Physics of the Impossible Part 3

In 1905 Einstein had shown that waves of light can have particle-like properties; that is, they can be described as packets of energy called photons. But by the 1920s it was becoming apparent to Schrodinger that the opposite was also true: that particles like electrons could exhibit wavelike behavior. This idea was first pointed out by French physicist Louis de Broglie, who won the n.o.bel Prize for this conjecture. (We demonstrate this to our undergraduate students at our university. We fire electrons inside a cathode ray tube, like those commonly found in TVs. The electrons pa.s.s through a tiny hole, so normally you would expect to see a tiny dot where the electrons. .h.i.t the TV screen. Instead you find concentric, wavelike rings, which you would expect if a wave had pa.s.sed through the hole, not a point particle.) One day Schrodinger gave a lecture on this curious phenomenon. He was challenged by a fellow physicist, Peter Debye, who asked him: If electrons are described by waves, then what is their wave equation?

Ever since Newton created the calculus, physicists had been able to describe waves in terms of differential equations, so Schrodinger took Debye's question as a challenge to write down the differential equation for electron waves. That month Schrodinger went on vacation, and when he came back he had that equation. So in the same way that Maxwell before him had taken the force fields of Faraday and extracted Maxwell's equations for light, Schrodinger took the matter-waves of de Broglie and extracted Schrodinger's equations for electrons.

(Historians of science have spent some effort trying to track down precisely what Schrodinger was doing when he discovered his celebrated equation that forever changed the landscape of modern physics and chemistry. Apparently, Schrodinger was a believer in free love and would often be accompanied on vacation by his mistresses and his wife. He even kept a detailed diary account of all his numerous lovers, with elaborate codes concerning each encounter. Historians now believe that he was in the Villa Herwig in the Alps with one of his girlfriends the weekend that he discovered his equation.) When Schrodinger began to solve his equation for the hydrogen atom, he found, much to his surprise, the precise energy levels of hydrogen that had been carefully catalogued by previous physicists. He then realized that the old picture of the atom by Niels Bohr showing electrons whizzing around the nucleus (which is used even today in books and advertis.e.m.e.nts when trying to symbolize modern science) was actually wrong. These orbits would have to be replaced by waves surrounding the nucleus.

Schrodinger's work sent shock waves, as well, through the physics community. Suddenly physicists were able to peer inside the atom itself, to examine in detail the waves that made up its electron sh.e.l.ls, and to extract precise predictions for these energy levels that fit the data perfectly.

But there was still a nagging question that haunts physics even today. If the electron is described by a wave, then what is waving? This has been answered by physicist Max Born, who said that these waves are actually waves of probability. These waves tell you only the chance of finding a particular electron at any place and any time. In other words, the electron is a particle, but the probability of finding that particle is given by Schrodinger's wave. The larger the wave, the greater the chance of finding the particle at that point.

With these developments, suddenly chance and probability were being introduced right into the heart of physics, which previously had given us precise predictions and detailed trajectories of particles, from planets to comets to cannon b.a.l.l.s.

This uncertainty was finally codified by Heisenberg when he proposed the uncertainty principle, that is, the concept that you cannot know both the exact velocity and the position of an electron at the same time. Nor can you know its exact energy, measured over a given amount of time. At the quantum level all the basic laws of common sense are violated: electrons can disappear and reappear elsewhere, and electrons can be many places at the same time.

