中奥科学家合作首次实现了复杂量子隐形传态 诸平 中国科学家 和 奥地利科学家首次成功地转移了三维量子态。在未来的量子计算机中，高维隐形传态将发挥重要作用。 来自奥地利科学院和维也纳大学的研究人员，与中国科学技术大学的量子物理学家一起，他们成功地实现了复杂高维量子态的远程传输。相关研究结果于2019年8月15日在《物理评论快报》（ Physical Review Letters ）杂志发表——Yi-Han Luo, Han-Sen Zhong, Manuel Erhard, Xi-Lin Wang, Li-Chao Peng, Mario Krenn, Xiao Jiang, Li Li, Nai-Le Liu, Chao-Yang Lu, Anton Zeilinger, and Jian-Wei Pan.Quantum Teleportation in High Dimensions.Phys. Rev. Lett., 2019,123, 070505. DOI: 10.1103/PhysRevLett.123.070505 – Published 15 August 2019.更多信息请注意浏览原文或者相关报道。 Complex quantum teleportation achieved for the first time by University of Vienna Austrian and Chinese scientists have for the first time succeeded in transferring three-dimensional quantum states (symbolic image). Credit: ÖAW/Harald Ritsch Austrian and Chinese scientists have succeeded in teleporting three-dimensional quantum states for the first time. High-dimensional teleportation could play an important role in future quantum computers. Researchers from the Austrian Academy of Sciences and the University of Vienna have experimentally demonstrated what was previously only a theoretical possibility. Together with quantum physicists from the University of Science and Technology of China, they have succeeded in teleporting complex high-dimensional quantum states. The research teams report this international first in the journal Physical Review Letters . In their study, the researchers teleported the quantum state of one photon (light particle) to another distant one. Previously, only two-level states (qubits) had been transmitted, i.e., information with values 0 or 1. However, the scientists succeeded in teleporting a three-level state, a so-called qutrit. In quantum physics , unlike in classical computer science, 0 and 1 are not an 'either/or' – both simultaneously, or anything in between, is also possible. The Austrian-Chinese team has now demonstrated this in practice with a third possibility 2. Novel experimental method It has been known since the 1990s that multidimensional quantum teleportation is theoretically possible. However: First, we had to design an experimental method for implementing high-dimensional teleportation, as well as to develop the necessary technology, says Manuel Erhard from the Vienna Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences. The quantum state to be teleported is encoded in the possible paths a photon can take. One can picture these paths as three optical fibers. Most interestingly, in quantum physics a single photon can also be located in all three optical fibers at the same time. To teleport this three-dimensional quantum state, the researchers used a new experimental method. The core of quantum teleportation is the so-called Bell measurement. It is based on a multiport beam splitter, which directs photons through several inputs and outputs and connects all optical fibers together. In addition, the scientists used auxiliary photons—these are also sent into the multiple beam splitter and can interfere with the other photons. Through clever selection of certain interference patterns, the quantum information can be transferred to another photon far from the input photon, without the two ever physically interacting. The experimental concept is not limited to three dimensions, but can in principle be extended to any number of dimensions, as Erhard emphasizes. Higher information capacities for quantum computers With this, the international research team has also made an important step towards practical applications such as a future quantum internet, since high-dimensional quantum systems can transport larger amounts of information than qubits. This result could help to connect quantum computers with information capacities beyond qubits, says Anton Zeilinger, quantum physicist at the Austrian Academy of Sciences and the University of Vienna, about the innovative potential of the new method. The participating Chinese researchers also see great opportunities in multidimensional quantum teleportation. The basics for the next-generation quantum network systems is built on our foundational research today, says Jian-Wei Pan from the University of Science and Technology of China. Pan recently held a lecture in Vienna at the invitation of the University of Vienna and the Academy. In future work, the quantum physicists will focus on how to extend the newly gained knowledge to enable teleportation of the entire quantum state of a single photon or atom. ABSTRACT Quantum teleportation allows a “disembodied” transmission of unknown quantum states between distant quantum systems. Yet, all teleportation experiments to date were limited to a two-dimensional subspace of quantized multiple levels of the quantum systems. Here, we propose a scheme for teleportation of arbitrarily high-dimensional photonic quantum states and demonstrate an example of teleporting a qutrit. Measurements over a complete set of 12 qutrit states in mutually unbiased bases yield a teleportation fidelity of 0.75(1), which is well above both the optimal single-copy qutrit state-estimation limit of 1 / 2 and maximal qubit-qutrit overlap of 2 / 3 , thus confirming a genuine and nonclassical three-dimensional teleportation. Our work will enable advanced quantum technologies in high dimensions, since teleportation plays a central role in quantum repeaters and quantum networks.
