Quantum Information Science: Lecture Notes

1995: Thought error correction to be impossible! 1. States collapse on measurement 2. Classically error occurs or does not occur. In Q. M., errors are continuous: The Solutions: 1. Measure only the effect of the environment, not the state (i.e. did an error occur?) 2. & 3. Orthogonalize errors using entanglement: the environment has done one thing, or another, in an entangled way. Example: The Quantum Bit Flip Code: