Quantum qubits with ten times longer superposition stability

Engineers from UNSW’s Centre for Quantum Computation & Communication Technology (CQC2T) have created a new quantum bit which 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.

UNSW is focused on developing quantum computers — theoretical processors based on quantum mechanics, with the potential to solve problems far beyond the scope of today’s supercomputers — in silicon, the material that has underpinned the information technology industry for decades.

The feat, outlined this morning in the journal Nature Nanotechnology, is the latest record achieved by the UNSW centre and partner research groups. They include creating the world’s first single-atom transistor, achieving the longest-lived quantum memory and the most enduring qubits in the solid state, and fashioning the narrowest conducting wires ever made in silicon.

The team has now created a “dressed qubit”, a single atom merged with an electromagnetic field. The researchers say it can remain in stable “superposition” — multiple states and locations — for 10 times as long as standard qubits.

These multiple states give quantum computers their extraordinary potential, allowing numerous interactions rather than being limited to the binary actions of classical transistors, and increasing processing power exponentially every time another particle is added to the network.

Lead author Arne Laucht said the new quantum bit was “more versatile and long-lived” than previous attempts. “(It) will allow us to build more reliable quantum computers.”

Team leader Andrea Morello likened the improved control potential to the difference between AM and FM radio signals. “The dressed qubit is more immune to noise,” he said.

A scanning electron microscope image of a qubit, similar to the one used. Highlighted are the positions of the tuning gates (pink), the microwave antenna (blue/grey), and the single electron transistor used for spin readout (green). Credit – Guilherme Tosi and Arne Laucht/UNSW

The UNSW team is world leader in one of five separate approaches to creating quantum computers — a global competition that has been dubbed the space race of the 21st century.

Quantum computers are expected to have particular potential in searching large databases, solving complicated sets of equations and modelling atomic systems, such as biological molecules. Advocates say they could boost medical research and manufacturing by accelerating the computer-aided design of new materials and pharmaceuticals.

They could also have unprecedented applications in finance, security, defence and traffic control, among other fields.

SOURCES- youtube, The Australian