(Ironically, Einstein, the G.o.dfather of the quantum theory who helped to start the revolution in 1905, and Schrodinger, who gave us the wave equation, were horrified by the introduction of chance into fundamental physics. Einstein wrote, "Quantum mechanics calls for a great deal of respect. But some inner voice tells me that this is not the true Jacob. The theory offers a lot, but it hardly brings us any closer to the Old Man's secret. For my part, at least, I am convinced that He doesn't throw dice.") Heisenberg's theory was revolutionary and controversial-but it worked. In one sweep, physicists could explain a vast number of puzzling phenomena, including the laws of chemistry. To impress my Ph.D. students with just how bizarre the quantum theory is, I sometimes ask them to calculate the probability that their atoms will suddenly dissolve and reappear on the other side of a brick wall. Such a teleportation event is impossible under Newtonian physics but is actually allowed under quantum mechanics. The answer, however, is that one would have to wait longer than the lifetime of the universe for this to occur. (If you used a computer to graph the Schrodinger wave of your own body, you would find that it very much resembles all the features of your body, except that the graph would be a bit fuzzy, with some of your waves oozing out in all directions. Some of your waves would extend even as far as the distant stars. So there is a very tiny probability that one day you might wake up on a distant planet.) The fact that electrons can seemingly be many places at the same time forms the very basis of chemistry. We know that electrons circle around the nucleus of an atom, like a miniature solar system. But atoms and solar systems are quite different; if two solar systems collide in outer s.p.a.ce, the solar systems break apart and planets are flung into deep s.p.a.ce. Yet when atoms collide they often form molecules that are perfectly stable, sharing electrons between them. In high school chemistry cla.s.s the teacher often represents this with a "smeared electron," which resembles a football, connecting the two atoms together.

But what chemistry teachers rarely tell their students is that the electron is not "smeared" between two atoms at all. This "football" actually represents the probability that the electron is in many places at the same time within the football. In other words, all of chemistry, which explains the molecules inside our bodies, is based on the idea that electrons can be many places at the same time, and it is this sharing of electrons between two atoms that holds the molecules of our body together. Without the quantum theory, our molecules and atoms would dissolve instantly.

This peculiar but profound property of the quantum theory (that there is a finite probability that even the most bizarre events may happen) was exploited by Douglas Adams in his hilarious novel The Hitchhiker's Guide to the Galaxy. He needed a convenient way to whiz through the galaxy, so he invented the Infinite Improbability Drive, "a wonderful new method of crossing vast interstellar distances in a mere nothingth of a second, without all that tedious mucking around in hypers.p.a.ce." His machine enables you to change the odds of any quantum event at will, so that even highly improbable events become commonplace. So if you want to jet off to the nearest star system, you would simply change the probability that you will rematerialize on that star, and voila! You would be instantly teleported there.

In reality the quantum "jumps" so common inside the atom cannot be easily generalized to large objects such as people, which contain trillions upon trillions of atoms. Even if the electrons in our body are dancing and jumping in their fantastic journey around the nucleus, there are so many of them that their motions average out. That is, roughly speaking, why at our level substances seem solid and permanent.

So while teleportation is allowed at the atomic level, one would have to wait longer than the lifetime of the universe to actually witness these bizarre effects on a macroscopic scale. But can one use the laws of the quantum theory to create a machine to teleport something on demand, as in science fiction stories? Surprisingly, the answer is a qualified yes.

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 Schrodinger 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. Apparently G.o.d does play dice with the universe.

Did information really travel faster than light? Was Einstein wrong about the speed of light being the speed limit of the universe? Not really. Information did travel faster than the speed of light, but the information was random, and hence useless. You cannot send a real message, or Morse code, via the EPR experiment even if information is traveling faster than light.

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.

For years the EPR experiment was used as an example of the resounding victory of the quantum theory over its critics, but it was a hollow victory with no practical consequences. Until now.

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 compet.i.tive 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 Inst.i.tute 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 Inst.i.tute in Copenhagen and the Max Planck Inst.i.tute 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."

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 "cla.s.sical 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 s.p.a.ce; 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.

QUANTUM COMPUTERS.

Ultimately, the fate of quantum teleportation is intimately linked to the fate of the development of quantum computers. Both use the same quantum physics and the same technology, so there is intense cross-fertilization between these two fields. Quantum computers may one day replace the familiar digital computer sitting on our desks. In fact, the future of the world's economy may one day depend on such computers, so there is enormous commercial interest in these technologies. One day Silicon Valley could become a Rust Belt, replaced by new technologies emerging from quantum computing.

