Google are among a handful of organisations at the forefront of the quantum computing space. Now with this month’s announcement of the new 72 qubit ‘Bristlecone’ processor, they have moved right to the front of the qubit race, surpassing IBM’s 50 qubit processor unveiled at the end of last year.

Google researchers claim that the team needs to do more testing but it is ‘pretty likely’ that this year, or even in just a few months that the new chip can achieve ‘quantum supremacy’. This is the point at which a quantum computer can do calculations beyond the reach of today’s fastest supercomputers.

But what does this actually mean? After all, the term ‘quantum supremacy’ is misleading. It suggests that when these machines achieve this monumental moment everything will change – smart-phones and laptops will be discarded as products of a bygone era.

However, the reality is something else. Firstly, the principals for which these machines are based are radically different and future quantum computers will be used and applied in very distinct ways. There is also a long list of technical obstacles holding these quantum devises back from commercial use. And this could be several years away. For researchers battling to overcome these technical challenges – that’s the real dream – to reach useful quantum computers.

Vasil Denchev, Chief Quantum Software Architect at Google Quantum AI Lab

This week Quantum Business secured an exclusive interview with Vasil Denchev, Chief Quantum Software Architect of the Quantum AI Lab at Google. Vasil is a visionary member of the Google quantum team. His PhD in Computer Science at Purdue University provided important techniques that enabled the successful application of quantum annealing to statistical machine learning and computer vision problems. This gave impetus to the founding of the Quantum Artificial Intelligence Lab.

He told us that his favourite quote about quantum computing comes from David Deutsch’s book, “The Fabric of Reality”“Quantum computation is… a distinctively new way of harnessing nature… It will be the first technology that allows useful tasks to be performed in collaboration between parallel universes.”

Vasil spoke to us and described the work being done by the Google team. “Google has assembled an extraordinary team of world-class quantum scientists and engineers, all of whom have very strong academic background as well as extensive records of very successful pioneering research in the area. In the scientific community our team is widely held in very high regard. We publish our research in the best scientific journals in the world and various team members regularly receive invitations to present our work at all the top conferences related to what we do.”

“Being at Google, we also always work with the inspiration to do great things and try to change the world for the better. We are not afraid to take risks and we strive to push the boundaries of humankind’s knowledge until we achieve the ultimate goal – useful quantum computers.”

Harnessing Nature

Achieving useful quantum computers will occur in stages over the next decade. According to Vasil the Google quantum team is now looking at many subsets of the field for short-term and medium-term quantum computing. The main objective is to overcome the obstacles that hold the technology back. Each field is faced with challenges.

Quantum-assisted optimisation 

Within ‘the most exciting area of research’, Vasil claims that part of the team is developing a general-purpose quantum-classical hybrid algorithm. “This combines the best quantum and classical optimization techniques to solve hard and impactful optimization problems better/faster than anything that can be done via classical optimization alone.” The main challenges here come from hardware constraints that limit  the supported interactions between different sets of variables in the optimization problem and the maximum precision with which we can represent optimization problems in hardware.”

Quantum supremacy theory 

Vasil tells us that “another part of the team is focused on how to successfully and convincingly demonstrate the superior computational capabilities of medium-size quantum devices.” Vasil claims that the challenge here is to formulate a well-defined computational problem that could reliably and verifiably be solved quickly on a quantum device and would take significantly longer on any classical hardware.

The Quantum AI Lab noted that software and hardware integration is a fundamental part of the process towards ‘quantum supremacy’ and that “several iterations” might be required before quantum computing can solve problems that current computers cannot.


According to Vasil, “quantum hardware engineers and scientists at Google are constantly iterating on building better and better state-of-the-art quantum devices. Our team takes pride in consistently achieving best-in-the-world technical characteristics that make our devices the most viable candidates for the first successful demonstration of quantum supremacy as well as the subsequent quest for successfully solving important practical problems with them. The challenges here are many as would always be expected when pushing the frontiers of engineering and science.”

