CAS Center for Excellence in Quantum Information and Quantum Physics: exploring frontiers of quantum physics and quantum technology

Abstract

In 2014, the Chinese Academy of Sciences (CAS) launched its ‘Pioneer Initiative’ program, aiming to make significant contributions to the country's major needs in the nation's development, take the lead in academic excellence at the frontiers of science and technology worldwide, cultivate a national talent pool for innovation, and develop advanced think-tank teams and world-class scientific research institutions. One of the most important initiatives in this ‘Pioneer Initiative’ program is the establishment of Centers for Excellence in innovation that would have substantial influence internationally. The Center for Excellence in Quantum Information and Quantum Physics was established in January 2014 under the directorship of Prof. Jian-Wei Pan, an academician of the CAS. The University of Science and Technology of China (USTC) serves as the main body of innovation and works on major frontier issues of quantum technology, in cooperation with Shanghai Institute of Technical Physics of the CAS, Institute of Semiconductors of the CAS, Institute of Optics and Electronics of the CAS and other domestic research institutions. There are two strategic objectives of the center within about 15 years. One is to build a wide-area quantum communication network, to apply the quantum communication in national defense, government affairs, finance, etc., and to create strategic industries with China taking a leading international role and a next-generation national information-secure ecosystem. The other is to realize coherent manipulation of approximately 100 qubits, to transcend comprehensively the capacity of classical computers in tackling specific problems, and to achieve practical quantum-enhanced precision measurement technologies and finally explore a practical way for universal quantum computers. The center concentrates on quantum information sciences and technologies. Quantum information, including quantum communication, quantum computation and simulation, and quantum metrology, can overcome the bottleneck of classical information technology in ensuring information security, enhancing computing capacity and improving measurement precision. In quantum information and related fields, the constantly emerging frontiers stimulate the revolutionary scientific and technological innovation, and nurture new scientific ideas and technological revolution. The breakthroughs in these fields will satisfy the major requirements for the development of science and technology, social economy and national competitiveness. Quantum key distribution (QKD) overcomes the security risk of classical encryption and, to date, has been proven as the only unconditional secure communication method. It can solve security issues for military, finance, government, business and other sectors. Quantum computers use quantum superposition to store information and parallel processing of information, which has fundamental computing advantages compared with classical computers and has profound influence on both physics and social economy. Quantum metrology will accomplish ultra-high-sensitivity measurements of gravity, time and position, and immensely enhance the accuracy and precision of navigation, medical detection, gravitational wave detection, etc. Developing quantum communication technology aims to build a quantum communication network for the whole country and even on a global scale (Fig. 1). The implementation of a metropolitan quantum communication network can be achieved via fiber, while intra-city network can be maintained via quantum repeaters. In addition to satellite relays connecting any two distant nodes, an ideal route would be formed for a wide-area quantum communication. Roadmap of a wide-area quantum communication technology development. The ultimate goal of quantum computing research is to achieve scalable universal quantum computers beyond the classic computing technology. Therefore, extensive studies are required on major fundamental technical and engineering problems in physical systems such as photons, ultracold atoms, superconducting circuits, solid-state spins, ion traps and topological states. These studies will establish large-scale qubit coherent manipulation technology to realize practical quantum computation and simulation, and quantum metrology. In accordance with the principle of ‘limiting targets, making breakthroughs’, the center focuses research directions on three most promising physical systems: photon and cold atomic systems, molecular systems and solid-state systems. Moreover, the center works on quantum engineering in several well-developed research fields, e.g. wide-area quantum communication. Accordingly, the center is divided into four research divisions. The main research fields of this division include: high-performance single-photon detectors and frequency conversion, multi-photon entanglement, cold-atom