Science of the Impossible, "Teleportation" (Class 1 Impossibility)

           
Science of the Impossible, "Teleportation" (Class 1 Impossibility)

by : Aria Ratmandanu

             Teleportation, or the ability to transport a person or object instantly from one place to another, is a technology that could change the course of civilization and alter the destiny of nations. It could irrevocably alter the rules of warfare: armies could teleport troops behind enemy lines or simply teleport the enemy’s leadership and capture them. Today’s transportation system—from cars and ships to airplanes and railroads, and all the many industries that service these systems—would become obsolete; we could simply teleport ourselves to work and our goods to market. Vacations would become effortless, as we teleport ourselves to our destination. Teleportation would change everything.

                The earliest mention of teleportation in science fiction occurred in Edward Page Mitchell’s story “The Man Without a Body,” published in 1877. In that story a scientist was able to disassemble the atoms of a cat and transmit them over a telegraph wire. Unfortunately the battery died while the scientist was trying to teleport himself. Only his head was successfully teleported.

                Sir Arthur Conan Doyle, best known for his Sherlock Holmes novels, was fascinated by the notion of teleportation. After years of writing detective novels and short stories he began to tire of the Sherlock Holmes series and eventually killed off his sleuth, having him plunge to his death with Professor Moriarty over a waterfall. But the public outcry was so great that Doyle was forced to resurrect the detective. Because he couldn’t kill off Sherlock Holmes, Doyle instead decided to create an entirely new series, featuring Professor Challenger, who was the counterpart of Sherlock Holmes. Both had a quick wit and a sharp eye for solving mysteries. But while Mr. Holmes used cold, deductive logic to break open complex cases, Professor Challenger explored the dark world of spirituality and paranormal phenomena, including teleportation. In the 1927 novel The “Disintegration Machine, the professor encountered a gentleman who had invented a machine that could disintegrate a person and then reassemble him somewhere else. But Professor Challenger is horrified when the inventor boasts that his invention could, in the wrong hands, disintegrate entire cities with millions of people with a push of a button. Professor Challenger then uses the machine to disintegrate the inventor, and leaves the laboratory, without reassembling him.”

The EPR Experiment

          The key to quantum teleportation lies in a celebrated 1935 paper by Albert Einstein and his colleagues Boris Podolsky and Nathan Rosen, who, ironically, proposed the EPR experiment (named for the three authors) to kill off, once and for all, the introduction of probability into physics. (Bemoaning the undeniable experimental successes of the quantum theory, Einstein wrote, “the more success the quantum theory has, the sillier it looks.

           If two electrons are initially vibrating in unison (a state called coherence) they can remain in wavelike synchronization even if they are separated by a large distance. Although the two electrons may be separated by light-years, there is still an invisible Schrödinger wave connecting both of them, like an umbilical cord. If something happens to one electron, then some of that information is immediately transmitted to the other. This is called “quantum entanglement,” the concept that particles vibrating in coherence have some kind of deep connection linking them together.”

           Let’s start with two coherent electrons oscillating in unison. Next, let them go flying out in opposite directions. Each electron is like a spinning top. The spins of each electron can be pointed up or down. Let’s say that the total spin of the system is zero, so that if the spin of one electron is up, then you know automatically that the spin of the other electron is down. According to the quantum theory, before you make a measurement, the electron is spinning neither up nor down but exists in a nether state where it is spinning both up and down simultaneously. ”

             Once you make an observation, the wave function “collapses,” leaving a particle in a definite state. Next, measure the spin of one electron. It is, say, spinning up. Then you know instantly that the spin of the other electron is down. Even if the electrons are separated by many light-years, you instantly know the spin of the second electron as soon as you measure the spin of the first electron. In fact, you know this faster than the speed of light! Because these two electrons are “entangled,” that is, their wave functions beat in unison, their wave functions are connected by an invisible “thread” or umbilical cord. Whatever happens to one automatically has an effect on the other. (This means, in some sense, that what happens to us automatically affects things instantaneously in distant corners of the universe, since our wave functions were probably entangled at the beginning of time. In some sense there is a web of entanglement that connects distant corners of the universe, including us.) Einstein derisively called this “spooky-action-at-distance,” and this phenomenon enabled him to “prove” that the quantum theory was wrong, in his mind, since nothing can travel faster than “the speed of light.

