Asymmetric quantum decision-making

Light orbital angular momentum (OAM) has been recognized as a new promising resource for classical and quantum information applications. In contrast to the spin angular momentum, the OAM is an inherently multidimensional. Thus, the information can be encoded in the higher-dimensional OAM alphabets. Recently, Marrucci et al. have invented a new device named q-plate (QP), made of liquid crystal cell patterned in such a way to introduce a topological charge q at the transverse plane, which is able to generate a well-defined values of photon OAM. My research has been aimed at investigating the physics of the QP, of the optical fields that it generates and of its possible applications for optical communication and quantum information. We studied both theoretically and experimentally a novel set of non-orthogonal but over-complete paraxial modes, named Hypergeometric-Gaussian modes, that is typically associated with OAM-carrying optical fields. We have also found the light propagation kernel inside the QP and we have shown analytically that if small losses due to reflection, absorption, and scattering are neglected, the QP can convert the photon spin into OAM with up to 100 \% efficiency. We implemented a technique to control the QP optical retardation by tuning the QP temperature. At the optimal temperature, the QP can generate a beam with up to 97\% efficiency. Moreover, the OAM state generated by QP can be rotated easily in the 2D OAM Hilbert space by proper manipulation of the input polarization state, a fact which opens a new way of beam shape controlling in MHz scale. We also performed a novel way to encode and read two bits information on the 4D OAM space by using only one QP. Finally, we experimentally demonstrated the transfer of quantum information from spin to OAM and vice versa, including the case of bi-photon states having quantum correlations. Furthermore, by exploiting these quantum information transfer devices, we demonstrated the Hong-Ou-Mandel effect and the optimal quantum cloning with OAM-carrying photons.

Orbital angular momentum (OAM) of light has drawn increasing attention due to its intriguingly rich physics and potential for a variety of applications. Having an unbounded set of orthogonal states, OAM has been used to enhance the channel capacity of data transmission. We propose and demonstrate the viability of using OAM to create an automultiscopic 3D display. Multi-view image information is encoded using an OAM beam array, then sorted into different view directions using coordinate transformation elements. A three-view demonstration was achieved to encode and decode 9 × 9 pixel images. These demonstrations suggest that OAM could potentially serve as an additional platform for future 3D display systems.

Orbital angular momentum (OAM) light is nowadays an intriguing resource in classical and quantum optics due to the richness of physical properties it shows in interaction with matter. A key ingredient needed to exploit the full potential of OAM light is the control of quantum interference, a crucial resource in fields like quantum communication and quantum optics. Here, we study the vortex four-wave mixing (FWM) via multi-photon quantum interference in an ultraslow propagation regime. We find that the structured information can be manipulated via two-photon detuning and three photon detuning, which manifests itself as a spatial modulation. The detailed explanations based on the dispersion relation are given, which are in good agreement with our simulations. Furthermore, in order to clearly show the modulated mechanism, we perform the interference between the FWM field and a same-frequency Gaussian beam. It is found that the interference patterns are also manipulated by adjusting the multi-photon detunings. This work may have some potential applications in quantum control based on OAM light.

Beams carrying orbital angular momentum (OAM) already play significant roles in many domains. Here we propose a practical design of an OAM beam splitter based on a single phase-only multi-ring azimuthal-quadratic diffraction optical element that can sort different OAM components into various spatial positions, and OAM state probing is also achieved. The performance is demonstrated through proof-of-principle experiments and shows favorable results. Furthermore, the intensity proportion of each OAM component, namely the OAM spectrum, is also diagnosed. This work offers high applicability and practicability for the recognition and separation of photon OAM, and thus paves the way for many advanced scenarios such as quantum communication, holographic encryption, and remote sensing.

Both spin angular momentum (SAM) and orbital angular momentum (OAM) can be used to carry information in classical optics and quantum optics. In this paper, the encoding of angular momentum (AM) information of photons onto surface plasmon polaritons (SPPs) is demonstrated using a nano-ring plasmonic lens. Near-field energy distribution on the metal surface is measured using a near-field scanning optical microscope (NSOM) when the plasmonic lens is excited by photons with different combinations of SAM and OAM. It is found that both the SAM and OAM can influence the near field energy distribution of SPPs. More interestingly, numerical and experimental studies reveal that the energy distribution on the plasmonic lens surface is determined by the absolute value of the total AM. This gives direct evidences that SPPs can be encoded with the photonic SAM and OAM information simultaneously and the spin degeneracy of the photons can be removed using the interactions between photonic OAM and plasmonic lens. The findings are useful not only for the fundamental understanding of the photonic AM but also for the future design of plasmonic quantum optics devices and systems.

