How to Destroy the Universe (13 page)

This is how it's possible to get round Heisenberg's uncertainty principle for teleportation. The uncertainty principle stops you from measuring the information stored on a particle, but entanglement means that you can still send that information even though you don't know it. It's rather like someone asking you to post a letter for them—you don't need to know the contents of the envelope in order to put it in the post on their behalf.

Here's how it works. Say you want to teleport a particle, A, from the surface of Mars up to the Starship
Enterprise
. You first need two other particles, call them B and C, which have been entangled together at an earlier time. B is with you on the surface of Mars, while C is already up on the
Enterprise
. Next, you join A with B and then make an ordinary measurement of the relationship between A and B. Although uncertainty prevents us from knowing the exact state of particles A and B, knowing the relationship between them is permitted and turns out to be all you need in order to teleport the state of A. The result of the measurement is then radioed ahead to the
Enterprise
where it can be used to extract an exact copy of A from particle C. For example, if the measurement showed that A and B are in opposite states to one another then since B and C are also opposite—because they are entangled particles—that reveals that A and C are already in exactly the
same state. In other words the state of A has been transferred to C. What's more, the original particle A is destroyed in the process. A has effectively been teleported.

The discovery wasn't confined to humble pen and paper for long. In 1997, scientists at the University of Innsbruck were able to put the scheme into practice. They used an entangled pair of particles to teleport photons—particles of light—2 m (6 ft) across their lab. Although the experiments aren't quite up to trips into space just yet, they demonstrate the reality of beating Heisenberg's uncertainty principle in practice. In 2002, a collaboration between the universities of Oxford and Calcutta put forward a modified version of the technique that can teleport not just light but solid particles of matter, including atoms and molecules. The first atoms were teleported experimentally by a US/Austrian team in 2004.

So if we can teleport atoms, how soon might it be possible to send larger objects and, maybe, people? Don't hold your breath. The teleportation experiments conducted so far have been largely about communicating information, such as the “qubits” of quantum data that are processed on a quantum computer (see
How to crack unbreakable codes
). Qubits are fragile entities,
suffering from a problem known as “decoherence”—where interactions with their local environment can disrupt the delicate quantum balance by which the information they hold is encoded. And this means that they cannot be sent over conventional channels, such as by radio or electronically down a wire.

The real trouble with teleporting large objects is the sheer volume of information to be sent. An averagesized human is composed of roughly 10
²⁸
atoms—that's 10 billion billion billion times the largest units of matter that have been successfully teleported to date. If you assume that each atom can be specified by just one bit of information, a simple binary 1 or 0 (and that's a generous assumption—it takes more data than that to specify the state of an atom) then that's 10
²⁸
bits that need to be communicated from the transmitter to the receiver. The fastest internet backbones in service today can ship data at a fairly blistering rate—some 100 billion bits per second. But even at this not-inconsiderable rate, getting the information needed to specify the state of every one of Captain Kirk's atoms is going to take about 3 billion years—two-thirds the age of Earth.

The other difficulty is that teleportation machines would be needed at both ends of the process. So whereas the
Enterprise
can beam crew members in or
out, from and to, pretty much anywhere, in reality only transportation between established destinations and jumping off points would be possible. Other researchers wonder what the implications for the self would be if you were to teleport yourself using quantum entanglement. After all, what comes out the other end isn't actually you—it's a copy built from a completely new set of atoms, while the original you is destroyed in the transmission process. Would you notice the difference? Would your brain structure be accurately preserved—would the new you have the same memories and psychological outlook as the original? And what would really happen if a fly got into the teleportation pod with you? Teleportation of even everyday objects—let alone people—is still many decades, probably even centuries, away.

• Ultimate energy source

• Dirac's discovery

• The asymmetric Universe

• Antimatter power

• Storing antimatter

Many a sci-fi yarn is spun around antimatter as the superfuel of the future. Antimatter generates vast quantities of energy from the tiniest volumes of fuel. Now some NASA engineers are taking note. They've already produced designs for the antimatter-powered spacecraft that they hope will fly in the coming centuries. Others have suggested that antimatter mined from space could be a possible future energy source on Earth.

Antimatter is what you get when you take a particle of matter and reverse key properties such as its electric charge. It's potent stuff. When a particle of matter meets its antiparticle the two annihilate, releasing their
combined mass and energy in a flash of radiation. Converting mass into radiation in this way was one of the predictions of Einstein's special theory of relativity. The equation
E
=
mc
²
links mass and energy by a fundamental constant of physics—the speed of light. The speed of light is very large—300 million m/s—and the speed of light squared is even larger. This means that a very small amount of mass translates into a huge amount of energy. Indeed, annihilating just a quarter of a gram of antimatter would match the total energy output of the atom bomb that was dropped on Hiroshima in 1945.

The discovery of antimatter is also thanks to Einstein—albeit indirectly. In the early 1900s, physicists were beginning to realize that matter on the smallest scales doesn't behave at all like matter in the everyday world. Bounce a ball on the ground and it accelerates and rebounds according to Isaac Newton's well-established laws of motion. But subatomic particles, it seemed, obeyed a new set of laws entirely.

