Rewriting the quantum computing blueprint

Parity Quantum Computing in Innsbruck, Austria, spun off from the University of Innsbruck, Austria, in 2020.

In 2013, Wolfgang Lechner had an idea that he thought was too good to be true: a mathematical trick that would change how quantum computers encode information. If it worked, he reasoned, it would be a big deal. Quantum computers can theoretically perform certain calculations many times faster than conventional digital computers, but they are extremely sensitive to interference and are difficult to scale up. Lechner’s brainwave was to give these computers an architecture based on the concept of ‘parity’. This could transform them from small laboratory devices into large, commercial machines capable of solving problems that are currently difficult to solve.

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Lechner, a physicist at the University of Innsbruck in Austria, discussed the proposal with a colleague, but they managed to convince themselves that it was a non-starter. Over the next two years, he kept turning the idea over in his mind and says it became an obsession. Finally, at 3 a.m. in a hotel room, he had a flash of inspiration that might mean his parity-based approach should work after all.

He quickly filed a patent and just six months later received an offer for the intellectual property from a major technology company. (Lechner declined to disclose the company or the size of the offer.) This told him that the architecture had commercial potential and that it might be better to try to reap the rewards directly. So he and his colleagues at the University of Innsbruck decided to reject the offer and set up a spin-off company. ParityQC was launched in 2020 and has been named a finalist in The Spinoff Prize 2023.

Three years after its establishment, the company now employs around 30 employees. It has won significant contracts from high-tech manufacturers and from governments – with one deal alone worth several tens of millions of euros. According to Lechner’s co-CEO Magdalena Hauser, this early success – combined with grants from the EU and the governments of Austria and Germany – has meant that the company has avoided having to pitch for support from venture capitalists. “We got revenue from the start,” says Hauser.

Push boundaries

Quantum computers owe their computational power to certain quantum phenomena of atomic scale objects. These computers encode data in the form of qubits, which can exist as 0 and 1 at the same time – unlike conventional bits, which only exist as one or the other. Multiple qubits can be entangled to generate all possible values ​​from a string of 0s and 1s simultaneously, enabling parallel processing not possible with classical computers.

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But qubits are fragile. Their states can be disturbed by the slightest amount of heat or other interference. Their durability varies depending on the physical qubit used – ions, neutral atoms, superconducting circuits or quantum dots. They can remain intact for a few seconds if they are perfectly isolated, or they can disappear after milliseconds if they interact with other qubits during a calculation.

Another major problem for quantum computing is the spatial properties of qubits. The physical processes that connect qubits to each other usually only occur over very short distances, such as the overlapping of two electron clouds around atomic nuclei or the connection of two superconducting circuits. This means that each qubit typically only interacts with its nearest neighbors, rather than qubits further away.

ParityQC’s architecture helps quantum computers deal with both limitations. It does this by changing how the data is encoded in the qubits. Instead of representing the values ​​of individual logic qubits—as specified by the program being executed—physical qubits instead record the relationship between pairs of logic qubits in terms of parity. If the qubits in a pair have the same value, then the parity is 1; if the values ​​are different, the parity is 0 (see ‘Blueprint for quantum computing’).

This change in coding to a system based on parity transforms all operations involving multiple qubits, no matter how far apart they are, into what amounts to local interactions. It eliminates the need for interactions over long distances. And operations can be performed on all qubits in a computer simultaneously, maximizing the complexity of calculations that can be performed in the short period that qubits remain intact.

A commercial mindset

Since the dream of the parity architecture¹, Lechner and his colleagues at ParityQC and the University of Innsbruck have since had dozens of papers published elaborating on the scheme. In one of the latest²have they proposed a specific set of operations or gates that rely on parity encoding and have confirmed³ that this set would speed up several of the most important quantum algorithms devised so far. These include an algorithm that would enable quantum computers to find the prime factors of large numbers, posing a threat to Internet encryption systems that rely on the difficulty of such calculations.

To turn this knowledge into revenue, ParityQC licenses its intellectual property to hardware developers to build chips incorporating the architecture. According to Hauser, the company has sold licenses to Japanese electronics giant NEC to produce a superconducting quantum chip and has entered into several consortia created in response to the German government investing 2 billion euros ($2.2 billion) to fund the development of quantum technologies.

Notably, the company jointly received an 83 million euro contract awarded by the German Aerospace Center in Cologne to build ion-trap computers. Together with manufacturers eleQtron in Siegen, Germany and NXP Semiconductors in Eindhoven, the Netherlands, it won the contract to build a 10-qubit demonstration computer and then develop modular and scalable devices. (This type of computer is also being developed by another The Spinoff Prize 2023 finalist, Alpine Quantum Technologies, although Alpine is not part of ParityQC’s collaboration.)

Sue Sundstrom, a start-up coach based in Clevedon, UK, and judge for The Spinoff Prize 2023, is impressed by what she describes as ParityQC’s analysis of “how radically different technologies have previously been able to enter the market and make money “. She notes a parallel with Arm in Cambridge, UK, a company that began selling blueprints for reduced-instruction-set computer chips in the 1980s. She also praises the hiring of people with commercial expertise. “For quantum companies, it’s quite rarely,” she says.

Fellow judge Emily MacKay, a technology strategist at Siemens Energy based in Cambridge, UK, applauds ParityQC’s efforts to make its architecture scalable and applicable to different types of hardware. “Their research approach is as future-proof as possible,” she says. (Her comments to ParityQC do not necessarily reflect the views of Siemens Energy.)

But MacKay adds that the company faces an “elephant in the room” – having to decide whether to compete or partner with the world’s largest provider of cloud computing, Amazon Web Services. Lechner says ParityQC would be “an ideal supplier” to the larger company, and claims its parity architecture is well-suited to Amazon — which plans to build quantum computers that mitigate errors, partly in hardware and partly through software. “We are not in touch [with Amazon] at the moment but would happily [be],” he says.

However, not all specialists are convinced that the parity architecture will achieve the desired results, at least when it comes to solving optimization problems (such as maximizing the return of a financial portfolio or minimizing the distance traveled by freight vehicles). Itay Hen, a numerical physicist at the University of Southern California in Los Angeles, questions whether a quantum computer equipped with the architecture could solve such problems faster than a classical computer—given what he says is the absence of a quantum algorithm that guarantee such a result. “Even if we had the perfect quantum computer, we still wouldn’t know if it’s better than a laptop computer,” he says.

Lechner acknowledges that there is no general proof that quantum computers have an advantage over their classical counterparts when it comes to optimization problems. But he is confident that at some point in the next few years – perhaps around 2030 – the parity architecture will enable a quantum computer to pass this milestone for one or more problems, with classically impossible optimization made possible by new algorithms emerging . “That’s our dream,” says Lechner, “and the goal we’re working towards.”