Researchers in Australia and the U.S. have made exciting headway in the quantum computing arms race. A multi-institutional team including the University of New South Wales and Sandia National Laboratory announced that they have accomplished a 99 percent accuracy rate with nuclear-spin qubits embedded in silicon.  

Led by Professor Andrea Morello of UNSW, the work was published in the journal Nature on Jan. 19. Accuracy achieved for 1-qubit operation fidelity was up to 99.95 percent, while 2-qubit fidelity was 99.37 percent within their three-qubit silicon quantum processor. 

Finding and correcting quantum errors has been a challenge in the journey to quantum advantage, which is a term for the much-anticipated time when quantum computers will solve real-world problems faster than classical computers. 

Building quantum processors large enough for these real-world applications is the ultimate goal, which can only be realized by addressing computing errors that compound the longer a quantum operation runs. Error detection and mitigation are crucial in scaling quantum computing because with more qubits in play, there are more chances for introducing errors. 

“When the errors [become] so rare, it becomes possible to detect them and correct them when they occur. This shows that it is possible to build quantum computers that have enough scale, and enough power, to handle meaningful computation,” said Morello. 

The team validated their findings using a method called gate set tomography, which is a technique for measuring qubit performance through quantum logic operations, or “gates,” that generates precise error reports, according to the team at Sandia National Laboratory which developed the diagnostic tool. 

This news comes on the heels of an earlier announcement that researchers from the University of Melbourne honed the technique of embedding single atoms into a silicon wafer. This research was led by David Jamieson who was also an author of this study. The scientists inserted phosphorus ions into a silicon substrate, which creates what Jamieson calls a qubit ‘chip’ that not only has potential for larger-scale applications but is also promising for current semiconductor manufacturers.

Regarding this new quantum accuracy research, Jamieson said, “The phosphorous atoms were introduced in the silicon chip using ion implantation, the same method used in all existing silicon computer chips. This ensures that our quantum breakthrough is compatible with the broader semiconductor industry.” 

Reaching an error rate of less than one percent is an important milestone that allows for easier quantum error correction. Morello is confident that because this goal has been achieved, “we can start designing silicon quantum processors that scale up and operate reliably for useful calculations.” 

To learn more, visit UNSW’s official announcement and the published Nature research.