Ordinary computers compute on a binary system of 0s and 1s, called bits. But quantum computers are far more powerful. They can compute on qubits, which can take values between 0 and 1. Think of an atom placed in a magnetic field. It is spinning like a top, so its spin axis can point either up or down. Common sense tells us that the spin of the atom can be either up or down but not both at the same time. But in the strange world of the quantum, the atom is described as the sum of two states, the sum of an atom spinning up and an atom spinning down. In the netherworld of the quantum, every object is described by the sum of all possible states. (If large objects, like cats, are described in this quantum fashion, it means that you have to add the wave function of a live cat to that of a dead cat, so the cat is neither dead nor alive, as I will discuss in greater detail in Chapter 13.) Now imagine a string of atoms aligned in a magnetic field, with the spin aligned in one fashion. If a laser beam is shone on this string of atoms the laser beam will bounce off this collection of atoms, flipping the spin axis of some of the atoms. By measuring the difference between the incoming and outgoing laser beam, we have accomplished a complicated quantum "calculation," involving the flipping of many spins.

Quantum computers are still in their infancy. The world's record for a quantum computation is 3 5 = 15, hardly a calculation that will supplant today's supercomputers. Quantum teleportation and quantum computers both share the same fatal weakness: maintaining coherence for large collections of atoms. If this problem can be solved, it would be an enormous breakthrough in both fields.

The CIA and other secret organizations are intensely interested in quantum computers. Many of the world's secret codes depend on a "key," which is a very large integer, and one's ability to factor it into prime numbers. If the key is the product of two numbers, each with one hundred digits, then it might take a digital computer more than a hundred years to find these two factors from scratch. Such a code is essentially unbreakable today.

But in 1994 Peter Shor of Bell Labs showed that factoring large numbers could be child's play for a quantum computer. This discovery immediately piqued the interest of the intelligence community. In principle a quantum computer could break all the world's codes, throwing the security of today's computer systems into total disorder. The first country that is able to build such a system would be able to unlock the deepest secrets of other nations and organizations.

Some scientists have speculated that in the future the world's economy might depend on quantum computers. Silicon-based digital computers are expected to reach their physical limits in terms of increased computer power sometime after 2020. A new, more powerful family of computers might be necessary if technology is going to continue to advance. Others are exploring the possibility of reproducing the power of the human brain via quantum computers.

The stakes, therefore, are very high. If we can solve the problem of coherence, not only might we be able to solve the challenge of teleportation; we might also have the ability to advance technology of all kinds in untold ways via quantum computers. This breakthrough is so important that I will return to this discussion in later chapters.

As I pointed out earlier, coherence is extraordinarily difficult to maintain in the lab. The tiniest vibration could upset the coherence of two atoms and destroy the computation. Today it is very difficult to maintain coherence in more than just a handful of atoms. Atoms that are originally in phase begin to decohere within a matter of nanoseconds to, at best, a second. Teleportation must be done very rapidly, before the atoms begin to decohere, thus placing another restriction on quantum computation and teleportation.

In spite of these challenges, David Deutsch of Oxford University believes that these problems can be overcome: "With luck, and with the help of recent theoretical advances, [a quantum computer] may take a lot less than 50 years.... It would be an entirely new way of harnessing nature."

To build a useful quantum computer we would need to have hundreds to millions of atoms vibrating in unison, an achievement far beyond our capabilities today. Teleporting Captain Kirk would be astronomically difficult. We would have to create a quantum entanglement with a twin of Captain Kirk. Even with nanotechnology and advanced computers, it is difficult to see how this could be accomplished.

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 Cla.s.s 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, a.s.suming it is possible at all. Hence I would qualify that kind of teleportation as a Cla.s.s II impossibility.

5: TELEPATHY.

If you haven't found something strange during the day, it hasn't been much of a day.

-JOHN WHEELER.

Only those who attempt the absurd will achieve the impossible.

-M. C. ESCHER.

A. E. van Vogt's novel Slan captures the vast potential and our darkest fears a.s.sociated with the power of telepathy.

Jommy Cross, the protagonist in the novel, is a "slan," a dying race of superintelligent telepaths.

