." Though, with his typical half-serious jokiness, Fort added, "I shall be accused of

having assembled lies, yarns, hoaxes, and superstitions. To some degree I think so myself. To

some degree, I do not. I offer the data." Fort suggested that teleportation might explain various

allegedly paranormal phenomena, though, typically, it's sometimes difficult to tell if Fort took

his own "theory" seriously or instead used it to point out what he saw as the inadequacy of

mainstream science to account for strange phenomena.

One proposed means of teleportation is the transmission of data which is used to precisely

reconstruct an object or organism at its destination. However, it would be impossible to travel

from one point to another instantaneously; faster than light travel, as of today, is believed to be

impossible. The use of this form of teleportation as a means of transport for humans still has

considerable unresolved technical issues, such as recording the human body with sufficient

accuracy to allow reproduction elsewhere and whether destroying a human in one place and



recreating a copy elsewhere would provide a sufficient experience of continuity of existence.

Dimensional teleportation is another proposed means of teleportation. Often shown in

fictional works, particularly in fantasy and comic books, it involves the subject exiting one

physical universe or plane of existence, then re-entering it at a different location. This method is

rarely seriously considered by the scientific community, as the currently predominant theories

about parallel universes assume that physical travel is not possible between them.

A third proposed means of teleportation common in science fiction (and seen in The

Culture novels and The Terminator series of films) sends the subject through a wormhole or

similar phenomenon, allowing transit faster than light while avoiding the problems posed by the

uncertainty principle and potential signal interference. In both of the examples above, this form

of teleportation is known as "Displacement" or "Topological shortcut" (Scientific American)

which implies that this kind of teleportation may be similar in mechanism to time travel.

Displacement teleporters would eliminate many probable objections to teleportation on religious

or philosophical grounds, as they preserve the original subject intact — and thus continuity of

existence.

Far from being a science fiction dream, teleportation now happens routinely in laboratories

all around the world in the form of quantum teleportation. This is restricted at present to tiny

particles, such as individual photons, or to quantum properties of atoms; although in January

2009 scientists announced that for the first time they had managed to teleport a single ion of the

element ytterbium. The future is promising that we can even teleport a man.



2. MECHANISM OF QUANTUMTELEPORTATION

Before going into more detail about the teleportation experiments performed to date, let

us firstly get a better idea about what teleportation actually is. To begin with, a key part of this

process involves something getting from one place to another without it moving through any

places in between. For example, imagine that you can teleport from school to home. This means

that you are able to get home without having to walk, catch a bus or a train, ride your bike or

indeed use any other type of everyday transport. Instead, you are simply “beamed” there.

In science-fiction stories, teleportation often involves three things:

1. Firstly, a machine scans some object to find out everything about it. For example, this may

mean that some device scans a space explorer on board her spaceship to find out what she’s like.

This includes finding her height, her mass, the colour of her hair, what sort of shoes she is

wearing etc.

2. Next, the machine “disassembles” the space explorer and sends or “beams” all the things that

she’s made up of to some uncharted planet nearby. These include, for example, all the atoms in

her body. The machine also sends a message to the planet containing everything that it found out

about her.

3. Finally, we resemble the space explorer on the nearby planet using all the things she’s made

up of and the message.

Teleportation is now complete.



Though quantum teleportation involves many facets, entanglement is the magical

ingredient that is the key to its operation. Somehow, in a manner that we still have much to learn

about, it is entanglement that allows quantum teleportation to transmit a message directly from

Alice to Bob, whilst skipping all the places in between.

3. TELEPORTATION OF LIGHT

Fig. 3.1. Teleportation of light

The sender is known as Alice and receiver is known as Bob. In order to teleport light from Alice to Bob three steps have to be taken place.

1. The object has to be scanned to extract all data

2. This large quantity of information has to be sent by some means

3. Finally the object has to be reassembled based on data



The whole process seems to be very simple. But as we go deeper into the logistic details

it becomes very difficult to explain. Scanning means to record from each particle the quantity

that specifies the properties of an object. Two such properties are position and momentum. So

the first step is to measure these two canonically conjugate properties.

