A Big Step Toward a Silicon Quantum Computer
Quantum computers could more easily become a reality if they incorporated the silicon semiconductor processing used by the modern electronics industry. Physicists in Australia have recently taken a new step toward that vision by reading and writing the nuclear spin state of a single phosphorus atom implanted in silicon.
In a breakthrough reported in the 18 April edition of the journal Nature, physicists have finally achieved an idea first proposed in 1998 by Bruce Kane, a physicist at the University of Maryland, in College Park. Such success could lead to quantum computers based on the same silicon-processing technology used for computer chips.
“What we are trying to do is demonstrate that there is a viable way to take the same physical platform and fabrication technology used to make any computer and mobile phone in the world, and twist it into a technology for quantum information processing,” says Andrea Morello, a quantum physicist at the University of New South Wales, in Australia.
Scientists envision quantum computers as the ideal devices for cracking modern encryption codes, searching through huge databases, and understanding the biological interactions of molecules and drugs. Quantum computing’s potential comes from harnessing the laws of quantum physics that allow the spin state of an electron or an atom’s nucleus to achieve “superposition”—existing in more than one state at a time. A classical computer bit can exist either as a 1 or a 0, but a quantum bit, or qubit, is capable of existing in multiple states at the same time.
With other quantum computing approaches, researchers have tried trapping and isolating atoms by using electromagnetic fields or superconductor materials. By comparison, Kane suggested harnessing the nuclear spin of phosphorus atoms embedded in a silicon crystal as a qubit.
Silicon-based quantum computing also offers long coherence times for electron and nuclear spins, Kane says. That means the electron spin states and nuclear spin states acting as qubits could hold on to their information for long periods of time, something that other quantum computing schemes have struggled with.
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