Google unveils new 72-qubit quantum processor

Many major tech companies – including IBM, Intel, Microsoft and Google – have teams dedicated to developing quantum computers; computers which harness physical phenomena arising on the atomic scale.

While classical computers store information as a series of 0s and 1s, quantum computers store information using particles which can exist in multiple states (both 0 and 1) at once. This allows for data to be stored and processed vastly more quickly than with classical computers. Problems which could take hours of processing time on supercomputers (or which it may be impractical to even attempt) – such as climate simulations or major cryptographic challenges – could be solved in moments.

While the emergence of practical, commercially viable quantum computers will undoubtedly be world changing, a number of major challenges face researchers attempting to build these machines and at present, no quantum computers have achieved “quantum supremacy”: the point at which they can solve problems faster than classical computers.

This is largely due to the challenge of maintaining the stability of extremely fragile systems of particles which can provide high accuracy.

However, Google has now announced in a blog post that its Quantum AI Lab is taking steps towards quantum supremacy with the development of “Bristlecone”, its latest quantum processor. Bristlecone is intended to allow researchers to run tests on system error rates, scalability of their quantum information storage solutions, and to test various applications, such as in machine learning.

Google previously developed a nine-qubit processor, which demonstrates promisingly low error rates: one per cent for readout, 0.1 per cent for a single qubit and 0.6 per cent for a two-qubit gate. Their new 72-qubit device is of a similar design to its predecessor, but scaled up significantly.

“We chose a device of this size to be able to demonstrate quantum supremacy in the future, investigate first and second order error-correction […] and to facilitate quantum algorithm development on actual hardware,” the blog post said.

In order to protect the fragile quantum systems from outside stimuli and keep error rates low, quantum computers today must be run at close to absolute zero. Under these conditions, Google is hoping that they can achieve error rates as low as with their nine-qubit processor. This is necessary if a quantum computer is to stand a chance of achieving quantum supremacy.

“We believe Bristlecone would then be a compelling proof-of-principle for building larger scale quantum computers,” Google said. “Operating a device such as Bristlecone at low system error requires harmony between a full stack of technology ranging from software and control electronics to the processor itself. Getting this right requires careful systems engineering over several iterations.”

“We are cautiously optimistic that quantum supremacy can be achieved with Bristlecone”

Google faces intense challenges in the race for quantum supremacy from Intel, which presented a 49-qubit processor at CES 2018 in January, and IBM, which unveiled its 50-qubit machine in November 2017.