In this presentation, we shed light on electromagnetic time interfaces using the principles of quantum optics. We begin by explaining the transformation of bosonic mode operators in response to a temporal discontinuity in the macroscopic parameters. Accordingly, our discussion extends to the general analysis of photon statistics and the degree of second-order coherence of the generated forward and backward modes. Focusing on input number states, we meticulously detail the quantum states produced after the time interface, elucidating the associated probability distributions. By virtue of this study, we specifically highlight the controllable nature of photon statistics of the output forward mode for particular input states. We show that this capability, in general, is not present for the backward mode generated through the time interface. Also, we reveal that photon-pair generation is a fundamental inherent feature of the time interface. By unveiling all these insights, we aim to pave the way for exploring photonic time crystals within the domain of quantum optics.
In this presentation, we shed light on electromagnetic time interfaces using the principles of quantum optics. We begin by explaining the transformation of bosonic mode operators in response to a temporal discontinuity in the macroscopic parameters. Accordingly, our discussion extends to the general analysis of photon statistics and the degree of second-order coherence of the generated forward and backward modes. Focusing on input number states, we meticulously detail the quantum states produced after the time interface, elucidating the associated probability distributions. By virtue of this study, we specifically highlight the controllable nature of photon statistics of the output forward mode for particular input states. We show that this capability, in general, is not present for the backward mode generated through the time interface. Also, we reveal that photon-pair generation is a fundamental inherent feature of the time interface. By unveiling all these insights, we aim to pave the way for exploring photonic time crystals within the domain of quantum optics.
Modulating macroscopic parameters of materials in time offers innovative avenues for manipulating electromagnetic waves. Due to such enticing prospects, the general research subject of time-varying systems is expanding today in different branches of electromagnetism and optics. However, compared with the research efforts and progresses that have taken place in the realm of classical electrodynamics, the quantum aspects of this emerging subject have been less explored. Here, through the lens of quantum optics, we study the scattering of electromagnetic fields from an isotropic and nondispersive material with a suddenly changing refractive index, creating a time interface. We revisit the transformation of the bosonic mode operators and corresponding quantum states due to this interface, governed by the two-mode squeeze operator. Building on this foundation, at the core of the investigation, our analysis focuses on the quantum state engineering and photon statistics of the scattered light. Notably, such an analysis reveals and connects various quantum optical phenomena and opportunities arising from the time interface, including photon-pair production and destruction, photon bunching and antibunching, vacuum generation, quantum state discrimination, and quantum state freezing. To bridge theory and experiment, we propose a possible circuit quantum electrodynamics approach for validating our theoretical predictions. We hope that our work inspires experimental investigations of such quantum state engineering and photon statistics phenomena, as well as further quantum optical explorations of electromagnetic field interaction with photonic time crystals or with dispersive time-varying materials.
Non-Gaussian quantum states of light are of paramount importance to quantum computing. Nevertheless, their deterministic generation is challenging problem due to the difficulty to control nonlinearities in physical systems. In this work, we characterize the light stemming from one of the most fundamental quantum optics configurations: the unidirectional scattering of multimode and multiphoton light by a two-level system. We provide an analytic and explicit description of the output light solely in terms of the corresponding input temporal modes which allows a straightforward physical interpretation and is computationally more effective compared to numerical methods. Then, we focus on the specific case of the scattering of two photons in a single mode. By numerically decomposing the output state in terms of its principal modes, we find that it is possible to map single-mode two-photon inputs to be into two-mode entangled output states, i.e., two-photon NOON states, to very good approximation. The latter states, in turn, are known to have more Wigner negativity compared to the associated input, which ultimately suggests a potential application of our considered setup in the deterministic generation of non-Gaussian states.
This presentation offers a fresh perspective on the quantum theory of electromagnetic time interfaces.Notably, by critically examining established assumptions, we uncover that, in addition to photon-pair production, photon-pair annihilation is also a salient feature of time interfaces.Our analysis reveals that this characteristic enables the generation of quantum vacuum states and facilitates quantum state discrimination.Thus, these findings not only expand our understanding of time interfaces, but also may open new avenues for applications in quantum optics.