Heisenberg in his uncertainty paper proved that both position and momentum of a particle

cannot be known simultaneously with any degree of certainty. This principle has been proved by

many experiments. When we attempt to find out the position its momentum may change and vice

versa, so scientists at first thought that teleportation would be impossible.

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 ultimately leading to a “quantum

internet”), and making it much easier to build a working quantum computer. 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 sound 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. In brief, they found a way to scan out part of the information from an object, which one

wishes to teleport, while causing the remaining, unscanned, part of the information to pass, via

the Einstein-Podolsky-Rosen-Effect.

4. QUANTUM ENTANGLEMENT (EPR EFFECT)

Suppose a friend who likes to dabble in physics and party tricks has brought you a

collection of pairs of dice. He lets you roll them once, one pair at a time. You handle the first

pair gingerly, and then finally, you roll the two dice and get double 3. You roll the next pair,

double 6. The next: double 1. They always match.

The dice in this fable are behaving as if they were quantum entangled particles. Each die

on its own is random and fair, but its entangled partner somehow always gives the correct

matching outcome. Such behavior has been demonstrated and intensively studied with real

entangled particles. In typical experiments, pairs of atoms, ions or photons stand in for the dice,

and properties such as polarization stand in for the different faces of a die.

Consider the case of two photons whose polarizations are entangled to be random but

identical. Beams of light and even individual photons consist of oscillations of electromagnetic

fields, and polarization refers to the alignment of the electric field oscillations [see illustration on

next page]. Suppose that Alice has one of the entangled photons and Bob has its partner. When

Alice measures her photon to see if it is horizontally or vertically polarized, each outcome has a

50 percent chance. Bob’s photon has the same probabilities, but the entanglement ensures that he

will get exactly the same result as Alice. As soon as Alice gets the result “horizontal,” say, she

knows that Bob’s photon will also be horizontally polarized. Before Alice’s measurement the

two photons do not have individual polarizations; the entangled state specifies only that a

measurement will find that the two polarizations are equal.



An amazing aspect of this process is that it doesn’t matter if Alice and Bob are far away

from each other; the process works so long as their photons’ entanglement has been preserved.

Even if Alice is on Alpha Centauri and Bob on Earth, their results will agree when they compare

them. In every case, it is as if Bob’s photon is magically influenced by Alice’s distant

measurement, and vice versa.

Fig.4.1 Polarization of light

It might be wonder if we can explain the entanglement by imagining that each particle

carries within it some recorded instructions. Perhaps when we entangle the two particles, we

synchronize some hidden mechanism within them that determines what results they will give

when they are measured. This would explain away the mysterious effect of Alice’s measurement

on Bob’s particle. In the 1960s, however, Irish physicist John Bell proved a theorem that in

certain situations any such “hidden variables” explanation of quantum entanglement would have

to produce results different from those predicted by standard quantum mechanics. Experiments

have confirmed the predictions of quantum mechanics to a very high accuracy.



Austrian physicist Erwin Schrödinger, one of the co‐inventors of quantum mechanics,

called entanglement “the essential feature” of quantum physics. Entanglement is often called the

EPR effect and the particles EPR pairs, after Einstein, Boris Podolsky and Nathan Rosen, who in

1935 analyzed the effects of entanglement acting across large distances. Einstein talked of it as

“spooky action at a distance.” If one tried to explain the results in terms of signals traveling

between the photons, the signals would have to travel faster than the speed of light. Naturally,

many people have wondered if this effect could be used to transmit information faster than the

speed of light.

Unfortunately, the quantum rules make that impossible. Each local measurement on a

photon, considered in isolation, produces a completely random result and so can carry no

information from the distant location. It tells you nothing more than what the distant

measurement result probabilities would be, depending on what was measured there.

Nevertheless, we can put entanglement to work in an ingenious way to achieve quantum

teleportation.



5. GENERATION OF ENTANGLED PHOTONS



Fig.5.1. Pair of Entangled Photons

6. Putting Entangles Photons to Work

Alice and Bob anticipate that they will want to teleport a photon in the future. In

preparation, they share an entangled auxiliary pair of photons, Alice taking photon A and Bob

photon B. Instead of measuring them, they each store their photon without disturbing the delicate

entangled state.