PNAS:中国研究人员成功实现 反事实量子通讯 诸平 Credit:CC0 Public Domain 据物理学家组织网 ( Phys.org ) 2017 年 5 月 5 日报道，中国研究人员成功实现直接反事实量子通讯。在非直观的量子领域（ non-intuitive quantum domain ） , 反事实性（ counterfactuality ）现象被定义为是一种从一个地点到另一个地点转移的量子态，而在此之间没有任何量子和经典粒子的传输。反事实性在两个地点之间需要一种量子通道 , 这意味着量子微粒穿过此通道的可能性极小 , 如果能够穿过 , 会丢弃此系统的运行 , 而开启一个新运行系统。因为波粒二象性使其运作，但是波粒二象性是粒子物理学的基础 : 粒子可以单独由波函数来描述。 由物理学家很好理解为一个可行的方案 , 反事实通信理论方面的研究已经在各种期刊上有所报道 , 但直到最近 , 一直没有反事实通讯现象的实际示范。现在 , 来自中国科技大学上海分校 （ University of Science and Technology of China , Shanghai 201315 ）和合肥分校（ University of Science and Technology of China , Hefei, Anhui 230026 ） 以及清华大学（北京）的中国科学家的合作，已经设计和实验测试了一种反事实的通信系统 , 用 嵌套式的量子芝诺效应（ quantum Zeno effect ） ，成功地将一张单色位图从甲地传到乙地。此项研究结果于 2017 年 3 月 29 日在《美国国家科学院院刊》（ Proceedings of the National Academy of Sciences , PNAS ）网站发表—— Yuan Cao , Yu-Huai Li , Zhu Cao , Juan Yin , Yu-Ao Chen , Hua-Lei Yin , Teng-Yun Chen , Xiongfeng Ma （ 马雄峰 ，清华 ） , Cheng-Zhi Peng , Jian-Wei Pan （ 潘建伟，院士 ） . Direct counterfactual communication via quantum Zeno effect . PNAS 2017 ; published ahead of print April 25, 2017, DOI:10.1073/pnas.1614560114 Significance Recent theoretical studies have shown that quantum mechanics allows counterfactual communication, even without actual transmission of physical particles, which raised a heated debate on its interpretation. Although several papers have been published on the theoretical aspects of the subject, a faithful experimental demonstration is missing. Here, by using the quantum Zeno effect and a single-photon source, direct communication without carrier particle transmission is implemented successfully. We experimentally demonstrate the feasibility of direct counterfactual communication with the current technique. The results of our work can help deepen the understanding of quantum mechanics. Furthermore, our experimental scheme is applicable to other quantum technologies, such as imaging and state preparation. Abstract Intuition from our everyday lives gives rise to the belief that information exchanged between remote parties is carried by physical particles. Surprisingly, in a recent theoretical study , quantum mechanics was found to allow for communication, even without the actual transmission of physical particles. From the viewpoint of communication, this mystery stems from a (nonintuitive) fundamental concept in quantum mechanics—wave-particle duality. All particles can be described fully by wave functions. To determine whether light appears in a channel, one refers to the amplitude of its wave function. However, in counterfactual communication, information is carried by the phase part of the wave function. Using a single-photon source, we experimentally demonstrate the counterfactual communication and successfully transfer a monochrome bitmap from one location to another by using a nested version of the quantum Zeno effect. Researchers achieve direct counterfactual quantum communication May 5, 2017 by Christopher Packham report Credit: CC0 Public Domain ( Phys.org )—In the non-intuitive quantum domain, the phenomenon of counterfactuality is defined as the transfer of a quantum state from one site to another without any quantum or classical particle transmitted between them. Counterfactuality requires a quantum channel between sites, which means that there exists a tiny probability that a quantum particle will cross the channel—in that event, the run of the system is discarded and a new one begins. It works because of the wave-particle duality that is fundamental to particle physics: Particles can be described by wave function alone. Well understood as a workable scheme by physicists, theoretical aspects of counterfactual communication have appeared in journals, but until recently, there have been no practical demonstrations of the phenomenon. Now, a collaborative of Chinese scientists has designed and experimentally tested a counterfactual communication system that successfully transferred a monochrome bitmap from one location to another using a nested version of the quantum Zeno effect . They have reported their results in the Proceedings of the National Academy of Sciences . The quantum Zeno effect occurs when an unstable quantum system is subjected to a series of weak measurements. Unstable particles can never decay while they are being measured, and the system is effectively frozen with a very high probability. This is one of the implications of the well known but highly non-intuitive principle that looking at something changes it in the quantum realm. Using this effect, the authors of the new study achieved direct communication between sites without carrier particle transmission. In the setup they designed, two single-photon detectors were placed in the output ports of the last of an array of beam splitters. According to the quantum Zeno effect, it's possible to predict which single-photon detector will click when photons are allowed to pass. The system's nested interferometers served to measure the state of the system, thereby preventing it from changing. Alice transfers a single photon to the nested interferometer; it is detected by three single photon detectors, D 0 , D 1 and D f . If D 0 or D 1 click, Alice concludes a logic result of one or zero. If D f clicks, the result is considered inconclusive, and is discarded in post-processing. After the communication of all bits, the researchers were able to reassemble the image—a monochrome bitmap of a Chinese knot. Black pixels were defined as logic 0, while white pixels were defined as logic 1. The idea came from holography technology. The authors write, In the 1940s, a new imaging technique—holography—was developed to record not only light intensity but also the phase of light. One may then pose the question: Can the phase of light itself be used for imaging? The answer is yes. In the experiment, the phase of light itself became the carrier of information, and the intensity of the light was irrelevant to the experiment. The authors note that besides applications in quantum communication, the technique could be used for such activities as imaging ancient artifacts that would be damaged by directly shining light .
