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2 February 2018
Interview with professor David Poulin

The need to develop a quantum computer

Invited to speak at the World Economic Forum in Davos that took place from January 23 to 26, in Switzerland, Microsoft’s CEO Satya Nadella, among other things, argued for the need to develop a quantum computer.

Interview with professor David Poulin, researcher at Institut quantique. Professor Poulin’s research focuses on quantum computing.

How is the current capacity of computers approaching saturation ?

 

For decades, processor speed has doubled every 18 months. This is largely due to the miniaturization of electronic components. For example, in 1993, we were very proud to announce that we had just purchased a computer equipped with a 60MHz Pentium processor, i. e. that performs 60 million operations per second. In 2006, the same manufacturer supplied processors operating at 4GHz, i. e. 4 billion operations per second, about 100 times faster than in 1993. The laptop I use to reply to my emails is equipped with processors that operate at the same speed as in 2006. The only difference is that he has 4 hearts, so he can do 4 times as many operations. We can see that the computational speed reaches saturation, the only way to increase the number of operations is by multiplying the number of processors, we can no longer accelerate the performance of the processors themselves. In particular, miniaturization becomes more difficult as the size of electronic components approaches the size of the atom, so quantum effects become important.

What more could quantum computers do, and how would they do it ?

 

Quantum effects become inevitable to continue the acceleration of electronic components. However, they can be seen as a nuisance, an obstacle to continuing the steady progress of the past 50 years, or they can be exploited by using the strange behaviours of quantum objects for computational purposes. This is the approach advocated in quantum computing. It must be understood, however, that quantum computing is not simply a way of speeding up information processing. In fact, it is very likely that a future quantum computer will perform a very small number of operations per second. In terms of processor speed, it is likely that the quantum computer will be comparable to an 80s computer. What the quantum computer offers is another way to manipulate information. Any computation takes data A as input and produces a response B. An algorithm performing this computation is a route from point A to point B. The streets composing this route are the elementary operations of the computer: addition, multiplication, etc. The calculation takes data A as input.

A quantum computer offers new streets, operations that do not exist in a conventional computer. More precisely, these streets do not exist in our usual way of conceiving the world, they are not operations that can be intuitively explained, they do not respect our logic.

Although all this is counterintuitive, the existence of new streets leads to the possibility of finding much shorter paths, and thus much more efficient algorithms. So, even if the quantum computer had a processor 1000 times slower than my laptop, it would be able to do some calculations much more efficiently.

Without revealing trade secrets, you collaborate with Microsoft, could you elaborate on the subject ?

 

I have a long history of scientific collaborations with researchers who are now based at Microsoft Research in Redmond, Washington. Microsoft is one of the most important players in quantum computing and their team is expanding rapidly. Among the questions that concern Microsoft, two are at the heart of my research activities: how can I achieve a more robust quantum computer while minimizing resources and what are the problems that can benefit from quantum acceleration? The first theme is quantum error correction, a software method for eliminating errors that occur during quantum computation. The second theme is to develop new algorithms for a quantum computer. In both cases, it is a matter of programming a computer that does not yet exist! I have made a good international reputation in these fields, and for about a year I have been consulting for Microsoft on these topics. My job is to help them make progress on these issues. From my perspective, this is a way of consolidating very successful research collaborations and creating new scientific and professional opportunities for my graduate students.

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