Interview with Prof. Dr. Jonathan Home on quantum computer

Jonathan Home has been an Assistant Professor (tenure track) for Experimental Quantum Optics and Photonics, Physics Department, since 2010. He was born in Newcastle upon Tyne, England, in 1979. He obtained a DPhil Physics from the University of Oxford in 2006. From 2005-2006 he worked as a postdoc, remaining in Oxford for a year, demonstrating the cooling of a two-isotope crystal of calcium ions to the ground state, and studying qubit coherence while the cooling progressed. Postdoc 2006-2010: He worked at the National Institute of Standards and Technology in Boulder, Colorado. Jonathan is currently working at the Institut für Quantenelektronik at ETH Zurich.

Can you explain in short, what a quantum computer is?

It is a computer, ie. a device that performs calculations according to a program, but the systems used to store information are objects following the rules of quantum mechanics, such as individual atoms. This means that the “rules” of computation are those of quantum mechanics, not those of our everyday experience.

What is the difference to the “binary based computer” we know now, let’s say in functionality?

The quantum bits (qu-bits) are allowed to take more than one value simultaneously, which means that a quantum computer can simultaneously act on all possible inputs. Although this seems highly parallel it is not, because only one answer can be produced from the quantum computer. Therefore we must be careful to ask the correct questions to be output – this is a big challenge of making algorithms for quantum computers.

What will be different or better by the use?

There are problems which cannot be solved by classical computers, which we believe a quantum computer will solve. One such problem is relevant for breaking types of cryptography. Other relevant problems are in computing chemical compounds, which might greatly improve the efficiency of industrial processes.

What are the requirements for quantum computer?

Individual quantum systems must be controlled and connected together in a very precise manner. They must be very well isolated from the outside world in order to preserve the quantum behavior of the computer.

Is it possible to estimate how the performance of quantum computers will develop?

I find this difficult. We are close to having devices which have 50 qubits, which is enough to play with an interesting system for physicists, and may be able to behave in ways which we cannot model on a normal (super)-computer. I think there may be interesting computations which come out of systems with hundreds of qubits, although we don’t know of any yet. However a useful quantum computer for the problems listed above is predicted to need 1 million qubits – we are very far from this goal.

When can we realistically expect first deployments and in which areas will it be most likely so far?

We don’t know, because this seems too far off. As noted above, we expect to learn interesting physics in the next few years, but for relavent computational problems, this seems like decades.

How serious do you think IBM’s announcement is to launch the first quantum computer on the market within 2 years?

They may launch the first quantum computer, but I doubt whether anyone will find it useful.

Who does all the research on technology (companies/organisations)?

This is currently a mix. University groups still play a major role, including the most impressive demonstrations of quantum computing to date. Companies are also now investing heavily, both start-ups and international firms.

Do you believe that, analogous to Steve Jobs’ statement at that time “every home will have its own computer”, in the future everyone will also have a quantum computer at home?

No. A quantum computer will be part of a supercomputer, required for very specific tasks. Just as you don’t need a supercomputer in your home, you won’t need a quantum computer. Your laptop will be much better at most tasks.