TL;DR: Quantum LDPC codes are a family of error-correcting codes that promise constant overhead (O(1) physical qubits per logical qubit) compared to the surface code's O(d²). This could reduce the total qubi
Quantum LDPC codes are a family of error-correcting codes that promise constant overhead (O(1) physical qubits per logical qubit) compared to the surface code's O(d²). This could reduce the total qubit count needed for fault-tolerant quantum computing by orders of magnitude. IBM's 2025 roadmap explicitly targets LDPC codes for their future fault-tolerant architecture.
Overhead
Potentially O(1) physical qubits per logical qubit (constant overhead)
Threshold
Varies by construction; some achieve ~0.5%
Key Result
IBM and others showing LDPC codes can dramatically reduce overhead vs surface codes