The Qiskit Circuit Library contains many operations and circuits that may be used as building blocks for implementing quantum algorithms. Here are some standard operations categorized as instructions, singlequbit gates, and multiqubit gates.
The standard instruction classes implement quantum operations that aren’t necessarily unitary. They are subclasses of the Instruction
class (see “The Instruction Class”).
The Barrier
class creates a barrier instruction (see “Creating a Barrier”) with a given number of qubits. A barrier provides both visual and functional separation between gates on a wire in a quantum circuit.
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The Measure
class creates a measurement instruction for measuring a quantum state in the computational basis, placing the binary result in a classical register (see “Measuring a quantum circuit”).
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The Reset
class creates a reset instruction that reset the qubit state to (see “Using the reset() method”).
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The standard singlequbit gates implement unitary quantum operations. They are subclasses of the Gate
class (see “The Gate Class”). These gates may be created and applied to a circuit via the singlequbit gate methods of the QuantumCircuit
class that appear in Table 11.
The HGate
class creates a singlequbit H gate. It performs a π rotation around the X+Z axis. It also has the effect of changing the computational basis from , to , and viceversa.
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The IGate
class creates a singlequbit I gate, which has no effect on the state of a qubit.
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The PhaseGate
class creates a singlequbit Phase gate that performs a given phase rotation.
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The RXGate
class creates a singlequbit RX gate that performs a given rotation around the X axis.
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The RYGate
class creates a singlequbit RY gate that performs a given rotation around the Y axis.
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The RZGate
class creates a singlequbit RZ gate that performs a given rotation around the Z axis.
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The SGate
class creates a singlequbit S gate that performs a π/2 phase rotation.
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The SdgGate
class creates a singlequbit S† gate that performs a π/2 phase rotation.
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The SXGate
class creates a singlequbit square root of X gate that performs a π/2 rotation around the X axis while shifting the global phase by π/4.
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The SXdgGate
class creates a singlequbit inverse square root of X gate that performs a π/2 rotation around the X axis while shifting the global phase by π/4.
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The TGate
class creates a singlequbit T gate that performs a π/4 phase rotation.
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The TdgGate
class creates a singlequbit T† gate that performs a π/4 phase rotation.
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The UGate
class creates a singlequbit U gate with 3 Euler angles.
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The XGate
class creates a singlequbit X gate that performs a π rotation around the X axis.
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The YGate
class creates a singlequbit Y gate that performs a π rotation around the Y axis.
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The ZGate
class creates a singlequbit Z gate that performs a π rotation around the Z axis.
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The standard multiqubit gates implement unitary quantum operations. They are subclasses of the ControlledGate
class (see “The ControlledGate Class”). Some of these gates may be created and applied to a circuit via the multiqubit gate methods of the QuantumCircuit
class, many of which appear in Table 12.
The C3XGate
class creates a fourqubit gate that has an X gate and three control qubits.
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The C3SXGate
class creates a fourqubit gate that has a square root of X gate and three control qubits.
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The C4XGate
class creates a fivequbit gate that has an X gate and four control qubits.
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The CCXGate
class creates a threequbit gate that has an X gate and two control qubits. This is also known as a Toffoli gate.
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The CHGate
class creates a controlledHadamard gate, applying the Hadamard according to the control qubit state.
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The CPhaseGate
class creates a controlledPhase gate, applying the PhaseGate
according to the control qubit state.
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The CRXGate
class creates a controlledRX gate, applying the RX
according to the control qubit state.
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The CRYGate
class creates a controlledRY gate, applying the RY
according to the control qubit state.
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The CRZGate
class creates a controlledRZ gate, applying the RZ
according to the control qubit state.
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The CSwapGate
class creates a threequbit gate whose Swap gate is applied according to the control qubit state.
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The CSXGate
class creates a controlledSX (square root of X) gate, applying the gate according to the control qubit state.
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The CUGate
class creates a controlledU gate, applying the U gate including a global phase argument, according to the control qubit state.
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The CXGate
class creates a controlledX gate, applying the X gate according to the control qubit state.
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The CYGate
class creates a controlledY gate, applying the Y gate according to the control qubit state.
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The CZGate
class creates a controlledZ gate, applying the Z gate according to the control qubit state.
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The DCXGate
class creates a doubleCNOT gate. This is a twoqubit gate that has two CNOT gates with their controlqubits on different wires.
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The iSwapGate
class swaps the qubit states of two quantum wires. It also changes the phase of and amplitudes by i.
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The MCPhaseGate
class creates a multicontrolled Phase gate with a given number of control qubits.
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The MCXGate
class creates a multicontrolled X gate with a given number of control qubits.
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The SwapGate
swaps the qubit states of two quantum wires.
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