Implementation of a simultaneous message-passing protocol using optical vortices

• Published in: Optics and laser technology 2021-01, Vol.133, p.106516, Article 106516
• Main Authors: Szatkowski, Mateusz, Koechlin, Julian, Lopez-Mago, Dorilian
• Format: Article
• Language: English
• Subjects: Controlled SWAP; Digital micro-mirror device; Error analysis; Fredkin gate; Gaussian beams (optics); Laser beam shaping; Light beams; Message passing; Message-passing protocol; Optical vortices; Qubits (quantum computing); Spatial light modulators
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2020.106516

•Benefits of quantum systems can be combined with the comfort of using intense light beams.•Optical vortices have been used to implement an optical controlled-SWAP gate.•Presented message-passing protocol compares two signals without revealing their content.•Messages have been encoded through a high-speed spatial light modulator.•The comparison of two 40-bits messages within a single data point is possible. 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 micro mirror 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.