# Surface codes

## Introduction

On this platform, several physical systems are explored for their use in quantum computing. However, none of these systems perform sufficiently well to serve directly as computational qubits. It is possible to construct a logical qubit from a collection of physical qubits, such that the logical qubit performs much better than the individual physical qubits. One approach to building such logical qubits is based on surface codes, operating as stabilizer codes.

Did you see these surface codes before but didn't fully understand the diagrams? In this video, postdoctoral researcher Ben Criger gives an in-depth explanation of how these surface codes operate and how to interpret the diagrams.

## Prerequisite knowledge

- Qubit operations
- Quantum Error Correction
- Surface codes

## Further thinking

Can you tell why someone would be interested in these kind of codes?

We have seen n=9 physical qubits have been used to encode 1 logical qubit. This seems like a waste of qubits, but it is not. What is the advantage in the long term?

## Further reading

- This paper was written by A. Fowler et al. as an introduction to surface codes. Surface codes: Towards practical large-scale quantum computation
- This is the original paper that proposes the use of surface codes. https://arxiv.org/abs/quant-ph/9811052
- Dive deeper into the topic of QEC, and try this scientific paper. https://arxiv.org/pdf/0905.2794.pdf
- Or, if you prefer watching over reading, you could try this video: https://www.youtube.com/watch?v=hV5FTsyKE8A&feature=youtu.be