Theoretical Quantum Computing (THEQUCO)

After a titanic effort, and more than twenty years of development, first prototypes of quantum computers have been built and demonstrated so-called quantum supremacy. At the same time, selected problems exist for which it is known that quantum algorithms can accelerate the solution. This has raised hopes that quantum computers will soon be able to address important problems that cannot be addressed with their classical counterparts.

The story is, however, far from being complete. Firstly, all existing and planned quantum computers are noisy and plagued with errors. Secondly, most quantum algorithms do not tolerate errors, which severely limits the applicability of quantum computers until they become error free. There exist some heuristic quantum algorithms, which might work under low error rates but whose efficiency over classical ones needs to be demonstrated. Additionally, algorithms for scalable devices are scarce. At the same time, the new prototypes of quantum computers have initiated several fundamental questions, ranging from their complexity to their capability of being used in machine learning.

This consortium addresses the theoretical questions raised above. It contributes to the development of the quantum information theory behind Noisy Intermediate-Scale Quantum (NISQ) and analog devices. It constructs new quantum algorithms both for present and planned scalable generations of devices. It also builds new methods and protocols to certify quantum computers and their capability of demonstrating a quantum advantage. Finally, it investigates the improvement of current quantum computers by establishing new control and error mitigation methods, and helps scaling them up by devising and improving error correction techniques.