In due course, Alice has a third photon—calls it photon X—that she wants to teleport to

Bob. She does not know what photon X’s state is, but she wants Bob to have a photon with that



same polarization. She cannot simply measure the photon’s polarization and send Bob the result.

In general, her measurement result would not be identical to the photon’s original state. This is

Heisenberg’s uncertainty principle at work.

Instead, to teleport photon X, Alice measures it jointly with photon A, without determining

their individual polarizations. She might find, for instance, that their polarizations are

“perpendicular” to each other (she still does not know the absolute polarization of either one,

however). Technically, the joint measurement of photon A and photon X is called a Bell‐state

measurement. Alice’s measurement produces a subtle effect: it changes Bob’s photon to

correlate with a combination of her measurement result and the state that photon X originally

had. In fact, Bob’s photon now carries her photon X’s state, either exactly or modified in a

simple way.

To complete the teleportation, Alice must send a message to Bob—one that travels by

conventional means, such as a telephone call or a note on a scrap of paper. After he receives this

message, if necessary Bob can transform his photon B, with the end result that it becomes an

exact replica of the original photon X. Which transformation Bob must apply depends on the

outcome of Alice’s measurement. There are four possibilities, corresponding to four quantum

relations between her photons A and X. A typical transformation that Bob must apply to his

photon is to alter its polarization by 90 degrees, which he can do by sending it through a crystal

with the appropriate optical properties.

Which of the four possible results Alice obtains is completely random and independent of

photon X’s original state. Bob therefore does not know how to process his photon until he learns

the result of Alice’s measurement. One can say that Bob’s photon instantaneously contains all

the information from Alice’s original, transported there by quantum mechanics. Yet to know

how to read that information, Bob must wait for the classical information, consisting of two bits

that can travel no faster than the speed of light.



Skeptics might complain that the only thing teleported is the photon’s polarization state or,

more generally, its quantum state, not the photon “itself.” But because a photon’s quantum state

is its defining characteristic, teleporting its state is completely equivalent to teleporting the

particle.

.

Fig.6.1. Ideal Quantum Teleportation

Note that quantum teleportation does not result in two copies of photon X. Classical

information can be copied any number of times, but perfect copying of quantum information is



impossible, a result known as the no‐cloning theorem, which was proved by Wootters and

Wojciech H. Zurek of Los Alamos National Laboratory in 1982. (If we could clone a quantum

state, we could use the clones to violate Heisenberg’s principle.) Alice’s measurement actually

entangles her photon A with photon X, and photon X loses all memory, one might say, of its

original state. As a member of an entangled pair, it has no individual polarization state. Thus, the

original state of photon X disappears from Alice’s domain.

6.1 Circumventing Heisenberg

Furthermore photon X’s state has been transferred to Bob with neither Alice nor Bob

learning anything about what the state is. Alice’s measurement result, being entirely random,

tells them nothing about the state. This is how the process circumvents Heisenberg’s principle,

which stops us from determining the complete quantum state of a particle but does not preclude

teleporting the complete state so long as we do not try to see what the state is!

Also, the teleported quantum information does not travel materially from Alice to Bob. All

that travels materially is the message about Alice’s measurement result, which tells Bob how to

process his photon but carries no information about photon X’s state itself.

In one out of four cases, Alice is lucky with her measurement, and Bob’s photon

immediately becomes an identical replica of Alice’s original. It might seem as if information has

traveled instantly from Alice to Bob, beating Einstein’s speed limit. Yet this strange feature

cannot be used to send information, because Bob has no way of knowing that his photon is

already an identical replica. Only when he learns the result of Alice’s Bell‐state measurement,

transmitted to him via classical means, can he exploit the information in the teleported quantum

state.

Suppose he tries to guess in which cases teleportation was instantly successful. He will be

wrong 75 percent of the time, and he will not know which guesses were correct. If he uses the



photons based on such guesses, the results will be the same as if he had taken a beam of photons

with random polarizations. In this way, Einstein’s relativity prevails; even the spooky

instantaneous action at a distance of quantum mechanics fails to send usable information faster

than the speed of light.

