IQC Colloquium featuring Francesco Di Colandrea

Large-scale quantum walks via complex polarization transformations

Francesco Di Colandrea | University of Naples Federico II

Optical losses are the main barrier to photonic simulations of large-scale quantum dynamics. In fact, within the standard approach, the complexity of the setup increases with the extension of the simulated evolution in time. In the case of discrete-time quantum walks, experimental realizations have typically been limited to a few tens of steps, involving at most a hundred modes.

By focusing on different protocols of discrete-time quantum walks, we experimentally demonstrate a photonic circuit technology that compresses multiple time steps into only three liquid-crystal metasurfaces. Exploiting spin-orbit effects, these metasurfaces enable the simultaneous activation of several hundred optical modes from a single localized input, allowing for a precise and efficient reproduction of the target dynamics. Acting as waveplates with artificially patterned optic-axis orientations, the metasurfaces implement space-dependent polarization transformations that mix circularly polarized optical modes carrying quantized units of transverse momentum.

The performance of our circuit is validated for walker dynamics spanning both one-dimensional [1] and two-dimensional [2] lattices, up to 320 and 20 time steps, respectively. The experimental results certify that our setup can process a huge number of modes while maintaining a high level of coherence. In principle, the metasurfaces can be designed for an arbitrarily large walk extension and number of connected modes, by keeping optical losses constant. Our platform thus paves the way to the simulation of extreme quantum dynamics in the multi-photon regime.

[1] F. Di Colandrea, A. Babazadeh, A. Dauphin, P. Massignan, L. Marrucci, F. Cardano, “Ultra-long quantum walks via spin-orbit photonics”, Optica, 10(3), 2023

[2] M. G. Ammendola, F. Di Colandrea, L. Marrucci, F. Cardano, “Large-scale spin-orbit photonic circuits in two dimensions”, arXiv:2406.08652

Biography

Francesco Di Colandrea is a researcher at the University of Naples Federico II and a visiting scientist at the University of Ottawa. His research focuses on the manipulation of structured light for quantum simulations, particularly in the study of topological physics and open quantum systems. His work also extends to quantum communications and the application of machine-learning techniques in optical experiments.

Location

QNC 0101