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Journal of Optics

Bipartite and tripartite continuous variable entanglement in a circular array of coupled optical waveguides

Tonipe Anuradha, Amit Rai

Published Aug 3, 2023• 2 citations
Publisher

Abstract

Abstract Integrated optical systems have evolved into suitable platforms in the field of photonic quantum technologies. New technologies open up new possibilities for multimode quantum operations. Here we study how circularly coupled waveguide arrays generate bipartite and tripartite continuous-variable (CV) entanglement. We focus on the single-mode squeezed state as input to the circular array of the waveguide system. Our findings suggest that the circularly coupled arrays can be used to generate entangled sources in CV quantum technologies. So the generation of entanglement makes the circular arrays more critical for further investigation and in the applications of photonic CV quantum-information processing.

DOI
10.1088/2040-8986/ace53b

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Abstract Integrated optical systems have evolved into suitable platforms in the field of photonic quantum technologies. New technologies open up new possibilities for multimode quantum operations. Here we study how circularly coupled waveguide arrays generate bipartite and tripartite continuous-variable (CV) entanglement. We focus on the single-mode squeezed state as input to the circular array of the waveguide system. Our findings suggest that the circularly coupled arrays can be used to generate entangled sources in CV quantum technologies. So the generation of entanglement makes the circular arrays more critical for further investigation and in the applications of photonic CV quantum-information processing.
We study the possibility of generating continuous-variable (CV) entanglement on an integrated chip through nonlinear optical waveguides coupled in a circular array. We show the simultaneous generation and manipulation of multimode CV entangled states of light in χ (2) nonlinear circular arrays (NCAs), a feat unattainable with linear optical waveguides and bulk optical elements. These weakly coupled integrated waveguide arrays are compact and can be fabricated using the femtosecond laser writing technique. This technique offers interferometric stability, scalability, and less sensitivity to decoherence. Our study investigates the potential of NCA to generate bipartite and tripartite CV entanglement. We present analytical results and numerical simulations based on coupled-mode equations for the evolution of field operators. Our findings suggest promising applications of compact on-chip sources in various photonic quantum technologies, such as communication, computing, and networking.
We present a scheme for generating and manipulating three-mode squeezed states with genuine tripartite entanglement by injecting single-mode squeezed light into an array of coupled optical waveguides. We explore the possibility to selectively generate single-mode squeezing or multimode squeezing at the output of an elliptical waveguide array, determined solely by the input light polarization. We study the effect of losses in the waveguide array and show that quantum correlations and squeezing are preserved for realistic parameters. Our results show that arrays of optical waveguides are suitable platforms for generating multimode quantum light, which could lead to novel applications in quantum metrology.
Abstract We investigate the applicability of the circular arrays of coupled single-mode optical waveguides in transferring the non-classical state of light for quantum information processing. We study the nonclassical states of light, such as a single-photon Fock state, a two-photon NOON state, a single-mode squeezed state and a two-mode squeezed state as inputs to the lattice, which are key resources for various applications in the field of quantum information science. In addition, for comparison, we also examine a coherent state. We investigate the transport of non-classical features and quantum states of light from one waveguide mode to another. For the single and two-mode squeezed states, we perform a detailed study of the evolution of the squeezing. Our work highlights the potential of the circular arrays of optical waveguides platform for the transport of non-classical features and quantum states of light. We expect our results should have applications in the physical implementation of photonic quantum technologies.
We study a class of nonlinear waveguide arrays in which the waveguides are endowed with ${\ensuremath{\chi}}^{(2)}$ nonlinearity and coupled through the evanescent overlap of the guided modes. We investigate the viability of such an array as a platform for generating both bipartite and tripartite continuous-variable entanglement. We explicitly address the effect of realistic losses on the entanglement produced, discuss the possible types of nonlinear materials that could be used, and suggest solutions for the possible phase matching issues in the waveguides. The simultaneous generation and manipulation of the light on a single waveguide chip circumvents the usual bandwidth problems associated with the use of external bulky optical elements and makes this avenue promising for further investigation.
Encoding continuous-variable quantum information in the optical domain has recently enabled the generation of large entangled states, yet robust implementation remains a challenge. Here, we present a straightforward protocol for generating multipartite entanglement based on spontaneous parametric down-conversion in a circular array of quadratic nonlinear waveguides. We provide a rigorous theoretical framework, including comprehensive derivations of the propagation equations and the identification of regimes where analytical solutions are possible. Crucially, our approach identifies the pump and detection configurations required to sustain and measure multipartite full inseparability across arbitrary propagation distances and for any number of waveguides N=4nN=4 nN=4n. This regime, elusive to standard numerical methods, represents a key requirement for scalable quantum protocols. Our scheme is inherently robust as it relies on phase-matched propagation eigenmodes, making it resilient against variations in sample length, coupling, and nonlinearity.
Multimode entanglement is an essential resource for quantum information in continuous-variable systems. Light-based quantum technologies will arguably not be built upon table-top bulk setups, but will presumably rather resort to integrated optics. Sequential bulk opticslike proposals based on cascaded integrated interferometers are not scalable with the current state-of-the-art low-loss materials used for continuous variables. We analyze the multimode continuous-variable entanglement capabilities of a compact currently available integrated bulk-optics analog: the array of nonlinear waveguides. We theoretically demonstrate that this simple and compact structure, together with a reconfigurable input pump distribution and multimode coherent detection of the output modes, is a versatile entanglement synthesizer in the spatial domain. We exhibit this versatility through analytical and numerically optimized multimode squeezing, entanglement, and cluster-state generation in different encodings. Our results re-establish spatial encoding as a contender in the game of continuous-variable quantum information processing.