quantum storage and quantum repeaters, quantum dots, quantum communication in free-space channel and ultracold atoms in optical lattices. The director is Prof. Jian-Wei Pan, from the USTC, and the joint-director is Prof. Shu-Shen Li, another academician of the CAS, from Institute of Semiconductors of the CAS. Current research programs in this division include: precise electronic and spin-state control, optoelectronic coupling and integration, and quantum information device design, integration and implementation in molecular systems; molecule-scale doping and precise interface control; molecule-scale energy conversion and quantum coherence effects. The division director and joint-director are Prof. Jin-Long Yang and Prof. Yi Luo, respectively, both from the USTC. This division focuses the main research fields in integrated quantum information-processing devices, semiconductor quantum-dot quantum information-processing devices, solid-state node-based quantum network, spin-based solid-state quantum information processing, N-doped diamond-based single-spin quantum computing and superconducting quantum computing. The division director and joint-director are Prof. Guang-Can Guo and Prof. Jiang-Feng Du, both academicians of the CAS and from the USTC. This division aims at: comprehensive localization of high-performance single-photon sources, single-photon detectors and other core quantum communication devices; establishment of a practical fiber quantum communication network over thousands of kilometers; high-rate satellite-ground quantum communication and connecting ground fiber quantum communication networks with the Quantum Science Satellite. The division director is Prof. Cheng-Zhi Peng, from the USTC, and the joint-director is Prof. Jian-Yu Wang, from Shanghai Institute of Technical Physics, CAS Quantum teleportation of single-photon spin and orbital angular momentum: the photon with orbital angular momentum travels forward in a helix; the spin angular momentum carried by the photon is represented by the arrow. 2) Realization of 2D spin-orbit coupling for Bose–Einstein condensate [Science 354, 83 (2016)]. Spin-orbit coupling is one of the fundamental effects in quantum physics, playing a central role in many exotic quantum phenomena such as spin-Hall effect and topological insulators. With the development of ultracold atomic physics, engineering spin-orbit couplings within ultracold quantum gases has become frontline research in the field of quantum simulation. The 1D spin-orbit coupling in ultracold quantum gases has been realized and gained many advances. But realizing 2D spin-orbit coupling and exploring more exotic topological quantum matter and phase transitions are still the hard challenges. Prof. Jian-Wei Pan and his colleagues Shuai Chen and Youjin Deng in USTC, together with Prof. Xiong-Jun Liu in Peking University, have teamed up to study this question. They have theoretically proposed a new scheme and experimentally realized 2D spin-orbit coupling within a Bose–Einstein condensate created in optical lattices. The new system has also proved to be topologically non-trivial, opening a new way to study the exotic topological quantum matter in the field of quantum simulation with ultracold quantum gases. Schematic of the experimental setup. 4) First experimental demonstration of generation, manipulation and detection of spin-qubit entangled states of ultracold atoms in optical lattices [Nature Physics 12, 783 (2016)]. Coherent manipulation of multiple qubits is the core technology of quantum information processing. The state-of-the-art experiments from around the world manipulate maximally about 10 qubits in an entangled state, but simultaneous manipulation of tens or even hundreds of qubits is required for practical quantum computation systems in the future. Therefore, there remain significant physical and technical challenges along the way towards practical quantum information processing. Ultracold atoms trapped in optical lattices form one ideal system for solving this crucial problem. Prof. Jian-Wei Pan, Prof. Zhen-Sheng Yuan and Prof. Yu-Ao Chen substantially enhanced the capability of coherently manipulating ultracold atoms with a series of technological breakthroughs. They, for the first time, prepared, manipulated and detected in parallel about 600 entangled pairs of ultracold atomic spins, taking an important step toward scalable quantum computing. The referees praised the work as paving ‘the way to create larger highly entangled states, such as 1D and 2D cluster states, the main resource for measurement based quantum computing’.(Fig. 4) Three-step scheme for the generation of scalable entangled states in a system of ultracold atoms: (a) creating the configuration of one atom per site in the two-dimensional optical lattice, and establishing an array of aligned spin-entangled pairs; (b) connecting neighboring pairs of entangled atomic spins along the horizontal direction; (c) connecting atomic entanglement chains to realize 2D entangled cluster states. The present work took the important first step of this scheme. (Left) Artistic rendering of the experiments. (Right) Images showing the real-space patterns for various dipole–dipole coupling modes of a zinc-phthalocyanine dye molecular dimer using sub-nanometer resolved spectral imaging technique. (Center) Raman excitations and spectrum. 