News on China's scientific and technological development.
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Periodic Drive-Based Operator Propagation in Superconducting Quantum Circuits
The propagation of operators is a new perspective to study the non-equilibrium dynamics of quantum many-body systems. It is closely related to concepts such as the Lieb-Robinson bound and information scrambling in quantum chaotic systems. The fields of condensed matter physics and statistical physics have aroused great interest. The propagation of the operator can be quantified by the out-of-time-order correlator (OTOC), while the OTOC measurement requires the system to evolve backward in time, that is, to reverse the sign of the Hamiltonian, which is very important for quantum simulation. Experiments present great challenges. Periodic actuation (Floquet engineering) can be used to change the coupling between qubits and has been widely used in the coherent control of quantum systems. This method provides a possible way to realize the reverse evolution of quantum many-body systems and measure OTOC.
Recently, researchers from the Q03 group of the Institute of Physics, Chinese Academy of Sciences/Beijing National Research Center for Condensed Matter Physics, Fan Yu, Zhao Shiping, and Xu Kai, research fellows, SC5 group researcher Zheng Dongning, Xiang Zhongcheng, deputy chief engineer, and Beijing Institute of Quantum Information Science Researcher Yu Haifeng Together with others, the OTOC was measured for the first time in a multi-bit superconducting circuit using the periodic drive method, and the propagation properties of the operator were studied.
The experiment was done in a one-dimensional array of 10 superconducting qubits. By precisely regulating the AC flux bias of a specific qubit to control the coupling strength between neighboring bits, the photon quantum walk, reverse time evolution and OTOC measurement of different coupled XY models were successfully demonstrated. In the experiment, Pauli Z and X operators are selected as butterfly operators in OTOC, respectively, and these two operators are mapped into local and non-local fermion operators under the Jordan-Wigner transform. It is experimentally demonstrated that a clear cone-like operator propagation of light can be exhibited in a multi-particle system with a velocity almost equal to the group velocity of a single-photon quantum walk. The OTOC of the Pauli Z operator recovers to its initial value after a rapid decay and finally approaches zero, which describes the athermalization process in the absence of information scrambling. In contrast, for the OTOC of Pauli X, no such information recovery was observed early in evolution, showing the characteristic of information scrambling. These results elucidate different behaviors of OTOCs in near-integrable systems, some of which behave similarly to non-integrable chaotic systems.
This work was recently published as Editor's suggestion in Phys. Rev. Lett. 129, 160602 (2022) under the title "Probing Operator Spreading via Floquet Engineering in a Superconducting Circuit". Doctoral students Zhao Shoukuan and Ge Ziyong (graduated) of the Q03 group and Xiang Zhongcheng, deputy chief engineer of the SC5 group, are the co-first authors. This work was funded by the National Natural Science Foundation of China, the Ministry of Science and Technology, the Beijing Natural Science Foundation, and the Chinese Academy of Sciences Pilot Project.
Cross post of new English captioned documentaries of China's recent sci-tech advancements across various fields:
Positive YouTube channels on China
Not sure where else to put this. Anyway, Condi Rice interviews Kevin Rudd about the US-China relationship. I don't think you understand what the word "Positive" means.
www.sinodefenceforum.com
Scientists from Tsinghua created a meta-imaging sensor that can "realize perfect optical imaging in 3D (实现完美的三维光学成像)".
"Here we propose an integrated scanning light-field imaging sensor, termed a meta-imaging sensor, to achieve high-speed aberration-corrected three-dimensional photography for universal applications without additional hardware modifications."
"Using the sensor, we achieve high-performance photography up to a gigapixel with a single spherical lens without a data prior, leading to orders-of-magnitude reductions in system capacity and costs for optical imaging."
"Moreover, high-density accurate depth maps can be retrieved simultaneously, facilitating diverse applications from autonomous driving to industrial inspections."
The lead scientist first brough up the idea of "self adaptive digital optics" in 2021 in an paper published on Cell. Now the team has integrated everything in a single imagine chip that can be used in almost all imaging applications, without modifying the existing imaging system.
Paper published in English (not paywalled at the moment):
News release in Chinese:
"Here we propose an integrated scanning light-field imaging sensor, termed a meta-imaging sensor, to achieve high-speed aberration-corrected three-dimensional photography for universal applications without additional hardware modifications."
"Using the sensor, we achieve high-performance photography up to a gigapixel with a single spherical lens without a data prior, leading to orders-of-magnitude reductions in system capacity and costs for optical imaging."
"Moreover, high-density accurate depth maps can be retrieved simultaneously, facilitating diverse applications from autonomous driving to industrial inspections."
The lead scientist first brough up the idea of "self adaptive digital optics" in 2021 in an paper published on Cell. Now the team has integrated everything in a single imagine chip that can be used in almost all imaging applications, without modifying the existing imaging system.
Paper published in English (not paywalled at the moment):
News release in Chinese:
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50 minute CCTV documentary about recent key Chinese advances in telecom and semiconductor industries, ENG captions available. Domestic optical fibre, 5G, 7 nm chip manufacture, FOLED, image recognition/surveillance, automation and smart logistics, cybersecurity are the topics covered.
Challenges and strategies in high-accuracy manufacturing of the world’s largest SiC aspheric mirror
Abstract
In the process of manufacturing the world’s largest silicon carbide (SiC) aspheric mirror, the primary difficulties are mirror blank preparation, asphere fabrication, and testing, as well as cladding and coating. Specifically, the challenges include the homogeneity of the complicated structure casting, accuracy and efficiency of the fabrication process, print-through effect, fidelity and precision of test procedure, stress and denseness of cladding process, the dynamic range of interferometric measurement, and air turbulence error due to the long optical path. To break through such a barrier of difficulties, we proposed the water-soluble room temperature vanishing mold and gel casting technology, homogeneous microstructure reaction-formed joint technology, nano-accuracy efficient compound fabrication, gravity unloading technology, high-denseness low-defect physical vapor deposition (PVD) Si-cladding technology, test data fusion method, and time-domain averaging method, etc. Based on the proposed technologies and methods, we have accomplished the world’s largest SiC aspheric mirror with a size of ⌀4.03 m. The impressive performance of the SiC aspheric mirror is validated by the characteristics of the fabricated SiC aspheric mirror. The aerial density of the SiC blank is less than 120 kg/m2, surface shape test accuracy is better than 6 nm RMS, thickness inhomogeneity of the cladding layer is less than 5%, and the final surface figure error and roughness are 15.2 nm RMS and 0.8 nm RMS, respectively.
This could be used to develop big EUV mirrors.