The quantum age is coming: thin-film lithium niobate quantum chips

     The quantum age, this mysterious new era of science and technology, is coming quietly. In this new era, quantum technology will completely change the way we live and may even subvert our world view. Among the many quantum technologies, the emergence of thin film lithium niobate quantum chips is undoubtedly an important step toward the quantum era.

     Lithium niobate (LiNbO3) is an excellent nonlinear optical material, which is widely used in optical communication, laser technology and other fields because of its excellent electro-optic and acousti-optic properties. Making it into a thin film and applying it to a quantum chip is an important breakthrough for researchers.

     Quantum chips, in simple terms, are tiny devices that can manipulate and read qubits. In a quantum computer, the quantum chip acts like the CPU in a traditional computer and is its core part. Thin film lithium niobate quantum chip is such a forward-looking and groundbreaking BSS63LT1G quantum chip.

     An interdisciplinary team of researchers from Denmark, Germany and the UK is focusing on the best ways to harness photonics and develop a platform that can scale quantum hardware using its properties. To this end, the team developed an integrated photonic platform based on thin-film lithium niobate, a single crystal of which is an important material for light waves and an ideal modulator for low-loss modes.

     The researchers will integrate the photon platform with a deterministic solid-state single-photon source interface based on quantum dots (semiconductor crystals) in a nanophoton waveguide. The resulting photons are processed through low-loss circuits that, according to the researchers, can be programmed at speeds of several thousand Hertz. The researchers point out that fast reprogrammable low-loss optical circuits are key to performing photonic quantum information processing tasks.

     The high-speed platform paves the way for researchers to implement several key photonic information processing functions. The first processing function the researchers observed in their experiments was quantum interference on the chip. The researchers used the Hong-OuMandel (HOM) effect, which occurs when two-photon interference is observed. 

     Another processing feature demonstrated by the team is the integrated single-photon router, which is key for photonic information processing. Researchers have demonstrated a full-chip photonic router for emitting photons from quantum dots. To achieve this, they leveraged the platform's capabilities to integrate a fast phase shifter with a quantum emitter wavelength, demonstrating an integrated single-photon router.

     The team also implemented a general purpose four-mode interferometer consisting of six Mach-Zehnder interferometers and 10 phase modulators, as shown in Figure 2. The programmable multimode quantum interferometer is very important to realize the basic function of photon quantum technology. The researchers also say their interferometer could enable quantum computing advantage experiments or circuits that mimic quantum simulations.

     The emergence of thin film lithium niobate quantum chips has brought new possibilities for the development of quantum technology. First of all, due to the special properties of lithium niobate, this quantum chip has first-class optical performance and electro-optical effect, which can achieve precise control of the quantum state. Secondly, the high stability of lithium niobate makes the quantum chip still maintain stable performance during long-term operation. Finally, the manufacturing process of thin film lithium niobate quantum chip is relatively mature and easy to large-scale production, which is conducive to the rapid promotion and application of quantum technology.

     However, the development of thin film lithium niobate quantum chips still faces some challenges. For example, how to improve the coherence time of quantum bits, how to improve the integration of quantum chips, and how to reduce manufacturing costs need to be further overcome by researchers.

     In general, the emergence of thin film lithium niobate quantum chips marks that we are moving towards a new era of science and technology - the quantum era. This era is very exciting because it is full of infinite possibilities. We have reason to believe that with the continuous development and progress of quantum technology, the world will become a better place in the future.