Photonic Spin Research Articles

Controllable photonic spin Hall effect induced by an off-axis polarization singularity

Controllable photonic spin Hall effect induced by an off-axis polarization singularity

Giant Plasmonic Enhancement of Chiroptical Properties by Anisotropic Gold Nanocrystals Grown In Situ in a Chiral Polymer

AbstractPolymer‐based chiral materials with exceptional optical activity can dramatically impact integrated chiral photonics due to the tunability of their optical responses coupled with ease of fabrication. Realizing these applications requires increasing the absorbance dissymmetry factor. Here, in situ, the synthesis of gold nanostars is introduced in a chiral polymer medium to produce chiral polymer‐anisotropic plasmonic nanocrystal nanocomposites. The optimized nanocomposite shows a tenfold enhancement of dissymmetry factor, gabs (up to 0.64) and a corresponding 46‐fold augmented circular dichroism (CD) value upon annealing, relative to the annealed pure chiral polymer film. Moreover, the enhancement relative to the non‐annealed polymer‐gold nanostar nanocomposite is strikingly higher: a 35‐fold increase in gabs and a 4272‐fold increase in CD. Based on computational analysis, it is concluded that the local plasmon field enhancement around the crevices and tips of nanostars is mainly responsible for the observed effect which is further supported by a signal enhancement in Surface Enhanced Raman Scattering (SERS). Thus, this study underscores the significant role of close‐range plasmon interactions in altering the chiroptical response of nanocomposite materials and a practical pathway toward the realization of next‐generation integrated photonics and optoelectronic circuitry with photon spin control.

Preparation of fidelity-robust quantum entanglement with error-detected blocks based on quantum-dot spins inside optical microcavities

Effective schemes are proposed for the generation of bipartite Bell states and theoretically scaling up to arbitrary multiparticle Greenberger–Horne–Zeilinger, cluster, and W states among quantum-dot (QD) spins. They are realized based on the interaction between an single incident photon and single QD spin. Errors from system nonuniformity and defective photon scattering are transformed into detectable photon losses. In the event of a failed experiment, the system allows for the reinjection of a single photon and the reinitiation of the quantum circuit, until a successful outcome is achieved. This loss-prediction and experiment-repeatability approach ensures that the schemes are implemented with uniform and robust fidelity. Compared with the previous methods, these schemes significantly simplify experimental procedures and analysis processes. Furthermore, upon successful execution of the experiment, the use of single-photon detector can faithfully differentiate between various types of entangled states, depending on the initial states of the QD spins. An analysis of the feasibility of the schemes under current experimental parameters suggests high efficiency even in the weak coupling region.

High-dimensional two-photon quantum controlled phase-flip gate

High-dimensional quantum systems have been used to reveal interesting fundamental physics and to improve information capacity and noise resilience in quantum information processing. However, it remains a significant challenge to realize universal two-photon quantum gates in high dimensions with high success probability. Here, by considering an ion-cavity QED system, we theoretically propose, to the best of our knowledge, the first high-dimensional, deterministic, and universal two-photon quantum gate. By using an optical cavity embedded with a single trapped Ca+40 ion, we achieve a high average fidelity larger than 98% for a quantum controlled phase-flip gate in four-dimensional space, spanned by photonic spin angular momenta and orbital angular momenta. Our proposed system can be an essential building block for high-dimensional quantum information processing, and also provides a platform for studying high-dimensional cavity QED. Published by the American Physical Society 2024

The First Law of Newton. Formula and Consequences: Changes in Weight and Forward Motion of Rotating Bodies

The aim of this work is to show that the first Newton’s law (law of inertia) is a manifestation of the law of conservation of angular momentum in the physical vacuum. The force of inertia arises in a body as a result of a change in the angular momentum of the body. The change in the angular momentum can emerge when changing the characteristics of spins of virtual photons created by quantum objects constituting the body. Due to the law of conservation of angular momentum a change in the angular momentum results in emergence of the processes compensating this change. One of these compensating processes is the emergence of force of inertia influencing the velocity of quantum objects constituting the body. Another compensating process is the emergence of rotation of these objects. Both these processes are observed in experiments. The force of inertia may arise in rotating bodies as rotation of body influences the characteristics of spins of virtual photons created by quantum objects of rotating body. If the force is directed along the vector of gravitation, the weight of rotating body is increased. If the force is directed against the vector of gravitation, the weight of rotating body is decreased. If the force is directed perpendicular to the vector of gravitation, the body is moving along the Earth surface. All these phenomena are observed in experiments.

