Short answer: Thin-film lithium niobate (TFLN) is an integrated photonics platform with strong electro-optic and nonlinear coefficients, low optical loss and fast modulation. A 2022 Light: Science & Applications paper used a TFLN phase modulator to shift the frequency of single photons by up to plus or minus 641 GHz and to compress their bandwidth more than eighteen-fold. Two review articles, from 2024 and 2025, survey the platform. These are laboratory demonstrations and reviews, not deployed systems.
Why lithium niobate
The 2025 review in Advanced Photonics ("Thin-film lithium niobate quantum photonics: review and perspectives") says photonics is attractive for quantum technologies because of high-fidelity qubits and room-temperature signal processing. It notes that integrated photonics is expected to move from few-photon architectures toward systems that generate and process tens, possibly hundreds, of photons. Each integrated platform has its own advantages and limitations, the authors say, and TFLN has recently emerged as a strong contender thanks to its low loss, large electro-optic and nonlinear coefficients, broad transparency window and ultra-fast modulation. The review examines recent developments and identifies directions and challenges for future work.
A general electro-optics review
The 2024 arXiv review "Integrated electro-optics on thin-film lithium niobate" (Hu and coauthors, April 2024) describes electro-optics as the bridge between electronics and photonics. The authors say TFLN offers strong electro-optic coupling, ultra-low optical loss and high microwave bandwidth, and that tight confinement and compatibility with nanofabrication allow reconfigurability and scalability. They also say the platform lets researchers explore physics such as photonic non-Hermitian synthetic dimensions, active topological physics and quantum electro-optics. These are the review authors' framing, and the paper is a preprint listing.
Controlling the color of single photons
The 2022 paper in Light: Science & Applications addresses a practical problem. Manipulating the frequency and bandwidth of nonclassical light matters for frequency-encoded or multiplexed quantum computing, communication and networking, and for bridging spectral mismatch between quantum systems. Doing so needs a strong nonlinearity mediated by light, microwaves or acoustics, which is hard to realize efficiently, with low noise, on a chip.
The authors demonstrate both frequency shifting and bandwidth compression of heralded single-photon pulses with an integrated TFLN phase modulator. They report what they describe as record-high electro-optic frequency shearing of telecom single photons over a terahertz range, plus or minus 641 GHz (5.2 nm), which enables high-visibility quantum interference between frequency-nondegenerate photon pairs. They also operate the modulator as a time lens and demonstrate more than eighteen-fold bandwidth compression, from 6.55 nm to 0.35 nm. They conclude the results show the viability and promise of on-chip quantum spectral control for scalable photonic quantum information processing, which is an outlook.
Limits
The experimental result is a single-photon spectral control demonstration, not a quantum computation or network. "Record-high" is the authors' claim as of 2022. The reviews describe progress and challenges, and the abstracts do not give a roadmap or timeline.
FAQ
What is TFLN?
Thin-film lithium niobate, a platform the 2025 review describes as low loss with large electro-optic and nonlinear coefficients.
What did the 2022 experiment achieve?
Frequency shifts of plus or minus 641 GHz and bandwidth compression from 6.55 nm to 0.35 nm, per the authors.
Why shift photon frequency?
To connect quantum systems with mismatched spectra and to support frequency-encoded protocols, the authors say.
Is this a quantum computer?
No. The sources report components and reviews.
Are the reviews peer reviewed?
The 2025 review is in a journal. The 2024 one was read as an arXiv listing.
All field notes