Decoherence & Noise
Understand how quantum information degrades over time
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Types of Quantum Errors
Introduction to Decoherence
Decoherence is the process by which quantum systems lose their quantum properties through interaction with the environment. It's the primary reason quantum computers must operate at ultra-low temperatures and with extreme isolation.
T₁
Energy Decay
T₂
Phase Loss
μs
Typical Scale
15mK
Operating Temp
Why Decoherence Matters
⏱️
Time Limit
Sets maximum circuit depth before errors dominate
🎯
Fidelity Loss
Quantum states gradually become classical mixtures
❄️
Cooling Need
Requires extreme isolation from thermal environment
🔬
Error Source
Dominant source of errors in quantum systems
Quantum vs Classical
⚛️Quantum System
- →Superposition states |ψ⟩ = α|0⟩ + β|1⟩
- →Phase relationships maintained
- →Quantum interference possible
💫After Decoherence
- →Classical mixture: p₀|0⟩ or p₁|1⟩
- →Phase information destroyed
- →No quantum advantage remains