It would seem that the theoretical proposal described above laid out a clear blueprint for

building a teleporter; on the contrary, it presented a great experimental challenge. Producing

entangled pairs of photons has become routine in physics experiments in the past decade, but

carrying out a Bell‐state measurement on two independent photons had never been done before.



7. QUANTUM TELEPORTATION

Scientists found a way to scan out part of the information from an object A, which

one wishes to teleport, while causing the remaining, unscanned, part of the information to pass,

via the Einstein- Podolsky-Rosen effect, into another object C which has never been in contact

with A. Later, by applying to C a treatment depending on the scanned-out information, it is

possible to maneuver C into exactly the same state as A was in before it was scanned. A itself is

no longer in that state, having been thoroughly disrupted by the scanning, so what has been

achieved is teleportation.



Fig.7.1. Quantum Teleportation

As the figures suggests, the unscanned part of the information is conveyed from A to C by an

intermediary object B, which interacts first with C and then with A. in order to convey

something from A to C, the delivery vehicle must visit A before C, not the other way around. But

there is a subtle, unscannable kind of information that, unlike any material cargo, and even

unlike ordinary information, can indeed be delivered in such a backward fashion. This subtle

kind of information, also called “Einstein-Podolsky-Rosen (EPR) correlation” or

“entanglement”, has been at least partly understood since the 1930s when it was discussed in a

famous paper by Albert Einstein, Bories Podolsky, and Nathan Rosen.

In the 1960s John Bell showed that a pair of entangled particles, which were once in contact

but later move too far apart to interact directly, can exhibit individually random behavior that is

too strongly correlated to be explained by classical statistics. Experiments on photons and other

particles have repeatedly confirmed these correlations, thereby providing strong evidence for the

validity of quantum mechanics, which neatly explains them. Another well-known fact about EPR

correlations is that they cannot by themselves deliver a meaningful and controllable message. It

was thought that their only usefulness was in proving the validity of quantum mechanics. But

now it is known that, through the part of the information in an object which is too delicate to be

scanned out and delivered by conventional methods.



Fig.7.2.Fascimile Transmission

Figure compares conventional facsimile transmission with quantum teleportation. In

conventional facsimile transmission the original is scanned, extracting partial information about

it, but remains more or less intact after the scanning process. The scanned information is sent to

the receiving station, where it is imprinted on some raw material (e.g. Paper) to produce an

approximate copy of the original. By contrast, in quantum teleportation, two objects B and C are

first brought into contact and then separated. Object B is taken to the sending station, while

object C is taken to the receiving station. At the sending station object B is scanned together with

the original object A which one wishes to teleport, yielding some information and totally

disrupting the state of A and B. the scanned information is sent to the receiving station, where it

is used to select one of several treatments to be applied to object C thereby putting C into an

exact replica of the former state of A.



8. THE INNSBRUCK EXPERIMENT

8.1 Building a Teleporter

A powerful way to produce entangled pairs of photons is spontaneous parametric down

conversion: a single photon passing through a special crystal sometimes generates two new

photons that are entangled so that they will show opposite polarization when measured.

A much more difficult problem is to entangle two independent photons that already exist,

as must occur during the operation of a Bell‐state analyzer. This means that the two photons (A

and X) somehow have to lose their private features. In 1997 a group of scientists at the

University of Innsbruck, applied a solution to this problem in their teleportation experiment.

In their experiment, a brief pulse of ultraviolet light from a laser passes through a crystal

and creates the entangled photons A and B. One travels to Alice, and the other goes to Bob. A

mirror reflects the ultraviolet pulse back through the crystal again, where it may create another

pair of photons, C and D. (These will also be entangled, but we don’t use their entanglement.)

Photon C goes to a detector, which alerts us that its partner D is available to is available to be

teleported. Photon D passes through a polarizer, which we can orient in any conceivable way.

The resulting polarized photon is our photon X, the one to be teleported, and travels on to Alice.

Once it passes through the polarizer, X is an independent photon, no longer entangled. And

although we know its polarization because of how we set the polarizer, Alice does not. We reuse

the same ultraviolet pulse in this way to ensure that Alice has photons A and X at the same time.



