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The Warsaw team, led by Professor Michał Karpiński of the Quantum Photonics Lab at the University of Warsaw’s Faculty of Physics, is internationally recognized for its work at the intersection of quantum optics and integrated photonics. The group is actively involved in several major European research programs and has a proven track record of innovation in quantum light-matter interfaces, quantum memories, and frequency-domain photonics. Their latest effort aimed to solve a key challenge in photonic quantum technology: producing indistinguishable photons from distinct quantum dots, which naturally emit at slightly different wavelengths.
Quantum dots are widely regarded as promising photon sources due to their on-demand operation and integration potential. However, tuning their emission wavelengths—necessary for photon interference and network synchronization—often relies on nonlinear optical processes that are inefficient and probabilistic.
To explore a more scalable solution, the team used Sparrow Core, Sparrow Quantum’s flagship photonic chip, as the single-photon source. The chip delivers highly pure, indistinguishable single photons using self-assembled InAs QDs embedded in photonic crystal waveguides—an architecture known for exceptional light-matter coupling (>95% β-factor).
By applying serrodyne electro-optic phase modulation, the researchers demonstrated aspectral shift of ±3.5 GHz (0.01 nm) while preserving photon quality. The process was deterministic: every photon experienced the same spectral transformation, unlike nonlinear mixing, where some photons are unconverted.
“For us, this experiment was about finding a clean, reliable way to shift single-photon wavelengths without losing their quantum nature,” said Professor Michał Karpiński of the University of Warsaw. “It was exciting to see that the photons kept their purity and indistinguishability even after modulation. Having access to a stable, high-quality source like the one provided by Sparrow made it possible to focus on the modulation itself, and that made all the difference.”
The experiment, detailed in the peer-reviewed journal Nanophotonics (DOI: 10.1515/nanoph-2024-0550), highlights several key outcomes:
1) Electro-optic phase modulation shifted photon frequencies deterministically, with no measurable degradation in single-photon purity or indistinguishability.
2) The method is scalable across wavelengths (visible to mid-IR) using commercially available modulators.
·3) The integration of QDs with thin-film lithium niobate photonics suggests a clear path toward on-chip implementation.
4) Tunability was demonstrated by varying modulation frequencies from 2.28 GHz to 5.32 GHz, showing flexible control over photon properties.
In summary, the team confirmed that electro-optic spectral shifting preserves key quantum properties: photon purity and indistinguishability remained effectively unchanged before and after modulation, validating Sparrow Core’s resilience under frequency shifting.
This result reinforces Sparrow Core’s position as a building block for scalable photonic quantum systems. By enabling deterministic spectral tuning of single photons, Sparrow empowers developers to synchronize distant sources, implement frequency-bin quantum encoding, and integrate heterogeneous systems into unified quantum networks.
With the University of Warsaw’s work, Sparrow Core has again proven itself as a reliable, high-performance source at the frontier of quantum photonics.
