Quantum error correction: From the blackboard to the cloud

It has been several decades since the idea of quantum error correction was first proposed. In that time, many different approaches have been developed and studied. Until the last decade, this work was almost exclusively restricted to theory, with a great gulf between the worlds of theory and experiment. For example, a theorist calculating a threshold during this era might regard a code with 1000 qubits as relatively small. But at the same time, an experiment with just 4 qubits could be seen as revolutionary.