Fig.8.1. INNSBRUCK Experiment

Now we arrive at the problem of performing the Bell‐state measurement. To do this, Alice

combines her two photons (A and X) using a semi reflecting mirror, a device that reflects half of

the incident light. An individual photon has a 50–50 chance of passing through or being

reflected. In quantum terms, the photon goes into a superposition of these two possibilities.



Fig.8.2. Beam Splitter

Now suppose that two photons strike the mirror from opposite sides, with their paths

aligned so that the reflected path of one photon lies along the transmitted path of the other, and

vice versa. A detector waits at the end of each path. Ordinarily the two photons would be

reflected independently, and there would be a 50 percent chance of them arriving in separate

detectors. If the photons are indistinguishable and arrive at the mirror at the same instant,

however, quantum interference takes place: some possibilities cancel out and do not occur,

whereas others reinforce and occur more often. When the photons interfere, they have only a 25

percent likelihood of ending up in separate detectors. Furthermore, when that occurs it

corresponds to detecting one of the four possible Bell states of the two photons—the case that we

called “lucky” earlier. The other 75 percent of the time the two photons both end up in one

detector, which corresponds to the other three Bell states but does not discriminate among them.



When Alice simultaneously detects one photon in each detector, Bob’s photon instantly

becomes a replica of Alice’s original photon X. We verified that this teleportation occurred by

showing that Bob’s photon had the polarization that we imposed on photon X. The experiment

was not perfect, but the correct polarization was detected 80 percent of the time (random photons

would achieve 50 percent). We demonstrated the procedure with a variety of polarizations:

vertical, horizontal, linear at 45 degrees and even a nonlinear kind of polarization called circular

polarization.

The most difficult aspect of the Bell state analyzer is making photons A and X

indistinguishable. Even the timing of when the photons arrive could be used to identify which

photon is which, so it is important to “erase” the time information carried by the particles. In the

experiment, team used a clever trick first suggested by Marek Zukowski of the University of

Gdansk: they sent the photons through very narrow bandwidth wavelength filters. This process

makes the wavelength of the photons very precise, and by Heisenberg’s uncertainty relation it

smears out the photons in time.

A mind‐boggling case arises when the teleported photon was itself entangled with another

and thus did not have its own individual polarization. In 1998 my Innsbruck group demonstrated

this scenario by giving Alice photon D without polarizing it, so that it was still entangled with

photon C. We showed that when the teleportation succeeded, Bob’s photon B ended up

entangled with C. Thus, the entanglement with C had been transmitted from A to B.



9. BELL STATE MEASUREMENTS

Here we shall prepare pairs of entangled photons with opposite polarizations; we shall call

them E1 and E2. The entanglement means that if we measure a beam of, say, E1 photons with a

polarizer, one‐half of the incident photons will pass the filter, regardless of the orientation of the

polarizer. Whether a particular photon will pass the filter is random. However, if we measure its

companion E2 photon with a polarizer oriented at 90 degrees relative to the first, then if E1

passes its filter E2 will also pass its filter. Similarly if E1 does not pass its filter its companion E2

will not.

We had half‐silvered mirrors, which reflect one‐half of the light incidents on them and

transmit the other half without reflection. These mirrors are sometimes called beam splitters

because they split a light beam into two equal parts.

We shall use a half‐silvered mirror to perform Bell State Measurements. The name is after

the originator of Bell's Theorem.

We direct one of the entangled photons, say E1, to the beam splitter.

Meanwhile, we prepare another photon with a polarization of 45degrees, and direct it to

the same beam splitter from the other side, as shown. This is the photon whose properties will be

transported; we label it K. We time it so that both E1 and K reach the beam splitter at the same

time.



Fig.9.1. One of the entangled photon along with a photon K is directed to the beam splitter.

The E1 photon incident from above will be reflected by the beam splitter some of the time and

will be transmitted some of the time. Similarly for the K photon that is incident from below. So

sometimes both photons will end up going up and to the right as shown.

Similarly, sometimes both photons will end up going down and to the right.

Fig.9.2. both photons going up and to the right

But sometimes one photon will end up going upwards and the other will be going

downwards, as shown. This will occur when either both photons have been reflected or both

photons have been transmitted.