His parents were brutally murdered by enraged mobs of humans, who fear and despise all telepaths, because of the enormous power wielded by those who can intrude on their private, most intimate thoughts. Humans mercilessly hunt down the slans like animals. With their characteristic tendrils growing out of their heads, slans are easy to spot. In the course of the book, Jommy tries to make contact with other slans who might have fled into outer s.p.a.ce to escape the witch hunts of humans determined to exterminate them.

Historically, mind reading has been seen as so important that it has often been a.s.sociated with the G.o.ds. One of the most fundamental powers of any G.o.d is the ability to read our minds and hence answer our deepest prayers. A true telepath who could read minds at will could easily become the wealthiest, most powerful person on Earth, able to enter into the minds of Wall Street bankers or to blackmail and coerce his rivals. He would pose a threat to the security of governments. He could effortlessly steal a nation's most sensitive secrets. Like the slans, he would be feared and perhaps hunted down.

The enormous power of a true telepath was highlighted in the landmark Foundation series by Isaac Asimov, often touted as one of the greatest science fiction epics of all time. A Galactic Empire that has ruled for thousands of years is on the verge of collapse and ruin. A secret society of scientists, called the Second Foundation, uses complex equations to predict that the Empire will eventually fall and plunge civilization into thirty thousand years of darkness. The scientists draft an elaborate plan based on their equations in an effort to reduce this collapse of civilization down to just a few thousand years. But then disaster strikes. Their elaborate equations fail to predict a single event, the birth of a mutant called the Mule, who is capable of controlling minds over great distances and hence able to seize control of the Galactic Empire. The galaxy is doomed to thirty thousand years of chaos and anarchy unless this telepath can be stopped.

Although science fiction is full of fantastic tales concerning telepaths, the reality is much more mundane. Because thoughts are private and invisible, for centuries charlatans and swindlers have taken advantage of the naive and gullible among us. One simple parlor trick used by magicians and mentalists is to use a shill-an accomplice planted in the audience whose mind is then "read" by the mentalist.

The careers of several magicians and mentalists, in fact, have been based on the famous "hat trick," in which people write private messages on strips of paper, which are then placed in a hat. The magician then proceeds to tell the audience what is written on each strip of paper, amazing everyone. There is a deceptively simple explanation for this ingenious trick (see the notes).

One of the most famous cases of telepathy did not involve a shill but an animal, Clever Hans, a wonder horse that astonished European audiences in the 1890s. Clever Hans, to the amazement of audiences, could perform complex mathematical feats of calculation. If, for example, you asked Clever Hans to divide 48 by 6, the horse would beat its hoof 8 times. Clever Hans, in fact, could divide, multiply, add fractions, spell, and even identify musical tones. Clever Hans's fans declared that he was either more intelligent than many humans, or he could telepathically pick people's brains.

But Clever Hans was not the product of some clever trickery. The marvelous ability of Clever Hans to perform arithmetic even fooled his trainer. In 1904 prominent psychologist Professor C. Strumpf was brought in to a.n.a.lyze the horse and could find no obvious evidence of trickery or covert signaling to the horse, only adding to the public's fascination with Clever Hans. Three years later, however, Strumpf's student, psychologist Oskar Pfungst, did much more rigorous testing and finally discovered Clever Hans's secret. All he really did was observe the subtle facial expressions of his trainer. The horse would continue to beat his hoofs until his trainer's facial expression changed slightly, at which point he would stop beating. Clever Hans could not read people's minds or perform arithmetic; he was simply a shrewd observer of people's faces.

There have been other "telepathic" animals in recorded history. As early as 1591 a horse named Morocco became famous in England and made a fortune for his owner by picking out people in the audience, pointing out letters of the alphabet, and adding the total of a pair of dice. He caused such a sensation in England that Shakespeare immortalized him in his play Love's Labour's Lost as "the dancing horse."

