Room-temperature ultrafast coherent manipulation of spin quantum bits achieved at Dalian Institute of Chemical Technology, Chinese Academy of Sciences
The research team of Kaifeng Wu at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences (1121 group) has made important progress in the study of spin photophysics of quantum dots, and is the first to realize the spin coherent manipulation of colloidal quantum dots prepared by low-cost solution method at room temperature. This achievement is of great significance in the fields of quantum information science and ultrafast optical coherent manipulation.
Quantum information technology is a technology that represents information in the quantum state of microscopic particles (or quasiparticles) and uses the principles of quantum mechanics for information storage, transmission and processing. Coherent manipulation of spin quantum bits in solid-state materials is one of the important ways to realize quantum information technology. Currently, the relevant solid-state systems reported include epitaxially grown quantum dots and "point-defect" materials (e.g., diamond color centers). However, epitaxially grown quantum dots are complicated and expensive to prepare, and their spin manipulation generally requires liquid helium temperature. Although room-temperature coherent manipulation of "point-defect" spins has been achieved, it is a great challenge to produce such materials in a scalable and controlled manner. Therefore, the realization of coherent spin manipulation of low-cost materials at room temperature will have a profound impact on the development of quantum information technology.
Kaifeng Wu's research team has been working on ultrafast photophysics and photochemistry of colloidal quantum dots. These quantum dots can not only be prepared macroscopically in solution by relatively mild chemical methods, but also have strong domain-limiting effects and precisely tunable properties such as photoelectricity and spin. In particular, the recent emergence of lead-halide chalcogenide quantum dots, with its spin-orbit coupling effect, is particularly conducive to the efficient injection of spin polarization by optical methods, while its strong light-matter interaction can promote the optical coherent manipulation of spin. The team also recently observed the systemic quantum beat frequency of excitonic spins in CsPbI3 chalcogenide quantum dots and resolved its physical mechanism (Nat. Mater. 2022).
In this work, considering the complex exciton splitting and optical orientation behavior due to the electron-hole exchange interaction in quantum dots, the team innovatively prepared single-hole spin polarization states of chalcogenide quantum dots and realized the room-temperature coherent manipulation based on the self-developed multi-pulse femtosecond magneto-optical technique. By chemically modifying an anthraquinone molecule on the surface of CsPbI3 quantum dots, the team captured the photogenerated electrons of the quantum dots at the sub-picosecond scale and burst the electron-hole exchange interaction to obtain a 100-picosecond hole spin at room temperature, which undergoes Larmor progression under an applied magnetic field. The coherent manipulation of the quantum state of the hole spin was successfully achieved by using a sub-bandgap photon pulse to generate a pseudo-field with optical Stark effect. Considering that the spin coherence lifetime is on the order of 100 picoseconds, the researchers can in principle perform thousands of effective manipulations before the spin decoherence with a laser pulse on the order of 100 femtoseconds (about 0.1 picoseconds).
The article, titled "Room-temperature coherent optical manipulation of hole spins in solution-grown perovskite quantum dots," was recently published in Nature Nanotechnology. The co-first authors of this work are Dr. Xu-Yang Lin and Dr. Yao-Yao Han, Ph.D. students in our 1121 group. The work was supported by the Young Team Program for Stable Support of Basic Research, the National Key Research and Development Program, the National Natural Science Foundation of China, and the Innovation Fund of the Institute of Chemical Physics of the Chinese Academy of Sciences. (Text/Image: Xuyang Lin and Yaoyao Han)
Article Link：
http://www.nature.com/articles/s41565-022-01279-x
