For thousands of years, humans relied on their intuition to understand how the world works. Sure, the approach may have led to a few mistakes along the way -- it turns out the Earth isn't flat, for instance -- but ultimately it worked fairly well. Slowly but surely, humanity gained an understanding of everything from the laws of motion to thermodynamics, and all of it made intuitive sense.
And then came quantum mechanics, the absolutely baffling branch of physics exploring the very smallest types of matter. The study of quantum mechanics led to some truly astounding conclusions. For instance, scientists found that electrons behave both as waves and as particles, and the mere act of observing them changes the way they behave. Revelations like this one simply defied logic, prompting Einstein to declare "the more success the quantum theory has, the sillier it looks."
Einstein's sentiments still resonate today, more than a century after humanity's first insights into the quantum world; quantum mechanics makes perfect sense mathematically but defies our intuition at every turn. So it might surprise you that, despite its strangeness, quantum mechanics has led to some revolutionary inventions over the past century and promises to lead to many more in the years to come. Read on to learn about 10 practical applications of quantum mechanics.
10. The Transistor
In the fall of 1945, the U.S. Army completed its work on ENIAC, the world's first vacuum-tube computer. All told, ENIAC weighed more than 30 tons (27 metric tons), had the footprint of a small house and cost nearly half a million dollars to create [source: Weik]. Fortunately, by the time ENIAC was built, Bell Laboratories was already well on its way to developing a replacement for power-hungry, space-consuming vacuum tubes: the transistor. Transistors act as both an amplifier and a switch for electronic signals, functions essential to virtually all modern electronic equipment, and without quantum mechanics, they likely wouldn't exist.
That's because transistors rely on the unique properties of semiconductors -- materials that can act as either a conductor or an insulator -- to operate. Thanks to groundbreaking discoveries in quantum mechanics, Stanford researcher Eugene Wigner and his student, Frederick Seitz, were the first to manipulate the properties of semiconductors in the 1930s. Armed with their research, scientists from Bell Laboratories developed the first rudimentary transistors over the next decade, and by 1954, the United States military had constructed TRIDAC, the first transistor-based computer. Unlike the monstrous, unreliable vacuum-tube computers that preceded it, TRIDAC occupied only 3 cubic feet (0.08 cubic meters) and needed only 100 watts of power to operate [source: PBS]. Today, companies like Intel and AMD fabricate cutting-edge microprocessors containing billions of microprocessors, and we have quantum mechanics to thank.
7. Quantum Cryptography
The Spartans were known for their bravery and ferocity in battle, but they had brains in addition to brawn. Knowing the importance of keeping their plans from their enemies, they used a device called a scytale to encode and decode secret messages. By wrapping a strip of parchment around the rodlike device, writing secret messages across the strip and then unwrapping the parchment, a Spartan commander could create a message that looked like gibberish unless it was wrapped around a scytale of the same size. The Spartan's rudimentary form of cryptography worked well enough in its day, but cryptography has come a long way since.
Today, quantum cryptography promises to be unbreakable (in theory, at least). Quantum cryptography takes advantage of some of the quirky properties of the smallest bits of matter to operate. For instance, simply measuring the properties of a quantum system changes those properties. Accordingly, if someone intercepts the quantum key to an encoded message, they will change the key in the process. When the intended recipient examines the key, that person then knows the key was intercepted and can request a new key.
You might think such an ingenious form of cryptography would be impossible to crack, but researchers from Norway and Singapore are proving otherwise. By fooling the instruments used to read quantum messages, they've been able to intercept messages without tipping off the intended recipient.
6. Randomness Generator
Believe it or not, a randomness generator isn't something the cast of Monty Python used to create their preposterous comedy skits. Instead, it summons up truly random numbers with the help of quantum mechanics. Why are scientists looking to the quantum world for random numbers when they could just roll a pair of dice? It turns out that the only true randomness occurs at the quantum level. If scientists had enough information about a dice roll, they could actually simulate the roll in advance and predict the outcome. The same goes for roulette wheels, lottery balls and even computer-generated random numbers; ultimately, all of them are predictable.
The quantum world, on the other hand, is completely unpredictable, and researchers at the Max Planck Institute for the Physics of Light have used that unpredictability to develop the equivalent of quantum dice. To do this, the researchers generate something called quantum noise by creating fluctuations in a vacuum. By then measuring the random levels of noise produced, the researchers can develop truly random numbers used for everything from data encryption to weather simulators. Better yet, their number generator fits on a solid-state chip, making it adaptable for a variety of different uses.
5. Lasers
Like quantum mechanics itself, the laser was once thought to be an academic curiosity with no practical use. Today, of course, lasers are at the core of everything from CD players to missile-destroying defense systems, but without an understanding of quantum mechanics, we likely wouldn't have lasers at all.