Gamblers also are able to read people's minds in a limited sense. When a person sees something pleasurable, the pupils of his eyes usually dilate. When he sees something undesirable (or performs a mathematical calculation), his pupils contract. Gamblers can read the emotions of their poker-faced opponents by looking for their eyes to dilate or contract. This is one reason that gamblers often wear colored visors over their eyes, to shield their pupils. One can also bounce a laser beam off a person's pupil and a.n.a.lyze where it is reflected, and thereby determine precisely where a person is looking. By a.n.a.lyzing the motion of the reflected dot of laser light, one can determine how a person scans a picture. By combining these two technologies, one can then determine a person's emotional reaction as he scans a picture, all without his permission.

PSYCHICAL RESEARCH.

The first scientific studies of telepathy and other paranormal phenomenon were conducted by the Society for Psychical Research, founded in London in 1882. (The term "mental telepathy" was coined that year by F. W. Myers, an a.s.sociate of the society.) Past presidents of this society included some of the most notable figures of the nineteenth century. The society, which still exists today, was able to debunk the claims of many frauds, but was often split between the spiritualists, who firmly believed in the paranormal, and the scientists, who wanted more serious scientific study.

One researcher connected with the society, Dr. Joseph Banks Rhine, began the first systematic and rigorous study of psychic phenomena in the United States in 1927, founding the Rhine Inst.i.tute (now called the Rhine Research Center) at Duke University, North Carolina. For decades he and his wife, Louisa, conducted some of the first scientifically controlled experiments in the United States on a wide variety of parapsychological phenomena and published them in peer-reviewed publications. It was Rhine who coined the term "extrasensory perception" (ESP) in one of his first books.

Rhine's laboratory, in fact, set the standard for psychic research. One of his a.s.sociates, Dr. Karl Zener, developed the five-symbol card system, now known as Zener cards, for a.n.a.lyzing telepathic powers. The vast majority of results showed absolutely no evidence of telepathy. But a small minority of experiments seemed to show small but remarkable correlations in the data that could not be explained by pure chance. The problem was that these experiments often could not be duplicated by other researchers.

Although Rhine tried to establish a reputation for rigor, his reputation was somewhat tarnished by an encounter with a horse called Lady Wonder. This horse could perform dazzling feats of telepathy, such as knocking over toy alphabet blocks and thereby spelling out words that members of an audience were thinking. Rhine apparently did not know about the Clever Hans effect. In 1927 Rhine a.n.a.lyzed Lady Wonder in some detail and concluded, "There is left then, only the telepathic explanation, the transference of mental influence by an unknown process. Nothing was discovered that failed to accord with it, and no other hypothesis proposed seems tenable in view of the results." Later, Milbourne Christopher revealed the true source of Lady Wonder's telepathic power: subtle motions of the whip carried by the horse's owner. The subtle movements of the whip were cues for Lady Wonder to stop beating her hoof. (But even after the true source of Lady Wonder's power was exposed, Rhine continued to believe that the horse was truly telepathic, but somehow had lost its telepathic power, forcing the owner to resort to trickery.) Rhine's reputation suffered a final crushing blow, however, when he was on the verge of retiring. He was seeking a successor with an untarnished reputation to carry on the work of his inst.i.tute. One promising candidate was Dr. Walter Levy, whom he hired in 1973. Dr. Levy was a rising star in the field, reporting sensational study results seeming to demonstrate that mice could telepathically alter a computer's random number generator. However, suspicious lab workers discovered that Dr. Levy was surrept.i.tiously sneaking into the lab at night to alter the results of the tests. He was caught red-handed doctoring the data. Further tests showed that the mice possessed no telepathic power whatsoever, and Dr. Levy was forced to resign from the inst.i.tute in disgrace.

TELEPATHY AND STAR GATE.

Interest in the paranormal took a deadly turn at the height of the cold war, during which a number of clandestine experiments on telepathy, mind control, and remote viewing were sp.a.w.ned. (Remote viewing is "seeing" a distant location by the mind alone, by reading the minds of others.) Star Gate was the code name for a number of secret CIA-sponsored studies (such as Sun Streak, Grill Flame, and Center Lane). The efforts got their start around 1970 when the CIA concluded that the Soviet Union was spending up to 60 million rubles a year on "psychotronic" research. There was concern that the Soviets might be using ESP to locate U.S. submarines and military installations, to identify spies, and to read secret papers.

