Quantum supremacy – a new era?

Google has achieved quantum supremacy – the ability to perform a calculation beyond the reach of conventional computers. This is a landmark scientific, mathematical and technical achievement. Though the road to general purpose quantum computing remains a long one, early applications will surprise many.

Google had planned to announce quantum supremacy through a paper in a formal peer reviewed scientific journal. However news that it believes it has been successful appears to have leaked and has now been widely reported in the mainstream press.

It has long been thought that 50+ qubits were enough in principle to demonstrate quantum supremacy provided that they could be sufficiently well controlled. That almost certainly explains why Google appears to have performed their supremacy calculation on a 53 superconducting qubit system codenamed Sycamore rather than their larger 72-qubit Bristlecone system.

For those new to quantum read an Introduction to Quantum Technology

Demonstrating a feat not possible on a conventional computer is a seminal achievement and, if confirmed by the scientific community, Fact Based Insight believes it will earn project leader John Martinis a Nobel Prize. However the actual calculation that Google has demonstrated it can perform is in fairness of quite limited scope.

What Google’s supremacy algorithm does is to calculate random numbers, but in a specifically controlled way so that the results are uniquely distributed. Their claim is that they can do this calculation in 3 minutes 20 seconds, a task that it would take today’s most advanced supercomputer 10,000 years to complete.

For more on Google’s approach and its limitations read Looking beyond quantum supremacy.

The NISQ era

Google’s success means that we have finally truly entered what Caltech professor John Preskill has termed the NISQ era. However what these early quantum devices will be able to achieve remains far from clear.

For a review of the short and long term prospects read Quantum software – over-hyped but underestimated.

Remarkably there is a short-term commercial application to which Google’s approach may be well suited – the provision of certified public random numbers. Random numbers are important for many commercial applications from encryption and cybersecurity to lotteries, gaming and election auditing. However we normally have to trust the provider of the random number to be behaving honestly, a significant limitation. Scott Aaronson (Univ. of Texas at Austin) has proposed a novel application for Google’s early quantum hardware that allows random numbers to be ‘publically certified’ through a challenge and verify process.

For a detailed discussion of one potential application of certified public random numbers read Quantum enhanced blockchain – sooner than you think.

One often discussed future application of quantum computers is to break the public key encryption on which Internet security currently depends. Fortunately, this is expected to be beyond NISQ era devices. Google’s success does not change that.

For an explanation of why business should still act now read A current business threat from future quantum computers.

For a review of the world’s preparations for this threat read Quantum safe cryptography – waiting to save the world.

Peak quantum hype

The next few months will see quantum computing at the very top of its hype cycle. Google’s Hartmut Neven has pointed out that we are currently seeing quantum computing power grow at a ‘double exponential rate’. Some have mooted ‘Neven’s law’ as a replacement for the exponential increase in computing power we have traditionally seen under ‘Moore’s law’. However, taken naively this could be very misleading.

To realise their transformative potential we need to radically scale-up today’s devices just so they can operate stably for general calculations – we need to achieve FTQC. Just how many more qubits are required is not certain, but it is likely to be at least in the 100,000’s and probably in the millions. That’s a long way from 53.

The long road to FTQC

Scaling up is a very significant challenge. In reality all quantum hardware groups have struggled to maintain the fidelity of qubit gate operations as they have moved up to even today’s very modest devices (a point that seems to have been confirmed again by Google’s experience with Bristlecone). In practice, controlling ‘cross-talk’ between qubits on these devices is clearly a major issue.

In addition, all currently proposed quantum computing architectures face their own specific medium term scaling challenges:

  • Superconducting qubits – how to scale beyond the confines of the dilution refrigerators required for ultra-low temperatures?
  • Trapped ions – how to manage the proliferation of lasers required for their high performance gates; or how to match that high performance with global field microwave gates?
  • Silicon spin qubits – how to deliver gates of sufficient fidelity while maintaining this technology’s promise of densely packed nanoscale architectures?
  • Photonic qubits – how to deal with photon loss in their alternative scheme of measurement based quantum computing?
  • Topological qubits – how to catch up with a promising idea, but one that still lags well behind in demonstrating practical qubit operations?

Its important to realise that this is a challenge as much for the full software stack as for the hardware.

For a review of some of the leading software approaches read Quantum error correction – from geek to superhero.

For a review of some of the other hardware approaches and whats going on across the wider quantum technology sector read Quantum Outlook 2019.

Despite the long road that lies ahead, the whole Google team deserves our congratulations on their remarkable achievement.

Actions for Business

  • Google’s announcement does nothing to accelerate the long timelines typically mooted before quantum computers break current Internet security. However prudent businesses should already have reviewed the specific time horizons of the threats their data and infrastructure face.
  • Businesses that will one day be significantly impacted by the unique new potentials of quantum computing, including financial services, pharmaceuticals, automotive and logistics, aerospace and defence, artificial intelligence, should be planning how to build the required skills within their future teams and partner networks.
  • Investors in quantum computing hardware should continue to support a wide diversity of platforms. This will be a long race and it is far from over. Watch out in particular for startups offering enabling parts of the solution with cross platform applicability.
  • Investors should not neglect other opportunities in the wider quantum technology value chain, particularly quantum imaging and sensing and quantum safe cryptography, which potentially have complimentary and earlier payback profiles.
David Shaw

About the Author

David Shaw has worked extensively in consulting, market analysis & advisory businesses across a wide range of sectors including Technology, Healthcare, Energy and Financial Services. He has held a number of senior executive roles in public and private companies. He has a degree in Physics from Oxford University, a PhD in Particle Physics from UCL and is a member of the Institute of Physics.

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