HomeSciencePhysicsQuantum computing engineers set new standard in silicon chip performance

Quantum computing engineers set new standard in silicon chip performance

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Two milliseconds – or two thousandths of a second – is an extraordinarily long time in the world of quantum computers. On these time scales, the blink of an eye – at a tenth of a second – is like an eternity.

Now a team of researchers from UNSW Sydney has broken new ground by proving that “spin qubits” — properties of electrons that represent the basic units of information in quantum computers — can hold information for up to two milliseconds. Known as ‘coherence time’, the length of time that qubits can be manipulated in increasingly complicated calculations, the performance is 100 times longer than previous benchmarks in the same quantum processor.

“A longer coherence time means you have more time about which you quantum information is stored – which is exactly what you need when performing quantum operations,” said PhD student Ms Amanda Seedhouse, whose work in theoretical quantum computing contributed to the achievement.

“The coherence time basically tells you how long you can do all the operations in any algorithm or order before you lose all the information in your qubits.”

With quantum computing, the more you can keep spins moving, the greater the chance that the information will be preserved during calculations. When spin qubits stop spinning, the calculation collapses and the values ​​are represented by each qubit are lost. The concept of extending coherence was: already experimentally confirmed by quantum engineers at UNSW in 2016.

Making the task even more challenging is the fact that working quantum computers of the future will need to track the values ​​of millions of qubits if they are to solve some of humanity’s greatest challenges, such as finding effective vaccines, modeling weather systems and predicting the effects of climate change.

End of last year the same team at UNSW Sydney solved a technical problem that had baffled engineers for decades on how to manipulate millions of qubits without generating more heat and interference. Instead of adding thousands of tiny antennas to control millions of electrons with magnetic waves, the research team devised a way to use just one antenna to control all the qubits in the chip by introducing a crystal called a dielectric resonator. . These results were published in scientific progress.

This solved the problem of space, heat and noise that would inevitably increase as more and more qubits are brought online to perform the mind-boggling calculations possible when qubits represent not just 1 or 0 like conventional binary computers, but both at once. using a phenomenon known as quantum superposition.

Global versus individual management

However, this proof-of-concept achievement left a few challenges to solve. Lead Investigator Ms Ingvild Hansen joined Ms Seedhouse to address these issues in a series of articles published in the journals Physical assessment B, Physical Assessment A and Applied Physics Reviews-the last article published just this week.

Being able to control millions of qubits with just one antenna was a big step forward. But while controlling millions of qubits at once is a great feat, working quantum computers will also have to manipulate them individually. If all the spin qubits rotate at nearly the same frequency, they have the same values. How can we check them individually so that they can represent different values ​​in a calculation?

“First, we theoretically showed that we can improve coherence time by continuously rotating the qubits,” says Ms. Hansen.

“If you imagine a circus performer spinning plates while they’re still spinning, the performance can go on. Similarly, if we continuously control qubits, they can hold information longer. We showed that such ‘dressed’ qubits had coherence over times of more than 230 microseconds [230 millionths of a second].”

After the team showed that coherence times could be extended with so-called ‘dressed’ qubits, the next challenge was to make the protocol more robust and show that the globally driven electrons can also be individually driven, so that they can hold different required values. for complex calculations.

This was accomplished by creating what the team called the “SMART” qubit protocol: sinusoidally modulated, always rotating, and custom-tailored.

Instead of spinning qubits in circles, they manipulated them to rock back and forth like a metronome. Then, if a electric field is applied individually to each qubit – bringing it out of resonance – it can be set at a different tempo than its neighbors, but still move in the same rhythm.

“Think of it like two kids on a swing going forward and back in almost synchronization,” says Ms. Seedhouse. “If we give one of them a nudge, we can get them to reach the end of their arc at opposite ends so that one can be a 0 while the other is now a 1.”

The result is that not only can a qubit be controlled individually (electronically) under the influence of global control (magnetic), but the coherence time is, as mentioned before, considerably longer and suitable for quantum calculations.

“We showed a simple and elegant way to control all qubits at once, which also comes with better performance,” said Dr. Henry Yang, one of the senior researchers on the team.

“The SMART protocol will be a potential path for large-scale quantum computing.”

The research team is led by Professor Andrew Dzurak, CEO and founder of Diraq, a UNSW spinout company developing quantum computer processors that can be made using standard silicon chip manufacturing.

Next steps

“Our next goal is to show that this works with two-qubit calculations after showing our proof-of-concept in our one-qubit experimental paper,” said Ms. Hansen.

“After that, we want to show that we can also do this for a handful of qubits, to show that the theory has proven itself in practice.”

Construction of robust and scalable molecular qubits

More information:
Amanda E. Seedhouse et al, Quantum Calculation Protocol for Clothed Spins in a Global Field, Physical assessment B (2021). DOI: 10.1103/PhysRevB.104.235411

Ingvild Hansen et al, Pulse engineering of a global field for robust and universal quantum computation, Physical Assessment A (2021). DOI: 10.1103/PhysRevA.104.062415

I. Hansen et al, Implementation of an advanced association protocol for global qubit control in silicon, Applied Physics Reviews (2022). DOI: 10.1063/5.0096467

Quote: For the longest time: Quantum computing engineers set new standard in silicon chip performance (2022, September 30) retrieved September 30, 2022 from -chip .html

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