Funding for the CIA studies began in 1972, and Russell Targ and Harold Puthoff of the Stanford Research Inst.i.tute (SRI) in Menlo Park were in charge. Initially, they sought to train a cadre of psychics who could engage in "psychic warfare." Over more than two decades, the United States spent $20 million on Star Gate, with over forty personnel, twenty-three remote viewers, and three psychics on the payroll.

By 1995, with a budget of $500,000 per year, the CIA had conducted hundreds of intelligence-gathering projects involving thousands of remote viewing sessions. Specifically, the remote viewers were asked to * locate Colonel Gadhafi before the 1986 bombing of Libya * find plutonium stockpiles in North Korea in 1994 * locate a hostage kidnapped by the Red Brigades in Italy in 1981 * locate a Soviet Tu-95 bomber that had crashed in Africa In 1995, the CIA asked the American Inst.i.tute for Research (AIR) to evaluate these programs. The AIR recommended that the programs be shut down. "There's no doc.u.mented evidence it had any value to the intelligence community," wrote David Goslin of the AIR.

Proponents of Star Gate boasted that over the years they had scored "eight-martini" results (conclusions that were so spectacular that you had to go out and drink eight martinis to recover). Critics, however, maintained that a huge majority of the remote viewing produced worthless, irrelevant information, wasting taxpayer dollars, and that the few "hits" they scored were vague and so general that they could be applied to any number of situations. The AIR report stated that the most impressive "successes" of Star Gate involved remote viewers who already had some knowledge of the operation they were studying, and hence might have made educated guesses that sounded reasonable.

In the end the CIA concluded that Star Gate had yielded not a single instance of information that helped the agency guide intelligence operations, so it canceled the project. (Rumors persisted that the CIA used remote viewers to locate Saddam Hussein during the Gulf War, although all efforts were unsuccessful.) BRAIN SCANS.

At the same time, scientists were beginning to understand some of the physics behind the workings of the brain. In the nineteenth century scientists suspected that electrical signals were being transmitted inside the brain. In 1875 Richard Caton discovered that by placing electrodes on the surface of the head it was possible to detect the tiny electrical signals emitted by the brain. This eventually led to the invention of the electroencephalograph (EEG).

In principle the brain is a transmitter over which our thoughts are broadcast in the form of tiny electrical signals and electromagnetic waves. But there are problems with using these signals to read someone's thoughts. First, the signals are extremely weak, in the milliwatt range. Second, the signals are gibberish, largely indistinguishable from random noise. Only crude information about our thoughts can be gleaned from this garble. Third, our brain is not capable of receiving similar messages from other brains via these signals; that is, we lack an antenna. And, finally, even if we could receive these faint signals, we could not unscramble them. Using ordinary Newtonian and Maxwellian physics, telepathy via radio does not seem to be possible.

Some believe that perhaps telepathy is mediated by a fifth force, called the "psi" force. But even advocates of parapsychology admit that they have no concrete, reproducible evidence of this psi force.

But this leaves open the question: What about telepathy using the quantum theory?

In the last decade, new quantum instruments have been introduced that for the first time in history enable us to look into the thinking brain. Leading this quantum revolution are the PET (positron-emission tomography) and MRI (magnetic resonance imaging) brain scans. A PET scan is created by injecting radioactive sugar into the blood. This sugar concentrates in parts of the brain that are activated by the thinking process, which requires energy. The radioactive sugar emits positrons (antielectrons) that are easily detected by instruments. Thus, by tracing out the pattern created by antimatter in the living brain, one can also trace out the patterns of thought, isolating precisely which parts of the brain are engaged in which activity.

