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Quantum computers with 10-fold boost in stability achieved

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Quantum computer
Science   In a future silicon quantum computer

UNSW engineers have created a new quantum bit that remains in a stable superposition for 10 times longer than previously achieved, dramatically expanding the number of calculations that could be performed in a future silicon quantum computer.


Engineers at the University of New South Wales (UNSW) have created a new quantum bit that remains in a stable superposition for 10 times longer than previously achieved, dramatically expanding the time during which calculations could be performed in a future silicon quantum computer.

The new quantum bit, made up of the spin of a single atom in silicon and merged with an electromagnetic field - known as 'dressed qubit' - retains quantum information for much longer that an 'undressed' atom, opening up new avenues to build and operate the superpowerful quantum computers of the future.

The results are published today in the international journal, Nature Nanotechnology.

"We have created a new quantum bit where the spin of a single electron is merged together with a strong electromagnetic field," said Arne Laucht, a Research Fellow at the School of Electrical Engineering & Telecommunications at UNSW, and lead author of the paper.

"This quantum bit is more versatile and more long-lived than the electron alone, and will allow us to build more reliable quantum computers."

Building a quantum computer has been called the 'space race of the 21st century' -- a difficult and ambitious challenge with the potential to deliver revolutionary tools for tackling otherwise impossible calculations, such as the design of complex drugs and advanced materials, or the rapid search of massive, unsorted databases.

Its speed and power lie in the fact that quantum systems can host multiple 'superpositions' of different initial states, which in a computer are treated as inputs which, in turn, all get processed at the same time.

"The greatest hurdle in using quantum objects for computing is to preserve their delicate superpositions long enough to allow us to perform useful calculations," said Andrea Morello, leader of the research team and a Program Manager in the ARC Centre for Quantum Computation & Communication Technology (CQC2T) at UNSW.

"Our decade-long research program had already established the most long-lived quantum bit in the solid state, by encoding quantum information in the spin of a single phosphorus atom inside a silicon chip, placed in a static magnetic field."

What Laucht and colleagues did was push this further: "We have now implemented a new way to encode the information: we have subjected the atom to a very strong, continuously oscillating electromagnetic field at microwave frequencies, and thus we have 'redefined' the quantum bit as the orientation of the spin with respect to the microwave field."


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