Ever since the wheel was invented more than 5,000 years ago, people have been inventing new ways to travel faster from one point to another. The chariot, bicycle, automobile, airplane and rocket have all been invented to decrease the amount of time we spend getting to our desired destinations. Yet each of these forms of transportation share the same flaw: They require us to cross a physical distance, which can take anywhere from minutes to many hours depending on the starting and ending points.
But what if there were a way to get you from your home to the supermarket without having to use your car, or from your backyard to the International Space Station without having to board a spacecraft? There are scientists working right now on such a method of travel, combining properties of telecommunications and transportation to achieve a system called teleportation. In this article, you will learn about experiments that have actually achieved teleportation with photons, and how we might be able to use teleportation to travel anywhere, at anytime.
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. 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.
Many 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. Viewers watched in amazement as Captain Kirk, Spock, Dr. McCoy and others beamed down to the planets they encountered on their journeys through the universe.
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. This revelation, first announced by Bennett at an annual meeting of the American Physical Society in March 1993, was followed by a report on his findings in the March 29, 1993 issue of Physical Review Letters. Since that time, experiments using photons have proven that quantum teleportation is in fact possible.
Teleportation: Recent 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 3.28 feet (about 1 meter) 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.
In 2002, researchers at the Australian National University successfully teleported a laser beam.
The most recent successful teleportation experiment took place on October 4, 2006 at the Niels Bohr Institute in Copenhagen, Denmark. Dr. Eugene Polzik and his team teleported information stored in a laser beam into a cloud of atoms. According to Polzik, "It is one step further because for the first time it involves teleportation between light and matter, two different objects. One is the carrier of information and the other one is the storage medium" [CBC]. The information was teleported about 1.6 feet (half a meter).
Quantum teleportation holds promise for quantum computing. These experiments 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.
Human Teleportation
We are years away from the development of a teleportation machine like the transporter room on Star Trek's Enterprise spaceship. The laws of physics may even make it impossible to create a transporter that enables a person to be sent instantaneously to another location, which would require travel at the speed of light.
For a person to be transported, a machine would have to be built that can pinpoint and analyze all of the 1028 atoms that make up the human body. That's more than a trillion trillion atoms. This machine would then have to send this information to another location, where the person's body would be reconstructed with exact precision. Molecules couldn't be even a millimeter out of place, lest the person arrive with some severe neurological or physiological defect.
In the Star Trek episodes, and the spin-off series that followed it, teleportation was performed by a machine called a transporter. This was basically a platform that the characters stood on, while Scotty adjusted switches on the transporter room control boards. The transporter machine then locked onto each atom of each person on the platform, and used a transporter carrier wave to transmit those molecules to wherever the crew wanted to go. Viewers watching at home witnessed Captain Kirk and his crew dissolving into a shiny glitter before disappearing, rematerializing instantly on some distant planet.
If such a machine were possible, it's unlikely that the person being transported would actually be "transported." It would work more like a fax machine -- a duplicate of the person would be made at the receiving end, but with much greater precision than a fax machine. But what would happen to the original? One theory suggests that teleportation would combine genetic cloning with digitization.
In this biodigital cloning, tele-travelers would have to die, in a sense. Their original mind and body would no longer exist. Instead, their atomic structure would be recreated in another location, and digitization would recreate the travelers' memories, emotions, hopes and dreams. So the travelers would still exist, but they would do so in a new body, of the same atomic structure as the original body, programmed with the same information.
But like all technologies, scientists are sure to continue to improve upon the ideas of teleportation, to the point that we may one day be able to avoid such harsh methods. One day, one of your descendents could finish up a work day at a space office above some far away planet in a galaxy many light years from Earth, tell his or her wristwatch that it's time to beam home for dinner on planet X below and sit down at the dinner table as soon as the words leave his mouth.
How Light Works
We see things every day, from the moment we get up in the morning until we go to sleep at night. We look at everything around us using light.
We appreciate kids' crayon drawings, fine oil paintings, swirling computer graphics, gorgeous sunsets, a blue sky, shooting stars and rainbows. We rely on mirrors to make ourselves presentable, and sparkling gemstones to show affection.
But did you ever stop to think that when we see any of these things, we are not directly connected to it? We are, in fact, seeing light -- light that somehow left objects far or near and reached our eyes. Light is all our eyes can really see.
The other way that we encounter light is in devices that produce light -- incandescent bulbs, fluorescent bulbs, lasers, lightning bugs, the sun. Each one uses a different technique to generate photons.
Ways of Thinking About Light
You have probably heard two different ways of talking about light:
* There is the "particle" theory, expressed in part by the word photon.
* There is the "wave" theory, expressed by the term light wave.
From the time of the ancient Greeks, people have thought of light as a stream of tiny particles. After all, light travels in straight lines and bounces off a mirror much like a ball bouncing off a wall. No one had actually seen particles of light, but even now it's easy to explain why that might be. The particles could be too small, or moving too fast, to be seen, or perhaps our eyes see right through them.
The idea of the light wave came from Christian Huygens, who proposed in the late 1600s that light acted like a wave instead of a stream of particles. In 1807, Thomas Young backed up Huygens' theory by showing that when light passes through a very narrow opening, it can spread out, and interfere with light passing through another opening. Young shined a light through a very narrow slit. What he saw was a bright bar of light that corresponded to the slit. But that was not all he saw. Young also perceived additional light, not as bright, in the areas around the bar. If light were a stream of particles, this additional light would not have been there. This experiment suggested that light spread out like a wave. In fact, a beam of light radiates outward at all times.
Albert Einstein advanced the theory of light further in 1905. Einstein considered the photoelectric effect, in which ultraviolet light hits a surface and causes electrons to be emitted from the surface. Einstein's explanation for this was that light was made up of a stream of energy packets called photons.
Modern physicists believe that light can behave as both a particle and a wave, but they also recognize that either view is a simple explanation for something more complex. In this article, we will talk about light as waves, because this provides the best explanation for most of the phenomena our eyes can see.
What is Light?
Why is it that a beam of light radiates outward, as Young proved? What is really going on? To understand light waves, it helps to start by discussing a more familiar kind of wave -- the one we see in the water. One key point to keep in mind about the water wave is that it is not made up of water: The wave is made up of energy traveling through the water. If a wave moves across a pool from left to right, this does not mean that the water on the left side of the pool is moving to the right side of the pool. The water has actually stayed about where it was. It is the wave that has moved. When you move your hand through a filled bathtub, you make a wave, because you are putting your energy into the water. The energy travels through the water in the form of the wave.
All waves are traveling energy, and they are usually moving through some medium, such as water. You can see a diagram of a water wave in Figure 1. A water wave consists of water molecules that vibrate up and down at right angles to the direction of motion of the wave. This type of wave is called a transverse wave.
Light waves are a little more complicated, and they do not need a medium to travel through. They can travel through a vacuum. A light wave consists of energy in the form of electric and magnetic fields. The fields vibrate at right angles to the direction of movement of the wave, and at right angles to each other. Because light has both electric and magnetic fields, it is also referred to as electromagnetic radiation.
Light waves come in many sizes. The size of a wave is measured as its wavelength, which is the distance between any two corresponding points on successive waves, usually peak-to-peak or trough-to-trough (Figure 1). The wavelengths of the light we can see range from 400 to 700 billionths of a meter. But the full range of wavelengths included in the definition of electromagnetic radiation extends from one billionth of a meter, as in gamma rays, to centimeters and meters, as in radio waves. Light is one small part of the spectrum.
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