Science 20 November 2009: Vol. 326. no. 5956, p. 1050 DOI: 10.1126/science.326.5956.1050 News of the Week Newsmaker Interview: University Head Zhu Qingshi Challenges Old Academic Ways Richard Stone BEIJING Every autumn when Nobel Prize winners are announced and the world's most populous nation misses outyet againthe mass media and blogs here blame an education system that values rote memorization over creativity. Widespread disaffection is a factor, Chinese state media observed, behind the National People's Congress's decision earlier this month to sack Education Minister Zhou Ji. But true change may come only from the bottom up. In September, the government of Shenzhen, a city in southern China, appointed physical chemist Zhu Qingshi as president of the planned South University of Science and Technology (SUST). Zhu insisted on also being appointed the university's Communist Party secretary, making it clear he would be calling the shots. A Sichuan native, Zhu, 63, graduated from the University of Science and Technology of China here in 1968 (USTC later moved to Hefei) and has been a visiting fellow at several top overseas labs, including the University of Oxford, the University of Cambridge, and the Massachusetts Institute of Technology. Zhu's pioneering research in laser spectroscopy won him election to the Chinese Academy of Sciences at the tender age of 45. He became known as a reformer during his tenure as USTC president from 1998 to 2008. CREDIT: PHOTO COURTESY OF XU WENGE/NDDAILY Shenzhen, near Hong Kong, was the cradle of China's market economy 30 years ago. In its bid to become a paragon of education reform, the city paid nearly $1 billion for the land for SUST's campus, expected to open in 2012 with an enrolment of 1500 undergraduates and 500 graduate students in science and engineeringall on scholarships covering tuition and living expenses. (SUST will launch with a small group of students in temporary digs next year.) In an interview with Science , Zhu explained how he intends to shake up China's university systemwhether the education ministry likes it or not. Q: What did you do in Hefei to earn your reputation as a reformer? Z.Q.: My most important contribution to USTC was not what I did but what I did not do. In the past several years, Chinese universities grew very quickly, buying up land and enlarging enrollments. But teaching staffs were not expanded. We wanted to maintain academic standards, so we rejected this approach. Secondly, the Ministry of Education evaluates teaching and research activities at all universities. Evaluation is a good thing. But the ministry's evaluation now is not a real evaluation; it's a formal exercise. Q: An exercise in wining and dining? Z.Q.: Exactly. The evaluators would come to our university, and we didn't prepare anything special; instead we asked them to observe the professors and students. Q: Did the education ministry appreciate your approach? Z.Q.: No, they did not appreciate it. We didn't get perfect marks, but around 70% of China's universities did. Everybody knows the evaluation has no meaning. Of course, it's connected to funding, and our university got less money from the central government. But we kept a very high level of education and research. Q: In what way will SUST be different from other Chinese universities? Z.Q.: We will abolish rank: what we call debureaucratization of the administration. Q: How will that help? Z.Q.: The main problem in higher education is bureaucratic power. Many professors now pursue bureaucratic rank instead of academic excellence. If you attain a high rank, you get money, a car, research funding. This is why Chinese universities have lost vitality. Q: How will you persuade people to work for SUST rather than top universities like Tsinghua or Beida ? Z.Q.: First, the Shenzhen government promised that we can hire professors at the same salary as professors at Hong Kong University of Science and Technology. That's higher than Beida, even higher than many U.S. universities. Also, SUST will be the first university in China with a significant budget for research. This is something I'm pursuing very hard. We don't want our professors to have to continuously apply for funding. Q: A lot of critics say that China's education system suppresses creativity. At the teaching level, what needs to change? Z.Q.: We feel that the whole year of grade three of high school is wasted just preparing for the Gao Kao . At SUST, we will not enroll students based on Gao Kao results. We will enroll them directly from grade two of high school. Next year, we will take 50 students from grade two. Q: Does the education ministry see your rebel attitude as a threat to its authority? Z.Q.: They might not forbid us to carry out our plan, but they also might not encourage us. There is a danger that our students may not get a diploma issued by the education ministry. My goal is to ensure that my students are accepted by society and get good jobs after they graduate. If I accomplish that, this experiment will be a success. People are looking for a university to challenge the education system and show an effective path for reform. SUST is going to face many problems. I am prepared to be the first to try true education reform, but maybe someone after me will be the first to succeed.
标签: 中国科技大学
