This change in encoding to a system based on parity transforms all operations involving several qubits, no matter how far apart they are, into the equivalent of local interactions. That eliminates the need for interactions over long distances. And operations can be carried out on all qubits in a computer simultaneously, maximizing the complexity of calculations that can be performed in the brief period during which qubits remain intact.

A commercial mindset

Since dreaming up the parity architecture1, Lechner and his colleagues at ParityQC and the University of Innsbruck have gone on to have dozens of papers published that elaborate the scheme. In one of the most recent2, they have 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 allow quantum computers to find the prime factors of large numbers, posing a threat to Internet encryption schemes that rely on the difficulty of such calculations.

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

Notably, the company jointly received an €83-million contract awarded by the German Aerospace Center in Cologne to build ion-trap computers. Along 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 a judge for The Spinoff Prize 2023, is impressed by what she describes as ParityQC’s analysis of “how previously radically different technologies have been able to get into the market and make money”. She notes a parallel with Arm in Cambridge, UK, a firm which started selling blueprints of chips for reduced-instruction set computers in the 1980s. She also praises the hiring of people with commercial expertise. “For quantum companies that is quite rare,” she says.

Fellow judge Emily MacKay, who is a technology strategist at Siemens Energy and is based in Cambridge, UK, applauds ParityQC’s efforts to make its architecture scalable and applicable to various types of hardware. “Their research approach is future-proofing as far as possible,” she says. (Her comments on 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 collaborate with the world’s biggest provider of cloud computing, Amazon Web Services. Lechner says that ParityQC would be “an ideal supplier” to the larger firm, arguing that 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 contact [with Amazon] at the moment but would be happy to [be],” he says.

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

Lechner acknowledges that there is no general proof showing 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 by 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 that emerge. “That is our dream,” Lechner says, “and the target we are working towards.”