Frequency-encoded Lithium Niobate Quantum Photonic Integrated Circuit

Description

In October 2019, Google officially announced the achievement of quantum “supremacy” using its latest superconducting quantum processor – Sycamore, solving a specially designed problem (but nothing more) one billion times faster than the best supercomputer on earth. This breakthrough marks a new start of an open contest worldwide to pursue the holy grail of general-purpose quantum computing, which is expected to become the game changer for a variety of industries including cybersecurity and drug discovery. Such realizations, however, will require at least 20 times more quantum bits that can operate in parallel and free of errors.To achieve this ambitious up-scaling goal, integrated photonics has recently emerged as a particularly attractive platform. Photons are excellent quantum information host, featuring long coherence times and high communication speeds. An integrated platform allows large numbers of optical devices to be patterned on a tiny chip, thus providing the much needed compactness, scalability and stability.A major challenge in concurrent quantum integrated photonics is the lack of frequency-domain encoding. As a fundamental property of light, frequency is a natural candidate to create high-dimensional entanglement to further increase the quantum computation power. Frequency encoding, however, has not been possible in popular integrated photonic platforms, e.g. silicon photonics, due to difficulties in achieving efficient and low-loss frequency manipulation simultaneously.The goal of this project is to address this challenge by developing a frequency-encoded quantum photonic platform using lithium niobate (LiNbO3, or LN), which features excellent electro-optic properties and is ideally suited for frequency-domain operations. However, most integrated LN devices to date are tailored for classical applications only. This project will, instead, focus on the critical performance trade-offs from quantum perspectives and develop the key components for a frequency-encoded quantum circuit. This will be achieved leveraging the complementary expertise of the two PIs: PI (HK) has previously demonstrated a range of ultra-high-performance integrated LN photonic devices, which form the device basis of the project; PI (Mainland) has achieved several milestone quantum integrated photonics demonstrations, and will provide strong theoretical and quantum characterization support for this project.The successful accomplishment of this project will create a quantum integrated photonic circuit that could achieve the generation, frequency manipulation and quantum interference of frequency-encoded multi-photon states all in one chip. Such technology could find numerous opportunities in quantum computation, secure communications and precision metrology, which could benefit the broad academic and industrial communities both in China and across the globe.