2) Distinguishing different adjacent molecules by Raman spectroscopy in real space for the first time [Nature Nanotechnology 10, 865 (2015)]. Chemical identification of different materials at nanoscale is an important goal of nanotechnology. Conventional Raman techniques fail to identify microscopic composition and structure of materials at the molecular level, in consequence of the optical diffraction limit. Tip-enhanced Raman spectroscopy (TERS) is a novel surface analysis technique that combines high chemical specificity of Raman spectroscopy with high spatial resolution of scanning probe microscopy. Prof. Zhen-Chao Dong's team has developed an ultra-high-resolution nonlinear TERS technique and used it to chemically distinguish different adjacent molecules within van der Waals contact (about 0.3 nm). Their respective Raman spectra are characterized by molecule-specific vibrational finger-prints, which can clearly resolve molecular ‘identity’ and structure. The work represents an important advance in overcoming chemical identification limits and is of great scientific interest and practical value in any field that requires the identification of composition and structure of materials at the molecular scale (Fig. 6). Applications include but are not limited to surface reactions, heterogeneous catalyzation, molecular devices, and even DNA and protein sequencing. (a) Schematic of TERS. (b) STM image of two porphyrin molecules adsorbed alternately on the Ag step and within van der Waals contact (about 0.3 nm). (c) TERS spectra acquired at the center of the corresponding molecules in (b) together with spectra from simulations. First-time detection of a single-protein molecular magnetic resonance spectrum under ambient conditions [Science 347, 1135 (2015)]. Magnetic resonance is an accurate, fast and non-destructive method for obtaining information about the composition and structure of materials. It has been widely used in fundamental research and medicine. However, the current common magnetic resonance spectrometers receive signals from billions of molecules that provide an imaging resolution of only millimeters subject to detection methods. With nitrogen-vacancy centers in bulk diamond as a quantum probe, Prof. Jiangfeng Du's team has successfully obtained magnetic resonance spectroscopy of a single-protein molecular at room temperature and atmospheric conditions (Fig. 7). Not only does this work enable magnetic resonance technology to study a range of objects from billions of molecules to a single molecule, but ‘room temperature and atmospheric conditions’ ensure the wide use of this technology in life sciences and other fields in the future, making high-resolution and nanoscale magnetic resonance imaging and diagnosis possible. The technology is expected to help researchers explore mechanisms underlying life sciences and material science from a deeper level (of single molecules) and to have a profound significance for physics, biology, chemistry, materials and other disciplines. ‘A milestone toward the goal of imaging individual proteins in living cells in real time’ was the comment in the Perspective in the same issue of Science Magazine. The work was selected in China's Top Ten Scientific and Technological Progress of Higher Education 2015 by the Ministry of Education, and Top Ten Progresses in Chinese Science 2015 by Ministry of Science and Technology of China. Single-protein spin resonance spectroscopy under ambient conditions was achieved using a diamond probe: the green beam is excitation laser and the red beam is the detectable fluorescence signal. Schematic of Beijing-Shanghai Backbone. 2) Successful Launch of ‘Micius’ Quantum Science Experimental Satellite (QUESS): QUESS is one of the first five scientific experimental satellites approved by the CAS. It is undertaken by the USTC, in cooperation with Shanghai Institute of Technical Physics of the CAS, Shanghai Engineering Center for Microsatellites, National Astronomical Observatories of the CAS and the Institute of Optics and Electronics of the CAS, with Prof. Jian-Wei Pan as the chief scientist. ‘Micius’ weighs about 640 kg and will serve for two years, running at a height of about 500 km in a polar orbit (Fig. 9). Currently, ‘Micius’ has entered the scheduled orbit and began a series of on-orbit testing. After the completion of all tests, under the leadership of Prof. Pan, the scientists will have accomplished satellite–Earth high-speed QKD, a wide-area quantum communication network, satellite–Earth quantum entanglement distribution and Earth–satellite quantum teleportation, and other scientific experimental tasks, and in particular