The team of academician Guo Guangcan of the University of Science and Technology of China has made important progress in the research of optical quantum chips, and has realized the waveguide mode coding quantum logic gate for the first time in the world.
The team's Ren Xifeng research group cooperated with the Dai Daozin team of the School of Optoelectronic Science and Engineering of Zhejiang University/State Key Laboratory of Modern Optical Instruments to achieve the two-bit quantum logic gate operation of the on-chip waveguide mode encoding for the first time, and the results were recently published in the Physical Review Letters.
Image courtesy of Physical Review Letters
Both classical and quantum information applications need to greatly improve the information processing and communication capabilities of photonic chips to meet the growing demand for optical communication and interconnection. In order to achieve large-scale optical quantum systems, multi-photons, multi-degrees of freedom and high-dimensional coding are the inevitable paths. The unique properties of multimode waveguide modes, such as high-dimensional scalability, compactness, and arbitrary coherence conversion with other degrees of freedom, make waveguide mode coding have broad prospects in the field of integrated photonics. Therefore, in recent years, waveguide pattern coding has attracted much attention.
Previously, Ren Xifeng's research group and the Dai Daozin team of Zhejiang University have long cooperated to study silicon-based optical quantum devices and chips, and have made a series of important progress.
In 2016, the team used waveguide mode encoding for quantum information processing for the first time in the world, realizing coherent conversion between waveguide mode, polarization and path coding entanglement states. In 2019, the team realized the preparation of waveguide mode coding entangled light sources for the first time. In 2021, the team will build the world's smallest optical quantum controlled non-(CNOT) gate based on dense waveguide superlattices arrays.
Schematic diagram of photon waveguide mode encoded quantum control non-gate chip, picture from The University of Science and Technology of China
On this basis, the two sides further cooperated in the independent design and development of two new multimode photonic devices such as waveguide mode coupler (TMDDC) and mode attenuator (MMA), which were used to achieve specific mode-dependent coupling and pattern-dependent attenuation functions, and further integrated these new photonic functional devices, showing the two-bit controlled non-gated operation of waveguide mode coding for the first time in the world. The quantum-controlled non-gate in this experiment enables entanglement of two waveguide pattern encoded qubits with an average fidelity of between 0.87 and 0.91.
This achievement paves the way for quantum manipulation of waveguide mode encoding, which can also be used for on-chip multi-degree-of-freedom optical quantum information processing, laying the foundation for the realization of large-scale optical quantum systems. The Reviewers of The Physical Review Express agreed that this was an important research effort and spoke highly of it: "Both newly invented devices, TMDDC and MMA, are important" and "I believe this work will provide the necessary tools in the respective research areas."
Professor Ren Xifeng of the Key Laboratory of Quantum Information of the Chinese Academy of Sciences, Professor Dai Daozin of the School of Optoelectronic Science and Engineering of Zhejiang University/State Key Laboratory of Modern Optical Instruments are the co-corresponding authors of the paper, Feng Lantian, special associate researcher of the Key Laboratory of Quantum Information of the Chinese Academy of Sciences, and Zhang Ming, assistant researcher of Zhejiang University, are the co-first authors of the paper. The work was funded by the Ministry of Science and Technology, the State Foundation Of China, the Chinese Academy of Sciences, Anhui Province and the University of Science and Technology of China.