           Originally, Einstein designed the EPR experiment to serve as the death knell of the quantum theory. But in the 1980s Alan Aspect and his colleagues in France performed this experiment with two detectors separated by 13 meters, measuring the spins of photons emitted from calcium atoms, and the results agreed precisely with the quantum theory. ”

        Knowing that an electron on the other side of the universe is spinning down is useless information. You cannot send today’s stock quotations via this method. For example, let’s say that a friend always wears one red and one green sock, in random order. Let’s say you examine one leg, and the leg has a red sock on it. Then you know, faster than the speed of light, that the other sock is green. Information actually traveled faster than light, but this information is useless. No signal containing nonrandom information can be sent via this method.”

Quantum Teleportation

             Everything changed in 1993, when scientists at IBM, led by Charles Bennett, showed that it was physically possible to teleport objects, at least at the atomic level, using the EPR experiment. (More precisely, they showed that you could teleport all the information contained within a particle.) Since then physicists have been able to teleport photons and even entire cesium atoms. Within a few decades scientists may be able to teleport the first DNA molecule and virus.

             Quantum teleportation exploits some of the more bizarre properties of the EPR experiment. In these teleportation experiments physicists start with two atoms, A and C. Let’s say we wish to teleport information from atom A to atom C. We begin by introducing a third atom, B, which starts out being entangled with C, so B and C are coherent. Now atom A comes in contact with atom B. A scans B, so that the information content of atom A is transferred to atom B. A and B become entangled in the process. But since B and C were originally entangled, the information within A has now been transferred to atom C. In conclusion, atom A has now been teleported into atom C, that “is, the information content of A is now identical to that of C.

              Notice that the information within atom A has been destroyed (so we don’t have two copies after the teleportation). This means that anyone being hypothetically teleported would die in the process. But the information content of his body would appear elsewhere. Notice also that atom A did not move to the position of atom C. On the contrary, it is the information within A (e.g., its spin and polarization) that has been transferred to C. (This does not mean that atom A was dissolved and then zapped to another location. It means that the information content of atom A has been transferred to another atom, C.

             Since the original announcement of this breakthrough, progress has been fiercely competitive as different groups have attempted to outrace each other. The first historic demonstration of quantum teleportation in which photons of ultraviolet light were teleported occurred in 1997 at the University of Innsbruck. This was followed the next year by experimenters at Cal Tech who did an even more precise experiment involving teleporting photons.

          In 2004 physicists at the University of Vienna were able to teleport particles of light over a distance of 600 meters beneath the River Danube, “using a fiber-optic cable, setting a new record. (The cable itself was 800 meters long and was strung underneath the public sewer system beneath the River Danube. The sender stood on one side of the river, and the receiver was on the other.

           One criticism of these experiments is that they were conducted with photons of light. This is hardly the stuff of science fiction. It was significant, therefore, in 2004, when quantum teleportation was demonstrated not with photons of light, but with actual atoms, bringing us a step closer to a more realistic teleportation device. The physicists at the National Institute of Standards and Technology in Washington, D.C., successfully entangled three beryllium atoms and transferred the properties of one atom into another. This achievement was so significant that it made the cover of Nature magazine. Another group was able to teleport calcium atoms as well.

            In 2006 yet another spectacular advance was made, for the first time involving a macroscopic object. Physicists at the Niels Bohr Institute in Copenhagen and the Max Planck Institute in Germany were able to entangle a light beam with a gas of cesium atoms, a feat involving trillions upon trillions of atoms. Then they encoded information contained inside laser pulses and were able to teleport this information to the cesium atoms over a distance of about half a yard. “For the first time,” said Eugene Polzik, one of the researchers, quantum teleportation “has been achieved between light—the carrier of information—and atoms.

            So teleportation exists at the atomic level, and we may eventually teleport complex and even organic molecules within a few decades. But the teleportation of a macroscopic object will have to wait for several decades to centuries beyond that, or longer, if indeed it is even possible. Therefore teleporting complex molecules, perhaps even a virus or a living cell, qualifies as a Class I impossibility, one that should be possible within this century. But teleporting a human being, although it is allowed by the laws of physics, may take many centuries beyond that, assuming it is possible at all. Hence I would qualify that kind of teleportation as a Class II impossibility.

