Imagine if engineers could build a computer to be millions of times faster than anything that exists today, yet so small it’s microscopic. John Preskill, a theoretical physicist at the California Institute of Technology, explains the science behind quantum computing, the next great frontier in computer science. "Science Behind the News" is produced in partnership with the National Science Foundation.
Science Behind the News – Quantum Computing
ANNE THOMPSON reporting:
Whether at home, the office, or in the palms of our hands, computer technology is getting smaller, faster, and more inseparable from our everyday lives. But imagine if engineers could build a computer to be millions of times faster than anything that exists today, yet so small it's microscopic. In October 2012, the Nobel Prize in Physics was awarded to Serge Haroche and David Wineland for their research on a new type of computer that may revolutionize the way information is processed-the quantum computer.
Prof. JOHN PRESKILL (California Institute of Technology): It's really a qualitatively different way of encoding, using, processing information than the way we do it in the computers we have today.
THOMPSON: Dr. John Preskill is an NSF funded theoretical physicist at the California Institute of Technology, who works in the field of quantum computing. A quantum computer is made up of two or more atoms or electrons, called quantum bits, or "qubits." These qubits, like all atomic particles, operate according to the laws of quantum mechanics.
PRESKILL: The word quantum refers to the laws of physics that describe microscopic objects, the laws of physics that hold sway at the scale of individual atoms, single electrons.
THOMPSON: While quantum computers sound complex, in reality, the way qubits represent information is the same as in traditional computers-- by using binary digits, or bits, designated as 0's or 1's. Scientists can control how these qubits exchange information from one to another by using the laws of physics to manipulate their state, spin, or vibration. The first method involves isolating two individual atoms and altering their energy state.
PRESKILL: We can shine lasers on the atoms and in a controlled way change the state of an atom from say to ground state to some combination of the ground state and the excited state.
THOMPSON: Normally an atom's electrons occupy the "ground state", which is the lowest level of energy an electron can occupy. Its configuration is represented on the Periodic Table of the Elements. If an atom's electrons do not match the ground state, then it's considered to be in the "excited state." By manipulating the state of an atom's electrons, scientists can make them represent either the 0 or 1 bit.
PRESKILL: And we could store a bit, like we do in digital computers today, by preparing each atom in either its ground state or an excited state.
THOMPSON: The second method for building a quantum computer involves controlling the spin of two isolated electrons. This spin can either be up or down, allowing them to also represent either the 0 or 1 bit.
PRESKILL: Electrons are like little magnets. And so the electron has a north pole and a south pole. And so we could store just an ordinary bit by saying that the electron's spin, its magnet, is oriented either up or down.
THOMPSON: David Wineland received the Nobel Prize for devising a third type of quantum computer, by isolating charged atoms, or ions, in an ion trap.
PRESKILL: The trap is like a bowl, and the ion sits at the bottom of the bowl, and it can rock back and forth around the bottom. And we can excite those vibrational modes, depending on whether the atom is in its ground state or its excited state. And that allows the two atoms to talk to one another.
THOMPSON: Though today's quantum computers are only a few qubits long, scientists hope they will reach the scale of thousands or even millions of qubits and be able to perform calculations too large and complex for today's traditional computers. Such breakthroughs could spark incredible advances in cybersecurity, medicine, science, and countless other fields.
PRESKILL: Probably the most important applications are ones that we just haven't thought of yet. Because quantum computing is a very new idea.
THOMPSON: Quantum computing, a new idea that could pave the way for big changes, by operating in very small ways.
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