will have achieved scheduled scientific mission objectives: experiments on satellite–Earth high-speed QKD and wide-area quantum communication network to achieve breakthrough in applications of space quantum-secure communication; experiments on quantum entanglement distribution and quantum teleportation, and fundamental test of quantum mechanics in space. On 16 August 2016, the quantum scientific experiment satellite ‘Micius’ was successfully launched in Jiuquan Satellite Launch Center. The successful development and launch of ‘Micius’ have enabled China to further enhance its leading position in the field of quantum communication. The satellite will perform a series of quantum science experiments in space and be devoted to moving national security and information technology forward in great leaps by the application of quantum communication technology. The satellites and ‘Beijing–Shanghai Backbone’ will constitute the first infrastructure of a space-ground integrated global quantum network in China, promote further application of quantum communication technology and create a strategic emerging industry. ‘Micius’ will also test the non-locality principle of quantum mechanics over space scales to deepen the understanding of its basic principles and pave the way for an ultimate examination of non-locality. The establishment of an experimental platform for space quantum science will also provide a brand new platform for fundamental tests of quantum foundations and general relativity as well over macro-scales in the future. Yang Yu, School of Physics, Nanjing University Yu: Quantum information is currently attracting much attention since it has significance in fundamental theory and promising applications. The applications are mainly in three areas known as quantum communication, quantum simulation and quantum computation. The center has produced many milestones in the field of quantum communication and quantum simulation. For instance, the longest measurement for device-independent quantum key distribution (MDIQKD) in the world has been realized. This will greatly speed up the application of MDIQKD. Recently, they reported the realization of two-dimensional spin-orbit coupling for Bose–Einstein condensates. This pushes the advance of quantum simulations with cold atoms. Zhen-Yu Zhang, National Lab for Physical Sciences at the Microscale, University of Science and Technology of China Zhang: As the first CAS center for excellence, the center has been serving as an exceptionally effective base for catalysing synergistic, fundamental, and applied research with increasing visibility and leadership on an international scale in a range of vital areas in which the center has emphasis. The center promotes the culture of belonging, enabling every scientist to strive for excellence in his or her own field of research, and for multiplying the impact of the research as a collegial collective. Through the years, the center has made several major visionary strategic plans, resulting in defining breakthroughs in fundamental quantum science as well as quantum information and quantum technology. These milestone achievements cover the full spectra, including photonic, atomic, molecular and solid systems. Xiang-Bin Wang, Department of physics, Tsinghua University Wang: The center focuses on cutting-edge research in quantum technology, especially quantum communication, quantum computation, precise quantum state control and quantum precision measurements. The center and its supporting institutions have a number of significant original scientific contributions. Several world records were created: longest-distance QKD, longest cold-atom quantum storage and most quantum bit entanglement. The center's state-of-the-art research will make considerable contribution to the country and science. The center will be constantly achieving innovation and breakthroughs. Zhang: Judging by the initial eye-catching successes since its inauguration, the center is bound to ‘fly high’ in its excellence and international distinction. It is believed by default and surely a natural expectation that the center will continue to serve as the major national base for China's quantum-related scientific and technological developments as the country competes in and contributes to this ever expanding and enriching field of immense potential. Yu: The center provides a platform for many top scientists in different fields collaborating with each other. Therefore, they can make breakthroughs continuously in interdisciplinary fields such as quantum Wang: The center both and It is and to be a great talent pool for of Ministry of Education, and of National Yu: It is a world leading center in the field of quantum information, which is important for fundamental and practical applications. Zhang: The center up to its and is to many Wang: The center will achieve scientific and create excellence for the Jian-Wei Pan Jian-Wei Pan, is a full of physics at USTC. 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