Optical skyrmions are quasiparticles of light characterized by topologically protected vectorial field textures, with possible applications in optical communications, imaging, and metrology. Encoding the topology of an optical skyrmion onto a solid-state spin system would provide a route to transferring structured optical information into a quantum degree of freedom. In this study, we experimentally demonstrate the transduction of an optical skyrmion onto the quantum polarization cloud of nitrogen-vacancy (NV) centers in diamond. We exploit coherent light-matter interaction at cryogenic temperature (77 K) and demonstrate a phase shift in quantum impurities which depends on optical skyrmion properties. Employing Hahn-echo magnetometry for NV phase readout and Stokes polarimetry for optical skyrmion characterization, we show a transduction efficiency exceeding 95 % of a topological feature - polarity. This work establishes a framework for interfacing topological phenomena across optical and microwave frequency regimes, paving the way for skyrmion phenomena in optical transduction technologies.
Optical skyrmions are quasiparticles of light characterized by topologically protected vectorial field textures, with possible applications in optical communications, imaging, and metrology. Encoding the topology of an optical skyrmion onto a solid-state spin system would provide a route to transferring structured optical information into a quantum degree of freedom. In this study, we experimentally demonstrate the transduction of an optical skyrmion onto the quantum polarization cloud of nitrogen-vacancy (NV) centers in diamond. We exploit coherent light-matter interaction at cryogenic temperature (77 K) and demonstrate a phase shift in quantum impurities which depends on optical skyrmion properties. Employing Hahn-echo magnetometry for NV phase readout and Stokes polarimetry for optical skyrmion characterization, we show a transduction efficiency exceeding 95 % of a topological feature - polarity. This work establishes a framework for interfacing topological phenomena across optical and microwave frequency regimes, paving the way for skyrmion phenomena in optical transduction technologies.
Optical skyrmions are quasiparticles of light characterized by topologically protected vectorial field textures, with possible applications in optical communications, imaging, and metrology. Encoding the topology of an optical skyrmion onto a solid-state spin system would provide a route to transferring structured optical information into a quantum degree of freedom. In this study, we experimentally demonstrate the transduction of an optical skyrmion onto the quantum polarization cloud of nitrogen-vacancy (NV) centers in diamond. We exploit coherent light-matter interaction at cryogenic temperature (77 K) and demonstrate a phase shift in quantum impurities which depends on optical skyrmion properties. Employing Hahn-echo magnetometry for NV phase readout and Stokes polarimetry for optical skyrmion characterization, we show a transduction efficiency exceeding 95 % of a topological feature - polarity. This work establishes a framework for interfacing topological phenomena across optical and microwave frequency regimes, paving the way for skyrmion phenomena in optical transduction technologies.
Abstract Photonic spin texture (PST), the spatial distribution of the spin angular momentum of light, is connected to unique properties of light, such as optical skyrmions and topological optical N-invariants. There has been recent progress on the generation and manipulation of PST using various methodologies. However, a challenge remains for the sub-wavelength characterization of PST. Here, we demonstrate nitrogen–vacancy (NV) centers in diamond as nanoscale quantum sensors for imaging the PST of a beam with orbital angular momentum. Leveraging the coherent interaction between photon spin and NV center electron spin at cryogenic temperature (77 K), and using the Hahn-echo magnetometry technique, we experimentally demonstrate the imprinting of the PST on the quantum phase shift of NV centers. Our work can lead to the development of a quantum imaging platform capable of characterization of the spin texture of light at sub-wavelength scales.
Topological quasiparticles of light, such as classical and quantum optical skyrmions, have so far relied on fully coherent or pure quantum states whose topology is encoded in the entanglement between polarization and two-dimensional spatial modes. Here we show that skyrmionic topology can emerge directly within the density matrix of a mixed quantum state. We introduce a framework in which a coherence-Stokes vector defines a topological texture over the density matrix, enabling the realization of quantum skyrmions using only a pseudospin and a real or synthetic one-dimensional space of modes. For a single photon, the density matrix is analogous to the coherence matrix of classical light, and can be encoded using partially coherent electromagnetic fields. We further analyze the topological texture encoded in a bipartite entangled photon pair, showing how skyrmions arise not only in the full bi-photon system, but also in its reduced subspaces with any pseudospin-mode combination simultaneously. We then explore the robustness of such skyrmions to environmental noise, and discover their persistence in mixed-quantum states of multiple photons. Finally, we propose a feasible experimental route to generate and measure such skyrmions using integrated photonic networks, and suggest avenues for similar implementations in other quantum systems. Our work paves the way for robustly encoding classical information on partially coherent light or on mixed quantum states and for encoding topological charges on many-body quantum systems.
