When the students present knew that the topic he was going to talk about was related to quantum mechanics, a large number of liberal arts students were stunned for a while before they listened, because they knew that as long as quantum mechanics was involved, it would definitely be a series of persuasions, which was too difficult to understand.

Liberal arts students are probably most familiar with quantum mechanics as the "Schrödinger's cat", which is both a dead cat and a living cat. Then, after being stunned for a while, can there still exist in two states at the same time, both dead and alive?

The lecture was also broadcast live on the campus forum, and the naughty comments had already begun to "bother".

However, the science and engineering men present were excited, especially the students who specialized in computer science, who were as stable as old dogs and said that they had no pressure.

On the stage, Ye Hua said eloquently:

“…… What we are doing now is a superconducting technology applied to computers, called Josephson knot, and it can be seen from the name that Josephson is a pioneer. It's amazing, superconductivity itself is magical, I try to make it easy to understand, so what is superconductivity? Everyone should know that, simply put, there is no resistance, and the phenomenon of superconductivity was discovered by humans more than a hundred years ago, and it must be a quantum effect, at the microscopic level, because this phenomenon does not occur at the macroscopic level. ”

"CBS Microscopic Theory of Superconductivity...... In order to take care of other non-professional students, let's not delve into what this CBS is, it says that the formation of superconductivity is the formation of two electrons in a metal, and these two electrons have opposite spins and momentum to each other. It can move without loss in the crystal lattice, so there is superconducting current, and on this basis, people have begun to conduct further research, and of course we also have a scientific research team that is studying in depth. ”

"Some people have found that in some special cases, superconductors can pass through current even if there is no voltage, which is not difficult to understand, because there is no resistance, but how is it formed?"

"The middle of the two superconductors is connected by a very thin material, and this material can be an insulator, a normal conductor, or a weakened superconductor, such as a section in the middle to make it a little thinner, in these three cases, as long as the current passes through the superconductor, then there is no need to continue to apply voltage, and the current continues to flow through the device, which is the so-called Josephson junction."

"You may have questions, how can you continue to conduct electricity after insulation? Ay! It's just that, the quantum world is so magical, in the industry's terminology, this is called quantum tunneling effect, also called quantum tunneling effect. ”

"For a quantum, even if it is a hard and dense wall in front of it, it can be uploaded with a very high probability, which is the best interpretation of a wall without airtightness, that is, quantum tunneling."

"This effect is very important, and if there is no quantum tunneling effect, it is likely that the earth would not have the conditions for the birth of life, because the sun will not be so hot, and the radiation inside the sun will reach the outside through the quantum tunneling effect."

"It is worth mentioning that the scientist Josephson, who once again made outstanding contributions, was strange in his later years, not too late, and probably, in middle age, since he saw Bell's inequality, he felt that quantum entanglement was too magical to 'ghostly over-distance effect', and he was fascinated and couldn't extricate himself, and since then he has begun to study telepathy and mind control."

"At that time, physicists thought that this brilliant brain had been ruined by physics, which was a pity."

"When the traditional chip accuracy has been achieved to the extreme, Moore's Law has failed, and the semiconductor industry has come to a standstill, people firmly believe that the next breakthrough is quantum chips and quantum computers."

"So about quantum computers, this is a long story, and there is a lot of professional knowledge involved, here I will briefly talk about the standards set by Diwenson as a scholar for quantum computers, which is the so-called Divinson standard, saying that the realization of quantum computers must have five standards at the same time, which five?"

"Number one: Have well-characterized qubits and be scalable."

"Extensibility means that it can be integrated, and of course we are all familiar with integrated circuits, and good characterization is very important in computer terms, which is that each qubit must be addressable individually."

"Number two: there must be a way to set all qubits to 0 before computation."

"That is, initialization, which is easy to say, but very difficult to do. Today's technology is basically to operate each qubit separately, because there are few, but the question is what happens after more? How do you go about one-click initialization? At present, there is no way, the problem has been found, and solving the problem is the theme of our scientific research department. ”

"Rule 3: There must be a set of universal quantum logic gates."

"What do you mean? We know that in classical computers, the state of a transistor is used to represent 1 or 0, how do you achieve this state? It is the high and low level, and then the operation is carried out through a series of logic gates, which are transistors, and the logic operation can be realized through special arrangement. ”

"For example, if two high levels come over, it represents two 1s, and then passes through an AND gate, and finally outputs a high level, which represents 1, then the overall process is true (1) and true (1) = true (1)."

"Why do computers generate heat? Because the two information 1 of the original two bits became one bit of information after passing through the gate, and one bit was lost, so heat was generated. ”

"Note that the generation of heat is related to the loss of information, and it is the direct cause, and there is no necessary connection between the process and whether it is reversible or not, what does it mean?"

"For example, just now, there is a problem, or there are two levels called, but I don't know the high and low, after passing through a and gate, and a 1 is output, so what is the information of the two inputs?"