Quantum simulation 

The simulation of chemical systems was one of the original applications of quantum computing proposed by the preeminent Physicist Richard Feynman in 1982. Since quantum mechanics provides the most accurate known description of the behaviour of atoms and molecules, it would be the most natural task for a quantum computer to be predicting for example the important properties of candidate materials for more efficient batteries.”

“Such tasks are known to be too difficult for our ordinary computers because the calculations that are involved often invoke the exponentially large mathematical spaces of quantum mechanics. The main challenge that our team members working in quantum simulation are facing is related to searching for interesting chemistry simulations that can be performed on our upcoming quantum devices yet are too difficult for classical computers.”

Quantum error correction 

Today, quantum machines require extensive error correction to make up for the fact that qubits are exceptionally fragile. Indeed, they only remain in a quantum state for a tiny amount of time, and are hard to read without interfering with the results. Vasil reveals that part of the team is building the code and algorithms to effectively perform quantum error correction. The objective here for future quantum devices to maintain ‘high-quality quantum states for long enough to complete demanding quantum computations in a fault-tolerant manner.’

“The main challenge here is to be efficiently calculating on classical computers the necessary error-correcting signals quickly enough in real time, so that the computation on the quantum device can proceed without delay as if an error never occurred.”

Google’s new Bristlecone 72 qubit quantum processor

The New Bristlecone Quantum Processor

“The Bristlecone quantum processor is an exciting new phase in our hardware development journey towards useful error-corrected quantum computing technology.”

“With Bristlecone’s 72 qubits we aim to provide a proof-of-principle that our superconducting engineering can be successfully scaled to larger numbers of qubits while keeping the key quality characteristics (error rates on readout, single-qubit gates, two-qubit gates, etc.) good enough for error-correcting theory to remain applicable and for classical simulatability of our chips’ quantum computations to keep receding out of reach.”

“In this way Bristlecone is moving us closer to functionally useful quantum computers by providing a much needed testbed for continually improving our systems engineering and for studying potentially highly impactful applications in quantum simulation, optimization, and machine learning.”

 A Truly Transformative Technology

In May 2017, Google Research published ‘Commercialize Quantum Technologies in Five Years’. The paper argued that early adopters to new technology could see transformative effects for their organisations. Vasil was among the scientific contributors to the paper and he reveals that today corporate leaders need to be aware of the potential of quantum technology as a game-changer “in pretty much all areas of business, technology, and science.”

“History has shown that early adopters of groundbreaking technologies are poised to reap the most benefits as soon as they materialize.”

“When we consider the enormous upside of quantum computing, investing in this space or at least making sure to stay abreast of the latest developments and preparing for their impact should be an obvious no-brainer.”

Vasil believes that in order for industry leaders to capitalise they need to start forming in-house teams dedicated to studying the basics of the technology and investigate the possible ways it can be applicable to the local business and technology operations.

“Motivated early adopters would also benefit from engaging with pioneers in the space such as the Google quantum team and forming mutually beneficial partnerships that would allow both sides to make progress more quickly while benefiting from each other’s expertise more effectively.”

What Does the Future Hold?

We asked Vasil what the future of quantum computing holds over the next decade and what he is looking forward to. “I am mainly occupied with the quantum-assisted optimization project today and that excites me the most for the upcoming 5-10 years.  “Optimization problems abound in machine learning and many other fields such as science, business, and technology, however, current classical computing have largely saturated with state-of-the-art algorithms that tend to make progress mostly in just very small incremental steps. “Quantum-assisted optimization, on the other hand, will be qualitatively different from purely classical approaches”

Vasil claims that once it gets applied to important practical problems (e.g. in machine learning), it is expected to start setting new standards for acceptable solution quality, especially in high-value large-scale industrial applications that thrive under competitive pressure.

Vasil Denchev is the Chief Quantum Software Architect of the Quantum Artificial Intelligence Lab at Google

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Written by Hal Briggs from Quantum Business