Technique that uses multiple non-ideal qubits (physical qubits) to simulate/produce one perfect qubit (logical).
One is philosophically reminded of classical error correction codes, where we also have multiple input bits per actual information bit.
TODO understand in detail. This appears to be a fundamental technique since all physical systems we can manufacture are imperfect.
Part of the fundamental interest of this technique is due to the quantum threshold theorem.
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 "Jeremy O'Brien: "Quantum Technologies" by GoogleTechTalks (2014)" youtu.be/7wCBkAQYBZA?t=2778 describes an error correction approach for a photonic quantum computer.
Bibliography:
Quantum computers are not expected to solve NP-complete problems by
Ciro Santilli 40 Updated 2025-07-16
Only NP-intermediate, which includes notably integer factorization:
- quantumcomputing.stackexchange.com/questions/16506/can-quantum-computer-solve-np-complete-problems
- www.cs.virginia.edu/~robins/The_Limits_of_Quantum_Computers.pdf by Scott Aaronson
- cs.stackexchange.com/questions/130470/can-quantum-computing-help-solve-np-complete-problems
- www.quora.com/How-can-quantum-computing-help-to-solve-NP-hard-problems
The most comprehensive list is the amazing curated and commented list of quantum algorithms as of 2020.
English translation of papers that include the original Quantization as an Eigenvalue Problem by Schrödinger (1926).
There are unlisted articles, also show them or only show them.