Lasers work by exciting the electrons orbiting atoms, which then emit photons as they return to lower energy levels. The emitted photons emitted then cause other atoms to release photons of the same energy level and direction, creating a steady stream of photons we see as a laser beam.
The entire process operates on one of theoretical physicist Max Planck's founding principles of quantum mechanics, which states that atomic energy levels are discrete rather than continuous. In other words, when atoms radiate energy, they do so in discrete amounts known as quanta, and it's by stimulating the emission of a specific quanta of energy that lasers work.
4. Ultraprecise Thermometers
If you took the thermometer from your medicine cabinet and tried to measure temperatures less than a hundredth of a degree above absolute zero, it probably wouldn't fare very well. Fortunately, researchers from Yale have developed a thermometer capable of not just measuring such extreme temperatures, but doing so with unparalleled accuracy.
To build the thermometer, the team had to entirely reimagine a thermometer's design. In their search for a more accurate thermometer, the scientists found what they were looking for in quantum tunneling. Quantum tunneling is the quantum equivalent of digging through a mountain rather than climbing up and over it. The process generates quantum noise, which, when measured by the team's quantum thermometer, can precisely tell the temperature of a given object.
Granted, you'll probably never find a quantum thermometer on the shelves of your local drugstore, but the instrument does hold great potential for research laboratories, particularly those working with extremely low temperatures. In the meantime, the researchers are hoping to improve the accuracy of the thermometer over a variety of conditions, hoping that, as the thermometer becomes more versatile, more laboratories will use it moving forward.
3. Quantum Computers
In a paper published in April 1965, Intel co-founder Gordon Moore made some bold predictions about the future of computers. Among them was his assertion that the density of transistors on a square inch of silicon would double every couple of years, a prediction that's held true until today. But Moore's law, as the prediction came to be known, may be nearing its expiration date. As soon as 2020, silicon chips may reach their physical limits, with transistors becoming so small that they're affected by the laws of the quantum world.
But what if, instead of fighting against the laws of the quantum world, we leveraged them? Researchers developing quantum computers seek to do just that. Quantum computers would have one huge advantage over current computers: parallel processing. With parallel processing, quantum computers could execute multiple tasks concurrently rather than sequentially, as current processors do. As a result, quantum computers could be exponentially more powerful than the computers we have now.
Before quantum computing becomes a reality, scientists will have to tackle some big challenges. Quantum computers operate using qubits, which are capable of holding much more information than the "1" or "0" values of conventional bits. Unfortunately, qubits are notoriously difficult to create because they require the entanglement of multiple particles. To date, only 12 particles have been entangled at once, and that number would have to increase ten- or even one-hundred-fold before quantum computers could be commercially viable. Still, we're likely much closer to seeing quantum computers than the next item on our list.
2. Instantaneous Communication
Between cell phones, e-mail and texting, you might think we have instantaneous communication covered. In reality, your voice, e-mail and text all take a little time to get to their destination, but not enough time to cause a problem. In the distant future, though, humans may need to communicate across galaxies rather than continents, in which case even light speed communication might not be fast enough. But there may be hope for those future interstellar citizens yet; some scientists think that quantum mechanics could hold the key to making communication truly instantaneous, regardless of the distance.
The key to making instantaneous communication a reality may lie in something known as quantum entanglement, which Einstein referred to as "spooky action at a distance." When two particles are entangled, any change to one of the particles creates an instantaneous change in the other, regardless of the distances separating them. Using quantum entanglement, we may one day be able to relay messages across the universe by manipulating one particle and causing a corresponding change in its entangled counterpart. Whether instantaneous communication is actually possible is still a matter of debate, as some physicists insist that entangled particles can't actually transfer information. If that's the case, the next item on our list might never become a reality.
1. Teleportation
You've seen teleportation in all sorts of science-fiction movies and television shows, and now it's finally a reality. Sort of. While scientists are nowhere near being able to beam objects wherever they like, they've made a step in the right direction. In this case, though, researchers from the University of California, Berkeley, succeeded in teleporting information rather than matter. Specifically, the team was able to manipulate the properties of one atom while simultaneously affecting another atom located about 3 feet (1 meter) away using quantum entanglement. The team's breakthrough was just the latest development in the admittedly fledgling study of teleportation.
Previously, a team of six engineers working at IBM proved that, at least in theory, teleportation of whole objects is possible. It's worth noting, however, that the original object must be destroyed in the process. That's because the process of "copying" the original object actually changes the object in the process, like a demented fax machine that can't help but shred your document as it sends it out to another fax machine. And of course, simply knowing that teleportation is possible doesn't mean that we'll ever actually teleport an object. In the meantime, research in the field is also proving useful in areas like quantum cryptography and communication.
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