Vector vortex beams are structured states of light that non-separable in their polarisation and spatial mode, they eigenmodes free-space many fibre systems, have the capacity to be used as a modal basis for both classical quantum communication. Here we outline recent progress our understanding these modes, from creation characterization detection. We then use tools study propagation behaviour such modes optical show cross-talk results decay vector into separable scalar with concomitant loss...

Quantum mechanics is now a mature topic dating back more than century. During its scientific development, it fostered many technological advances that are integrated into our everyday lives. More recently, over the past few decades, authors have seen emergence of second quantum revolution, ushering in control states. Here, spatial modes light, “patterns light,” hold tremendous potential: light weakly interacting and so an attractive avenue for exploring entanglement preservation open...

A tomographic measurement is a ubiquitous tool for estimating the properties of quantum states, and its application known as state tomography (QST). The process involves manipulating single photons in sequence projective measurements, often to construct density matrix from which other information can be inferred, laborious it complex. Here we unravel steps QST outline how may demonstrated fast simple manner with intense (classical) light. We use scalar beams time reversal approach simulate...

Structured light has become topical of late, where controlling in all its degrees freedom offered novel states long predicted, enhanced functionality applications, and a modern toolbox for probing fundamental science. Structuring as single photons entangled allows the spatial modes to be used encode large alphabet, accessing high dimensional Hilbert spaces tests quantum mechanics improved information processing tasks. In this tutorial, we outline basic concepts expressed basis (structured...

A quantitative analysis of optical fields is essential, particularly when the light structured in some desired manner, or there perhaps an undesired structure that must be corrected for. ubiquitous procedure community mode projections-a modal light-for unveiling amplitude and phase information a field. When correctly performed, all salient features field can deduced with high fidelity, including its orbital angular momentum, vectorial properties, wavefront, Poynting vector. Here, we present...

Optical communication is an integral part of the modern economy, having all but replaced electronic systems. Future growth in bandwidth appears to be on horizon using structured light, encoding information into spatial modes and transmitting them down fibre free-space, latter crucial for addressing last mile digitally disconnected communities. Unfortunately, patterns light are easily distorted, case free-space optical communication, turbulence a significant barrier. Here we review recent...

The global quantum network requires the distribution of entangled states over long distances, with substantial advances already demonstrated using polarization. While Hilbert spaces higher dimensionality, e.g., spatial modes light, allow information capacity per photon, such mode entanglement transport custom multimode fiber and is limited by decoherence-induced coupling. Here, we circumvent this transporting multidimensional down conventional single-mode (SMF). By entangling spin-orbit...

Abstract Vector beams, non-separable in spatial mode and polarisation, have emerged as enabling tools many diverse applications, from communication to imaging. This applicability has been achieved by sophisticated laser designs controlling the spin orbital angular momentum, but so far is restricted only two-dimensional states. Here we demonstrate first vectorially structured light created fully controlled eight dimensions, a new state-of-the-art. We externally modulate our beam control, for...

Quantum photonic platforms have proven to be essential in realizing fundamentally secure quantum transfer of information, with commercially ready systems already deployed municipal and terrestrial links. The drive toward higher bit rates robustness eavesdropping noisy channels has focused attention on moving from the present two-dimensional states polarization, harnessing all light's degrees freedom for multi-dimensional coding structured photons. In this Perspective, we outline...

Fast and secure sharing of information is among the prime concerns almost any communication system. While commonly used cryptographic algorithms cannot provide unconditional security, high-dimensional (HD) quantum key distribution (QKD) offers an exceptional means to this end. Here, we a tutorial demonstrate that HD QKD protocols can be implemented in effective way using optical elements are known most optics labs. We use spatial modes light as our basis show how simulate experiments with...

Abstract Increasing the information capacity of communication channels is a pressing need, driven by growing data demands and consequent impending crunch with existing modulation schemes. In this regard, mode division multiplexing (MDM), where spatial modes light form encoding basis, has enormous potential but impeded noise due to imperfect channels. Here, challenge overcome breaking MDM paradigm using themselves as discrete basis instead exploiting polarization inhomogeneity (vectorness)...

Single-pixel quantum ghost imaging involves the exploitation of non-local photon spatial correlations to image objects with light that has not interacted them and, using intelligent scanning projective masks, reduces detection a single pixel. Despite many applications, extension complex amplitude remains challenging. Here, we reveal necessary interference for phase retrieval is naturally embedded in correlation measurements formed from traditional masks bi-photon imaging. Using this, develop...

Abstract Encoding information in high-dimensional degrees of freedom photons has led to new avenues various quantum protocols such as communication and processing. Yet fully benefit from the increase dimension requires a deterministic detection system, e.g., reduce dependent photon loss key distribution. Recently, there been growing interest using vector vortex modes, spatial modes light with entangled freedom, basis for encoding information. However, is at present no method detect these...

One of the most captivating properties diffraction-free optical fields is their ability to reconstruct upon propagation in presence an obstacle both, classically and quantum regime. Here we demonstrate that local entanglement, or non-separability, between spatial polarisation degrees freedom also experience self-healing. We measured quantified degree non-separability two when propagating behind various obstructions, which were generated digitally. Experimental results show even though...

Abstract Quantum secret sharing is the art of securely information between more than two people in such a way that its reconstruction requires collaboration certain number parties. Here, by taking advantage high‐dimensional Hilbert space for orbital angular momentum and using Perfect Vortex beams as their carriers, proof‐of‐principle implementation quantum scheme presented. This experimentally implemented with fidelity 93.4%, 10 participants dimensions—the highest dimensions to date. The can...

When structured light is propagated through the atmosphere, turbulence results in modal scattering and distortions. An extensively studied example that of carrying orbital angular momentum (OAM), where atmosphere treated as a phase distortion numerical tools extract resulting cross-talk. This approach focuses on itself, perturbed by yet does not easily lend itself to physical insights, fails ask pertinent question: did OAM beam gained or lost come from? Here, we address this forgoing instead...

Abstract In a conventional quantum imaging experiment, the image of object is retrieved directly with single photon camera technology, or computationally single‐pixel detector and pixelated projective masks. all these approaches, resolution dictated by pixel detection devices. this paper, traditional spatial basis pixels replaced modes, exploiting their unique features to enhance fidelity improve reconstruction accuracy through modal sparsity. This approach can be used even when modes are...

Laguerre–Gaussian (LG) modes are solutions of the paraxial Helmholtz equation in cylindrical coordinates and associated with light fields carrying orbital angular momentum (OAM). It is customary to modulate such beams using phase-only vortex profiles, e.g. when increasing (laddering up) or decreasing down) OAM content some given LG mode. However, resulting have been shown be hypergeometric-Gaussian modes, due changing radial amplitudes on propagation. In this work, we show that these fact...

Light's spatial degree of freedom is emerging as a potential resource for myriad applications, in both classical and quantum domains, including secure communication, sensing imaging. However, it has been repeatedly shown that complex medium (atmosphere, optical fibre, turbid media, etc.) can perturb the amplitude, phase polarization structured light fields leading to degradation their performance. A promising solution this use invariant modes whom appears transparent. While creation...

Tailoring the degrees of freedom (DoF) light for a desired purpose, so-called structured light, has delivered numerous advances over past decade, ranging from communications and quantum cryptography to optical trapping, microscopy. The shaping toolkit traditionally been linear in nature, only recently extended nonlinear regime, where input beams overlap crystal generate output beam. Here we show how enhance fidelity by aligning with light. Using orbital angular momentum modes difference...