Important work enables the generation and processing of high-dimensional quantum states in a single spatial mode.

Optical quantum states based on entangled photons are essential for solving questions in fundamental physics and are at the heart of quantum information science. Integrated photonics has recently become a leading platform for the compact, cost-efficient, and stable generation and processing of non-classical optical states. However, so far, integrated entangled quantum sources have been limited to qubits (D = 2).

A passively mode-locked laser was coupled into the integrated micro-ring resonator after being spectrally filtered to excite precisely a single resonance.

Here is demonstrated the on-chip generation of entangled qudit states, where the photons are created in a coherent superposition of multiple high-purity frequency modes, confirming the realization of a quantum system with at least one hundred dimensions, formed by two entangled qudits with D = 10. This introduces coherent manipulation platform with which to control frequency-entangled states, capable of performing deterministic high-dimensional gate operations, using state-of-the-art, yet off-the-shelf telecommunications components,. The platform is validated by measuring Bell inequality violations and performing quantum state tomography.

See: Original work at Nature.com

Related link: The multi-coloured photons that might change quantum information science