Remote Anonymous Quantum Transmission (RAQT) in NetSquid

NetSquid simulation of Robust Anonymous Quantum Transmission (Christandl-Wehner 2004 protocol)

This repository provides a functional implementation of the Remote Anonymous Quantum Transmission (RAQT) protocol using the NetSquid discrete-event simulation framework.

The simulation demonstrates how a Greenberger–Horne–Zeilinger (GHZ) state can be utilized to transmit a secret bit across a network of participants while maintaining the absolute anonymity of the sender.

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🔬 Protocol Logic

The RAQT protocol leverages the parity properties of entangled states. By performing measurements in the $X$-basis, the global phase shift applied by a single participant (the sender) can be recovered through the XOR sum of all outcomes.

The Quantum Circuit

1. State Preparation: A 4-qubit GHZ state is initialized: $$\frac{1}{\sqrt{2}}(|0000\rangle + |1111\rangle)$$
2. Encoding: The sender (e.g., sender_id = 2) applies a $Z$ gate to their local qubit if their secret bit is 1. If the bit is 0, no operation is performed.
3. Basis Transformation: All participants apply a Hadamard ($H$) gate to rotate their qubits from the computational basis ($Z$) to the transverse basis ($X$).
4. Measurement: Every participant performs a standard measurement.
5. Parity Check: The XOR sum (parity) of all measurement results is calculated.

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🛠 Technical Implementation

The script uses the NetSquid Qubit API (qapi) and mathematical Operators to verify the protocol logic in an ideal state-vector environment. This avoids the ProcessorBusyError associated with discrete-event timing while maintaining physical accuracy.

Dependencies

• Python: 3.8+
• NetSquid: Quantum network simulator (pip install netsquid)

Core Code Structure

RAQTNetSquid.py