Decoherence
- A QC achieves exponential speedup because of superposition
- Qbit wavefunctions are entangled
- Decoherence: The superposition decays into a classical state
- Example: The 2-slit electron experiment
- Between the two cases of the 2-slit experiment (interference pattern versus no interference pattern) lies a continuum of information leaks
- In a QC, wavefunction superposition can leak into the universe
- As information about the superpositions leaks out, the quantum parallelism degrades
- Key concept is the decoherence time
- In present day QCs (a few qbits), tdecohere ~ 100µs