Thus there are three possible arrangements for the photons from the beam splitter: both

upwards, both downwards, or one upwards and one downwards.

Which of these three possibilities has occurred can be determined if we put detectors in

the paths of the photons after they have left the beam splitter.

However, in the case of one photon going upwards and the other going downwards, we

cannot tell which is which. Perhaps both photons were reflected by the beam splitter, but perhaps

both were transmitted.

This means that the two photons have become entangled.

If we have a large beam of identically prepared photon pairs incident on the beam splitter,

the case of one photon ending up going upwards and the other downwards occurs, perhaps

surprisingly, 25% of the time.

Also somewhat surprisingly, for a single pair of photons incident on the beam splitter, the

photon E1 has now collapsed into a state where its polarization is ‐45 degree, the opposite

polarization of the prepared 45 degree one. This is because the photons have become entangled.

So although we don't know which photon is which, we know the polarizations of both of them.

The explanation of these two somewhat surprising results is beyond the level of this

discussion, but can be explained by the phase shifts the light experiences when reflected, the

mixture of polarization states of E1, and the consequent interference between the two photons.



Fig.9.3. one photon going up and the other down

Now we shall think about the E2 companion to E1.

25 percent of the time, the Bell‐state measurement resulted in the circumstance shown, and

in these cases we have collapsed the state of the E1 photon into a state where its polarization is ‐

45 degree.

But since the two photon system E1 and E2 was prepared with opposite polarizations, this

means that the companion to E1, E2, now has a polarization of +45degree. Thus the state of the

K photon has now been transferred to the E2 photon. We have teleported the information about

the K photon to E2.

Although this collapse of E2 into a 45 degree polarization state occurs instantaneously, we

haven't achieved teleportation until we communicate that the Bell‐state measurement has yielded

the result shown. Thus the teleportation does not occur instantaneously.

Note that the teleportation has destroyed the state of the original K photon.



Quantum entanglements such as that exist between E1 and E2 in principle are independent

of how far apart the two photons become. This has been experimentally verified for distances as

large as 10km. Thus, the Quantum Teleportation is similarly independent of the distance.

Fig.9.4. Teleportation of information from K to E2.

The Original State of the Teleported Photon Must Be Destroyed.

Above we saw that the K photon's state was destroyed when the E2 photon acquired it.

Consider for a moment that this was not the case, so we end up with two photons with identical

polarization states. Then we could measure the polarization of one of the photons at, say,

45degree and the other photon at 22.5degree. Then we would know the polarization state of both

photons for both of those angles.

As we saw in our discussion of Bell’s Theorem, the Heisenberg Uncertainty Principle

says that this is impossible: we can never know the polarization of photon for these two angles.

Thus any teleporter must destroy the state of the object being teleported.



10. PHOTON EXPERIMENTS

In 1998, physicists at the California Institute of Technology (Caltech), along with two

European groups, turned the IBM ideas into reality by successfully teleporting a photon, a

particle of energy that carries light. The Caltech group was able to read the atomic structure of a

photon, send this information across 1 meter (3.28 feet) of coaxial cable and create a replica of

the photon. As predicted, the original photon no longer existed once the replica was made.

In performing the experiment, the Caltech group was able to get around the Heisenberg

Uncertainty Principle, the main barrier for teleportation of objects larger than a photon. This

principle states that you cannot simultaneously know the location and the speed of a particle. But

if you can't know the position of a particle, then how can you teleport it? In order to teleport a

photon without violating the Heisenberg Principle, the Caltech physicists used a phenomenon

known as entanglement. In entanglement, at least three photons are needed to achieve quantum

teleportation:

• Photon A: The photon to be teleported

• Photon B: The transporting photon

• Photon C: The photon that is entangled with photon B

If researchers tried to look too closely at photon A without entanglement, they would

bump it, and thereby change it. By entangling photons B and C, researchers can extract some

information about photon A, and the remaining information would be passed on to B by way of

entanglement, and then on to photon C. When researchers apply the information from photon A



to photon C, they can create an exact replica of photon A. However, photon A no longer exists as

it did before the information was sent to photon C.

