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quantumCircuit

Quantum computing circuit

Since R2023a

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Installation Required: This functionality requires MATLAB Support Package for Quantum Computing.

Description

A quantumCircuit object represents a quantum computing circuit with a specific number of qubits and gates. An example of a quantum circuit with two qubits and two gates is shown in this diagram.

Quantum circuit with Hadamard and CNOT gates

Each solid horizontal line in the diagram represents a qubit. The symbols Hadamard gate symbol and Controlled X gate symbol represent the gates that operate on the qubits. The symbols represent the Hadamard gate and the controlled X gate, respectively. For more details about quantum circuits, see Quantum Circuit.

Creation

Syntax

c = quantumCircuit(numQubits)
c = quantumCircuit(gates)
c = quantumCircuit(gates,numQubits)
c = quantumCircuit(___,Name=name)

Description

c = quantumCircuit(numQubits) creates a quantum computing circuit with the specified number of qubits and no gates.

This syntax sets the NumQubits property to numQubits.

example

c = quantumCircuit(gates) creates a quantum computing circuit with the specified quantum gates and the required number of qubits from the gate operations.

This syntax sets the Gates property to gates and the NumQubits property to the number of automatically created qubits.

c = quantumCircuit(gates,numQubits) creates a quantum computing circuit with the specified quantum gates and number of qubits. The input numQubits must be greater than or equal to the largest qubit index used in gates.

example

c = quantumCircuit(___,Name=name) additionally specifies a name for the circuit using any of the input argument combinations in the previous syntaxes.

This syntax sets the Name property to name.

Input Arguments

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Name of the quantum circuit, specified as a string. The name input must start with a letter, followed by letters, digits, or underscores (with no white space). The default is an empty string "".

When you create a composite gate from an existing circuit using the compositeGate function, then this name will also be used as the label for the composite gate (unless you specify a new name when using compositeGate). This name will be used in the plot of the composite gate and the function name in the generated QASM code.

Example: "multi_controlled_Z"

Properties

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Number of qubits in the circuit, specified as a nonnegative integer scalar.

Example: 4

Quantum gates in the circuit, specified as a vector of gates. The array of gates is always returned as a column vector. The elements of this vector must be of type quantum.gate.SimpleGate or quantum.gate.CompositeGate.

During quantum circuit creation with multiple gates, you can specify gates as a row or column vector of gates. However, the Gates property always returns a column vector of gates.

Name of the circuit, specified as a string scalar or character vector. This property returns a string scalar. If you do not specify the circuit name when creating the circuit, the default value of this property is an empty string, "". Otherwise, the Name property value must start with a letter, followed by letters, digits, or underscores (with no white space).

When you construct a composite gate from an existing circuit using the compositeGate function, this name is used as the label for the composite gate (unless you specify a new name when using compositeGate). This name is also used in the plot of the composite gate and the function name in the generated QASM code.

Example: "multi_controlled_Z"

Object Functions

plotPlot quantum circuit or composite gate
simulateSimulate quantum circuit
runRun circuit on quantum device
getMatrixMatrix representation of quantum circuit or gate
invInverse of quantum circuit or gate
generateQASMGenerate QASM code
unpackUnpack composite gates in quantum circuit

Examples

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Create a quantum circuit that consists of a Hadamard gate and a controlled X gate to entangle two qubits.

gates = [hGate(1); cxGate(1,2)];
c = quantumCircuit(gates);

Plot the circuit.

plot(c)

Quantum circuit with Hadamard and CNOT gates

Create a quantum circuit that consists of Hadamard and controlled NOT gates to entangle two qubits. Name the circuit as "bell".

innerGates = [hGate(1); cxGate(1,2)];
innerCircuit = quantumCircuit(innerGates,Name="bell")
innerCircuit = 

  quantumCircuit with properties:

    NumQubits: 2
        Gates: [2×1 quantum.gate.SimpleGate]
         Name: "bell"

Create an outer circuit that contains two composite gates constructed from this inner "bell" circuit. The first composite gate acts on qubits 1 and 3 of the outer circuit containing this gate. The second composite gate acts on qubits 2 and 4 of the outer circuit containing this gate.

outerGates = [compositeGate(innerCircuit,[1 3])
              compositeGate(innerCircuit,[2 4])];
outerCircuit = quantumCircuit(outerGates)
outerCircuit = 

  quantumCircuit with properties:

    NumQubits: 4
        Gates: [2×1 quantum.gate.CompositeGate]
         Name: ""

Plot the outer circuit.

plot(outerCircuit)

Quantum circuit with two composite gates named bell

The outer circuit consists of four qubits with indices 1, 2, 3, and 4. The plot shows that qubits 1 and 3 of the outer circuit are mapped to qubits 1 and 2 of the inner circuit of the first composite gate, and qubits 2 and 4 of the outer circuit are mapped to qubits 1 and 2 of the inner circuit of the second composite gate.

Click one of the composite gate blocks in the plot. A new figure showing the internal gates of the composite gate appears.

Internal gates of the bell composite gate

Version History

Introduced in R2023a

See Also

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