Implementation of a simultaneous message passing protocol using optical vortices

TL;DR

This paper demonstrates a classical optical implementation of a controlled-SWAP gate using structured light, enabling fast, dynamic signal comparison without revealing content, with potential applications in secure communications.

Contribution

It introduces a novel classical optical approach to implement a c-SWAP gate using Laguerre-Gauss beams and digital micromirror devices, enhancing speed and error analysis capabilities.

Findings

Achieved signal comparison at kHz modulation speeds.

Implemented dynamic error analysis and normalization.

Reduced comparison times by avoiding data postprocessing.

Abstract

The implementation of optical quantum gates comes at the cost of incorporating a source of nonclassical light, which suffers from a low flux of photons, and thus, long acquisition times. Quantum-mimetic optical gates combine the benefits of quantum systems with the convenience of using intense light beams. Here, we are concerned with the classical implementation of a controlled-SWAP (c-SWAP) gate using the tools of structured light. A c-SWAP gate is a three-qubit gate, where one of the input qubits controls the exchange of information between the other two qubits. We use Laguerre-Gauss beams to realize the c-SWAP gate and demonstrate one of its primary applications: the comparison of two signals without revealing their content, i.e., a simultaneous message-passing protocol. We achieve signal-comparison measurements with modulation speeds of kHz using a digital micromirror device as a spatial light modulator. Our system is capable of performing dynamic error analysis and a normalization procedure, which overcomes the necessity of data postprocessing and largely reduces comparison times.