Version 5.4.0
=============

This release introduces the **Quantum Circuit Editor**, a visual drag-and-drop interface for building quantum circuits directly in the Web Modeling Editor, along with Qiskit code generation capabilities.

New Features and Improvements
-----------------------------

**Quantum Circuit Editor**

* Added a new **Quantum Circuit Editor** component to the Web Modeling Editor, enabling users to visually design quantum circuits using a drag-and-drop interface.
* Implemented a comprehensive **gate palette** with support for:
    * **Single-qubit gates**: Hadamard (H), Pauli-X/Y/Z, S, T, and parametric rotation gates (RX, RY, RZ, Phase)
    * **Multi-qubit gates**: CNOT, SWAP, Toffoli (CCX), Fredkin (CSWAP), and controlled versions of single-qubit gates
    * **Measurement operations**: Standard measurement and post-selection
    * **Special gates**: QFT, barriers, spacers, and custom user-defined gates
* Added **nested circuit support** allowing users to create reusable gate definitions and composite operations.
* Implemented **undo/redo functionality** with keyboard shortcuts (Ctrl+Z / Ctrl+Y) for circuit editing.
* Added **circuit persistence** with automatic saving to the project storage.
* Introduced **example templates** (Bell State, GHZ State, Quantum Teleportation, Grover's Algorithm, Bernstein-Vazirani) accessible from the gate palette.
* Implemented **minimum qubit validation** ensuring circuits have the required number of qubits for selected gates.
* Added **measurement blocking** that prevents placing gates after measurement operations on the same qubit.

**Qiskit Code Generator**

* Added a new **Qiskit code generator** that converts visual quantum circuits to executable Python code using the Qiskit framework.
* Implemented support for configurable **backend options**:
    * Aer Simulator for local simulation
    * Fake Backend for testing
    * IBM Quantum for real quantum hardware execution
* Added **configurable shot count** for quantum circuit execution.
* Integrated the Qiskit generator into the Web Modeling Editor's Generate menu for seamless code export.

**Quantum Metamodel**

* Extended the B-UML metamodel with comprehensive **quantum circuit primitives** including:
    * ``QuantumCircuit``, ``QuantumRegister``, and ``ClassicalRegister`` classes
    * Gate classes for all supported quantum operations
    * Support for parameterized gates with angle specifications
    * Control state definitions for multi-qubit controlled operations

**Web Modeling Editor**

* Added **Quantum Circuit** as a new diagram type in the sidebar navigation.
* Integrated the quantum editor route (``/quantum-editor``) into the application routing.
* Extended project types to support ``QuantumCircuitDiagram`` alongside existing UML diagram types.
* Added automatic diagram type detection for proper menu rendering in the quantum editor context.

Fixes
-----

* Fixed issue: `#367 <https://github.com/BESSER-PEARL/BESSER/issues/367>`_