Spin-orbit photonics for quantum simulations

by Mr Francesco Di Colandrea (Universit`a degli Studi di Napoli Federico II)

Wednesday 23 Nov 2022, 11:00 → 12:00 Europe/Zurich

Light represents a powerful tool for a plethora of promising applications, ranging from quantum communications to in-formation processing, and metrological tasks. Manipulating the spatial and vectorial structure of photons in a controlledway lies at the basis of simulating quantum dynamics with light. A prototypical example of quantum evolution is providedby quantum walks (QWs), modeling the discrete-time dynamics of a particle moving on a lattice. QWs have been profi-ciently employed in the context of topological physics, transport phenomena, and quantum computation. The standardapproach to photonic simulations of QWs requires a number of optical elements (or equivalently optical operations) linearlyincreasing with the number of time-steps. For this reason, photonic implementations of large-scale evolutions have beenmainly limited by optical losses thus far. To overcome this limitation, we propose a new approach to the generation of QWevolutions, realizing hundreds of discrete time-steps within only three liquid-crystal metasurfaces. These are essentiallypatterned waveplates, whose opticaxis orientation is non-uniform in space. By exploiting spin-orbit effects, the diffractiveaction of these metasurfaces mixes circularly polarized optical modes carrying quantized transverse momentum. We succeedto implement unitary transformations equivalent to 320 time-steps of different one-dimensional QW evolutions, far beyondstate-of-the-art experiments. With this setup, we also report the first experimental observation of asymptotic maximalentanglement generation in a dynamically disordered QW. Our platform grants experimental access to ultralong unitaryevolutions while keeping optical losses constant, thus proving particularly fitting for massive multi-photon multi-modequantum simulations. Remarkably, our platform does not limit us to the implementation of standard QW dynamics, butit allows for the simulation of any translation-invariant evolution, permitting to directly design custom energy bands andHamiltonian eigenstates

References

F. Di Colandrea et al., arXiv:2203.15051