Giant and nonreciprocal photonic spin hall effect in asymmetric multilayered structure with bulk dirac semimetal

Abstract The nonreciprocal photonic spin Hall effect features the different reflected or transmitted spin shifts along two opposite incident wave propagating directions. However, previous investigations have always focused on the features of the photonic spin Hall effect along one incident wave propagating direction. How to achieve the nonreciprocal photonic spin Hall effect remains obscure. Here, we theoretically study the nonreciprocal photonic spin Hall effect in the asymmetric multilayered structure containing the Bulk Dirac Semimetal and other dielectric materials. It is found that under the horizontal polarization the maximum reflected spin shift value along one direction is up to around times of the incident wavelength at , but it is only times of the incident wavelength at along the other direction, which reflects the nonreciprocity of photonic spin Hall effect and thus can act as the photonic spin Hall diode. Such a sizeable directional difference between the reflected spin shifts along these two opposite directions originates from the fact that this structure loses its mirror symmetry and becomes an asymmetrical one, and the obvious difference in the values of the reflected spin shifts along the two directions can be attributed to the large difference in the values of . At the same time, we find that the Fermi energy of the Bulk Dirac Semimetal can effectively tune the spin shift along the backward direction, as well as the difference between the spin shifts for two different propagating directions, which causes the controllable nonreciprocal photonic spin Hall effect. Our results establish the alternative configuration for realizing the nonreciprocal photonic spin Hall effect, which facilitates the potential applications in the spin photonic devices.

Optical Spin Waves.

Chirality is inherent to a broad range of systems, including solid-state and wave physics. The precession (chiral motion) of the magnetic moments in magnetic materials, forming spin waves, has various properties and many applications in magnetism and spintronics. We show that an optical analogue of spin waves can be generated in arrays of plasmonic nanohelices. Such optical waves arise from the interaction between twisted helix eigenmodes carrying spin and orbital angular momenta. We demonstrate that these optical spin waves are reflected at the interface between successive domains of enantiomeric nanohelices, forming a heterochiral lattice regardless of the wave propagation direction within the lattice. Optical spin waves may be applied in techniques involving photon spin, ranging from data processing and storage to quantum optics.

Physical unclonable function using photonic spin Hall effect

This study presents a novel method leveraging surface wave-assisted photonic spin Hall effect (PSHE) to construct physical unclonable functions (PUFs). PUFs exploit inherent physical variations to generate unique Challenge–Response pairs, which are critical for hardware security and arise from manufacturing discrepancies, device characteristics, or timing deviations. We explore PSHE generation-based PUF design, expanding existing design possibilities. With recent applications in precise sensing and computing, PSHE offers promising performance metrics for our proposed PUFs, including an inter-Hamming distance of 47.50% , an average proportion of unique responses of 62.5% , and a Pearson correlation coefficient of − 0.198. The PUF token demonstrates robustness to simulated noise. Additionally, we evaluate security using a machine learning-based attack model, employing a multi-layer perceptron (MLP) regression model with a randomized search method. The average accuracy of successful attack prediction is 9.70% for the selected dataset. Our novel PUF token exhibits high non-linearity due to the PSHE effect, resilience to MLP-based attacks, and sensitivity to process variation.

Non-Hermitian photonic spin Hall insulators

Non-Hermitian photonic spin Hall insulators

Enhancing photonic spin Hall effect in the long-range surface plasmon resonance structure with antimonene

In this paper, a long-range surface plasmon resonance (LRSPR) structure with antimonene is proposed to enhance the photonic spin Hall effect (PSHE). By exploiting the LRSPR with antimonene, the maximum transverse displacement of the incident beam with a wavelength of 633 nm can reach 121.4λ (76.9 µm), which is much larger than the previously reported value in the insulator-metal LRSPR structure. Given the high sensitivity of spin splitting to alterations in the refractive index of the sensing layer, PSHE finds application in sensors. Remarkably, the LRSPR structure featuring antimonene demonstrates a sensitivity of 7 × 104 µm/RIU, an order of magnitude higher than that of conventional SPR structures. These results present a promising avenue for integrating PSHE into biosensing applications.

Topological Directional Coupler

AbstractInterferometers and beam splitters are fundamental building blocks for photonic neuromorphic and quantum computing machinery. In waveguide‐based photonic integrated circuits, beam‐splitting is achieved with directional couplers that rely on transition regions where the waveguides are adiabatically bent to suppress back‐reflection. In this study, a novel, compact approach for introducing guided mode coupling is presented. Along the multimodal domain wall between topological photonic crystals, the photonic spin is conserved to suppress back‐reflection, and the topological protection of the valley degree of freedom is relaxed to implement tunable beam splitting. Rapid advancements in chip‐scale topological photonics suggest that the proposed simultaneous utilization of multiple topological degrees of freedom could benefit the development of novel photonic computing platforms.