In particular, it seemed like solid matter on these tiny scales has wave-like properties—more like a beam of light. Subatomic particles can be diffracted (spread out) as they pass through small apertures, and can interfere with one another just like waves. In the first
few decades of the 20th century physicists began piecing together a mathematical description of this behavior, which came to be known as quantum theory. One of the most significant developments came in 1926, when an Austrian physicist called Erwin Schrödinger published an equation describing the wave-motion of solid particles. Schrödinger specified the position of a particle in space by a “probability wave”—with peaks of the wave corresponding to locations where the particle was most likely to be found. The Schrödinger equation, as it became known, revealed how this wave evolved in time. Enter British physicist Paul Dirac. As the Schrödinger equation stood it only described the motion of slow-moving particles. Dirac wondered whether it might be possible to formulate a version that was consistent with Einstein's special theory of relativity, taking into account the behavior of objects moving at close to light speed. After a little mathematical gymnastics, he produced the Dirac equation—a relativistic version of Schrödinger's wave equation.

When Dirac applied his equation to electrons, he was surprised to find that it had not one but two solutions: one for the electron and one describing a particle with opposite electric charge. Dirac had predicted the existence of the positron—the antimatter partner to the electron. In 1932, just five years later, the first positron was detected experimentally. US physicist Carl
Anderson observed high-energy particles from space known as cosmic rays using a cloud chamber—an enclosure in which the air is saturated with alcohol vapor. When a high-energy particle passes through the vapor, it causes a trail of droplets to condense behind it. Placing a magnet over the chamber caused the trajectories of electrically charged particles to bend into a circle, and the radius of the circle revealed the particle's mass. Anderson observed plenty of electrons in his experimental set-up, but now and again he saw a particle with the same mass as the electron but curling in the opposite direction—signifying that it had opposite charge. Anderson had identified the first particle of antimatter.

The prediction and subsequent detection of antimatter was a resounding triumph for the emerging field of quantum physics, and for theoretical physics as a whole. But it brought with it a very big problem that physicists have still not been able to fully resolve—namely, why is our Universe made predominantly of matter and not antimatter? The standard model of particle physics says that the Big Bang, in which our Universe was born, should have generated equal amounts of matter and antimatter, which would have annihilated each other completely, leading to a Universe filled with radiation and nothing else—no
planets, no stars and certainly no physicists. But our Universe is filled with matter. Observations have shown that the Universe contains around a billion photons (particles of light) for every baryon (large particles, such as protons and neutrons). Each annihilation of a baryon with an antibaryon in the early Universe will have produced one photon. So the implication is that there was a tiny imbalance of matter to antimatter—roughly a billion antimatter particles to every billion-and-one matter particles. In 1967, the Russian physicist Andrei Sakharov showed that the only way around this problem—known as the “baryon asymmetry”—is through a phenomenon called CP violation. CP is a kind of symmetry in physics—short for charge-parity invariance. Symmetries are transformations of the laws of physics that leave the results unchanged. Initially particle physics was understood to be CP-invariant, which means that if you simultaneously reverse a particle's electric charge (that is switching matter for antimatter) and parity (its sense of left and right) then its behavior remains unchanged. It's essentially a statement of Anderson's observation that positrons curve in the opposite direction to electrons in a magnetic field.

In 1964, evidence of CP-violating interactions was observed for the first time in particle-physics experiments. The standard model of particle interactions embraced the phenomenon theoretically in the 1970s
with the development of the electroweak theory, which unified electromagnetism (the theory of electricity and magnetism) with the weak nuclear force (one of the two forces that hold together the nuclei of atoms, and which is responsible for radioactive beta decay—where nuclei can give off electrons and positrons). The electroweak model has been verified by experiments, yet the degree of CP violation it accounts for is still insufficient to explain the baryon asymmetry—yielding an amount of matter from the Big Bang equivalent to about one galaxy (whereas our Universe is home to some 80 billion). It's hoped new experiments at the Large Hadron Collider particle accelerator, at the CERN laboratory on the Swiss–French border, will offer new insights into CP violation by smashing together subatomic particles to produce showers of smaller particles called “b quarks,” which are a key marker of CP symmetry.

Some researchers are already looking beyond pure science to practical uses for antimatter. Positrons are already used in PET (positron emission tomography) scans. Here, a patient is injected with a radioactive substance that emits positrons. The substance is embedded in a biological molecule that travels to regions of high-metabolic activity in the body. The positrons it emits then annihilate with nearby electrons,
emitting gamma rays and causing the high metabolic regions to glow. This is useful in the treatment heart disease, neurological disorders and cancer. But what about other applications? The quantity of energy per kilogram extracted from antimatter fuel is about 10,000 times what you would expect from nuclear fission. Could antimatter ever be used as a power source? The problem is that antimatter does not occur naturally on Earth. It has to be manufactured in particle accelerators. Currently, making antimatter takes 10 billion times more energy than it releases when it annihilates. Physicists estimate that the world's accelerator labs can make about 10 billionths of a gram of antimatter per year, at a cost of $600,000. At that rate, making 1 g (0.035 oz) of the stuff—equivalent in energy yield to about 10 kg (22 lb) of uranium—would then take several hundred million years and cost about $60 trillion. There is one exciting possibility, though. Antimatter could be mined from space. Violent events in space clash together subatomic particles, some of which break apart to form antimatter. James Bickford, a scientist working at the Draper Laboratory in Massachusetts, has calculated that nearly 4 tons of this antimatter drifts into our Solar System every year—enough to meet about two-thirds of the world's annual energy demand. This, and other antimatter formed by cosmic rays, would be attracted by the magnetic fields of the planets—because it's electrically charged—where it would form belts rather like the Van Allen particle belts
that surround Earth. A rich mining site would be Jupiter, which has a particularly potent magnetic field—about 14 times stronger than Earth's. Bickford believes a spacecraft equipped with powerful magnetic scoops could be send to retrieve this material.