Is quantum computing here at last?

Quantum computing, first proposed by Richard Feynman and Yuri Manin back in the 1980s, is one of those technologies that for years has been just over the horizon.

Now, though, it's moving into the real world, with consultancy McKinsey predicting that the technology will have a global market value of $1 trillion by 2035.

So, how does quantum computing work?

With a standard computer, information is stored as bits that have only two possible states: zero and one. Quantum computers, however, take advantage of the fact that subatomic particles can exist in more than one state simultaneously - so one, zero or both at the same time.

This means that a qubit can perform two calculations at once; two qubits linked through entanglement can carry out four; three can handle eight calculations, and so on.

There are problems, though. Most notably, creating a quantum computer with enough qubits to out-perform conventional machines - a situation known as quantum supremacy. And to complicate matters further, the number of qubits isn't the only factor determining the power of a quantum computer, with other factors such as decay rates and noise playing a part.

Last October, IonQ unveiled its next generation quantum computer system, boasting 32 qubits and claimed to be the most powerful in the world, thanks to its error-correcting techniques.

But the company conceded that there's still a long way to go.

"In a single generation of hardware, we went from 11 to 32 qubits, and more importantly, improved the fidelity required to use all 32 qubits," says CEO and president Peter Chapman.

"Depending on the application, customers will need somewhere between 80 and 150 very high-fidelity qubits and logic gates to see quantum advantage."

Other major players have made recent strides too. IBM made a 65-qubit quantum computing system available on the cloud last September, and has released a quantum hardware roadmap that calls for a 127-qubit system this year, building to a 1,121-qubit system in 2023.

And last month, Honeywell Quantum Solutions quadrupled the performance of its System Model H1, achieving the highest 'quantum volume' - a widely-used measure of performance - ever recorded, at 512.

Quantum computing use cases

Microsoft, Google and Amazon have all released quantum tools for their cloud platforms, allowing users to design, build and test quantum algorithms. And a number of use cases are emerging.

Pharmaceutical company Boehringer Ingelheim, for example, recently signed up with Google Quantum AI to evaluate quantum computing for pharmaceutical R&D, and specifically molecular dynamics simulations.

"Extremely accurate modelling of molecular systems is widely anticipated as among the most natural and potentially transformative applications of quantum computing."

Ryan Babbush, head of quantum algorithms at Google.

Other major applications for the technology include financial services, where it's expected to increase the speed of transactions; route optimization in manufacturing and logistics; and cybersecurity, with cryptography and secure communications through quantum key distribution.

"Qubits can allow us to create algorithms for the completion of a task with reduced computational complexity that cannot be achieved with traditional bits," says Kiran Raj, principal disruptive tech analyst at GlobalData.

"Given such advantages, quantum computers can solve some of the intractable problems in cybersecurity, drug research, financial modelling, traffic optimization and batteries, to name a few."