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Atoms are one of the freakiest objects in the universe. What’s weird is that electrons inside atoms can be thought of as particles that behave like waves. It’s like saying you have a baseball that doesn’t definitely exist here or there, but has an indefinite position spread out everywhere, like a wave. From cell phones and computers to Blu-rayTM and the internet, nature’s ability to unify a wave and a particle has empowered us to create more cool technology than any other idea in history. Explore why the future is quantum! What’s the big idea? Small is different. In the tiny world of atoms, nature plays by bizarre rules that clash severely with commonsense. For instance, particles like electrons behave as if they can be in multiple places—or be moving in multiple directions—at the same time. Such remarkable behaviour is not only fascinating, it’s essential for the very existence of our day-to-day world. For example, in the Particle animation we see the best possible commonsense model of an atom: electrons behaving like ordinary particles, orbiting the atomic nucleus like planets orbit the sun. But this model is terribly wrong. If electrons moved like that they would emit electromagnetic waves, as do the oscillating electrons in a cell phone antenna. In a cell phone, powering those waves drains the battery. In an atom, powering those waves would drain the electrostatic energy stored between the nucleus and the electrons, causing the electrons to spiral into the nucleus and the atom to collapse. In other words, commonsense leads us to a model of the atom—and hence rocks, trees and people— that cannot exist in our universe! So what does an atom look like? Clearly, an atomic electron can’t stand still (electrostatic attraction would just pull it straight into the nucleus), nor can it move (as it would emit energy and the atom would collapse). So what does it do? Here’s a clue: if an electron was spread out along its orbit, so instead of a rotating particle it was a rotating ring, then no electromagnetic waves would be emitted, and the atom would be stable. Why? Because waves are created by things that oscillate, and there’s nothing oscillating about a rotating ring. A rotating ring of charge would create static electric and magnetic fields, but no electromagnetic waves that would carry energy away from the atom. So is this what’s happening? Well, not quite, because whenever we look at an electron, we always find a whole point-like particle here or there, never something spread out into a ring, or any other shape. Instead, the electron is a particle, but one that does not definitely exist here or there at any instant of time. It has an indefinite position that is spread evenly around its orbit (other spreads of indefinite position are also possible, but this is the closest quantum analogue to an orbiting particle). At any instant of time the electron could potentially be found anywhere in its orbit, and so, while not literally www.perimeterinstitute.ca/powerofideas so, it is effectively spread out into a rotating ring (actually, more of a rotating donut—see the Quantum Mechanics animation). In essence, the electron is a particle that behaves as if it is in many places at once! and a particle. Atoms work by rules that are completely alien to our everyday experience with the world, and yet, atoms underlie every such experience. It is a fantastic universe we live in! What’s it good for? Computers TM What is a xenopus? Google it and you’ll quickly learn everything there is to know about this claw-bearing African frog. How is this frog related to quantum mechanics? Answer: the internet, which is powered by computers, which in turn are powered by quantum mechanics. Computers have not only dramatically increased our ability to share This “ghostly” existence is described by a donutshaped wave circulating around the nucleus, which can circulate either way (see animation). Moreover, like the two waves moving in opposite directions in the Wave animation, which combine to produce a standing wave that is not moving, a single electron can, in essence, be circulating both ways simultaneously, and in this way can be effectively standing still! An electron inside an atom can move or stand still, but not in any ordinary sense of these words. An atom is an extraordinary object, whose very existence relies on nature’s ability to unify a wave knowledge, they also allow us to generate new knowledge—do calculations that wildly exceed human capacity. Supercomputers today are able to simulate complex physical processes on a global scale, in an attempt to better understand everything from earthquakes to global warming, and are even used to simulate the evolution of the entire universe—from the big bang to the present— to probe what it is made of and how it works. The profound positive impact that computers have had on science, engineering and society in general is, well, incalculable. Lasers Orange juice, 600 mL, $6.53—this information is obtained from simply passing the container over the scanning laser at the grocery store. Laser light is not ordinary light—it’s “quantum light”: a coherent shower of little packets of pure energy, called photons, capable of transmitting information over the internet, cutting through steel, surgically welding a TM torn retina, playing a Blu-ray Disc , printing a document or measuring the distance to the moon. It’s even being used to search for an answer to our global energy needs. One of the world’s largest lasers at the National Ignition Facility in the United States is attempting to spark miniature suns—to generate energy through fusion. Imagine a world with safe, clean, and virtually limitless energy. www.perimeterinstitute.ca/powerofideas Cryptography Imagine the ability to send secret messages anywhere in the world with absolute security. A new class of technologies that can detect eavesdroppers regardless of how clever they are or how sophisticated their snooping equipment; a perfect security guaranteed by the very laws of nature themselves—quantum laws. These quantum technologies have already been proven over short distances, and there are even commercially available systems. Governments, banks and a host of other organizations are extremely interested, with visions of new ways to do commerce and bolster national security. What’s the next step? Scientists and engineers have their eyes on an absolutely secure global satellite quantum communication network. Welcome to the quantum information age! Quantum Computers Quantum superposition, entanglement, and teleportation—three ingredients needed for a quantum computer. What’s a quantum computer? A new breed of computer that might make today’s supercomputers look like mere hand calculators. Instead of processing bits of information (binary digits, 0 or 1) they would process qubits of quantum information: quantum superpositions of both 0 and 1—simultaneously; a new kind of “quantum parallel” computer. Using quantum entanglement—one of the weirdest aspects of quantum mechanics—this quantum information would be quantum teleported between different parts of the computer. Scientists have already built small prototypes, and know of a few kinds of problems quantum computers can solve—like quantum database searching, or breaking the encryption codes we use today for secure communications. A huge, worldwide effort is currently underway attempting to scale up these prototypes and find new kinds of problems these amazing machines could solve. If successful, we may be in for a second computer revolution, possibly even more profound than the first. www.perimeterinstitute.ca/powerofideas