Quantum Cipher: BB84 Quantum Key Distribution Simulation

A Python-based simulation of the BB84 Quantum Key Distribution (QKD) protocol — one of the earliest and most secure quantum cryptography methods.
This project demonstrates qubit encoding, measurement, basis comparison, and shared key generation using Qiskit, along with Bloch sphere visualizations of quantum states.

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Features

• Step-by-step BB84 protocol simulation
• Random qubit generation for Alice and Bob
• Basis matching and bit comparison
• Bloch sphere visualization of qubit states
• Final shared secret key generation

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BB84 Overview

1. Alice sends qubits to Bob encoded randomly in two bases: Rectilinear (+) and Diagonal (×).
2. Bob measures each qubit using a random basis.
3. They publicly compare bases (not the bit values).
4. Bits where the bases matched form the shared secret key.

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Quick Start

1. Clone the repository

git clone https://github.com/your-username/quantum-cipher.git
cd quantum-cipher

2. Install dependencies

pip install -r requirements.txt

3. Run the simulation

python bb84_simulation.py

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Simulation Outputs

1. Bloch Sphere Visualization

2. Final Shared Secret Key

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References

BB84 Quantum Key Distribution - Wikipedia
IBM Quantum Cloud Documentation