A world-record result in reducing errors in semiconductor electron ‘spin qubits’, a type of building block for quantum computers, has been achieved using the theoretical work of quantum physicists at the University of Sydney Nano Institute and School of Physics.
The experimental result by UNSW engineers demonstrated error rates as low as 0.043 percent, lower than any other electron spin qubit. The joint research paper by the Sydney and UNSW teams was published this week in Nature Electronics and is the journal’s cover story for April.
“Reducing errors in quantum computers is needed before they can be scaled up into useful machines,” said Professor Stephen Bartlett, a corresponding author of the paper.
“Once they operate at scale, quantum computers could deliver on their great promise to solve problems beyond the capacity of even the largest supercomputers. This could help humanity solve problems in chemistry, drug design and industry.”
There are many types of quantum bits, or qubits, ranging from those using trapped ions, superconducting loops or photons. A ‘spin qubit’ is a quantum bit that encodes information based on the quantised magnetic direction of a quantum object, such as an electron.
Australia, and Sydney in particular, is emerging as a global leader in quantum technology. The recent announcement to fund the establishment of a Sydney Quantum Academy, underlines the huge opportunity in Australia to build a quantum economy based on the world’s largest concentration of quantum research groups here in Sydney.
No practice without theory
While much of the recent focus in quantum computing has been on advances in hardware, none of these advances have been possible without the development of quantum information theory.
The University of Sydney quantum theory group, led by Professor Stephen Bartlett and Professor Steven Flammia, is one of the world powerhouses of quantum information theory, allowing for engineering and experimental teams across the globe make the painstaking physical advances needed to ensure quantum computing becomes a reality.
The work of the Sydney quantum theory group was essential for the world-record result published in Nature Electronics.
Professor Bartlett said: “Because the error rate was so small, the UNSW team needed some pretty sophisticated methods to even be able to detect the errors.
“With such low error rates, we needed data runs that went for days and days just to collect the statistics to show the occasional error.”
Professor Bartlett said once the errors were identified they needed to be characterised, eliminated and recharacterised.
“Steve Flammia’s group are world leaders in the theory of error characterisation, which was used to achieve this result,” he said.
The Flammia group recently demonstrated for the first time an improvement in quantum computers using codes designed to detect and discard errors in the logic gates, or switches, using the IBM Q quantum computer.
Professor Andrew Dzurak, who leads the UNSW research team, said: “It’s been invaluable working with professors Bartlett and Flammia, and their team, to help us understand the types of errors that we see in our silicon-CMOS qubits at UNSW.
“Our lead experimentalist, Henry Yang, worked closely with them to achieve this remarkable fidelity of 99.957 percent, showing that we now have the most accurate semiconductor qubit in the world.”
Professor Bartlett said that Henry Yang’s world-record achievement will likely stand for a long time. He said now the UNSW team and others will work on building up towards two qubit and higher-level arrays in silicon-CMOS.
Fully functioning quantum computers will need millions, if not billions, of qubits to operate. Designing low-error qubits now is a vital step to scaling up to such devices.
Professor Raymond Laflamme is Chair of Quantum Information at the University of Waterloo in Canada and was not involved in the study. He said: “As quantum processors become more common, an important tool to assess them has been developed by the Bartlett group at the University of Sydney. It allows us to characterise the precision of quantum gates and gives physicists the ability to distinguish between incoherent and coherent errors leading to unprecedented control of the qubits.”
The joint University of Sydney-UNSW result comes soon after a paper by the same quantum theory team with experimentalists at the Niels Bohr Institute in Copenhagen.
That result, published in Nature Communications, allows for the distant exchange of information between electrons via a mediator, improving the prospects for a scaled-up architecture in spin-qubit quantum computers.
The result was significant because it allows for the distance between quantum dots to be large enough for integration into more traditional microelectronics. The achievement was a joint endeavour by physicists in Copenhagen, Sydney and Purdue in the US.
Professor Bartlett said: “The main problem is that to get the quantum dots to interact requires them to be ridiculously close – nanometres apart. But at this distance they interfere with each other, making the device too difficult to tune to conduct useful calculations.”
The solution was to allow entangled electrons to mediate their information via a ‘pool’ of electrons, moving them further apart.
He said: “It is kind of like having a bus – a big mediator that allows for the interaction of distant spins. If you can allow for more spin interactions, then quantum architecture can move to two-dimensional layouts.”
