The most common way to construct multi-qubit gates is to use single-qubit gates as part of a controlled quantum gate.
The first two that you should study are:
Controlled quantum gates are gates that have two types of input qubits:These gates can be understood as doing a certain unitary operation only if the control qubits are enabled or disabled.
- control qubits
- operand qubits (terminology made up by Ciro Santilli just now)
The Hadamard gate takes or (quantum states with probability 1.0 of measuring either 0 or 1), and produces states that have equal probability of 0 or 1.
Equation 1.
Hadamard gate matrix
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