Text by Nina Beier / Interview with Ulrich Eberl / Photo: Y. Colombe/NIST

There has been a lot of talk lately about quantum technologies. Among other things, the EU has created the Quantum Flagship, which supports research in this field with one billion euros. At the forefront of this is talk of quantum computers, a new type of computer that uses the rules of quantum physics. You can read more about how they work in this article.

I talked with the renowned science journalist Ulrich Eberl about quantum computers and their significance in the future. In his books, he describes many developments that will shape the future – in different fields such as environment and energy, mobility, urban development or health. What role do quantum computers play for him?

 

Quantum computers: A conversation with Ulrich Eberl

 

Since last year Google announced “quantum superiority” quantum computers have become more public. But what’s the hype about it?

Google was able to show that a quantum computer can do in a few minutes what a conventional supercomputer would take thousands of years to do. The point is that it was all about creating random numbers. At the moment, this could at most be used to perhaps make random number generators even better, but quantum computers are still far from a really useful practical application.

How far away?

Google had about 50 qubits in its quantum computer. It is assumed that a quantum computer for commercial applications probably needs thousands of qubits. So you have to go from 50 to 1000 first. On top of that you also have to add error corrections. These become more difficult the larger the number of qubits is. Probably you need another factor of 1000 in error corrections. This means that I am not at 1000 qubits, but at one million, and nobody today knows how to build such a quantum computer. But what inspires researchers, of course, are the fundamentally possible applications.

What kind of applications would these be?

If you have a functioning quantum computer, you can crack practically all the encryptions used today – at lightning speed. This makes military and intelligence agencies extremely nervous, but the privacy of any smartphone would of course be at risk. Then there are many other possible applications, such as optimizing the flow of goods or simulating proteins. When a cell reads the genetic material, i.e. the DNA, and builds proteins from it, many thousands of atoms often interact. The proteins must fold; they form a three-dimensional structure. Even supercomputers have great difficulty in calculating such a thing and simulating the dynamics. However, this would be very exciting because it would enable the rapid development of new drugs, something that has been very important not only since the corona virus. Quantum computers could also analyse large amounts of data. This would be interesting for applications in artificial intelligence, for example in image recognition.

What are the big problems on the way to a functioning quantum computer?

The difficulties are related to how quantum computers work. You have to prepare quantum states. There are two main methods used today for this. One is ion traps. The qubits are ions which are kept in certain states and which should then exchange with other ions. The other are superconducting qubits, where the current runs without electrical losses in mini-circuits that are connected to each other.

The crucial point about qubits is that they have to be massively separated from the environment. This means that every air particle that would bump into a qubit would already ruin the condition. Or if it gets too warm, the qubits start to wobble and bump into walls or each other, and that ruins the condition too. So you have to go to extremely low temperatures, a few thousandths of a degree above absolute zero, and you have to maintain this isolation from the environment as long as possible. That is still feasible in principle, but I also need a way to read out the quantum state without destroying it, and that is almost contradictory. How to do this sensibly is difficult, and that’s why these error corrections are also extremely important.

Thank you for the interview!