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Direct interferometric measurement of non-reciprocity induced by a plasmonic metasurface with false chirality
Authors:
Ahmed Lafeef Ettapuram Naduvilepurayil,
Harel Ginat,
Fernando Loren,
Luis Martin-Moreno,
Shmuel Sternklar,
Yuri Gorodetski
Abstract:
Nonreciprocity is an important scientific concept related to the broken symmetry of light propagation through a system in forward and reverse directions. This effect lies in the origin of various applications including signal processing, noise reduction, unidirectional propagation and sensing. Here we show that propagation of Surface Plasmons (SP) within a structure having a false chirality exhibi…
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Nonreciprocity is an important scientific concept related to the broken symmetry of light propagation through a system in forward and reverse directions. This effect lies in the origin of various applications including signal processing, noise reduction, unidirectional propagation and sensing. Here we show that propagation of Surface Plasmons (SP) within a structure having a false chirality exhibits a non-reciprocity. The SP waves propagating in opposite directions within the structure acquire opposite Pancharatnam-Berry (PB) phases. To detect this phase difference we introduce a novel interferometric technique based on a customized Sagnac set-up. The main advantages of our proposed system are high sensitivity to non-reciprocal phase changes, high precision incidence angle alignment and the inspection of the k-space enabled by sufficiently wide range of incidence angles. We believe that a pivotal role of the non-reciprocity and its detection in numerous physical and chemical processes suggests a wide range of practical applications as well as deeper scientific insights.
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Submitted 10 June, 2025;
originally announced June 2025.
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Quantum Large Language Models via Tensor Network Disentanglers
Authors:
Borja Aizpurua,
Fernando Loren,
Saeed S. Jahromi,
Sukhbinder Singh,
Roman Orus
Abstract:
We introduce a framework for seamlessly integrating quantum computing into pretrained large language models (LLMs). The key idea is to construct a hybrid quantum-classical representation that exactly reproduces the original model, providing a principled starting point from which quantum resources can only improve performance. Our approach replaces the weight matrices in self-attention and multilay…
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We introduce a framework for seamlessly integrating quantum computing into pretrained large language models (LLMs). The key idea is to construct a hybrid quantum-classical representation that exactly reproduces the original model, providing a principled starting point from which quantum resources can only improve performance. Our approach replaces the weight matrices in self-attention and multilayer perceptron layers with two variational quantum circuits coupled to a matrix product operator (MPO). Tensor network disentanglers transfer much of each layer's information into the quantum circuits, enabling the remaining tensor network to be compressed to a bond-dimension-one MPO with over three orders of magnitude fewer classical parameters (in our experiments, from 110,592 to approximately 36 for the replaced layer) and less than a 0.3\% increase in perplexity. Training an added unitary adapter on top of this representation then surpasses the original model, reducing perplexity by up to 1.6\%. Finally, we validate the hybrid architecture on a real quantum processor, demonstrating a practical route towards quantum-enhanced language models.
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Submitted 17 August, 2026; v1 submitted 22 October, 2024;
originally announced October 2024.
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Spin-momentum locking breakdown on plasmonic metasurfaces
Authors:
Fernando Lorén,
Cyriaque Genet,
Luis Martín-Moreno
Abstract:
We present a scattering formalism to analyze the spin-momentum locking in structured holey plasmonic metasurfaces. It is valid for any unit cell for arbitrary position and orientation of the holes. The spin-momentum locking emergence is found to originate from the unit cell configuration. Additionally, we find that there are several breakdown terms spoiling the perfect spin-momentum locking polari…
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We present a scattering formalism to analyze the spin-momentum locking in structured holey plasmonic metasurfaces. It is valid for any unit cell for arbitrary position and orientation of the holes. The spin-momentum locking emergence is found to originate from the unit cell configuration. Additionally, we find that there are several breakdown terms spoiling the perfect spin-momentum locking polarization. We prove that this breakdown also appears in systems with global symmetries of translation and rotation of the whole lattice, like the Kagome lattice. Finally, we present the excitation of surface plasmon polaritons as the paramount example of the spin-momentum locking breakdown.
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Submitted 30 October, 2023; v1 submitted 3 July, 2023;
originally announced July 2023.
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Circular dichroism induction in WS2 by a chiral plasmonic metasurface
Authors:
Fernando Lorén,
Cyriaque Genet,
Luis Martín-Moreno
Abstract:
We investigate the interaction between a monolayer of WS2 and a chiral plasmonic metasurface. WS2 possesses valley excitons that selectively couple with one-handed circularly polarised light. At the same time, the chiral plasmonic metasurface exhibits spin-momentum locking, leading to a robust polarisation response in the far field. Using a scattering formalism based on the coupled mode method, we…
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We investigate the interaction between a monolayer of WS2 and a chiral plasmonic metasurface. WS2 possesses valley excitons that selectively couple with one-handed circularly polarised light. At the same time, the chiral plasmonic metasurface exhibits spin-momentum locking, leading to a robust polarisation response in the far field. Using a scattering formalism based on the coupled mode method, we analyse various optical properties of the WS2 monolayer. Specifically, we demonstrate the generation of circular dichroism in the transition metal dichalcogenide (TMD) by harnessing the excitation of surface plasmon polaritons (SPPs) in the metasurface. Moreover, we observe the emergence of other guided modes, opening up exciting possibilities for further exploration in TMD-based devices.
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Submitted 30 October, 2023; v1 submitted 5 June, 2023;
originally announced June 2023.
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Microscopic analysis of spin-momentum locking on a geometric phase metasurface
Authors:
Fernando Lorén,
Gian L. Paravicini-Bagliani,
Sudipta Saha,
Jérôme Gautier,
Minghao Li,
Cyriaque Genet,
Luis Martín-Moreno
Abstract:
We revisit spin-orbit coupling in a plasmonic Berry metasurface comprised of rotated nanoapertures, which is known to imprint a robust far-field polarization response. We present a scattering formalism that shows how that spin-momentum locking emerges from the geometry of the unit cell without requiring global rotation symmetries. We find and confirm with Mueller polarimetry measurements that spin…
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We revisit spin-orbit coupling in a plasmonic Berry metasurface comprised of rotated nanoapertures, which is known to imprint a robust far-field polarization response. We present a scattering formalism that shows how that spin-momentum locking emerges from the geometry of the unit cell without requiring global rotation symmetries. We find and confirm with Mueller polarimetry measurements that spin-momentum locking is an approximate symmetry. The symmetry breakdown is ascribed to the elliptical projection of circularly polarized light into the planar surface. This breakdown is maximal when surface waves are excited, and a new set of spin-momentum locking rules is presented for this case.
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Submitted 11 April, 2023; v1 submitted 20 May, 2022;
originally announced May 2022.