Researchers from the University of Pavia, CEA-Leti, and STMicroelectronics have demonstrated a fully integrated quantum frequency processor built entirely on a single silicon chip, according to a paper published in Nature Communications.
The platform relies on frequency-bin encoding, a photonic quantum architecture that offers high dimensionality and compatibility with existing telecommunications networks. Earlier deployments were restricted by the lack of a single platform capable of combining state generation, coherent frequency mixing, and programmable spectral control. The team addressed this restriction by unifying these functions on a 4 × 7 mm² silicon photonic chip.
Hardware integrated directly on the chip includes a microresonator-based biphoton quantum frequency comb source, a pump-rejection filter, high-speed phase modulators, and a four-channel line-by-line pulse shaper. These integrated elements allowed the team to generate and coherently manipulate high-dimensional frequency-bin entangled states without relying on off-chip optical routing.
Experimental tests demonstrated tunable frequency beamsplitters operating with success probabilities above 94% and fidelities exceeding 99.9%. The processor also synthesized single-qubit gates and directed two-photon quantum walks across the device. For state verification, the researchers performed on-chip frequency-bin quantum state tomography on an entangled Bell-state, recording a fidelity of 95.7(3)%.
The collaboration included researchers Sara Congia, Leopold Virot, Elena Rovetta, Matteo Galli, Massimo Borghi, Antonio Fincato, Frederic Boeuf, and Daniele Bajoni. CEA-Leti provided wafer-scale characterization and dicing, while funding came from the European Union’s STARLight and HyperSpace projects alongside Italy's PNRR MUR project NQSTI. The peer-reviewed paper was accepted on August 19, 2026, and published on September 15, 2026.
