Engineers Turn Nucleus Of Silicon Atom Into Quantum Bit
Researchers have achieved a quantum breakthrough, turning the nucleus of an atom into a qubit or quantum bit – the building blocks of super powerful quantum computers of the future.
AsianScientist (Apr. 18, 2013) - Australian engineers have demonstrated that quantum information can be "written" onto the nucleus of a single atom in silicon and "read" out with incredible accuracy.
The results, published today in the journal Nature, have significant implications: by turning the nucleus of an atom into a qubit or quantum bit, we are now one step closer to super powerful quantum computers of the future.
"We have adapted magnetic resonance technology, commonly known for its application in chemical analysis and MRI scans, to control and read-out the nuclear spin of a single atom in real time," says senior author Associate Professor Andrea Morello from the School of Electrical Engineering and Telecommunications (EE&T) at UNSW.
The nucleus of a phosphorus atom is an extremely weak magnet, which can point along two natural directions, either "up" or "down." In the strange quantum world, the magnet can exist in both states simultaneously – a feature known as quantum superposition.
The natural positions are equivalent to the "zero" and "one" of a binary code, as used in existing classical computers. In this experiment, the researchers controlled the direction of the nucleus, in effect "writing" a value onto its spin, and then "reading" the value out – turning the nucleus into a functioning qubit.
"We achieved a read-out fidelity of 99.8 percent, which sets a new benchmark for qubit accuracy in solid-state devices," says UNSW Scientia Professor Andrew Dzurak, who is also Director of the Australian National Fabrication Facility at UNSW, where the devices were made.
Previously, the team reported in Nature the first functional quantum bit based on an electron bound to a phosphorus atom embedded in silicon, "writing" information onto its spin and then "reading" the spin state back out.
With their latest result, the team has dug even deeper into the atomic structure to manipulate and measure the spin of its nucleus. This is the core of an atom, containing most of its mass, but its diameter is only about one-millionth that of the atom’s diameter.
"This means it's more challenging to measure, but it's almost completely immune to disturbances from the outside world, which makes it an exceptional quantum bit,” says lead author and UNSW engineering student Jarryd Pla. "Our nuclear spin qubit can store information for longer times and with greater accuracy. This will greatly enhance our ability to carry out complex quantum calculations once we put many of these qubits together."
The article can be found at: Pla JJ et al. (20130 High-fidelity readout and control of a nuclear spin qubit in silicon.
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