Peter Zoller and Ignacio Cirac (Photos: Munich Center for Quantum Science and Technology/Christoph Lackner)

Yesterday, Nature Review Physics honored the beginning of experimental quantum computation 25 years ago. In May 1995, Ignacio Cirac and Peter Zoller published a comprehensive concept for the creation of a quantum computer using trapped ions. The article established a new field of research that has been decisively shaped by Innsbruck quantum physics in recent years.

In 1994, the American mathematician Peter Shor presented his quantum algorithm for the factorization of large numbers, thereby impressively demonstrating the great potential of a quantum computer. At the International Conference on Atomic Physics in Boulder, USA, in the same year, the British physicist Artur Ekert challenged his colleagues with the question: How can we build such a quantum computer? The two theorists Ignacio Cirac and Peter Zoller were also in the audience at the time. And they immediately knew how to solve this question. In an intensive three-month collaboration, they developed a model for building a quantum computer. They used the experience with trapped ions, which at that time were already being used in atomic clocks. Cirac and Zoller show how these ions can be used as quantum bits and how quantum gates can be built with them. To do so, they had to find a way to exchange information between the quantum bits. After several attempts, they had the key idea: the internal states of the ions could be coupled to their external motional degrees of freedom. "Cirac and Zoller’s idea to use a common degree of freedom as data bus to enable two-qubit operations is simple and elegant and for this reason it was adopted in other platforms," writes Iulia Georgescu in an article in Nature Review Physics. "In 1995, Cirac and Zoller came up with the blueprint for an ion trap quantum computer, and circuit-based quantum computer architecture in general."

Joint success

Over the past 25 years, the research field has developed enormously. Academic research groups all over the world are working on the theoretical and experimental aspects of quantum computers, and numerous IT companies have entered the race and are starting to market first prototypes. “While we take the credit for the idea and vision, the success would not have been possible without the really outstanding experimental development of Rainer Blatt, Dave Wineland, Chris Monroe and others. The fact that our ideas have survived the course of history and that even some companies have taken up some of them are due to people like them and their groups and, in a broader sense, to a number of AMO theorists and experimentalists who have made outstanding contributions in the field," stated Ignacio Cirac und Peter Zoller.