Photonics: A Quantum Leap For Data Centres

Last week, I saw an actual quantum computer go online. Bristol University has a quantum computer, that can be programmed and used over the web. By anyone!

That’s exciting enough, but the technology that enabled this is also involved in new technology which could help re-design data centres for the better.

Quantum computing for all

Let’s start with Bristol’s Qcloud. It won’t give you access to a system which can crack all your friends’ encryption codes (yet). It is an experimental system designed for testing the science of both quantum mechanics and quantum computing.

But it’s a super piece of kit. The Bristol group designed and built a 2 quantum bit (qubit) system a couple of years back, and now they are using bigger and better ones, so they put this one online. It’s done useful work, including demonstrating profound and strange quantum effects such as entanglement, and there’s lots more it could be used for.

As quantum computers get closer to reality, what’s needed is to get them out beyond the specialised labs they are currently in. “There are a small number of quantum scientists compared to the number of computer scientists in the world,” said Professor Jeremy O’Brien of the Bristol centre. He hopes that “hundreds of thousands” of people can test quantum features and algorithms on the system.

“It’s the Raspberry Pi of quantum computing, “ said his colleague Mark Thompson. I see what he means, but I think it’s more like the Altair 8800, or Heathkits. In the 1970s, Heathkits and the Altair packaged up early microprocessors such as the 8080 in kits that people could build for themselves. Computing had been the preserve of academics and large organisations, but became something everyone could use.

Steve Jobs and Steve Wozniak cut their  teeth on Heathkits, while Bill Gates and Paul Allen made home computing accessible by releasing a BASIC compiler for the Altair. They then all went on to use these principles to build systems for more general use.

In just the same way, the Qcloud should allow amateurs and hobbyists to play with the technology, and create new things. O’Brien and Thompson both get asked “how will quantum computing change our smartphones?” But that is the wrong question. Quantum computing, like microprocessors, will create things that we haven’t yet thought of, not making upgrades to what we have.

Silicon photonics

But how did Bristol’s machine come to exist? It uses photons carried in waveguides, which can be manipulated and made to interfere with each other.

This is great for science, because photons show quantum behaviour at room temperature. Other approaches to quantum computing require systems kept close to absolute zero with a need for a lot of cooling.

Silicon waveguides are available because of research intended for the next generations of “classical” chips and data centers.

As chip makers put more and more cores on chips, the bottleneck is how quickly you can move data on and off the processor, between the cores, and up and down racks.

Light is simply the best way to do this (nothing moves faster), so there has been a lot of effort going into silicon photonics. This week saw Intel announcing some of the fruits of that labour:
Intel and Corning have come up with the MXC optical interconnect, which can connect components at 100Gbps over distances of 300m. Intel is talking about reaching terabit speeds.

A single MXC fibre could replace ten PCI-E cables. In conventional racks, that means a clearer space for air flow – but it also will allow a complete redesign of the whole rack so less cooling is needed.

Professor O’Brien and his team have picked up on silicon photonics because photons show interesting quantum behaviour at room temperature, without a lot of cooling.
Meanwhile others are using the technology to help keep servers closer to normal temperatures without wasting energy on chillers.

This article is based on one which appeared in Green Data Center News.

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