“…… Based on the above presentations, we can roughly describe the popular concept of a quantum entangled state, that is, two particles that become supermates have a certain connection even after separation, and this mysterious connection ignores distance. For example, if two particles are separated by 100,000 light-years, as long as the spin of one of the particles is observed to be to the right, then even if the spin of the other particle is 100,000 light-years away, it can be immediately determined that the spin of the other particle is to the left, or if one particle moves upward, the other is moving downward. So, this way of transmitting information is the basic principle that I am going to talk about today, that is, quantum communication technology based on quantum entangled states. ”

"We know that in 1977, the world's first fiber-optic communication system was put into commercial use in Chicago, USA, at a rate of 45 Mb/s, and by 1979, the transmission loss was reduced to 0.2 dB/km. These two data fully illustrate the advent of the era of optical fiber communication, and many people here will be exposed to optical fiber to a greater or lesser extent when they are communicating or researching. ”

"But ......" Junxin said with a smile on the corner of his mouth, "optical fiber communication is not very safe, because light is a kind of electromagnetic wave, in the process of transmission, there are not only different degrees of loss itself, but also affected by external environmental factors, resulting in different degrees of loss, if someone bends the optical fiber, so that part of the optical signal leaks, and receives it through some corresponding special instruments, then because of the influence of temperature and pressure, the optical fiber loss is originally erratic. As a result, the loss caused by eavesdropping will be drowned in the environmental changes and cannot be detected by the receiver. ”

"In addition, there are many factors that can cause signal leakage, such as the scattering method, which is basically the same, and I won't go into the details of this. Summarizing the possible information security risks of the rising optical fiber communication, there are two shortcomings in optical fiber communication: the first is that the eavesdropping method is simple, and the second is that the eavesdropping signal is not easy to be found. After a pause, Junxin continued, "These are two very serious problems, although we can use software encryption, such as the RSA public-key encryption algorithm invented by Mit a few years ago, which is based on a very simple number theory fact: it is very easy to multiply two large prime numbers, but it is extremely difficult to factor their products, so the product can be exposed as an encryption key. It's so difficult to crack that even the fastest supercomputers can't crack it quickly. We need to think about the future, and in the future there may be breakthroughs in computer technology, such as the development of supercomputer technology and the emergence of quantum computers (which is another topic), etc., which will make the decipherment of software encryption faster and faster, making decipherment possible. ”

"Quantum communication is based on quantum mechanics in physics, according to the principle of inaccuracy, the principle of quantum unclonability and the irreparability of a single photon, when the information is carried by quantum, according to the principle of quantum mechanics, the position of particles in the microscopic world is impossible to be determined, it always exists in different places with different probabilities, which can refer to Schrödinger's cat. And every measurement of an unknown state system will inevitably change the original state of the system. In other words, the measured particles will inevitably change compared to those before the measurement. At the same time, due to the principle of quantum unclonability, the eavesdropper cannot clone any quantum state, so when the eavesdropper eavesdrops on the quantum message, he has to destroy the quantum state particle he intercepts. This is the advantage and inevitability of quantum communication. ”

"Of course, this is just a concept that I have come up with and a possible approach, but I think it is theoretically feasible. I also have some papers on this, and if you are interested, you can read them in the near future. ”

"There are two disciplines in the world that are generally more difficult: one is cryptography and the other is quantum physics. The reason for the difficulty is completely different: cryptography is difficult because there are people in the world who are too smart, and the difficulty lies in the ingenious construction and breathtaking analysis; Quantum physics is difficult because nature is profound and unpredictable, and its microscopic laws are far from people's intuition, and it is difficult to truly understand and grasp them. Bohr once said that behind a profound truth there may be another profound truth, which epitomizes the difficulty of quantum mechanics. The combination between the two is indeed a skillful existence. ”

………………

"Professor Paley, it's an honor to meet you!" After the rush of questions, Junxin followed the staff to the backstage, where Professor Quillen and Professor Paley were already sitting opposite each other waiting for Junxin.

"Don't dare to be, don't dare to be!" Professor Paley put down the teacup in his hand, smiled and said two times in a row, "Your report today is very wonderful, the method of combining quantum mechanics with communication technology and even computer technology is something I have never thought of before, and this will be a very feasible direction!" ”

"You've won a prize!" Jun Xin said humbly. After consulting almost all the information about Alan Pelly in the Institute for Advanced Study in Princeton, Junxin naturally knows this legendary professor very well. Perhaps he doesn't have the Turing or Neumann ability to structure multiple disciplines to create new ones. But he's definitely the kind of frog-like character who has studied a lot in a certain field. Taishan Beidou in the American computer science community, and even in the world computer science community, is not just talking, he really has such strength and influence.

Professor Alan Pelley may not be very familiar with the creative principles of computer implementation, but he is very good at applying these creative theories. Therefore, he has indeed been at the forefront of the world in the creation of computers, both in theory and actual experimental research.

It is based on this that Junxin attaches much more importance to Alan Pelly than von Neumann, who provided the working principle of the computer. Because he knows the development trend and principles of computers in the future, but he is still confused about how to apply these principles to actual operations. And Professor Alan Paley in front of him is the best among them, which is the main reason why Junxin didn't look for others and ran to Mit alone.