The identification of orbital angular momentum (OAM) as a fundamental property of a beam of light nearly 25 years ago has led to an extensive body of research around this topic. The possibility that single photons can carry OAM has made this degree of freedom an ideal candidate for the investigation of complex quantum phenomena and their applications. Research in this direction has ranged from experiments on complex forms of quantum entanglement to the interaction between light and quantum states of matter. Furthermore, the use of OAM in quantum information has generated a lot of excitement, as it allows for encoding large amounts of information on a single photon. Here, we explain the intuition that led to the first quantum experiment with OAM 15 years ago. We continue by reviewing some key experiments investigating fundamental questions on photonic OAM and the first steps to applying these properties in novel quantum protocols. At the end, we identify several interesting open questions that could form the subject of future investigations with OAM.This article is part of the themed issue 'Optical orbital angular momentum'.

Vortex light carrying orbital angular momentum (OAM) is a beam with a helical phase structure. The OAM light has great potential in the field of communication, due to the fact that it can greatly improve the efficiency and capacity of information transmission. One of the popular information propagation methods is coding and decoding by different single OAM light or combined multiple OAM lights. However, Laguerre–Gaussian (LG) beams (LGB) carrying OAM, which is a classical vortex light, are prone to distortion of intensity under atmospheric turbulence (AT) disturbances. Due to the influence of AT, the effective recognition of the OAM mode in a free space becomes an important challenge for information propagation. For mitigating the influence of AT, a scheme combining AT extraction and OAM modes recognition is proposed, which can efficiently identify both AT intensity and OAM modes. A 99 % identification accuracy of AT can be reached by the proposed scheme. Besides, the obtained results also show that the recognition rate of OAM modes is greatly improved after the introduction of AT extraction module, especially under strong turbulence conditions. Compared to direct-mode-identification method without extracting AT, the recognition accuracy can be improved by 8 % and 3 % when the AT intensity is 1 × 10 − 13 and 5 × 10 − 14 m − 2 / 3 , respectively. Consequently, the proposed scheme can be used to identify the OAM modes with a high accuracy, which is beneficial to OAM coding and decoding in an OAM-based communication system.

Emerging applications based on optical beams carrying orbital angular momentum (OAM) will likely require photonic integrated devices and circuits for miniaturization, improved performance and enhanced functionality. This paper reviews the state-of-the art in the field of OAM of light, reports recent developments in silicon integrated OAM emitters, and discusses the applications potentials and challenges in silicon integrated OAM devices which can be used in future OAM based optical communications systems.

Optical beams carrying orbital angular momentum (OAM) have gained significant interest due to their unique properties, enhancing various communication systems and enabling applications such as the characterization of material or molecular chirality. Generating and detecting the OAM of light is thus crucial for numerous applications but poses challenges. This paper proposes a method utilizing stimulated Raman scattering to detect the magnitude of OAM. By exploring the strong Raman coupling between the pump and Stokes beams in higher-order Laguerre-Gauss modes, we demonstrate the discrimination of different optical vortex beams through nonlinear optical measurements. Numerical and experimental results support the feasibility of this approach, potentially advancing optical communication and sensing technologies.

In addition to a plethora of emergent phenomena, the spatial topology of optical vortices enables an array of applications in optical communications and quantum information science. Multibeam nonlinear optical processes, augmented by optical vortices, are essential in this context, providing robust access to an infinitely large set of quantum states associated with the orbital angular momentum of light. Here, we push the boundaries of vortex nonlinear optics to the ultimate limits of material dimensionality. By exploiting multipulse difference frequency, sum frequency, and four-wave mixing in monolayer quantum materials, we demonstrate their ability to independently control the orbital angular momentum and radial distribution of vortex light-fields in addition to their wavelength. Due to the atomically thin nature of the host crystal, this control spans a broad spectral bandwidth in a highly integrable platform that is unconstrained by the traditional limits of bulk nonlinear optical materials. Our work heralds an innovative path for ultracompact and scalable hybrid nanophotonic technologies empowered by twisted nonlinear light-matter interactions in van der Waals nanomaterials.