Multi-functional photonic spin Hall effect sensor controlled by phase transition

Abstract Photonic spin Hall effect (PSHE), as a novel physical effect in light–matter interaction, provides an effective metrological method for characterizing the tiny variation in refractive index (RI). In this work, we propose a multi-functional PSHE sensor based on VO2, a material that can reveal the phase transition behavior. By applying thermal control, the mutual transformation into different phase states of VO2 can be realized, which contributes to the flexible switching between multiple RI sensing tasks. When VO2 is insulating, the ultrasensitive detection of glucose concentrations in human blood is achieved. When VO2 is in a mixed phase, the structure can be designed to distinguish between the normal cells and cancer cells through no-label and real-time monitoring. When VO2 is metallic, the proposed PSHE sensor can act as an RI indicator for gas analytes. Compared with other multi-functional sensing devices with the complex structures, our design consists of only one analyte and two VO2 layers, which is very simple and elegant. Therefore, the proposed VO2-based PSHE sensor has outstanding advantages such as small size, high sensitivity, no-label, and real-time detection, providing a new approach for investigating tunable multi-functional sensors.

Chirality-enabled topological phase transitions in parity-time symmetric systems

Photonic spin Hall effect (PSHE) in chiral PT-symmetric systems exhibits many exotic features, but the underlying physical mechanism has not been well elucidated. Here, through rigorous calculations based on full-wave theory, we reveal the physical mechanism of the exotic PSHE and identify a chirality-enabled topological phase transition. When circularly polarized light is incident on a chiral PT-symmetric system, the transmitted beam contains two components: a spin-flipped abnormal mode that acquires a geometric phase (exhibiting a vortex or a spin-Hall shift), and a spin-maintained normal mode that does not exhibit such a phase. If the phase difference between the cross-polarized Fresnel coefficients cannot be ignored, it results in a chirality-enabled phase and intensity distribution in the abnormal mode, which induces an exotic PSHE. Consequently, as the incident angle increases, a chirality-induced topological phase transition occurs, namely the transition from the vortex generation to the exotic PSHE. Finally, we confirm that the asymmetric and periodic PSHE in the chiral slab is also related to the phase difference between the cross-polarized Fresnel coefficients. These concepts and findings also provide an opportunity for unifying the phenomena of topological phase transitions in various spin-orbit photonic systems.

Observation of the spin Hall effect of light by a single-photon detector.

We use a single-photon detector to detect the spin Hall effect of light (SHEL) of a quasi-single-photon beam obtained in this Letter. The physics of the spin Hall effect and its quantum weak measurement method with a dimensionless pointer are elucidated through particle number representation. Our weak measurement scheme obviates the necessity of high-resolution single-photon array detectors. Consequently, we have successfully observed the spin Hall effect within a 20 ns temporal window using a position-resolution-independent single-photon detector with remarkably low-noise levels. The weak measurement of the dimensionless pointer presented in this Letter boosts both the detection accuracy and the response speed of the photonics spin Hall effect, thereby contributing significantly to fundamental theoretical research in spin photonics and precise measurements of physical property parameters.

Simultaneous observation of transverse and longitudinal photonic spin splitting in monolayer WSe2 via quantum weak measurement

Simultaneous observation of transverse and longitudinal photonic spin splitting in monolayer WSe2 via quantum weak measurement

Coherent Microwave, Optical, and Mechanical Quantum Control of Spin Qubits in Diamond

AbstractDiamond has emerged as a highly promising platform for quantum network applications. Color centers in diamond fulfill the fundamental requirements for quantum nodes: they constitute optically accessible quantum systems with long‐lived spin qubits. Furthermore, they provide access to a quantum register of electronic and nuclear spin qubits and they mediate entanglement between spins and photons. All these operations require coherent control of the color center's spin state. This review provides a comprehensive overview of the state‐of‐the‐art, challenges, and prospects of such schemes, including high‐fidelity initialization, coherent manipulation, and readout of spin states. Established microwave and optical control techniques are reviewed, and moreover, emerging methods such as cavity‐mediated spin–photon interactions and mechanical control based on spin–phonon interactions are summarized. For different types of color centers, namely, nitrogen–vacancy and group‐IV color centers, distinct challenges persist that are subject of ongoing research. Beyond fundamental coherent spin qubit control techniques, advanced demonstrations in quantum network applications are outlined, for example, the integration of individual color centers for accessing (nuclear) multiqubit registers. Finally, the role of diamond spin qubits in the realization of future quantum information applications is described.

