© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

arXiv:2603.17716

Reconfigurable circuit for mode tunable topological structured light

Pedro Ornelas, Tatjana Kleine, André G. de Oliveira, Carmelo Rosales-Guzmán, Andrew Forbes, Isaac Nape

quant-phphysics.opticsSubmitted Mar 18, 2026• Announced Mar 19, 2026• 0 citations

v1 · Mar 18, 2026 v2 · Mar 20, 2026

Abstract

Structured light in the quantum regime has garnered considerable attention due to the opportunities it offers when mixing light's internal degrees of freedom, for high-dimensional and multi-dimensional quantum states of light. A popular example is to harness polarisation and spatial entangled photons with a shared topological invariant that is robust against numerous families of noisy quantum channels. Yet, producing such states with high purity and adaptability remains challenging. Here we introduce a compact, self-locking Mach-Zehnder interferometer that integrates digital spatial light modulators with static beam displacers to map spatial-mode entanglement from a parametric down-conversion source onto topological entanglement with high fidelity. The device also mimics the action of a reprogrammable controlled-unitary gate, digitally driven by the spatial light modulator. This approach is an enabling platform and provides a practical route to generating reliable, high-purity quantum-structured light with topological features, both at the single-photon level and as entangled states, a direction of growing topical interest.

Comments: 8 pages, 3 figures

Related papers

A complex media platform for quantum networking using structured light

Natalia Herrera Valencia, Annameng Ma, Suraj Goel +5 more

We harness the complex light-scattering process inside a multi-mode fibre to implement reconfigurable circuits for transverse spatial photonic modes. With this architecture, we have demonstrated high-dimensional quantum gates to manipulate spatial-mode entanglement in the bipartite and multipartite regimes, enabling a multiplexed programmable network that distributes and swaps entanglement between 4 parties using structured light.

Complex Light and Optical Forces•Mar 19, 2025•0 citations

Quantum structured light takes shape

Andrew Forbes

Quantum structured light offers a roadmap to high-dimensional and multi-dimensional quantum states by exploiting all of light’s many degrees of freedom at the quantum level. In this talk, I will review the recent progress in quantum entanglement of photons in their spatial degree of freedom: quantum structured light. I will explain how to create high-dimensional quantum states in the laboratory, how to measure them, and review the present state of the art in the field. I will show how the patterns can be abstracted, mixing degrees of freedom to produce quantum topologies in light, introducing new paradigms for quantum state observables and classification. Finally, I will outline the advantages and disadvantages of using such single photon and entangled states in real-world applications, offering a perspective on the present challenges and exciting opportunities in the field.

Complex Light and Optical Forces•Mar 19, 2025•0 citations

An all-digital approach for versatile hybrid entanglement generation

Isaac M. Nape, André Gonçalves de Oliveira, Donovan Slabbert +4 more

Abstract Hybrid entangled states exhibit non-local correlations between photons with independent degrees of freedom and are currently gaining much interest. In particular, hybrid entanglement between polarisation and spatial modes of two photons are promising candidates for future heterogeneous quantum channels, but their versatility is limited by current generation methods that rely on static elements. Here, we present a technique that exploits polarisation and spatial mode dependent phase modulation in an all-digital approach using spatial light modulators. We show that we can tailor hybrid entangled states using spatial modes with Cylindrical and Cartesian symmetry, making our approach flexible, dynamic, and adaptable.

Journal of Optics•Mar 3, 2022•10 citations

Tunable generation of entangled photons in a nonlinear directional coupler

Frank Setzpfandt, Alexander S. Solntsev, James Titchener +6 more

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA. The on-chip integration of quantum light sources has enabled the realization of complex quantum photonic circuits. However, for the practical implementation of such circuits in quantum information applications, it is crucial to develop sources delivering entangled quantum photon states with on-demand tunability. Here we propose and experimentally demonstrate the concept of a widely tunable quantum light source based on spontaneous parametric down-conversion in a simple nonlinear directional coupler. We show that spatial photon-pair correlations and entanglement can be reconfigured on-demand by tuning the phase difference between the pump beams and the phase mismatch inside the structure. We experimentally demonstrate the generation of split states, robust N00N states, various intermediate regimes and biphoton steering on a single chip. Furthermore we theoretically investigate other regimes allowing all-optically tunable generation of all Bell states and flexible control of path-energy entanglement. Such wide-range capabilities of a structure comprised of just two coupled nonlinear waveguides are attributed to the intricate interplay between linear coupling and nonlinear phase matching. This scheme provides an important advance towards the realization of reconfigurable quantum circuitry. An integrated all-optically tunable source of two-photon quantum states based on spontaneous parametric down-conversion is experimentally demonstrated in a directional coupler consisting of two lithium niobate waveguides. The degree of entanglement and shape of two-photon spatial correlations is widely tunable by varying the phase mismatch and relative phases of the two pump beams. The operating principle is suitable for practical implementation of reconfigurable photon sources in on-chip quantum circuits.

