Quantum features of structured light

Yuan Qin, Zi Wang, Qiang Liu +1 more

Quantum–classical analogy reveals the shared mathematical framework and dynamical physical behaviors between quantum and classical systems. This work reviews structured light as a versatile platform for realizing such analogies. Theoretical mappings between quantum states and optical modes are summarized, followed by representative cases including entanglement state, cat state, coherent state, and squeezed state, where quantum features are emulated through tailored amplitude, phase, and polarization structures. Applications in quantum-inspired communication, teleportation, random walks, and billiard are further discussed. This work provides a systematic overview of the connections between quantum phenomena and classical optics and offers methodological guidance for future photonic implementations.

Sintayehu Tesfa

Alessio D’Errico

The manipulation of the spatial structure of a light beam has many application in both classical and quantum physics. The possibility to exploit high dimensional degrees of freedom carried by a light beam can be employed, among the various applications, for simulating the dynamics on quantum particles in multidimensional spaces. Coupling these degrees of freedom, like the orbital angular momentum or the transverse linear momentum, with the polarization of light (also associated with the spin) allows to implement quantum walks on one and two dimensional lattices. This work presents a series of experiments where these implementations of photonic quantum walks were realized exploiting patterned liquid crystal devices. In particular, the experimental setup allows to investigate interesting effects of the non-trivial topological features of the simulated processes, and test methods for the experimental measurement of topological invariants. This research has also led to the introduction of a novel method of characterizing unknown structured light beams and to the study of the stability of polarization singularities in laser beams.

Pedro Ornelas, Tatjana Kleine, André G. de Oliveira +3 more

Structured light in the quantum regime has garnered considerable attention due to the opportunities it offers when mixing light's internal degrees of freedom, for high-dimensional and multi-dimensional quantum states of light. A popular example is to harness polarisation and spatial entangled photons with a shared topological invariant that is robust against numerous families of noisy quantum channels. Yet, producing such states with high purity and adaptability remains challenging. Here we introduce a compact, self-locking Mach-Zehnder interferometer that integrates digital spatial light modulators with static beam displacers to map spatial-mode entanglement from a parametric down-conversion source onto topological entanglement with high fidelity. The device also mimics the action of a reprogrammable controlled-unitary gate, digitally driven by the spatial light modulator. This approach is an enabling platform and provides a practical route to generating reliable, high-purity quantum-structured light with topological features, both at the single-photon level and as entangled states, a direction of growing topical interest.

Andrew Forbes, Fazilah Nothlawala, Adam Vallés

S. Chua