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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Ultra-fast wave-optical computing

Tobias J. Haist

Published Aug 28, 2008• 2 citations
Publisher

Abstract

I present a method for optical computing based on white-light interferometry. The problem to be solved is coded by optical path lengths and the superposition of all possible paths that a photon can travel is used for computing the solution. The solution itself is chosen by interference with the reference light. Several gedankenexperiments demonstrate how this method can be used for solving computational hard problems. Especially, I will introduce the basic principle with two maze-type puzzles and then concentrate on how the method can be employed for performing ultra-fast (sub-ps) digital-optical arithmetic with arbitrary precision.

DOI
10.1117/12.794843

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I present a method for optical computing based on white-light interferometry. The problem to be solved is coded by optical path lengths and the superposition of all possible paths that a photon can travel is used for computing the solution. The solution itself is chosen by interference with the reference light. Several gedankenexperiments demonstrate how this method can be used for solving computational hard problems. Especially, I will introduce the basic principle with two maze-type puzzles and then concentrate on how the method can be employed for performing ultra-fast (sub-ps) digital-optical arithmetic with arbitrary precision.
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Quantum computers harnessing the principles of quantum mechanics hold the potential to outperform classical systems. Continuous-variable quantum information processing with light offers advantages such as THz-order clock frequencies, scalability via temporal multiplexing, and compatibility with ultra-fast optical communication technologies. This type of quantum computer can be described as an ultra-fast analog quantum computer, making it particularly well-suited for applications involving continuous variables, such as neural networks and optimization problems. However, challenges in universal computation and error correction persist due to weak light-matter interactions. This presentation introduces our advancements in optical quantum computing using waveguide optical parametric amplifiers (OPAs) and non-Gaussian quantum state generation with photon-number resolving detectors (PNRDs). We also propose an all-optical scheme leveraging OPAs to achieve fault-tolerant quantum computing, enabling logical qubit generation and clock frequencies exceeding THz.
Interference has long been used for precision measurement of path-length changes. Since the advent of the laser, interference has become one of the most versatile tools in metrology. Specifically, ultra-short laser pulses allow unprecedented resolution in absolute length measurements. While ultra-short laser pulses lead to high resolution, for example in white-light interferometry, they are very susceptible to dispersion. \n \nQuantum resources have been proposed to overcome some of the problems related to distortions in the interferometric signal. For example, the Hong-Ou-Mandel (HOM) interferometer relies on frequency-entangled photon pairs and features automatic even-order dispersion cancellation and high interference visibility resilient to unbalanced loss. Quantum-OCT is a technique based on HOM interferometry, that promises to overcome Optical Coherence Tomography (OCT) a classical imaging technique based on low coherence light. Furthermore, straightforward modifications of the HOM interferometer can display several different interferometric signals, including the HOM peak, quantum beating, and phase super-resolution. However, the quantum resources required are hard to produce and dim, leading to long integration times and single-photon counting. \n \nIn this thesis, we introduce the theory behind Chirped-Pulse Interferometry (CPI), a new technique that combines all the advantages of Q-OCT, including even-order dispersion cancellation, but without the need for any quantum resources. We then experimentally implement CPI and demonstrate all the important characteristics shared by the HOM interferometer, but at dramatically larger signal levels. We show how CPI can be used to measure dispersion cancelled axial profiles of an optical sample and show the improvement in resolution over white-light interferometry. Finally, we show that by modifying CPI in analogous ways to HOM, CPI can also be made to produce interferometric signal identical to the HOM peak, quantum beating, and phase super-resolution.