A group of scientists at the National Institute of Standards and Technology recently came a step closer to figuring out where the boundary lies between the quantum and classical physical worlds, and their discovery has big implications for the future of quantum computers— which would have much faster and more powerful processors than our computers do today.
The field of quantum mechanics deals with the behavior of atoms and subatomic particles. In this world, the rules of classical physics seem to go right out the window. Particles can be in two places at the same time (called superposition) and generally act in ways you’d never expect to see in our everyday world. One of the strangest phenomenon in quantum mechanics is called quantum entanglement, where two or more particles are “entangled” and an action performed on one effects the others. (This would be sort of like having an object on Earth and another on the moon, and if you did something to the one on earth it would instantly affect the one on the moon.) Once entangled, the two particles stay inextricably linked. Quantum entanglement is so strange, in fact, that Einstein called it “spooky action at a distance.”
Until recently, physicists had only been able to demonstrate quantum entanglement through highly esoteric examples, such as entangling the spins of electrons in atoms. But the NIST group was able to entangle the mechanical motion of two sets of vibrating ions. “This experiment demonstrates entanglement in a system that everybody can relate to: Mechanical oscillators,” says John Jost, a graduate student at the University of Colorado at Boulder, who worked on the team of researchers. “Mechanical oscillators pervade our everyday life, from vibrating violin strings to the pendulum on a grandfather clock.”
The NIST group, who published their findings in the June 4 issue of Nature, separated two pairs of ions in a container where the air had been removed. The pairs consisted of a beryllium and magnesium ion each. First they manipulated the four ions with laser beams to entangle an internal property in the two beryllium ions, then separated the pairs a quarter of a millimeter apart—which is a huge distance when it comes to atoms. As Jost explains, if the ions were the size of soccer balls (roughly 20 million times their size), you’d place one pair 88 meters apart at the penalty kick marks of a soccer field, and the other set of ions the same distance apart, but nearly 5 kilometers away. When the researchers changed the movement of one set of the ions, the other set immediately responded.
So what does this mean for the future of computers? Theoretically, quantum computers would harness the power of molecules and atoms for memory and processing. Although quantum computing is still only in a nascent stage, it could lead to vastly more powerful and sophisticated machines. Computer technology is improving all the time—you just need to take a walk through any electronics store to see that—and quantum computers could essentially be the next step after we’ve reached the boundary of where we can go with classical machines. While today’s computers manipulate bits that exist in only two states— 0 or 1— quantum computers would also be able to encode information in qubits. These quantum bits can exist in superposition—so they’d be in two places at once. Of course this is a long ways off, but scientists can dream. “One of the most popular ideas for building a quantum computer with trapped ions would involve having many ions (thousands or millions), entangled and in superpositions, whizzing around and being manipulated by laser beams,” says Jost. “This experiment should play an important role in building a quantum computer with trapped ions.”
Want to know more about the NIST team's experiment? Check out an animation of what they did, here.
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