# Student Colloquium, Christian Lange

*Supervisor: Klaus Mølmer*

Title: The Toric code – quantum computing on a donut

Quantum computing is one of the most funded areas of research withing physics with private companies also participating in the pursuit of making an actual quantum computer. The fundamental building block of a quantum computer is a quantum bit (qubit). Qubits are in general not very stable which makes quantum computing is very difficult. There are many proposals on how to make a qubit more stable. One if these is the so-called toric code which manifests itself on the manifold of a torus – the same shape as the surface of a donut. In this colloquium I will briefly motivate why quantum computing is worth pursuing, what kind of qubits we have today, and their related problems. Then I will explain the toric code in-depth and look at how we can have non-local qubits, that is qubits that live as a collective state on the torus. These states are robust against noise from the environment and are thus a candidate on how to make a robust qubit useful for actual quantum computation.