TELEPORTATION WITHOUT ENTANGLEMENT

         Progress in teleportation is rapidly accelerating. In 2007 yet another breakthrough was made. Physicists proposed a teleportation method that does not require entanglement. We recall that entanglement is the single most difficult feature of quantum teleportation. Solving this problem could open up new vistas in teleportation.

          We’re talking about a beam of about 5,000 particles disappearing from one place and appearing somewhere else,” says physicist Aston Bradley of the Australian Research Council Centre of Excellence for Quantum Atom Optics in Brisbane, Australia, who helped pioneer a new method of teleportation.

         We feel that our scheme is closer in spirit to the original fictional concept,” he claims. In their approach, he and his colleagues take a beam of rubidium atoms, convert all its information into a beam of light, send this beam of light across a fiber-optic cable, and then reconstruct the original beam “of atoms in a distant location. If his claim holds up, this method would eliminate the number one stumbling block to teleportation and open up entirely new ways to teleport increasingly large objects.

          In order to distinguish this new method from quantum teleportation, Dr. Bradley has called his method “classical teleportation.” (This is a bit misleading, since his method also depends heavily on the quantum theory, but not on entanglement.

       The key to this novel type of teleportation is a new state of matter called a “Bose Einstein condensate,” or BEC, which is one of the coldest substances in the entire universe. In nature the coldest temperature is found in outer space; it is 3 K above absolute zero. (This is due to residual heat left over from the big bang, which still fills up the universe.) But a BEC is a millionth to a billionth of a degree above absolute zero, a temperature that can be found only in the laboratory.

         When certain forms of matter are cooled down to near absolute zero, their atoms all tumble down to the lowest energy state, so that all their atoms vibrate in unison, becoming coherent. The wave functions of all “the atoms overlap, so that, in some sense, a BEC is like a gigantic “super atom,” with all the individual atoms vibrating in unison. This bizarre state of matter was predicted by Einstein and Satyendranath Bose in 1925, but it would be another seventy years, not until 1995, before a BEC was finally created in the lab at MIT and the University of Colorado.

         Here’s how Bradley and company’s teleportation device works. First they start with a collection of supercold rubidium atoms in a BEC state. They then apply a beam of matter to the BEC (also made of rubidium atoms). These atoms in the beam also want to tumble down to the lowest energy state, so they shed their excess energy in the form of a pulse of light. This light beam is then sent down a fiber-optic cable. Remarkably the light beam contains all the quantum information necessary to describe the original matter beam (e.g., the location and velocity of all its atoms). Then the light beam hits another BEC, which then converts the light beam into the original matter beam.”

       This new teleportation method has tremendous promise, since it doesn’t involve the entanglement of atoms. But this method also has its problems. It depends crucially on the properties of BECs, which are difficult to create in the laboratory. Furthermore, the properties of BECs are quite peculiar, because they behave as if they were one gigantic atom. In principle, bizarre quantum effects that we “see only at the atomic level can be seen with the naked eye with a BEC. This was once thought to be impossible.

               The immediate practical application of BECs is to create “atomic lasers.” Lasers, of course, are based on coherent beams of photons vibrating in unison. But a BEC is a collection of atoms vibrating in unison, so it’s possible to create beams of BEC atoms that are all coherent. In other words, a BEC can create the counterpart of the laser, the atomic laser or matter laser, which is made of BEC atoms. The commercial applications of lasers are enormous, and the commercial applications of atomic lasers could also be just as profound. But because BECs exist only at temperatures hovering just above absolute zero, progress in this field will be slow, albeit steady.

                Given the progress we have made, when might we be able to teleport ourselves? Physicists hope to teleport complex molecules in the coming years. After that perhaps a DNA molecule or even a virus may be teleported within decades. There is nothing in principle to prevent teleporting an actual person, just as in the science fiction movies, but the technical problems facing such a feat are truly staggering. It takes some of the finest physics laboratories in the world just to create coherence between tiny photons of light and individual atoms. Creating quantum coherence involving truly macroscopic objects, such as a person, is out of the question for a long time to come. In fact, it will likely take many centuries, or longer, before everyday objects could be teleported—if it’s possible at all.