The MRI machine operates in the same way, except it is more precise. A patient's head is placed inside a huge doughnut-shaped magnetic field. The magnetic field makes the nuclei of the atoms in the brain align parallel to the field lines. A radio pulse is sent into the patient, making these nuclei wobble. When the nuclei flip orientation, they emit a tiny radio "echo" that can be detected, thereby signaling the presence of a particular substance. For example, brain activity is related to oxygen consumption, so the MRI machine can isolate the process of thinking by zeroing in on the presence of oxygenated blood. The higher the concentration of oxygenated blood, the greater the mental activity in that part of the brain. (Today "functional MRI machines" [fMRI] can zero in on tiny areas of the brain only a millimeter across in fractions of a second, making these machines ideal for tracing out the pattern of thoughts of the living brain.) MRI LIE DETECTORS.

With MRI machines, there is a possibility that one day scientists may be able to decipher the broad outlines of thoughts in the living brain. The simplest test of "mind reading" would be to determine whether or not someone is lying.

According to legend, the world's first lie detector was created by an Indian priest centuries ago. He would put the suspect and a "magic donkey" into a sealed room, with the instruction that the suspect should pull on the magic donkey's tail. If the donkey began to talk, it meant the suspect was a liar. If the donkey remained silent, then the suspect was telling the truth. (But secretly, the elder would put soot on the donkey's tail.) After the suspect was taken out of the room, the suspect would usually proclaim his innocence because the donkey did not speak when he pulled its tail. But the priest would then examine the suspect's hands. If the hands were clean, it meant he was lying. (Sometimes the threat of using a lie detector is more effective than the lie detector itself.) The first "magic donkey" in modern times was created in 1913, when psychologist William Marston wrote about a.n.a.lyzing a person's blood pressure, which would be elevated when telling a lie. (This observation about blood pressure actually goes back to ancient times, when a suspect would be questioned while an investigator held on to his hands.) The idea soon caught on, and soon even the Department of Defense was setting up its own Polygraph Inst.i.tute.

But over the years it has become clear that lie detectors can be fooled by sociopaths who show no remorse for their actions. The most famous case was that of the CIA double agent Aldrich Ames, who pocketed huge sums of money from the former Soviet Union by sending scores of U.S. agents to their death and divulging secrets of the U.S. nuclear navy. For decades Ames sailed through a battery of the CIA's lie detector tests. So, too, did serial killer Gary Ridgway, known as the notorious Green River Killer; he killed as many as fifty women.

In 2003 the U.S. National Academy of Sciences issued a scathing report on the reliability of lie detectors, listing all the ways in which lie detectors could be fooled and innocent people branded as liars.

But if lie detectors measure only anxiety levels, what about measuring the brain itself? The idea of looking into brain activity to ferret out lies dates back twenty years, to the work of Peter Rosenfeld of Northwestern University, who observed that EEG scans of people in the process of lying showed a different pattern in the P300 waves than when those people were telling the truth. (P300 waves are often stimulated when the brain encounters something novel or out of the ordinary.) The idea of using MRI scans to detect lies was the brainchild of Daniel Langleben of the University of Pennsylvania. In 1999 he came upon a paper stating that children suffering from attention deficit disorder had difficulty lying, but he knew from experience that this was wrong; such children had no problem lying. Their real problem was that they had difficulty inhibiting the truth. "They would just blurt things out," recalled Langleben. He conjectured that the brain, in telling a lie, first had to stop itself from telling the truth, and then create a deception. He says, "When you tell a deliberate lie, you have to be holding in mind the truth. So it stands to reason it should mean more brain activity." In other words, lying is hard work.

Through experimenting with college students and asking them to lie, Langleben soon found that lying creates increased brain activity in several areas, including the frontal lobe (where higher thinking is concentrated), the temporal lobe, and the limbic system (where emotions are processed). In particular, he noticed unusual activity in the anterior cingulated gyrus (which is a.s.sociated with conflict resolution and response inhibition).

He claims to have attained consistent success rates of up to 99 percent when a.n.a.lyzing his subjects in controlled experiments to determine whether or not they were lying (e.g., he asked college students to lie about the ident.i.ty of playing cards).

