Twisting entangled photons on a chip

Mirko Lobino, Jeremy L. O’Brien

Hui‐Ming Wang, Mingyuan Chen, Yuan Chen +12 more

F. Zäh, Thomas Feurer

Jieshan Huang, Jun Mao, Xudong Li +11 more

Abstract Quantum vortices of light carrying orbital angular momentum stand as essential resources for quantum photonic technologies. Recent advancements in integrated photonics offer the potential to create and control quantum vortices using fully integrated circuits, eliminating the needs for intricate free-space alignment, modulation, and stabilization of bulky optical elements. However, generating quantum vortices in planar optical waveguides and circuits poses challenges, owing to the complexities of confining and guiding twisted photons, and importantly, the difficulties in preparing quantum superposition and entanglement of vortex states. Here, we report entangled quantum vortex emitters leveraging programmable integrated nanophotonic circuits. These circuits enable the generation and arbitrary control of resilient vortex-entanglement in free space, coherently converting from on-chip path-entanglement by a chip-free space interfacing technology. The emitters are plug-and-play, enabling swift reconfiguration within mere microseconds. Validation of multidimensional genuine entanglement is achieved through quantum tomography and dimension witnesses. Our work demonstrates integrated quantum vortex devices that combine the versatility of on-chip processing quantum information with the robustness of transmitting quantum vortices in free space, opening new avenues for applications in quantum communication, quantum light detection and ranging, quantum computation and storage.

Sophia E. Economou

Haoqi Zhao, Yichen Ma, Zihe Gao +7 more

Quantum technologies, if scaled into a high-dimensional Hilbert space, can dramatically enhance connection capabilities with supporting higher bit rates and ultrasecure information transfer. Twisted single photons, carrying orbital angular momentum (OAM) as an unbounded dimension, could address the growing demand for high-dimensional quantum information encoding and transmission. By hybrid integration of two-dimensional semiconductor WSe_{2} with a spin-orbit-coupled microring resonator, we demonstrate an integrated tunable twisted single photon source with the ability to precisely define and switch between highly pure spin-OAM states. Our results feature a single photon purity of g^{(2)}(0)∼0.13 with a cavity-enhanced quantum yield of 76% and a high OAM mode purity up to 96.9%. Moreover, the demonstrated quantum-chiral control can also enable new quantum functionality such as single photon routing for efficient quantum information processing on chip.