📏 Measurement Operations

Discover how quantum measurements collapse superpositions and extract classical information

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🎯 What is Quantum Measurement?

Quantum measurement is the process of extracting classical information from quantum states. Unlike passive classical observation, quantum measurement actively changes the system, collapsing superpositions into definite outcomes.

⚡ The Measurement Postulate

When measuring a qubit in state |ψ⟩ = α|0⟩ + β|1⟩, you get outcome |0⟩ with probability |α|² and |1⟩ with probability |β|². After measurement, the state irreversibly collapses to the observed outcome.

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Probabilistic Nature

Measurement outcomes are fundamentally random, governed by quantum amplitudes

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State Collapse

Superposition vanishes upon measurement, leaving only one classical outcome

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Born Rule

Probability = |amplitude|² connects quantum and classical worlds

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Irreversibility

Cannot recover the original superposition after measurement

📝 Measurement Example

Before:|ψ⟩ = (|0⟩ + |1⟩)/√2 (superposition)
Measure:50% chance |0⟩, 50% chance |1⟩
After:|0⟩ OR |1⟩ (collapsed to one outcome)

💡 Key Insight

Measurement is the bridge between quantum and classical worlds. While quantum gates are reversible and preserve information, measurement is irreversible and destroys quantum coherence—making it both the most powerful and most destructive quantum operation.