Package com.quantum4j.core.gates

Class SingleQubitGate

java.lang.Object

com.quantum4j.core.gates.SingleQubitGate

All Implemented Interfaces:

Gate

Direct Known Subclasses:

RXGate, RYGate, RZGate, StandardGates.HGate, StandardGates.RXGate, StandardGates.RYGate, StandardGates.RZGate, StandardGates.SGate, StandardGates.TGate, StandardGates.U1Gate, StandardGates.U2Gate, StandardGates.U3Gate, StandardGates.XGate, StandardGates.YGate, StandardGates.ZGate

public abstract class SingleQubitGate
extends Object
implements Gate

Abstract base class for single-qubit gates.

A single-qubit gate is represented by a 2×2 complex matrix. Subclasses provide specific gate matrices (e.g., Hadamard, Pauli X, Y, Z).

Field Summary

Fields

Modifier and Type	Field	Description
protected final Complex[][]	matrix	2x2 unitary matrix representing this gate

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	SingleQubitGate(Complex[][] matrix)	Construct a single-qubit gate with the given 2×2 matrix.

Method Summary

Modifier and Type	Method	Description
void	apply(StateVector state, int targetQubit)	Apply this single-qubit gate to the specified target qubit in the given state.
int	arity()	Get the arity (number of qubits) this gate acts upon.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.quantum4j.core.gates.Gate

name

Field Details

matrix

protected final Complex[][] matrix

2x2 unitary matrix representing this gate

Constructor Details

SingleQubitGate

protected SingleQubitGate(Complex[][] matrix)

Construct a single-qubit gate with the given 2×2 matrix.

Parameters:

matrix - a 2×2 complex matrix

Throws:

IllegalArgumentException - if the matrix is not 2×2

Method Details

arity

public int arity()

Description copied from interface: Gate

Get the arity (number of qubits) this gate acts upon.

Specified by:

arity in interface Gate

Returns:

1 for single-qubit gates, 2 for two-qubit gates, etc.

apply

public void apply(StateVector state,
 int targetQubit)

Apply this single-qubit gate to the specified target qubit in the given state.

This implementation performs sparse matrix-vector multiplication by updating only the amplitude pairs affected by the target qubit.

Parameters:

state - the quantum state to modify

targetQubit - the index of the qubit to apply the gate to (0 = LSB)

Throws:

IllegalArgumentException - if targetQubit is out of range