The interest in this technology has been so p.r.o.nounced that two commercial ventures have been started, offering this service to the public. In 2007 one company, No Lie MRI, took on its first case, a person who was suing his insurance company because it claimed that he had deliberately set his deli on fire. (The fMRI scan indicated that he was not an arsonist.) Proponents of Langleben's technique claim that it is much more reliable than the old-fashioned lie detector, since altering brain patterns is beyond anyone's control. While people can be trained to a degree to control their pulse rate and sweating, it is impossible for them to control their brain patterns. In fact, proponents point out that in an age of increased awareness of terrorism this technology could save countless lives by detecting a terrorist attack on the United States.

While conceding this technology's apparent success rate in detecting lies, critics have pointed out that the fMRI does not actually detect lies, only increased brain activity when someone is telling a lie. The machine could create false results if, for example, a person were to tell the truth while in a state of great anxiety. The fMRI would detect only the anxiety felt by the subject and incorrectly reveal that he was telling a lie. "There is an incredible hunger to have tests to separate truth from deception, science be d.a.m.ned," warns neurobiologist Steven Hyman of Harvard University.

Some critics also claim that a true lie detector, like a true telepath, could make ordinary social interactions quite uncomfortable, since a certain amount of lying is a "social grease" that helps to keep the wheels of society moving. Our reputation might be ruined, for example, if all the compliments we paid our bosses, superiors, spouses, lovers, and colleagues were exposed as lies. A true lie detector, in fact, could also expose all our family secrets, hidden emotions, repressed desires, and secret plans. As science columnist David Jones has said, a true lie detector is "like the atom bomb, it is best reserved as a sort of ultimate weapon. If widely deployed outside the courtroom, it would make social life quite impossible."

UNIVERSAL TRANSLATOR.

Some have rightfully criticized brain scans because, for all their spectacular photographs of the thinking brain, they are simply too crude to measure isolated, individual thoughts. Millions of neurons probably fire at once when we perform the simplest mental task, and the fMRI detects this activity only as a blob on a screen. One psychologist compared brain scans to attending a boisterous football game and trying to listen to the person sitting next to you. The sounds of that person are drowned out by the noise of thousands of spectators. For example, the smallest chunk of the brain that can be reliably a.n.a.lyzed by an fMRI machine is called a "voxel." But each voxel corresponds to several million neurons, so the sensitivity of an fMRI machine is not good enough to isolate individual thoughts.

Science fiction sometimes uses a "universal translator," a device that can read a person's thoughts and then beam them directly into another's mind. In some science fiction novels alien telepaths place thoughts into our mind, even though they can't understand our language. In the 1976 science fiction movie Futureworld a woman's dream is projected onto a TV screen in real time. In the 2004 Jim Carrey movie, Eternal Sunshine of the Spotless Mind, doctors pinpoint painful memories and erase them.

"That's the kind of fantasy everyone in this field has," says neuroscientist John Haynes of the Max Planck Inst.i.tute in Leipzig, Germany. "But if that's the device you want to build, then I'm pretty sure you need to record from a single neuron."

Since detecting signals from a single neuron is out of the question for now, some psychologists have tried to do the next best thing: to reduce the noise and isolate the fMRI pattern created by individual objects. For example, it might be possible to identify the fMRI pattern created by individual words, and then construct a "dictionary of thought."

Marcel A. Just of Carnegie-Mellon University, for example, has been able to identify the fMRI pattern created by a small, select group of objects (e.g., carpentry tools). "We have 12 categories and can determine which of the 12 the subjects are thinking of with 80 to 90% accuracy," he claims.

His colleague Tom Mitch.e.l.l, a computer scientist, is using computer technology, such as neural networks, to identify the complex brain patterns detected by fMRI scans a.s.sociated with performing certain experiments. "One experiment that I would love to do is to find words that produce the most distinguishable brain activity," he notes.

But even if we can create a dictionary of thought, this is a far cry from creating a "universal translator." Unlike the universal translator, which beams thoughts directly into our mind from another mind, an fMRI mental translator would involve many tedious steps: first, recognizing certain fMRI patterns, converting them into English words, and then uttering these English words to the subject. In this sense, such a device would not correspond to the "mind meld" found on Star Trek (but it would still be very useful for stroke victims).