Carbon nanotubes are explored as a means of coherently converting the orbital angular momentum of light to an excitonic form that is more amenable to quantum information processing. An analytical analysis, based on dynamical conductivity, is used to show that orbital angular momentum is conserved, modulo N, for a carbon nanotube illuminated by radially polarized, twisted light. This result is numerically demonstrated using real-time time-dependent density functional theory which captures the absorption of twisted light and the subsequent transfer of twisted excitons. The results suggest that carbon nanotubes are promising candidates for constructing optoelectronic circuits in which quantum information is more readily processed while manifested in excitonic form.

Allowing subwavelength-scale-digitization of optical wavefronts to achieve complete control of light at interfaces, metasurfaces are particularly suited for the realization of planar phase-holograms that promise new applications in high-capacity information technologies. Similarly, the use of orbital angular momentum of light as a new degree of freedom for information processing can further improve the bandwidth of optical communications. However, due to the lack of orbital angular momentum selectivity in the design of conventional holograms, their utilization as an information carrier for holography has never been implemented. Here we demonstrate metasurface orbital angular momentum holography by utilizing strong orbital angular momentum selectivity offered by meta-holograms consisting of GaN nanopillars with discrete spatial frequency distributions. The reported orbital angular momentum-multiplexing allows lensless reconstruction of a range of distinctive orbital angular momentum-dependent holographic images. The results pave the way to the realization of ultrahigh-capacity holographic devices harnessing the previously inaccessible orbital angular momentum multiplexing.

Summary form only given.The orbital angular momentum of light is distinct from the intrinsic angular momentum associated with the polarization state of the light. Thus linearly polarized laser modes can carry angular momentum. Such orbital angular momentum is associated with light beams with helical wave fronts, one class of which are Laguerre-Gaussian laser modes. The azimuthal phase factor exp(il/spl phi/) in their field distribution, gives rise to an orbital angular momentum equivalent to l/spl planck/ per photon. Our previous investigations of second-harmonic generation using Laguerre-Gaussian modes confirmed that the conservation of orbital angular determines the mode structure of the frequency-doubled beam. It was shown that a Laguerre-Gaussian mode with an azimuthal index l is transformed into a frequency-doubled mode with twice the azimuthal index 2l, thus conserving the angular momentum within the light fields. Degenerate parametric downconversion can be considered as the inverse process to second-harmonic generation. An incoming pump wave generates two new fields, signal and idler, with half the pump frequency. Accordingly, a Laguerre-Gaussian pump beam with an even value of the azimuthal index l produces signal and idler beams that can both have integer azimuthal mode indices of l/2. Away from degeneracy, the signal and idler frequencies do not in general have an integer ratio. Consequently, the orbital angular momentum of the pump cannot be divided to give integer l-values for the signal and idler beams in the same ratio as their energy. Even for degenerate phase matching, an integer division of the orbital angular momentum will not be possible when the pump mode has an odd value of l. We investigate the role that the conservation of orbital angular momentum plays in the downconversion process.

The ROAM (Revolutionizing optical fiber transmission and networking using the Orbital Angular Momentum of light) project investigates the orbital angular momentum (OAM) modes of light for communications and networking applications. OAM modes are exploited as a disruptive means of increasing fibre transmission capacity and as switching resource to improve the switches scalability and power consumption in data-centre scenarios.

We report on the storage of orbital angu- lar momentum (OAM) of light of a Laguerre-Gaussian mode in an ensemble of cold cesium atoms and its re- trieval along an axis different from the incident light beam. We employed a time-delayed four-wave mixing configuration to demonstrate that at small angle (2o), after storage, the retrieved beam carries the same OAM as the one encoded in the input beam. A calculation based on mode decomposition of the retrieved beam over the Laguerre-Gaussian basis is in agreement with the experimental observations done at small angle values. However, the calculation shows that the OAM retrieving would get lost at larger angles, reducing the fidelity of such storing-retrieving process. In addition, we have also observed that by applying an external magnetic field to the atomic ensemble the retrieved OAM presents Larmor oscillations, demonstrating the possibility of its manipulation and off-axis retrieval.