Humans like to build robust systems – ones that resist change and minimize unreliable or undesirable results. In quantum computing, this desire manifests itself as fault-tolerant quantum computing (FTQC), which aims to protect both the quantum state and the logic gates that manipulate it against interventions from the environment. Although quite a resource-intensive task, physicists at IBM Research recently showed that they could partially meet this requirement, thanks to some real-life quantum “magic”.
The process of cushioning quantum states against uncontrollable interventions is called quantum error correction (QEC). In this process, information that would ideally be stored in a few quantum bits, or qubits, is instead stored in many more. The resulting redundancy is used to detect and correct the enforced errors. In QEC jargon, the mapping of the ideal-case quantum state (the logical state) into the noise-protected state (the physical state) is termed encoding. There are multiple ways to perform this encoding, and each such scheme is called an error-correction code.
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