🔗 CNOT Gate
Master the controlled-NOT gate - the fundamental two-qubit operation for quantum entanglement
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What is the CNOT Gate?
The Controlled-NOT (CNOT) gate is the most important two-qubit gate in quantum computing. It performs a conditional operation: flip the target qubit if and only if the control qubit is |1⟩.
🎯 The Control Principle
- •Control Qubit: Determines whether operation happens (● in circuits)
- •Target Qubit: Gets flipped (X gate) if control is |1⟩ (⊕ in circuits)
- •Conditional Logic: Like an "IF control = 1 THEN flip target" statement
🔄 Circuit Notation
Control ——●——
|
Target ——⊕——
● = Control qubit (black dot)
⊕ = Target qubit (circle with plus)
| = Connection line⚛️
Two-Qubit Operation
Requires two qubits working together, unlike single-qubit gates
🔗
Creates Entanglement
Can create quantum correlations impossible in classical physics
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Reversible
CNOT is its own inverse - applying twice returns original state
🌍
Universal
CNOT + single-qubit gates can implement any quantum algorithm
💡 Why CNOT Matters
CNOT is fundamental because it's the simplest gate that creates quantum entanglement - the phenomenon where measuring one qubit instantly affects another, regardless of distance. This enables quantum teleportation, superdense coding, and quantum error correction.
Without CNOT gates, quantum computers would be no more powerful than classical computers. It's what makes quantum computing truly "quantum."