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Quantum gates
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Unitary operations on qubits.
Reversible unitary operations: Hadamard creates superposition, CNOT entangles two qubits, phase gates rotate relative phase. Circuits of gates implement algorithms.
H|0⟩ = (|0⟩ + |1⟩)/√2.
Gates must preserve probabilities.
In more detail
Quantum gates are unitary operations on qubits, such as the Hadamard, CNOT and Pauli gates. Combinations of gates form quantum circuits that implement algorithms.
Real-world uses
- Quantum circuits are built from gates on real hardware.
- Algorithms such as Grover search are described as gate sequences.
- Quantum programmers build algorithms from gates such as the Hadamard and CNOT that act on qubits.
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Frequently asked questions
What is a Hadamard gate?
A gate that creates an equal superposition of 0 and 1.
What is a CNOT gate?
A two-qubit gate that flips the second qubit when the first is one, creating entanglement.
Why must quantum gates be reversible?
Quantum evolution is unitary, so every gate must be reversible and preserve total probability.
Related topics in Quantum Mechanics
Decoherence · Interpretations of QM · Quantum computing: qubits · Quantum cryptography · Quantum teleportation · Lasers