Engineers At UNSW Discover New Fidelity Technique To Test Quantum Computing Accuracy

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UNSW

Silicon two-qubit gate achieves 98% fidelity

Global tech giants Google, IBM and several others are using tens of qubits to prototype quantum computers. Comprising qubits, also known as quantum bits, quantum computers are used to perform a series of calculations. In its present developed state, researchers are actively focused on the use of technologies like – trapped ions, superconducting circuits and semiconductor quantum dots to create the best qubits. After years of significant R&D undertaken by the computer industry, silicon has been found as the ideal material to build and integrate electronic devices.

Drawing on this, The University Of New South Wales’ approach has been to channel their energies into making qubits out of single atoms of phosphorus or quantum dots in silicon — the material that forms the basis of today’s computer chips. Back in 2015, researchers from the University discovered the way to enable quantum computer coding in silicon. Thus, they unveiled its achievement of having built a quantum logic gate in silicon, thereby making calculations between two qubits of information possible. 

Following up on this quantum computing breakthrough, engineers from UNSW have announced that they have measured the accuracy of silicon two-quantum bit (qubit) operations for the first time. With the university having measured the fidelity of two-qubit logic operations in silicon, its results have affirmed the use of silicon for quantum computing.

While researchers/teams across the globe have demonstrated two-qubit gates in silicon, UNSW revealed that the true accuracy of such a two-qubit gate was yet to be found, until its landmark achievement.

UNSW Scientia Professor Andrew Dzurak said, “All quantum computations can be made up of one-qubit operations and two-qubit operations — they’re the central building blocks of quantum computing,”. Once you’ve got those, you can perform any computation you want — but the accuracy of both operations needs to be very high.”

The University also revealed that while conducting its study, Clifford-based fidelity benchmarking was performed to assesses qubit accuracy across technology platforms. The result was an average two-qubit gate fidelity of 98%.

Dr Henry Yang, a senior research fellow at UNSW said, “Fidelity is a critical parameter which determines how viable a qubit technology is — you can only tap into the tremendous power of quantum computing if the qubit operations are near perfect, with only tiny errors allowed.” Dr. Yang conducted the experiment with Wister Huang, final-year PhD student in Electrical Engineering.

Following, this, Dr. Dzurak also explained that major issues would have cropped up in the realm of silicon quantum computing if the fidelity value of the research team was extremely low. He said, “And you’re going to have to correct quantum errors, even when they’re small. For error correction to be possible, the qubits themselves have to be very accurate in the first place — so it’s crucial to assess their fidelity. The more accurate your qubits, the fewer you need — and therefore, the sooner we can ramp up the engineering and manufacturing to realise a full-scale quantum computer.”

“The fact that it is near 99% puts it in the ballpark we need, and there are excellent prospects for further improvement. Our results immediately show, as we predicted, that silicon is a viable platform for full-scale quantum computing” he added while shedding light on how millions of qubits are essential for most of the application’s quantum computing promises. 

He believes that significantly higher fidelities can be achieved in the near future, thereby paving the way to full-scale, fault-tolerant quantum computation, as UNSW is on its way for a two-qubit accuracy, significant enough for quantum error correction.

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