We consider the potential for generating photon pars with high-dimensional entanglement in their orbital angular momentum through multiple simultaneous four-wave-mixing processes. We study a realistic fiber design and show that states with high entanglement negativity may be obtained.
Abstract Spin and orbital angular momenta of light are attractive resources to harness for encoding, and manipulating information, with applications in various quantum photonic technologies. However, to fully harness that potential, we require robust sources of high-order angular momentum photons exhibiting nonclassical correlations. Here, we propose a fiber-based source of polarization-entangled photons in high-order orbital angular momentum (OAM) modes. In our setup the pairs of photons are generated in a cylindrical fiber through a four-wave mixing process, which induces polarization, or spin entanglement. The photons are then converted to modes exhibiting large OAM by two helical gratings inscribed in the core of the fiber. We present a complete theoretical framework used to consistently describe this process, and demonstrate a robust control over the joint spectral amplitude of the generated photons.
High-bit-rate long-distance quantum communication is a proposed technology for future communication networks and relies on high-dimensional quantum entanglement as a core resource. While it is known that spatial modes of light provide an avenue for high-dimensional entanglement, the ability to transport such quantum states robustly over long distances remains challenging. To overcome this, entanglement swapping may be used to generate remote quantum correlations between particles that have not interacted; this is the core ingredient of a quantum repeater, akin to repeaters in optical fibre networks. Here we demonstrate entanglement swapping of multiple orbital angular momentum states of light. Our approach does not distinguish between different anti-symmetric states, and thus entanglement swapping occurs for several thousand pairs of spatial light modes simultaneously. This work represents the first step towards a quantum network for high-dimensional entangled states and provides a test bed for fundamental tests of quantum science.Entanglement swapping in high dimensions requires large numbers of entangled photons and consequently suffers from low photon flux. Here the authors demonstrate entanglement swapping of multiple spatial modes of light simultaneously, without the need for increasing the photon numbers with dimension.
In the realm of quantum information processing, harnessing high-dimensional photonic systems provides a pathway to overcome limitations of traditional two-level systems. Orbital angular momentum (OAM) of light has emerged as a powerful tool for creating and manipulating high-dimensional entanglement, promising increased information capacity and enhanced security in quantum communication protocols. However, conventional methods like spontaneous parametric downconversion encounter challenges due to non-uniform production rates of Laguerre–Gaussian modes. This study explores the potential of spontaneous four-wave mixing in ring-core fibers (RCFs) as a viable platform for generating OAM photon pairs with tailored spectral and spatial properties. We show that by controlling the topological charge of pump photons, correlated, uncorrelated, and anti-correlated photon pairs can be engineered across arbitrary spectral ranges, essential for diverse quantum applications. Experimental noise characterization of the RCF-based source demonstrates a high coincidence-to-accidental ratio exceeding 4000, and a low heralded second-order correlation function ( g H (2) <0.005), which confirms its operation well into the single-photon regime. This work demonstrates the potential of RCFs as a versatile platform for generating structured photon pairs, paving the way for future high-dimensional quantum communication and information processing applications.