Quantum Entanglement of Complex Structures of Photons

P. Tombesi

Robert Fickler, Mario Krenn, Radek Łapkiewicz +2 more

We developed a method to create custom tailored photonic entanglement of complex spatial modes. By taking advantage of the high timing and spatial resolution of an intensified CCD camera, we investigate the properties of the entangled photon pair.

David S. Simon, Gregg S. Jaeger, Alexander V. Sergienko

Yue Wang, Minggui Liang, J Liu +5 more

ABSTRACT The multi‐photon bunching effect, arising from intrinsic bosonic exchange symmetry in path interference, underpins numerous quantum information techniques. However, conventional bunching in real space faces challenges in tailoring complex structured light fields. Here, we leverage dielectric metasurfaces with polarization entanglement to generate conjugated structured photons and achieve active control over nonlocal spin bunching between two photons. In the prepared spin–orbit hybrid entangled state, projective spin measurement on the idler photon nonlocally heralds the creation of a conjugated structured photon in the signal arm, residing on a higher‐order Poincaré sphere. By adjusting the relative phase to alter entanglement properties, continuous control can be achieved from spin bunching to anti‐bunching. Exploiting this phase sensitivity enables reconstruction of the conjugated photon's complex amplitude. This work establishes spin bunching as a paradigm for quantum correlation control and demonstrates metasurfaces as a compact, multifunctional platform for structured photonic quantum state engineering and metrology.

Mario Krenn, Robert Fickler, Marcus Huber +4 more

Photons with complex spatial mode structures open up possibilities for new fundamental high-dimensional quantum experiments and for novel quantum information tasks. Here we show entanglement of photons with complex vortex and singularity patterns called Ince-Gauss modes. In these modes, the position and number of singularities vary depending on the mode parameters. We verify two-dimensional and three-dimensional entanglement of Ince-Gauss modes. By measuring one photon and thereby defining its singularity pattern, we nonlocally steer the singularity structure of its entangled partner, while the initial singularity structure of the photons is undefined. In addition we measure an Ince-Gauss specific quantum-correlation function with possible use in future quantum communication protocols.

Sang-Kyung Choi, Hee Su Park