P5: Towards Software for Fault Tolerant Quantum Computing

Members: Prof. Dr. Jens Eisert (FU Berlin), Prof. Dr. Markus Müller (RWTH Aachen, FZ Juelich), Prof. Dr. Robert Wille (TUM), Laura Herzog (TUM)

Building and operating large-scale quantum computers that are capable of running quantum applications that outperform classical supercomputers, or yield practical value, will require fault-tolerant quantum error correction. Since quantum systems are prone to decoherence, active detection and correction of errors during storage and processing of quantum information is essential to guarantee reliable computational output of quantum algorithms. Importantly, this requires on the one hand quantum error correcting codes that enable sufficiently powerful (universal) error-corrected quantum gate operation. On the other hand, implementation of these operations requires efficient quantum circuits which obey fault-tolerant design principles to prevent the uncontrollable proliferation of errors, and efficient fast decoders to classically process error syndrome information. However, most current state-of-the-art quantum circuit compilation and synthesis methods do not take error-correction and fault-tolerance into account at all – giving rise to a fatal gap between required and existing software for the operation of scalable error-corrected quantum computers. As a result, the construction of fault-tolerant quantum circuits is often performed manually (a tedious task which eventually is not scalable) and frequently ignores specific capabilities and constraints of actual physical quantum hardware. In this project, we aim to take first steps towards closing this severe gap by focusing on several concrete problems in the vast field of fault-tolerant circuit compilation. We accept that this challenge can only be reasonably tackled by bringing expertise from quantum information theory, physics, and software design together. We will develop methods that combine novel theoretical techniques, considerations from physical hardware constraints, as well as automated tools for fault-tolerant compilation. By this, we aim to lay the foundation for an envisioned comprehensive, automated circuit compilation framework for scalable fault-tolerant quantum computation.