The Role of the Observer in Quantum Measurement
- Can We Have Quantum Measurement without an Observer?
- Without Recorded Information, An Observation Is Not Possible
- Every interaction between quantum systems may lead to a collapse of the wave function. But most collapses are never recorded.
- When a change of quantum state is recorded as information in a macroscopic apparatus, it becomes available for observation at a later time.
- The Observer Can Then Look At the "Observable"
- When the new information is observed (recorded in a human mind), it becomes an observation. This last stage has no effect on the measurement (it's after the fact!),
but it does increase human knowledge.
- So When Does the Wave Function Collapse Without an Observer?
- At some random time and place, before which ψ evolution is determined.
- Radioactive nucleus decay; Spontaneous photon emission.
- If we could know when exactly, it would not be quantum mechanics.