•Jan 1, 2015•44 citations

Demonstration of a programmable source of two-photon multiqubit entangled states

S. Cialdi, Davide Brivio, Matteo G. A. Paris

We suggest and demonstrate a novel source of two-photon multipartite entangled states which exploits the transverse spatial structure of spontaneous parametric down-conversion together with a programmable spatial light modulator (SLM). The one-dimensional SLM is used to perform polarization entanglement purification and to realize arbitrary phase gates between polarization and momentum degrees of freedom of photons. We experimentally demonstrate our scheme by generating two-photon three-qubit linear cluster states with high fidelity using a diode laser pump with a limited coherence time and power on the crystal as low as $~2.5$ mW.

arXiv:0912.2975•Physical Review A•Apr 26, 2010•19 citations

Quantum cryptography with structured photons

Andrew Forbes, Mostafa Youssef, Sachleen Singh +2 more

Quantum photonic platforms have proven to be essential in realizing fundamentally secure quantum transfer of information, with commercially ready systems already deployed in municipal and terrestrial links. The drive toward higher bit rates and robustness to eavesdropping and noisy channels has focused attention on moving from the present two-dimensional quantum states of polarization, to harnessing all of light's degrees of freedom for multi-dimensional quantum coding with structured photons. In this Perspective, we outline the present state-of-the-art in achieving this control with spatial modes of light, both as single photon and entangled states, highlight the open challenges that remain, and consider the roadmap that might see its full potential realized.

Applied Physics Letters•Mar 11, 2024•22 citations

Structured light in the quantum regime has garnered considerable attention due to the opportunities it offers when mixing light's internal degrees of freedom, for high-dimensional and multi-dimensional quantum states of light. A popular example is to harness polarisation and spatial entangled photons with a shared topological invariant that is robust against numerous families of noisy quantum channels. Yet, producing such states with high purity and adaptability remains challenging. Here we introduce a compact, self-locking Mach-Zehnder interferometer that integrates digital spatial light modulators with static beam displacers to map spatial-mode entanglement from a parametric down-conversion source onto topological entanglement with high fidelity. The device also mimics the action of a reprogrammable controlled-unitary gate, digitally driven by the spatial light modulator. This approach is an enabling platform and provides a practical route to generating reliable, high-purity quantum-structured light with topological features, both at the single-photon level and as entangled states, a direction of growing topical interest.

Quantum structured light offers a roadmap to high-dimensional and multi-dimensional quantum states by exploiting all of light’s many degrees of freedom at the quantum level. In this talk, I will review the recent progress in quantum entanglement of photons in their spatial degree of freedom: quantum structured light. I will explain how to create high-dimensional quantum states in the laboratory, how to measure them, and review the present state of the art in the field. I will show how the patterns can be abstracted, mixing degrees of freedom to produce quantum topologies in light, introducing new paradigms for quantum state observables and classification. Finally, I will outline the advantages and disadvantages of using such single photon and entangled states in real-world applications, offering a perspective on the present challenges and exciting opportunities in the field.

Abstract Hybrid entangled states exhibit non-local correlations between photons with independent degrees of freedom and are currently gaining much interest. In particular, hybrid entanglement between polarisation and spatial modes of two photons are promising candidates for future heterogeneous quantum channels, but their versatility is limited by current generation methods that rely on static elements. Here, we present a technique that exploits polarisation and spatial mode dependent phase modulation in an all-digital approach using spatial light modulators. We show that we can tailor hybrid entangled states using spatial modes with Cylindrical and Cartesian symmetry, making our approach flexible, dynamic, and adaptable.

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA. The on-chip integration of quantum light sources has enabled the realization of complex quantum photonic circuits. However, for the practical implementation of such circuits in quantum information applications, it is crucial to develop sources delivering entangled quantum photon states with on-demand tunability. Here we propose and experimentally demonstrate the concept of a widely tunable quantum light source based on spontaneous parametric down-conversion in a simple nonlinear directional coupler. We show that spatial photon-pair correlations and entanglement can be reconfigured on-demand by tuning the phase difference between the pump beams and the phase mismatch inside the structure. We experimentally demonstrate the generation of split states, robust N00N states, various intermediate regimes and biphoton steering on a single chip. Furthermore we theoretically investigate other regimes allowing all-optically tunable generation of all Bell states and flexible control of path-energy entanglement. Such wide-range capabilities of a structure comprised of just two coupled nonlinear waveguides are attributed to the intricate interplay between linear coupling and nonlinear phase matching. This scheme provides an important advance towards the realization of reconfigurable quantum circuitry. An integrated all-optically tunable source of two-photon quantum states based on spontaneous parametric down-conversion is experimentally demonstrated in a directional coupler consisting of two lithium niobate waveguides. The degree of entanglement and shape of two-photon spatial correlations is widely tunable by varying the phase mismatch and relative phases of the two pump beams. The operating principle is suitable for practical implementation of reconfigurable photon sources in on-chip quantum circuits.

We suggest and demonstrate a novel source of two-photon multipartite entangled states which exploits the transverse spatial structure of spontaneous parametric down-conversion together with a programmable spatial light modulator (SLM). The one-dimensional SLM is used to perform polarization entanglement purification and to realize arbitrary phase gates between polarization and momentum degrees of freedom of photons. We experimentally demonstrate our scheme by generating two-photon three-qubit linear cluster states with high fidelity using a diode laser pump with a limited coherence time and power on the crystal as low as

~2.5

mW.

Quantum photonic platforms have proven to be essential in realizing fundamentally secure quantum transfer of information, with commercially ready systems already deployed in municipal and terrestrial links. The drive toward higher bit rates and robustness to eavesdropping and noisy channels has focused attention on moving from the present two-dimensional quantum states of polarization, to harnessing all of light's degrees of freedom for multi-dimensional quantum coding with structured photons. In this Perspective, we outline the present state-of-the-art in achieving this control with spatial modes of light, both as single photon and entangled states, highlight the open challenges that remain, and consider the roadmap that might see its full potential realized.