Photonic time crystals are exotic materials characterized by effective parameters that are uniform in space yet periodically vary over time. Recently, these materials have been the subject of extensive study from both theoretical and experimental perspectives. However, the quantum characteristics of light within photonic time crystals remain largely uncharted territory. In this presentation, we explore the interaction of light with these materials through the lens of quantum optics, addressing various topics ranging from mode operator transformation to the photon statistics of light in photonic time crystals.
Photon statistics is a branch of physics that involves observing the behavior of single or a small number of photons and then aggregating the results through statistical averaging. This process is essential to obtain meaningful and reliable data, especially in quantum optics research. Photon statistics provides valuable information about correlations in the electromagnetic field and characteristics of the type of light being measured. For example, second-order correlation function obtained via Hanbury Brown and Twiss experiment is the fundamental way to differentiate between coherent, chaotic and quantum light. Moreover, extensive investigations into the quantum properties of light resulted in significant progress that allows for precise control of quantum optical systems and sets the stage for genuine quantum engineering. This progress extends to applications in confirming the generation of entangled photons and exploring their properties for various purposes. The non-classical correlation between the entangled photons has resulted in various quantum optical techniques that enable the practical implementation of conceptual experiments that probe the core principles of quantum theory. This enhanced control over quantum phenomena offers exciting opportunities to explore novel information-processing approaches, with the potential to revolutionize technologies rooted in quantum information science. Driven by the significance and pivotal role of photon statistics, our research pursuits were directed toward two specific domains: the characterization of nanolasers and the characterization of time-bin entangled photons. In the first segment, we delve into the realm of metallic coaxial nanolasers, renowned for their intriguing threshold-less lasing behavior. Through comprehensive photon statistics analysis, we seek to unravel the coherence properties inherent in these nanolasers. Our focus also lies on understanding the elusive threshold-less operation, which has remained a subject of debate and intrigue. To evaluate this unique lasing characteristic, we conduct rigorous second-order coherence measurements alongside time-resolved second-order correlation analyses. The second segment of this study ventures into the generation and characterization of high-dimensional time-bin entangled states, a critical resource for quantum technological applications. We simulate a synthetic photonic lattice by employing a coupled fiber-loop system to perform various quantum walk schemes to generate and process high-dimensional time-bin entangled states. Our investigation focuses on the quantum interference phenomena through detailed photon statistics analysis, with an emphasis on their applications across diverse quantum technologies. Through these two interconnected research endeavors, this thesis demonstrates the profound significance of photon statistics as a versatile tool, bridging classical and quantum realms, and paving the way for advancements in diverse applications, ranging from nanolasers to quantum technologies.
Abstract We theoretically investigate the emergence of nonclassical features, two-mode squeezing, sub-Poissonian photon statistics, and bipartite entanglement, in the third harmonic generation (THG) process, employing a first-order interaction Hamiltonian within the short-time approximation. The study reveals that both first- and second-order squeezing exhibit strong dependence on the input field amplitudes, relative phase, and interaction strength. Asymmetric coherent inputs, where the harmonic mode carries greater intensity than the fundamental, enhance the degree of squeezing and lead to deeper nonclassical minima. The squeezing parameters display periodic phase-dependent oscillations, indicating phase-sensitive control of quantum correlations. Sub-Poissonian photon statistics in the fundamental mode further confirm the quantum nature of the generated light. Entanglement is analyzed through the Duan et al. inseparability criterion and the Hillery–Zubairy (HZ) criteria. While the Duan criterion fails to detect entanglement under purely coherent excitation in the short-time regime, both the HZ-1 and HZ-2 criteria confirm entanglement under specific phase conditions, with HZ-2 exhibiting greater sensitivity at elevated field strengths. These results underscore the potential of THG as a viable platform for the controllable generation of nonclassical light, with implications for continuous-variable quantum optics and integrated quantum photonics.