Tunable spin splitting of reflected Laguerre-Gaussian beams on controllable metamaterials with anti-PT symmetry

The intriguing photonic spin Hall effect (PSHE) of reflected Laguerre-Gaussian (LG) beams can be exhibited on the systems with optical anti-parity-time (Anti-PT) symmetry. During the reflection, the left/right circularly polarized (LCP/RCP) components of reflected LG beams are considered. By controlling parameters of the Anti-PT systems, the PSHE of reflected LCP/RCP can be identical and symmetrical with respect to incident-reflected plane (IRP). Due to gain/non-Hermitian effects of designed Anti-PT systems, special PSHE near the strong gain points (SGP) and exceptional points (EPs) can be obtained simulatively. Through analyses in PSHE of reflected LCP on four similar Anti-PT systems, specific conclusions that can even be extended to more general cases. Moreover, simulations of PSHE by simultaneously varying the incident angles * and imaginary/real dielectric constants Im/Re[ε] of the Anti-PT systems, specal PSHE and other novel optical phenomena with real applications can be revealed. So Anti-PT systems not only provide novel ways to regulate the PSHE of reflected LG beams, but also offer possibilities for new optical characteristics of devices.

Surface phonon resonance: A new mechanism for enhancing photonic spin Hall effect and refractive index sensor

Abstract Metal-based surface plasmon resonance (SPR) plays an important role in enhancing the photonic spin Hall effect (SHE) and developing sensitive optical sensors. However, the very large negative permittivities of metals limit their applications beyond the near-infrared regime. In this work, we theoretically present a new mechanism to enhance the photonic SHE by taking advantage of SiC-supported surface phonon resonance (SPhR) in the mid-infrared regime. The transverse displacement of photonic SHE is very sensitive to the wavelength of incident light and the thickness of SiC layer. Under the optimal parameter setup, the calculated largest transverse displacement of SiC-based SPhR structure reaches up to 163.8 μm, which is much larger than the condition of SPR. Moreover, an NO2 gas sensor based on the SPhR-enhanced photonic SHE is theoretically proposed with the superior sensing performance. Both the intensity and angle sensitivity of this sensor can be effectively manipulated by varying the damping rate of SiC. The results may provide a promising paradigm to enhance the photonic SHE in the mid-infrared region and open up new opportunity of highly sensitive refractive index sensors.

Quantum electrodynamics mediated by a photon with continuous spin

In recent work with Zhou, we studied classical interactions of matter with a “continuous spin” field, whose excitations have zero mass but nonzero spin Casimir (spin scale) ρ. We reported evidence that such theories are a calculable infrared deformation of familiar massless theories including electromagnetism. Building on the aforementioned work, this paper presents rules for computing scattering amplitudes involving charged scalar matter and continuous spin photons with nonzero spin scale. As a concrete example, we compute the pair annihilation and Compton scattering amplitudes in this theory and comment on their physical properties, including unitarity and scaling behavior at small and large ρ. Like the classical physics and soft factors studied in prior work, these amplitudes exhibit “helicity correspondence,” recovering familiar amplitudes at energy scales ≫ρ, but with calculable deviations that could be experimentally tested. These results bolster the conjecture that continuous spin particles with a very small ρ could mediate long-range forces in nature (e.g., the photon could be a continuous spin particle), and extend the range of physical effects that could be used to test this hypothesis. Published by the American Physical Society 2024

Coexistence of large photonic spin Hall effect and high efficiency in a dielectric grating structure

Large reflected photonic spin Hall effects have been discovered in various nanostructures under either horizontal (H) or vertical (V) polarized wave. However, their corresponding reflectance efficiencies are always quite low and they generally cannot be enhanced simultaneously for both H and V polarized waves. How to achieve the large photonic spin Hall effects and high efficiencies for both H and V polarized waves at the same wavelength, which are essential for their efficient spin photonic applications, remains acute. To overcome this difficulty, we design one dimensional subwavelength dielectric grating structure and find that it supports the remarkable reflected photonic spin Hall effects under both H and V polarized waves at the same incident angle via well-designed geometrical parameters, which are also accompanied with high reflectances in the visible frequency. We also elucidate that the reflected spin shifts in this structure are related to the incident angle and thus can be engineered by it. Our findings about the dielectric grating structures contribute to an alternative approach to achieve the decent reflected spin shifts and efficiencies for both polarized waves, which enables the next-generation spin photonic devices, such as, precision metrology and quantum information processing.