Associate Professor Ferdinand Kuemmeth from the Niels Bohr Institute in Copenhagen said: “We discovered that a large, elongated quantum dot between the left dots and right dots, mediated a coherent swap of spin states, within a billionth of a second, without ever moving electrons out of their dots.
Professor Bartlett said: “What I find exciting about this result as a theorist, is that it frees us from the constraining geometry of a qubit only relying on its nearest neighbours.”
Office of Global Engagement
The history of this experiment goes back a decade to an US Intelligence Advanced Research Projects Activity (IARPA) program led by Professor Charlie Marcus, a co-author who was then at Harvard before he moved to Copenhagen.
Professor Bartlett said: “We all went to Copenhagen for a workshop in 2018 in part to work on this problem. Thomas Evans, a co-author of the paper, stayed there for two months supported by the Office for Global Engagement. OGE also supported Dr Arne Grimsmo, who was working on another project.”
He said the experiment and our discussions were well advanced by the time we got the OGE funding. But it was this workshop and the funding for it that allowed the Sydney team to go to Copenhagen to plan the next generation of experiments based on this result.
Professor Bartlett said: “This method allows us to separate the quantum dots a bit further making them easier to tune separately and get them working together.
“Now that we have this mediator, we can start to plan for a two-dimensional array of these pairs of quantum dots.”
The Latest on: Quantum computing
via Google News
The Latest on: Quantum computing
- Stabilising quantum computers with 'noise-cancelling headphones' on May 22, 2019 at 7:05 pm
An international consortium, including three Australian universities, is exploring the quantum-equivalent of noise-cancelling headphones as a way to reduce external interference on sensitive quantum ... […]
- Businesses 'want quantum computing now' on May 22, 2019 at 8:30 am
Quantum computing is rapidly becoming one of the most in-demand technologies for businesses looking to take a step into the future, new research has found. A study from Fujitsu found that 70 percent ... […]
- Willis Towers Watson, Microsoft see quantum change in computing insurance risk on May 22, 2019 at 7:20 am
Willis Towers Watson (NASDAQ:WLTW) and Microsoft (NASDAQ:MSFT) team up to develop quantum computing for risk management and insurance clients. Willis Towers Watson sees potential to transform risk ... […]
- Quantum interferometry reveals the chosen pathway of coherent phonon generation on May 22, 2019 at 6:15 am
Shikano, who is working at Quantum Computing Center, Keio University. The probe beam reads the interference fringe pattern by reading off changes in optical properties (reflectivity) of the sample ... […]
- Willis Towers Watson and Microsoft announce quantum computing collaboration to transform risk management on May 22, 2019 at 6:01 am
ARLINGTON, May 22, 2019 (GLOBE NEWSWIRE via COMTEX) -- Willis Towers Watson WLTW, -0.52% a leading global advisory, broking and solutions company, announced today an exclusive deal with Microsoft to ... […]
- Quantum Computing Market Growing at a 24.9% CAGR and Projected to Reach US$ 283 Million by 2024 on May 21, 2019 at 7:37 am
May 21, 2019 (MarketersMedia via COMTEX) -- The Quantum Computing Market development trends and marketing channels are analyzed. Finally the feasibility of new investment projects are assessed and ... […]
- Amazon Prime Boss Named CEO of Google-Backed Quantum Computing Startup on May 21, 2019 at 3:35 am
Peter Chapman has had a varied career. The son of an astronaut, Chapman started programming at the Massachusetts Institute of Technology’s famed Artificial Intelligence Lab at the age of 16. ... […]
- Quantum cloud computing with self-check on May 20, 2019 at 6:16 am
With a quantum coprocessor in the cloud, physicists from Innsbruck, Austria, open the door to the simulation of previously unsolvable problems in chemistry, materials research or high-energy physics. ... […]
- Quantum Computing Market Worth $283 Million by 2024 - Exclusive Report by MarketsandMarkets™ on May 18, 2019 at 6:18 am
CHICAGO, May 17, 2019 /PRNewswire/ -- According to the new market research report "Quantum Computing Market by Offering (Systems and Consulting Solutions), End-User Industry, and Geography; QCaaS ... […]
- Quantum computing could change everything, and IBM is racing with Microsoft, Intel, and Google to conquer it. Here's what you need to know. on May 14, 2019 at 3:02 pm
Quantum computers are an extremely exciting technology, promising the raw computing power to crack previously-unsolvable problems. IBM has an early lead in quantum computing, experts say, with Google, ... […]
via Bing News