Quantum computers use qubits—quantum equivalents of the bits at the centre of conventional computing—in which ones and zeros are blended together rather than remaining separate, allowing them to perform calculations intractable to conventional bits.
The physical foundations were laid by John Clarke, John Martinis and Michel Devoret, who showed that quantum tunnelling—the ability of quantum objects to appear on the far side of an energy barrier without leaping over it—operates at a macroscopic scale in superconducting materials cooled near absolute zero. Using a copper tube filled with powdered copper attached to a Josephson junction (a tunnellable gap in a copper wire), they demonstrated that the current across the gap was itself quantised, ratcheting up and down stepwise rather than continuously. They called this set-up an artificial atom.
In 1999 Japanese researchers realised that controlling this up-and-down ratcheting could be used to build a device that processes qubits. This led to phase qubits—oscillations between quantised energy levels in a Josephson junction—and, in turn, to the transmon, a more robust qubit design that Dr Devoret helped develop. The trio won the 2025 Nobel physics prize for bridging the gap between sub-atomic quantum mechanics and the macro scale needed for computing.
Cryptographers fear quantum computers will make currently uncrackable ciphers crackable—possibly as soon as the 2030s, making post-quantum encryption urgent. Biologists hope they will unveil the details of how protein molecules fold. McKinsey reckons quantum computing could create between $620bn and $1.3trn of value across the automotive industry, chemicals, finance and life sciences by 2035.
Progress in error correction is making quantum systems more reliable, moving quantum computers from exciting in theory to practical within reach. The ability to combine qubits into machines that can solve some problems exponentially faster than today's computers now feels attainable. In 2024 researchers at Google proved that using more physical qubits to create a single "logical" qubit cuts the error rate, easing fears that quantum computers may never be useful in practice. Further progress became a solvable engineering challenge of creating more physical qubits.
Three public quantum-computing firms—D-Wave, IonQ and Rigetti—boast a combined market value of $33bn. Quantinuum, an $11bn startup backed by Nvidia, JPMorgan Chase and Honeywell, unveiled its new commercial quantum computer in New York in late 2025 and is already selling the hardware and access to it through the cloud.
Of the world's 513 firms focusing solely on quantum, some 64 are British—second only to America's 148. Key firms include Riverlane (error-correction systems), Phasecraft (algorithms), and Orca and Oxford Quantum Circuits, which are building full quantum computers using two different approaches. British quantum startups attract the second-most venture funding globally, albeit far behind American ones.
Britain launched the National Quantum Technologies Programme (NQTP) in 2014 to help commercialise research. The country has also rejoined Horizon, the European Union's €96bn ($111bn) research programme. Researchers are developing a quantum-navigation system for the London Underground.
In September 2025 IonQ, an American hardware company, bought Oxford Ionics, a British rival, for $1.1bn. The government used the National Security Investment Act of 2021 to insist that Oxford Ionics' hardware, research and intellectual property remain in Britain.
A Tony Blair Institute report highlights gaps: too few suppliers of enabling kit such as lasers and photonics, reliance on foreign providers of ultra-cold refrigerators, and little domestic capacity for quantum-chip packaging. Britain's largest quantum-hardware grants have been about one-tenth the size of those of Australia and France.
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