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Isolating the classical and quantum coherence of a multiphoton system

Chenglong You, Mingyuan Hong, Fatemeh Mostafavi, Jannatul Ferdous, Roberto de J. León‐Montiel, Riley B. Dawkins, Omar S. Magaña‐Loaiza

Published Nov 27, 2024• 3 citations
Publisher

Abstract

Abstract The classical properties of thermal light fields were instrumental in shaping our early understanding of light. Before the invention of the laser, thermal light was used to investigate the wave-particle duality of light. The subsequent formulation of the quantum theory of electromagnetic radiation later confirmed the classical nature of thermal light fields. Here, we fragment a pseudothermal field into its multiparticle constituents to demonstrate that it can host multiphoton dynamics mediated by either classical or quantum properties of coherence. This is shown in a forty-particle system through a process of scattering mediated by twisted paths endowed with orbital angular momentum. This platform enables accurate projections of the scattered pseudothermal system into isolated multiphoton subsystems governed by quantum dynamics. Interestingly, the isolated multiphoton subsystems exhibiting quantum coherence produce interference patterns previously attributed to entangled optical systems. As such, our work unveils novel mechanisms to isolate quantum systems from classical fields. This possibility opens new paradigms in quantum physics with enormous implications for the development of robust quantum technologies.

DOI
10.1186/s43074-024-00153-4

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Abstract The classical properties of thermal light fields were instrumental in shaping our early understanding of light. Before the invention of the laser, thermal light was used to investigate the wave-particle duality of light. The subsequent formulation of the quantum theory of electromagnetic radiation later confirmed the classical nature of thermal light fields. Here, we fragment a pseudothermal field into its multiparticle constituents to demonstrate that it can host multiphoton dynamics mediated by either classical or quantum properties of coherence. This is shown in a forty-particle system through a process of scattering mediated by twisted paths endowed with orbital angular momentum. This platform enables accurate projections of the scattered pseudothermal system into isolated multiphoton subsystems governed by quantum dynamics. Interestingly, the isolated multiphoton subsystems exhibiting quantum coherence produce interference patterns previously attributed to entangled optical systems. As such, our work unveils novel mechanisms to isolate quantum systems from classical fields. This possibility opens new paradigms in quantum physics with enormous implications for the development of robust quantum technologies.
Abstract Recent progress on quantum state engineering has enabled the preparation of quantum photonic systems comprising multiple interacting particles. Interestingly, multiphoton quantum systems can host many complex forms of interference and scattering processes that are essential to perform operations that are intractable on classical systems. Unfortunately, the quantum coherence properties of multiphoton systems degrade upon propagation leading to undesired quantum-to-classical transitions. Furthermore, the manipulation of multiphoton quantum systems requires nonlinear interactions at the few-photon level. Here, we introduce the quantum van Cittert-Zernike theorem to describe the scattering and interference effects of propagating multiphoton systems. This fundamental theorem demonstrates that the quantum statistical fluctuations, which define the nature of diverse light sources, can be modified upon propagation in the absence of light-matter interactions. The generality of our formalism unveils the conditions under which the evolution of multiphoton systems can lead to surprising photon statistics modifications. Specifically, we show that the implementation of conditional measurements may enable the all-optical preparation of multiphoton systems with attenuated quantum statistics below the shot-noise limit. Remarkably, this effect cannot be explained through the classical theory of optical coherence. As such, our work opens new paradigms within the established field of quantum coherence.
The quantum theory of the electromagnetic field uncovered that classical forms of light were indeed produced by distinct superpositions of nonclassical multiphoton wavepackets. Specifically, partially coherent light represents the most common kind of classical light. Here, for the first time, we demonstrate the extraction of the constituent multiphoton quantum systems of a partially coherent light field. We shift from the realm of classical optics to the domain of quantum optics via a quantum representation of partially coherent light using its complex-Gaussian statistical properties. Our formulation of the quantum Gaussian-Schell model unveils the possibility of performing photon-number-resolving detection to isolate the constituent quantum multiphoton wavepackets of a classical light field. We experimentally verified the coherence properties of isolated vacuum systems and wavepackets with up to sixteen photons. Our findings not only demonstrate the possibility of observing quantum properties of classical macroscopic objects, but also establish a fundamental bridge between the classical and quantum worlds.
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The quantum theory of the electromagnetic field uncovered that classical forms of light were indeed produced by distinct superpositions of nonclassical multiphoton wave packets. This situation prevails for partially coherent light, the most common kind of classical light. Here, for the first time, to our knowledge, we demonstrate the extraction of the constituent multiphoton quantum systems of a partially coherent light field. We shift from the realm of classical optics to the domain of quantum optics via a quantum representation of partially coherent light using its complex-Gaussian statistical properties. Our formulation of the quantum Gaussian-Schell model (GSM) unveils the possibility of performing photon-number-resolving (PNR) detection to isolate the constituent quantum multiphoton wave packets of a classical light field. We experimentally verified the coherence properties of isolated vacuum systems and wave packets with up to 16 photons. Our findings not only demonstrate the possibility of observing quantum properties of classical macroscopic objects but also establish a fundamental bridge between the classical and quantum worlds.
Recent progress on quantum state engineering has enabled the preparation of quantum photonic systems comprising multiple interacting particles. Interestingly, multiphoton quantum systems can host many complex forms of interference and scattering processes that are essential to perform operations that are intractable on classical systems. Unfortunately, the quantum coherence properties of multiphoton systems degrade upon propagation leading to undesired quantum-to-classical transitions. Furthermore, the manipulation of multiphoton quantum systems requires of nonlinear interactions at the few-photon level. Here, we introduce the quantum van Cittert-Zernike theorem to describe the scattering and interference effects of propagating multiphoton systems. This fundamental theorem demonstrates that the quantum statistical fluctuations, which define the nature of diverse light sources, can be modified upon propagation in the absence of light-matter interactions. The generality of our formalism unveils the conditions under which the evolution of multiphoton systems can lead to surprising classical-to-quantum transitions. Specifically, we show that the implementation of conditional measurements may enable the all-optical preparation of multiphoton systems with attenuated quantum statistics below the shot-noise limit. Remarkably, this effect had not been discussed before and cannot be explained through the classical theory of optical coherence. As such, our work opens new paradigms within the established field of quantum coherence.
Recent advances in quantum optics have highlighted the critical role of spatial propagation in controlling the quantum coherence of light beams. However, the evolution of quantum coherence for light beams undergoing fundamental optical processes at dielectric interfaces remains unexplored. Furthermore, manipulating multiphoton correlations typically requires complex interactions that challenge few-photon level implementation. Here, we introduce a quantum van Cittert-Zernike theorem for light beams, describing how their coherence-polarization properties are influenced by reflection and refraction, as well as how these properties evolve upon subsequent propagation. Our work demonstrates that the quantum statistics of photonic systems can be controllably modified through the inherent polarization coupling arising from reflection and refraction at an interface, without relying on conventional light-matter interactions. Our approach reveals regimes where thermal light can exhibit sub-Poissonian statistics with fluctuations below the shot-noise level through post-selected measurements, and this statistical property can be tuned by the incident angle. Remarkably, this quantum statistical modification is governed by a scaling law linking beam collimation to far-field thermalization. Our work establishes a robust, decoherence-avoiding mechanism for quantum state control, advancing the fundamental understanding of coherence in quantum optics and opening new avenues for applications in quantum information and metrology.