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Academician of the Chinese Academy of Sciences and Professor Guo Guangcan of the University of Science and Technology of China, the Key Laboratory of Quantum Information of the Chinese Academy of Sciences made a series of progresses in the field of orbital angular momentum (OAM) photon quantum frequency conversion research. The team led by Shi Baosen, the laboratory professor, realized for the first time in the world. The frequency up-conversion of OAM single photon, OAM entangled photon, and hybrid entangled photons composed of OAM and polarization proves that the quantum coherence of the single photon and the entanglement properties of the photon pair remain unchanged during the frequency conversion. The main research results were published in "Light: Science and Applications" [Light: Sci. & Appl. 5, e16019 (2016)] and in the August 29th Physical Review Letters [Phys. Rev. Lett. 117, 103601 ( 2016)]. The first author of the paper was postdoctoral Zhou Zhiyuan.
The OAM beam has important applications in precision measurement, micro-particle trapping and manipulation, and basic physics research. At the same time, OAM-based optical information processing has become a research hotspot in the field of optical communications due to its large channel capacity. The construction of high-dimensional quantum networks based on OAM coding is an important research direction in the field of quantum information, and has made many breakthroughs in recent years. For example, Shi Baosen's group first realized OAM single photon in the world [Nat. Commun. 4]. Quantum storage in 2527 (2013)] and OAM entanglement [Phys. Rev. Lett. 114, 050502 (2015)]. In quantum communication, a photon as an information carrier needs to be transmitted in a low-loss communication window, and the physical system as an information storage and processing unit does not normally operate in a communication window, so a quantum interface needs to be established between the two to satisfy the quantum. The basic requirements that information can be stored and transmitted over long distances, and photonic frequency conversion based on non-linear processes is an effective method for establishing quantum interfaces. A converter capable of implementing this function can be called a quantum frequency converter. The basic requirement is that in addition to the ability to transform the frequency of photons as needed, it is even more important that the quantum correlation and coherence properties of the original quantum state cannot be destroyed. Although people have realized the frequency conversion of Gaussian single photons and entangled photons, the frequency conversion of OAM photons and OAM entangled photons can still be implemented and how it is still an "open question".
Professor Shi Baosen of the Key Laboratory of Quantum Information at the Chinese Academy of Sciences and postdoctoral scientist Zhou Zhiyuan have started research on non-linear frequency conversion of OAM beams since 2012 [OL 37, 3270 (2012); PRA 85, 053815 (2012)]. OE 22, 20298 (2014); OE 22, 23673 (2014); J. Opt. Soc. Am. B 32, 407 (2015)], and on this basis made an important breakthrough: they use cyclic nonlinear crystals. As the frequency conversion medium, external cavity resonance technology is used to increase the conversion efficiency. For the first time, the frequency up-conversion of OAM single photon from infrared to the visible band is successfully achieved, and the non-classical correlation of photons and the retention of quantum coherence during frequency conversion are proved. Unchanged, taking a key step in implementing quantum interfaces based on frequency converters [light: Science & Applications 5, e16019(2016)]. Recently, they have taken this technology to a whole new level: for the first time in the world, the OAM entangled photons and the hybrid of OAM and polarized light entangled photons from infrared to visible bands have been converted, and the entanglement properties of photons have been verified. It remains unchanged during conversion [Phys. Rev. Lett. 117, 103601 (2016)]. This series of work is of great significance for implementing the docking and quantum information exchange of OAM quantum networks at different wavelengths.
This series of work has also opened up a new chapter in quantum optics and nonlinear optics, in order to study coherent wavelength conversion of high-dimensional OAM quantum states, upconversion detection of complex spatial light fields under extremely weak light intensity, and preparation of short-wavelength OAM beams. It is of great value. In addition, since infrared image signals have a very important role in remote sensing, night vision, astronomical observation and other fields, high-precision detection of infrared images is particularly important, but the commonly used infrared detection has low accuracy, low resolution, and low detection efficiency. And the equipment is expensive and a series of problems. Up-converting the image signal to the visible band by frequency, using a high-precision, high-sensitivity and low-cost visible band detection device for detection is an effective way to solve the above problems. The series of achievements made by the Shibaosen group is of great value to the construction of infrared signal upconversion detectors and to the detection of infrared image signals, especially weak signals.
This work was funded by the State Fund Committee, the Chinese Academy of Sciences, the Ministry of Science and Technology, and the Center for Quantum Information and Quantum Technology Collaborative Innovation.
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