Quantum computing in silicon hits 99 percent accuracy


Researchers in Australia have shown that near-error-free quantum computing is conceivable, clearing the path for developing silicon-based quantum devices that are compatible with existing semiconductor manufacturing technologies.

“Our procedures were 99 percent error-free, as shown by today’s publication in Nature,” says Professor Andrea Morello of the University of New South Wales, who led the research.

It becomes easy to identify and repair faults when they occur when the errors are so infrequent. This demonstrates that it is feasible to construct quantum computers with sufficient size and power to perform meaningful computing. ‘This piece of study represents a significant milestone on the route that will take us there,’ Professor Morello explains.

Quantum computing in silicon hits the 99% threshold

This is one of three papers published today in Nature that independently prove the existence of robust, reliable quantum computing in silicon. Morello’s study is the third to do so. The journal’s front cover shows a picture of this ground-breaking discovery.

Morello et al. obtained 1-qubit operating fidelity of up to 99.95 percent and a 2-qubit fidelity of 99.37 percent using a three-qubit system consisting of an electron and two phosphorus atoms implanted in silicon through ion implantation, according to their findings.

With electron spins in quantum dots generated in a stack of silicon and silicon-germanium alloy (Si/SiGe), a Delft team headed by Lieven Vandersypen obtained 99.87 percent one-qubit and 99.65 percent two-qubit fidelities, according to the researchers.

A team headed by Seigo Tarucha at RIKEN in Japan produced 99.84 percent 1-qubit and 99.51 percent 2-qubit fidelities in a two-electron system utilizing Si/SiGe quantum dots, which was comparable to the results obtained by the RIKEN team.

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To verify the performance of their quantum computers, the UNSW and Delft teams used a complex approach called gate set tomography, which was created by Sandia National Laboratories in the United States and made freely accessible to the scientific community.

As a result of the high isolation of nuclear spins from their surroundings, Morello had previously proved that he could store quantum information in silicon for up to 35 seconds using this technique.

In the quantum universe, Prof. Morello explains, “35 seconds is an eternity.” The lifespan of the well-known Google and IBM superconducting quantum computers is around one hundred microseconds — roughly one million times shorter than that of the newer technology.

However, the trade-off was that isolating the qubits made it seem as if they could not communicate, which was essential for them to do accurate calculations.

Nuclear spins learn to interact accurately.

Using an electron surrounding two phosphorus atom nuclei, as described in today’s study, he and his colleagues were able to overcome this challenge.

It is possible to do a quantum operation on two nuclei that are coupled to a single electron, according to Dr. Mateusz M? dzik, one of the study’s primary experimental authors.

“While you aren’t operating the electron, those nuclei are securely storing their quantum information. The electron, however, gives you the option of allowing them to communicate with one another, allowing you to realize universal quantum operations that may be applied to any computer issue.”

According to Dr. Serwan Asaad, another of the critical experimental authors, “This is an unlocking technique.” “The nuclear spins serve as the central processing unit of the quantum processor. If you entangle these qubit nuclei with the electron, the electron may be transferred to another location and entangled with other qubit nuclei that are farther away, paving the door for the creation of vast arrays of qubits capable of performing robust and useful calculations.”

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Dr. David Jamieson, a research leader at the University of Melbourne, gives more explanation: “Ion implantation was utilized to inject the phosphorus atoms into the silicon chip, which is the same approach that is now employed in all-silicon computer chips on the market. As a result, our quantum breakthrough is compatible with the entire semiconductor industry, which is a significant achievement.”

All modern computers use some error correction and data redundancy. Still, the constraints of quantum physics create significant limits on how error correction and data redundancy may be implemented in a quantum computer system. Prof. Morello provides the following explanation: “To use quantum error correction techniques, you often require error rates of less than one percent. With this accomplishment, we may now go on to constructing silicon quantum computers that can scale up and perform consistently for important computations in the future.”


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