How Far Away Is Quantum Supremacy?

The latest debate over the achievement of quantum supremacy began this spring after two companies said they had reached the milestone of a quantum system achieving performance impossible for a classical computer.

In March, D-Wave announced it performed a materials simulation using quantum technology. A few weeks later, Quantinuum published a paper in Nature detailing how it used the company’s six-qubit cloud-based H2-1 trapped-ion quantum computer to generate certifiably random bits.  

Several years ago, Canadian-based Xanadu announced its achievement of quantum advantage, a term now used interchangeably with quantum supremacy, with a demonstration of measurements that correspond to drawing a sample from a distribution.

Google made a similar declaration of quantum supremacy in 2019, although there was a fair amount of controversy about the claim, with IBM publicly stating that quantum supremacy had not been reached.

Stefan Leichenauer, vice president of engineering at AI solutions company Sandbox, said quantum supremacy means achieving a task with a quantum computer that would be functionally impossible with a conventional computer. He explained that such tasks require more resources than are available on an ordinary computer, meaning it could only be achieved with a quantum computer.

“Each of the demonstrations of quantum supremacy was of a single thing, albeit a hard equation, that a quantum computer was able to do that could not be reproduced by a classical computer,” said Leichenauer. “While it’s an interesting milestone, it’s not the same as having a business-relevant or practical use case for a quantum computer. However, the fact that we are having these discussions of quantum supremacy means that the next generation of this quantum technology will surely pass over the threshold to a business use.”

Christian Weedbrook, CEO and founder of Xanadu Quantum Technologies, whose team announced quantum supremacy in 2022, agrees that their achievement was solving a math problem, not a business problem. A classical computer would have taken seven million years to solve the math problem, which was accomplished in two minutes by the quantum computer, the company said. Each quantum supremacy demonstration shows the increasing power of quantum computing, Weedbrook said.

Using Quantum to Solve Business and Societal Problems 

The reason for the significant investment and focus of the tech industry on quantum computing is the power the technology holds to solve significant business and societal challenges. Leichenauer said that each of the demonstrations, such as D-Wave’s recent announcement, is part of a series of the complex stepping-stones of solving more and more challenging math problems that will eventually lead to solving business problems.

Leichenauer said one of the major cases of quantum computing is simulating the physical world through a very high fidelity and very accurate simulation of quantum physics to help design new materials and new medical treatments. He pointed to high-temperature superconductors as an example.

“Because high-temperature superconductors require materials that must be very cold to have the superconducting properties, it’s been very challenging to create a material that puts the atomic building blocks together for a high-temperature superconductor,” said Leichenauer. “With quantum computers capable of simulating materials of that level of complexity, we could understand the mechanics needed to better make a high-temperature superconductor.”

Weedbrook predicted that the first relevant business case of quantum computing will be next-generation battery development for electric vehicles. Because this falls under quantum computing and material design, which is already seeing theoretical breakthroughs, he said he considers improving battery life as likely the lowest-hanging fruit for quantum use cases. Weedbrook said Xanadu is currently working with car manufacturers on batteries, with the goal of making a single charge last ten times longer and making it possible to drive an electric vehicle ten times farther than it can at present.

Much of the discussion around quantum computing is increasingly concerned with AI. Bob Coecke, chief scientist at Quantinuum, said his organization is fully amplifying AI in the short term. Some problems tackled with quantum computing require high precision while others do not, he said, so combining AI and quantum technologies provides an edge. Because of high interest and investment in AI and quantum, Coecke said he expects this space will be where early, real-world quantum advantages occur.  

Roadblocks in the Way 

However, two big obstacles stand between current quantum computers and the hardware needed for business use cases. Leichenauer said that to achieve quantum supremacy for a demonstration with business value, an organization will need a bigger quantum computer than is available now, with fewer errors (defined as fidelity). The more quantum bits or qubits a computer can handle, the more efficiently it runs, which leads to fewer errors, he said. The number of errors is part of what limits the current use cases of quantum computing, he said. It’s not possible right now to build a big-enough quantum computer with enough qubits to bring the error rate down.

“For a business use case, we need quantum computers with at least 1,000 times more qubits than current computers. This means we need to be able to manufacture the qubits of high-enough quality in a repeatable manner,” says Leichenauer. “The quality of the qubits is almost where it needs to be but maintaining that quality at a much larger scale is very challenging.”

Weedbrook agreed that creating a physically large-enough quantum computer is one of the biggest current challenges. He explained that a quantum computer now takes up half a room, but for the computer to be able to solve business problems, it will need to be as large as one-to-two acres of land. Actually, instead of a computer, the next generation of use cases will require a quantum datacenter, he said. 

Predicted Timeline for Quantum Solving Business Problems

The big question remains: when will a quantum supremacy demonstration succeed in a real-world use case? Leichenauer said he would be surprised if there were a scaled quantum computer with the size and error rate needed for solving business challenges by 2030, and would put better odds on 10 to 20 years from now. However, if there is even a 1% chance of it happening by 2030, it’s very significant to consider such a short timeline a possibility.

As industry and the private sector continue to focus on bringing new investors to quantum computing, progress has moved in recent years at a pace not previously thought possible. Coecke said that pace of change and advancements make it challenging to give a firm prediction.

“The progress is incredible. The hardware progress is incredible. It’s beyond what was anticipated even by the scientists themselves,” said Coecke.

Jennifer Goforth Gregory is a technology journalist who has covered B2B tech for over 20 years. In her spare time, she rescues homeless dachshunds.