Quantum advantage milestone for photonic computing

Quantum advantage milestone for photonic computing

Technology News |
By Nick Flaherty

Chinese researchers have achieved a major milestone in the development of photonic quantum computer systems.

The demonstration of the Jiuzhang boson sampling system at the Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics is a key step in demonstrating quantum computational advantage. This is where a quantum computer can handle a task that is not possible with classical computing.

The photonic circuit has 100 inputs and 100 outputs with 300 beam splitters, and effectively acts as a matrix calculator. This has no practical application at the moment, other than to demonstrate quantum superiority, and took 200 s to make a calculation with 76 output photons. Simulating the problem on China’s Sunway TaihuLight supercomputer would take 1014 times longer, or 2.5 billion years, says the team, writing in Science.

“This is a very impressive demonstration which helps prove the potential of photonic quantum computing,” said Jeremy O’Brien, professor of physics at the University of Bristol in the UK and  Director of the Centre for Quantum Photonics (CQP) which back in 2013 developed a photonic quantum computer accessible via the cloud.


“A useful quantum computer will require error correction and 1 million qubits, and experiments such as these validate that the most viable path to building one is to use photonics,” added O’Brien, who is also CEO and co-founder of PsiQuantum in San Francisco which has raised $508m (E419) to build a large photonic quantum computer.

Quantum supremacy has been achieved in a research environment and is an important signifier of scientific progress, but it is just one step towards a useful, large scale, error corrected quantum computer, says the company.

PsiQuantum says it has deliberately avoided building small scale systems tied to the NISQ (Noisy Intermediate-Scale Quantum) regime. Instead it is using silicon photonics to build a room temperature quantum computer in a Tier 1 semiconductor fab.

Xanadu in Canada has developed a range of photon quantum computer that can be accessed over the cloud, offering 8 and 12 qubit machines.

The company can roughly double the number of qubits in its cloud systems every six months, says Christian Weedbrook, Xanadu’s founder and CEO. This uses continuous variable quantum computing that does not use single-photon generators. Instead, it uses “squeezed states” consisting of superpositions of multiple photons.

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