In other words, when Captain Kirk beams down to an alien planet, an analysis of his

atomic structure is passed through the transporter room to his desired location, where a replica of

Kirk is created and the original is destroyed.

A more recent teleportation success was achieved at the Australian National University,

when researchers successfully teleported a laser beam.

While the idea of creating replicas of objects and destroying the originals doesn't sound

too inviting for humans, quantum teleportation does hold promise for quantum computing. These

experiments with photons are important in developing networks that can distribute quantum

information. Professor Samuel Braunstein, of the University of Wales, Bangor, called such a

network a "quantum Internet." This technology may be used one day to build a quantum

computer that has data transmission rates many times faster than today's most powerful

computers.



11. FUTURE POSSIBILITIES OF TELEPORTATION

11.1 HUMAN TELEPORTATION

The man is standing on a platform called transporter and he is beamed up part by part and

teleported accordingly. The human body consists of 1028 atoms. So we have to teleport these

atoms with exact precision. A duplicate of the person would be made at the other end. Original

mind and body no longer exists, their atomic structure would be recreated at the other end. But

there are some limitations.

1. By reconstruction we may obtain the body, but can be a dead body.

2. Since a large quantity of information has to be teleported, it will take years to teleport a man.

3. Large quantity of light is involved there is a chance of genetic variation.



11.2 COMMUNICATION

Teleportation has many promising possibilities in the field of Communication

1. If teleportation be possible it becomes the fastest means of Communication.

2. Tremendous amount of chemicals are now shipped from one location to another, reactants

mixed at one location, sent to another to be used. Since each is a molecule we can teleport

chemicals, saving time and space.

3. Just as online shopping offers the opportunity to avoid shops. Teleportation provides instant

store free purchase.

4. This teleportation can be used in military purpose for data Encryption.

5. Space exploration can be enhanced. We can teleport machinery to space shuttles or space

colonies. Fuels for space stations can also be teleported.

6. Colonizing in mars is not possible today due to the lack of fresh water, if we can teleport water

directly from earth colonizing in mars is possible.

7. It can be used in war fare. Missiles and bombs can instantly be placed in enemy locations.

This can be done by setting a teleporting device at the enemy lines.



11.3 QUANTUM CRYPTOGRAPHY

Quantum cryptography is an effort to allow two users of a common communication

channel to create a body of shared and secret information. This information, which generally

takes the form of a random string of bits, can then be used as a conventional secret key for secure

communication. It is useful to assume that the communicating parties initially share a small

amount of secret information, which is used up and then \renewed in the exchange process, but

even without this assumption exchanges are possible. Purpose of cryptography is to transmit

information in such a way that access to it is restricted entirely to the intended recipient, even if

the transmission itself is received by others. Cryptography operates by a sender scrambling or

encrypting the original message or plain text in a systematic way that obtains its meaning. The

encrypted message of crypto text is transmitted, and the receiver recovers the message by

unscrambling or decrypting the transmission.

Quantum cryptographic techniques provide no protection against the classic bucket

brigade attack (also known as the “man-in-the middle attack”). In this scheme, an eavesdropper,

E (“Eve”) is assumed to have the capacity to monitor the communications channel and insert and

remove messages without inaccuracy or delay. When Alice attempts to establish a secret key

with Bob, Eve intercepts and responds to messages in both directions, fooling both Alice and

Bob into believing she is the other. Once the keys are established, Eve receives, copies, and

resends messages so as to allow Alice and Bob to communicate.



11.4 QUANTUM COMPUTERS

The basic data unit in a conventional (or classical) computer is the bit, or binary

digit .A bit stores a numerical value of either 0 or 1. An example of how bits are stored is given

by a CD rom: “pits” and “lands” (absence of a pit) are used to store the binary data. In quantum

computing, the byte is replaced by a single talk to you about the ‘Mona Lisa’, by just hearing the

name, you know what the picture looks like without having been given the enormous string of 1s

and 0s that the element called a qubit. A qubit is in effect a single entity rather like a

conventional computer’s bit, but actually it is a combination of many quantum states of atomic or

sub atomic particles. In a single qubit it is possible to carry lot of zeros and ones all together but

in a single quantum bit imagine a picture of Mona Lisa is stored in the computer as millions of

bits. However, if somebody computer needs to redraw it. In the same way, in a quantum

computer, the qubit is the equivalent of the name

‘Mona Lisa’.

