TL;DR: GKP codes encode a logical qubit in a continuous-variable quantum system (like a microwave resonator or optical mode). They provide protection against small displacement errors and can be concatenated
GKP codes encode a logical qubit in a continuous-variable quantum system (like a microwave resonator or optical mode). They provide protection against small displacement errors and can be concatenated with outer codes for full fault tolerance. GKP codes have been demonstrated experimentally in both superconducting and photonic systems and are a key component of several proposed fault-tolerant architectures.
Type
Bosonic code (continuous variable)
Overhead
Encodes logical qubit in oscillator; reduces physical qubit count
Threshold
~1-3% for Gaussian noise
Key Result
Demonstrated in superconducting and photonic systems