⚛️ Quantum Gate Simulator & GUI Visualizer

A simple Quantum Gate Simulator implemented in C++, paired with a Node.js-based GUI Visualizer for an interactive experience.

The simulator allows you to store and apply various quantum gates to qubit states and provides a visual interface to see the results of quantum operations in action.

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📖 Overview

This project is divided into two main parts:

🔹 Quantum Gate Simulator (C++)

• Implements basic quantum mechanics concepts such as qubit state representation and quantum gate operations.
• Provides a comprehensive set of quantum gates:
  • Single-qubit gates: Identity, Pauli-X/Y/Z, Hadamard, Phase (S), T-Gate, Rotation gates (Rx, Ry, Rz)
  • Two-qubit gates: CNOT, CZ, SWAP
  • Advanced multi-qubit gates: Toffoli (CCX), Fredkin (CSWAP), Multi-controlled X/Z, Quantum Fourier Transform (QFT)
• Uses manual matrix operations (without external libraries like Eigen) to evolve quantum states.
• Includes validation tests for advanced algorithms like Grover's search.

🔹 GUI Visualizer (Node.js)

• A frontend interface that communicates with the C++ simulator.
• Allows users to drag and drop gates onto qubits, build circuits, and see the resulting state evolution.
• Visualizes quantum states using:
  • Bloch spheres
  • Probability histograms

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✨ Features

• Quantum Gate Storage – Manage and apply common gates easily.
• State Evolution – Apply operations on qubits and observe transformations.
• Advanced Multi-Qubit Gates – Full support for Toffoli, Fredkin, multi-controlled gates, and QFT.
• Algorithm Implementation – Grover's search algorithm validation and testing.
• Interactive GUI – User-friendly Node.js frontend with drag-and-drop interface.
• Separation of Concerns – C++ handles computation, Node.js handles visualization.
• High Precision – Numerical accuracy with < 1e-12 error tolerance.

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⚙️ Installation & Setup

🔧 Prerequisites

• C++ Compiler (e.g., g++)
• Node.js (>= 16.0.0)
• npm (comes with Node.js)

🖥️ Backend (C++ Simulator)

# Navigate to the backend folder
cd backend

# Compile the simulator
g++ main.cpp -o simulator

# Run the simulator
./simulator

🌐 Frontend (Node.js GUI)

# Navigate to the frontend folder
cd frontend

# Install dependencies
npm install

# Start the GUI
npm start

The frontend will connect with the backend to visualize quantum gate operations.

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🚀 Usage Example

1. Start the C++ backend (./simulator).
2. Run the Node.js GUI (npm start).
3. Open the interface in your browser (default: http://localhost:3000).
4. Drag and drop gates onto qubits, then visualize state changes.

Example workflow:

• Initialize a |0⟩ qubit
• Apply a Hadamard gate → get a superposition state
• Apply a Pauli-Z gate → observe phase flip on the Bloch sphere

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🔧 Advanced Gates API

The simulator now includes advanced multi-qubit gates essential for quantum algorithms:

Toffoli Gate (CCX)

apply_toffoli_gate(state, len, ctrl1, ctrl2, target);

Applies X gate to target qubit when both control qubits are in |1⟩ state.

Fredkin Gate (CSWAP)

apply_fredkin_gate(state, len, ctrl, target1, target2);

Swaps target1 and target2 qubits when control qubit is in |1⟩ state.

Multi-Controlled Gates

// Multi-controlled X
apply_multi_controlled_x(state, len, controls, target);

// Multi-controlled Z
apply_multi_controlled_z(state, len, controls, target);

Apply X or Z gate when all control qubits are in |1⟩ state.

Quantum Fourier Transform

// Full QFT
apply_qft(state, len, qubits, inverse);

// Decomposed QFT (more efficient)
apply_qft_decomposed(state, len, qubits, inverse);

Performs quantum Fourier transform on specified qubits.

Grover's Algorithm

The included test file demonstrates Grover's search algorithm using the advanced gates:

# Build and run the test
cmake .
make grover_test
./grover_test

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🤝 Contribution Guidelines

We welcome contributions! To get started:

1. Fork the repository
2. Create a new branch for your feature/bugfix
3. Commit your changes with clear messages
4. Push your branch and submit a Pull Request (PR)

Please ensure:

• Code is well-documented
• New features include usage examples or tests

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📂 Project Structure

qubitverse/
│── .github/workflows/
│   └── cmake-single-platform.yml
│
│── qubitverse/
│   ├── simulator/            # C++ quantum gate simulator
│   │   ├── dep/
│   │   ├── gates/
│   │   ├── lexer/
│   │   ├── parser/
│   │   └── simulator/
│   │
│   └── visualizer/           # Node.js GUI visualizer
│       ├── public/
│       ├── src/
│       ├── eslint.config.js
│       ├── index.html
│       ├── package.json
│       └── vite.config.js
│
│── .clang-format
│── .clang-tidy
│── .clangd
│── .gitignore
│── CMakeLists.txt
│── compile.rc
│── CONTRIBUTING.md
│── LICENSE
│── README.md

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📌 Roadmap

• Add multi-qubit support
• Implement CNOT and controlled gates
• Implement advanced multi-qubit gates (Toffoli, Fredkin, QFT)
• Improve visualization with real-time animations
• Add export/import of circuits**
• Provide a hosted live demo
• Add quantum error correction support
• Implement variational quantum algorithms

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📜 License

This project is licensed under the MIT License.
See the LICENSE file for details.

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🌟 Acknowledgments

• Inspired by basic concepts of Quantum Computing.
• Educational references: Nielsen & Chuang - Quantum Computation and Quantum Information.
• Open-source tools and the developer community.

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