Quantum issues with structured light

Williams, Mathew D.; Andrews, Davıd L.

doi:10.1117/12.2214946

Cited by 3 publications

(1 citation statement)

References 49 publications

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“…This expression cast in terms of a Kronecker delta is in fact improper, as it contains a pair of indices that do not refer to an orthogonal basis. Instead it should be written as a Dirac delta, 29,38 Accordingly, the physical implication is that for photon propagation over a distance significantly smaller than the optical wavelength  (i.e.…”

Section:  mentioning

confidence: 99%

Conceptualization of the photon for quanta of structured light

Andrews

2020

Complex Light and Optical Forces XIV

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The development of optical modes with intrinsic structure has significantly redirected attention to the established concept and fundamental physics of the photon. In particular, to accommodate the modal structure of beams with transverse structure, two aspects of conventional representation invite special modification: the mathematical formulations, and figurative depictions. Reappraisals of the former highlight known deficiencies in simple plane wave mode expansions, at the price of associating the properties of individual quanta with macroscopic beam parameters wrought by the physical optics. Experimental proofs that such features do indeed reside in individual photons lead to conceptual problems, yet it is clear that alternative viewpoints engender still deeper difficulties. Such quandaries are also evident in the variety of diagrammatic representations used for structured radiation. Though such depictions cannot ever adequately represent the quantum physics, their incautious use can become seriously misleading, misrepresenting the underlying mathematics and supporting wrong conclusions. This analysis aims to expose and underscore some issues that invite closer attention.

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Section:  mentioning

confidence: 99%

Conceptualization of the photon for quanta of structured light

Andrews

2020

Complex Light and Optical Forces XIV

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Quantum features in the orthogonality of optical modes for structured and plane-wave light

Andrews

Forbes

2018

Opt. Lett.

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A fundamental photon creation-annihilation commutation relation underpins the familiar quantum formulation of optics. However, an internal inconsistency becomes apparent in the pursuit of structured light applications. This requires the relationship between operator commutation and mode orthogonality to be recast in a form ensuring full consistency with the precepts of quantum theory. A suitable reformulation, shown to register correctly an intrinsic quantum uncertainty in the associated interactions, has special relevance to optical vortex physics-particularly with regard to information content-through its connection to the degrees of freedom in the associated radiation modes. In the field of quantum optics, much of the basic theory is conventionally cast in terms that are primarily designed to apply to a single mode of radiation-a single wavelength, direction, and polarization. In the most obvious extension of these principles-allowing for more numerous modes of radiationthere are usually significant intervals between the accommodated frequencies, as, e.g., in the case of frequency combs [1], or else there are substantial differences in the directions of propagation. At the heart of most of the quantum formalism, there is a simple and widely familiar boson commutation relation between photon creation and annihilation operators [2]. One physical interpretation is that a photon propagating in a given radiation mode in vacuum cannot spontaneously divert into another mode.In the sphere of optics, the creation-annihilation commutation relation is often presented in a mathematically concise form, neglecting polarization features that ought also, for generality, to be accommodated. Although these features are not commonly given attention, they supplement the wave vector information in uniquely defining each radiation mode. The commutation relation is specifically cast in terms of a binary basis, for although polarization measurements can be made at a spatially localized location with high fidelity, it is well understood that two linear polarization states whose electric vectors differ by only a few degrees cannot be regarded as orthogonal. However, for the directions of propagation associated with the wave vector, the assumption of an orthonormal basis is not so straightforward. Moreover the wave vector of light does not commonly engage with detection apparatusunless weak quadrupole attributes are engaged, which is rarely the case.The difficulties of assuming an infinitely sharp distinction between modes of similar wave vectors are thrown into sharp relief in the case of structured radiation [3], in which there can be local variation of wave vector direction within the confines of a single well-defined beam. An optical vortex, or "twisted light," constitutes a prime example, where the wave vector represents the normal to a wavefront of helicoidal form. Significantly, it has been shown that the twisted character extends down to the level of individual photons [4,5], such that any given photon in a structured beam may ...

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Structured Light from Classical to Quantum Perspectives

Bokić,

de Coene,

Ferrara

et al. 2024

Symmetry

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Most optical phenomena result from the interaction of electromagnetic waves with matter. However, the light structure can be eminently more complex than plane waves, with many degrees of freedom and dimensions involved, yielding intricate configurations. Light transcends the conventional landscape of electromagnetism, offering the possibility to tailor light in three dimensions (intermixing all three electric field components), in four-dimensional spacetime (for fields manifesting both temporal and spatial patterns), and, beyond that, to make structured quantum light, tuning its characteristics at an unprecedented new level of control. This article addresses the physical foundations of structured light, its interactions with matter, including the nonlinear regime and probing chirality, its classical benefits with holography as a specific highlight, and quantum mechanical applications. It describes the various applications connecting structured light with material physics, quantum information, and technology. Notably, we discuss weak measurements with structured light acting as the meter with connections to probing structured-light beam shifts at interfaces. Ultimately, revealing the interplay between structured light and matter opens attractive avenues for different new technologies and applications, covering both the classical and the quantum realms.

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Quantum issues with structured light

Cited by 3 publications

References 49 publications

Conceptualization of the photon for quanta of structured light

Conceptualization of the photon for quanta of structured light

Quantum features in the orthogonality of optical modes for structured and plane-wave light

Structured Light from Classical to Quantum Perspectives

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