Coherent coupling between optical fields and solid-state spins is essential for building a spin–photon interface and exchanging quantum information. The nitrogen-vacancy (NV) center, a solid-state defect center in diamond, is a promising qubit system for its relatively high-temperature spin coherence. Here, we study the coherent coupling between the photonic spin texture (PST) and the quantum polarization cloud (phase shift) of NV centers spanning a temperature range from liquid nitrogen (77 K) to room temperature (295 K). We show that by optimizing the laser power and frequency detuning, it is possible to maintain coherence in NV–photon interaction even in this nonideal limit. The coherent NV–photon interaction in our experiment is encoded in the quantum phase shift of the NV center spin qubit, which can be read out using the Hahn-echo magnetometry technique. Our approach of studying light–matter interaction at an elevated temperature can build an unexplored regime of spin–photon interface, which has potential applications in diverse quantum applications.
Photonic spin density (PSD) in the near-field gives rise to exotic phenomena such as photonic skyrmions, optical spin-momentum locking and unidirectional topological edge waves. Experimental investigation of these phenomena requires a nanoscale probe that directly interacts with PSD. Here, we propose and demonstrate that the nitrogen-vacancy (NV) center in diamond can be used as a quantum sensor for detecting the spinning nature of photons. This room temperature magnetometer can measure the local polarization of light in ultra-subwavelength volumes through photon-spin-induced virtual transitions. The direct detection of light's spin density at the nanoscale using NV centers in diamond opens a new frontier for studying exotic phases of photons as well as future on-chip applications.
Electromagnetic (EM) fields can be engineered through controlled modulation of amplitude, phase, frequency, polarization, and angular momentum. Such engineered fields have enabled a wide range of promising applications in modern photonics, nanoscience, and quantum technologies. In the far-field regime, tailoring the spin and orbital angular momentum of light gives rise to structured optical fields with nontrivial topological properties, such as skyrmionic and vortex-like textures. These optical topologies have attracted considerable interest for applications in noise-resilient optical communications, super-resolution imaging, and advanced light-matter interactions. In contrast, near-field EM environments emerge from microscopic spin and charge dynamics within materials. By controlling material composition, dimensionality, and nanoscale structure, it becomes possible to engineer EM fluctuations. Probing the properties of engineered EM fields remains challenging because many of their features, including the nanoscale localization of topological features and the weak, broadband nature of near-field fluctuations, are difficult to access using conventional measurement techniques. This dissertation focuses on quantum probing of engineered EM fields using the nitrogen vacancy (NV) center in diamond, a versatile quantum sensing platform. Both far-field optical topologies and near-field EM fluctuations are investigated, demonstrating how quantum probes can be used to characterize novel EM phenomena across distinct spatial and spectral regimes.In this dissertation, the topological properties of optical beams are probed through the coherent interaction between the photonic spin texture (PST) of structured light and NV center spin qubits. The spatial distribution of photonic spin gives rise to distinct topological features of light. Through local coherent coupling with the NV spin qubit, the PST induces a measurable phase shift in the quantum superposition state of the NV center. By optically measuring the accumulated phase shift of the NV center spin qubits, the local spin texture is quantitatively reconstructed and the topological properties of the optical field are characterized. Through a coherent light-matter interaction, this work also introduces the concept of transducing topological features of light onto the phase texture of NV spin ensemble.To probe the near-field EM fluctuations, the phase coherence decay of NV center spin qubits is measured. Fluctuations arising from spin and charge dynamics within nearby materials induce random phase accumulation in the superposition state of the NV center, leading to dephasing of the spin qubit. Through frequency-selective and spectrally resolved measurements of the NV spin coherence decay rates, the local near-field EM environment is quantitatively characterized. The measured fluctuations are further connected to important materials properties and phenomena, including magnetic dynamics, superparamagnetism, and critical fluctuations in magnetic material and metastructures. Through quantum dephasing measurements, this work reveals previously unexplored material properties and near-field EM phenomena.