A millisecond – or two thousandths of a second – is an unusually long span in the world of quantum computing. On these time scales, a blink of an eye – at a tenth of a second – is like an eternity.
Now a team of researchers at the University of New South Wales in Sydney has broken ground in proving that “spin qubits” – properties of electrons that are the basic units of information in quantum computers – can hold information for up to a millisecond. Known as ‘correlation time’, it is the length of time during which qubits can be processed in increasingly complex computations, and the completion is 100 times longer than previous standards at the same time. Quantum processor.
“Longer consistency time means you have more time to spend Quantitative information They are stored—which is exactly what you need when performing quantum operations,” says doctoral student Ms. Amanda Sidhouse, whose work in theoretical quantum computing contributed to the achievement.
“Consistency time basically tells you how long you can go through all the operations of whatever algorithm or sequence you want to do before you lose all the information in your qubits.”
In quantum computing, the more you keep the spins moving, the higher the chance of preserving information during computations. When the rotating qubits stop spinning, the computation collapses and each represents the values qubit lost. The concept of expanding cohesion was Already confirmed experimentally 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 biggest challenges, such as searching for effective vaccines, modeling weather systems and predicting the effects of climate change.
late last year The same team at the University of New South Wales in Sydney solved a technical problem that has baffled engineers for decades on how to handle millions of qubits without generating more heat and interference. Instead of adding thousands of tiny antennas to control millions of electrons using magnetic waves, the research team came up with a way to use just one antenna to control all the qubits in the chip by inserting a crystal called a dielectric resonator. These results have been published in science progress.
This solved the problem of space, heat, and noise that would inevitably increase as more and more qubits were introduced online for mind-bending calculations that are possible when qubits are not just 1 or 0 like traditional binary computers, but both at the same time, Using a phenomenon known as quantum superposition.
Universal Control vs Single Control
However, this proof of concept achievement still leaves some challenges to be resolved. Principal Investigator Ms. Ingfield Hansen has joined Ms. Sidhouse to address these issues in a series of peer-reviewed papers. physical review bAnd the A . physical review And the Applied Physics Reviews—The last paper published this week only.
The ability to control millions of qubits with a single antenna was a huge step forward. But while controlling millions of qubits at once is a feat, working quantum computers will also need to manipulate them individually. If all qubits rotate at approximately the same frequency, they will have the same values. How can we control them individually so that they can represent different values in a calculation?
“First, we showed, in theory, that we can improve the coherence time by continuously rotating the qubits,” Hansen says.
“If you imagine paintings by circus artists spinning, while they are still spinning, performance can go on. In the same way, if we drive qubits constantly, they can retain information for much longer. We have shown that these ‘worn’ qubits have coherence times of more than 230 microseconds. [230 millionths of a second]. “
After the team showed that coherence times could be extended with so-called ‘wearable’ qubits, the next challenge was to make the protocol more robust and to show that the globally controlled electrons could also be individually controlled so that they could hold the different values required for complex computations.
This was achieved by creating what the team dubbed “SMART” – sine-modified, permanent, and custom qubits.
Instead of making the qubits spin in circles, they manipulated them to swing back and forth like a metronome. Then, if the electric field Applied individually to any qubit – making it out of resonance – it can be placed in a different rhythm than its neighbors, but still moves in the same rhythm.
“Think of it as two kids on a swing that pretty much go back and forth in sync,” says Ms. Sidhouse. “If we give one of them a push, we can make them come to the end of their arc at opposite ends, so one can be a zero while the other is now a 1.”
The result is that not only can the qubits be controlled individually (electronically) while under the influence of global control (magnetic) but the coherence time, as mentioned earlier, is significantly longer and suitable for quantum computations.
“We have demonstrated a simple and elegant way to control all qubits simultaneously which also comes with better performance,” says Dr. Henry Yang, one of the team’s senior researchers.
“The SMART protocol will be a potential pathway for large-scale quantum computers.”
The research team is led by Professor Andrew Dzurak, CEO and founder of Diraq, a University of New South Wales company that is developing quantum computer processors that can be made using standard silicon chip manufacturing.
“Our next goal is to demonstrate this work with two-qubit computations after demonstrating a proof-of-concept in our experimental paper with a single qubit,” Hansen says.
“Next, we want to show that we can do this for a few qubits as well, to show that the theory is proven in practice.”
Amanda E. Sidhouse et al., Protocol for the Quantitative Computation of Garment Turnover in a Global Sphere, physical review b (2021). DOI: 10.1103/ PhysRevB.104.235411
Ingvild Hansen et al, Pulse engineering in a global field of robust and comprehensive quantum computation, A . physical review (2021). DOI: 10.1103/ PhysRevA.104.062415
I.Hansen et al, Implementation of an advanced dislocation protocol for global qubit control in silicon, Applied Physics Reviews (2022). doi: 10.1063/5.0096467
University of New South Wales
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