Consequently, quantum computers have the potential ability to carry and process large

amounts of information in parallel and at very high speeds. It is for this reason that it is believed

that they could be useful in dealing with the most computationally intense tasks, such as code

breaking.

The key problem facing quantum computer developers is the one of finding a suitable

quantum register, which cannot only be set-up with the correct input data but can be manipulated

with quantum operations.



11.5 TIME TRAVEL

The concept of time travel can be explained based on some assumptions. We see an

object when light rays from that object reaches our eyes. The light rays from the sun take 8

minutes to reach the earth. So we are seeing the sun in the past. We see stars shining in the sky, it

may have died years before but we still see it because light rays takes a long time to reach the

earth.

Assume that time at point c is same as that of the earth. Consider a boy at the age of 10 is

standing on earth, the light rays from the star reaches the boy and is reflected from the boy to c.

at that point of reflection from the boy, the boy is traveling towards c with a speed greater than

the velocity of light, he reaches the point c at an approximate age of 15 and wait there. When the

reflected ray reaches his eyes he can see his image at the age of 10. He is seeing his past.



11.6 LATEST NEWS IN TELEPORTATION…

It was reported in the Jan.4,2010 edition of MALAYALA MANORAMA, one of the

leading daily news paper that for the first time, scientists have successfully teleported

information between two separate atoms in unconnected enclosures a meter apart – a significant

milestone in the global quest for practical quantum teleportation.

A team from the Joint Quantum Institute (JQI) at the University Of Maryland (UMD) and

the University of Michigan has succeeded in teleporting a quantum state directly from one atom

(Ytterbium) to another over a substantial distance. That capability is necessary for workable

quantum information systems because they will require memory storage at both the sending and

receiving ends of the transmission. In the Jan. 23 issue of the journal Science, the scientists

report that, by using their protocol, atom-to-atom teleported information can be recovered with

perfect accuracy about 90% of the time – and that figure can be improved.

“Our system has the potential to form the basis for a large-scale ‘quantum repeater’ that

can network quantum memories over vast distances,” says group leader Christopher Monroe of

JQI and UMD. “Moreover, our methods can be used in conjunction with quantum bit operations

to create a key component needed for quantum computation.” A quantum computer could

perform certain tasks, such as encryption-related calculations and searches of giant databases,

considerably faster than conventional machines. The effort to devise a working model is a matter

of intense interest worldwide…



12. CONCLUSION

Quantum teleportation is a direct descendant of the scenarios debated by

Einstein and Bohr. When we analyze the experiment, we would run into all kinds of problems if

we asked ourselves what the properties of the individual particles really are when they are

entangled. We have to analyze carefully what it means to “have” a polarization. We cannot

escape the conclusion that all we can talk about are certain experimental results obtained by

measurements. In the polarization measurement, a click of the detector lets us construct a picture

in our mind in which the photon actually “had” a certain polarization at the time of measurement.

Yet we must always remember that this is just a made‐up story. It is valid only if we talk about

that specific experiment, and we should be cautious in using it in other situations.

The future of teleportation is as varied as the past that led to its creation. Society’s

fascination with teleportation gives the drive for further research strong ensuring teleportation as

an integral part of society’s progress… Science, however, can only go as far as society will

allow, making ethical dilemmas a key issue in the potential uses of teleportation. Although the

advancement of teleportation is irrefutable, the route of such research is unknown and offers an

unpredictable and exciting future. So we can hope the best.



REFERENCES

1. Quantum entanglement – “Quantum Mechanics” by Maxwell.

2. Nature Magazine

3. New Scientist Magazine

4. IBM Research papers

5. www.ibmresearchpapers.com

6. www.newscientist.com

7. www.nature.com

8. www.qubit.org

9. www.umd.edu


http://www.qubit.org/

http://www.nature.com/

http://www.newscientist.com/

http://www.ibmresearchpapers.com/

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Teleportation

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