Technique that uses multiple non-ideal qubits (physical qubits) to simulate/produce one perfect qubit (logical).
TODO understand in detail. This appears to be a fundamental technique since all physical systems we can manufacture are imperfect.
For example, when PsiQuantum raised 215M in 2020, they announced that they intended to reach 1 million physical qubits, which would achieve between 100 and 300 logical qubits.
Video 140. "Jeremy O'Brien: "Quantum Technologies" by GoogleTechTalks (2014)" https://youtu.be/7wCBkAQYBZA?t=2778 describes an error correction approach for a photonic quantum computer.