Polarization and Orbital Angular Momentum Encoded Quantum Toffoli Gate Enabled by Diffractive Neural Networks

Area of Science:

• Quantum Information Science
• Quantum Computing
• Photonics

Background:

• Controlled quantum gates are essential for universal quantum operations and complex quantum algorithms.
• Three-qubit gates, like the Toffoli gate, are fundamental building blocks in quantum computation.
• Efficient implementation of multi-qubit gates is crucial for advancing quantum computing.

Purpose of the Study:

• To experimentally demonstrate a novel quantum Toffoli gate.
• To utilize a single photon's polarization and orbital angular momentum for quantum gate implementation.
• To simplify quantum circuit design for complex algorithms.

Main Methods:

• Implementation of the Toffoli gate using a polarized diffractive neural network scheme.
• Exploitation of single-photon polarization and orbital angular momentum.
• Characterization via quantum state tomography and quantum process tomography.

Main Results:

• Achieved a mean truth table visibility of 97.27±0.20% for the quantum Toffoli gate.
• Obtained a process fidelity of 94.05±0.02% through comprehensive tomography.
• Demonstrated a method that avoids exponential optical elements.

Conclusions:

• A novel and efficient experimental demonstration of a quantum Toffoli gate is presented.
• The method leverages single-photon properties and diffractive neural networks.
• This approach offers extensibility for implementing other crucial three-qubit gates.