"By outputting 1s through the AND gate, you can only input two 1s, so you can easily push out the answer in this process, so it's reversible."

"But why do you say that the door is still irreversible?"

"Just change it, for example, two inputs are called, and the result of the output through the AND gate is 0, so what is the input? It may be 0, it may be 1 above and 0 below, or it may be 0 above and 1 below, so you will find that if you can't determine it, you can't clearly map back to the input one-to-one, and this situation is irreversible. ”

"But 'non-gate' is different, you just tell me the output, no matter what it is, I know that the input is the opposite of the output, so the AND gate is an irreversible door, and the NAND gate is a reversible door."

"What are the characteristics of the reversible door? That is, I will output as much as you input, and there is no loss of information, so no heat will be generated in the process of the computer. ”

"Some students may be questioning, saying how can non-doors not produce heat? How is it possible for an on-current not to produce heat? Could it be that I'm taking a fake physics class? ”

A large number of liberal arts students laughed together in confusion, many of them looked unaware, and some of the sisters didn't care if they understood it or not, anyway, they came to see what the idol in their hearts said.

"Of course, everyone is right about physics, but note that what I'm talking about here is that there is no heat generated by the loss of information in the process of calculation, and the heat generated by the loss of information is the main source of heat generated by the CPU. So we found that as long as the computer is used, the CPU will get hotter and hotter when a large amount of information is transmitted, and this is the reason. ”

Non-professional students, most liberal arts students suddenly looked at each other, everyone is using computers, and they are familiar with electrical products, it is already common sense to know that the CPU of the computer will heat up, but why does it heat up, but many people don't know the reason there, Ye Hua said this and now knows.

"So can we turn the irreversible gate in the classical computer into a reversible door? There are really people who have given several solutions in theory, for example, one is to change the input and output of the logic gate to three, and another is a logical operation called XOR operation, which corresponds to the XOR gate, and the addition of binary is done through it. ”

"XOR gates and AND gates can form a semi-adder, the reversible version of XOR gates is called controlled NOT gates, and a very important quantum logic gate in quantum algorithms is the controlled NOT gate of double qubits, but it should be noted that this is achieved through quantum entanglement, not through traditional circuits."

"Then quantum computers are quantum, not transistors, so there are no circuits."

"Article 4: There must be an effective solution to the problem of decoherence."

"That's the quantum coding principle."

"One last point: you have to be able to measure the qubits to get the information you want."

"This hides a so-called efficiency problem, the famous quantum Schauer algorithm can achieve the desired results in the measurement coherent and long-term, and the unwanted results coherent and cancel. But the process needs to be measured repeatedly to get it, in other words, the more times you measure, the more accurate the result will be, but theoretically you can't give 100% of the correct answer, you can only get infinitely close, so is there a better way to get the answer by calculating the qubits? ”

"This is the research direction that our team is focusing on, and it is also a big mystery that research institutions or teams in the industry around the world are trying to unravel."

"So far, there is no machine in the world that can perfectly meet the above five criteria at the same time, so the research of quantum computers has a long way to go."

On the stage, near the end, Ye Hua looked at the audience and couldn't help but laugh to himself: "Okay, I think today's speech is the most unsuccessful one I have ever spoken, because a large number of people below are drowsy to listen." ”

Suddenly, the audience ushered in a burst of laughter, science and engineering students said that there was no pressure to listen, and if there were liberal arts students next to them, they felt inexplicably proud, so they swelled.

Ye Hua on the stage continued: "Anyway, I prefer to advertise myself as a scientific and technological worker and be proud of it, today's speech is an easy-to-understand popular science speech, in fact, I think that scientific and technological workers or scientists in addition to burying their heads in research, for the general public science popularization is the obligation of our group." ”

"Our country is not good enough to popularize science, I saw some articles about science on the Internet, and when I pulled it to the comment area, the messages I saw were all confused points in, and then left in a daze."

It caused a burst of laughter, Ye Hua said: "This leads to a very bad phenomenon, science gives the people the feeling that it has nothing to do with them, so far away and mysterious, so there are so many comments and messages that are confused." ”

"I don't think it's good for cultivating the scientific interests and hobbies of the masses. In fact, science is very simple, science is also very interesting, very wonderful, only if you understand it, you will find its beauty, it is not mysterious, because you don't understand the mystery of course, after understanding it is actually the same thing, science is a process of seeking truth. ”

"In general, this is a popular science speech, talking about the world's most cutting-edge and popular superconducting technology and quantum computers, which can only be talked about here due to time constraints."

"Superconductivity technology is one of the many technologies of quantum computers, and the research of quantum computers has a long way to go, but if we look at it according to the laws of history, at this point in time, there should be almost a genius god in the scientific field such as von Neumann and Dirac, opening a door for everyone, and I am very much looking forward to the birth of this genius, maybe it is one of the students here, who knows? You must know that we have produced many high-achieving students in the quantum field, such as Mr. Zhang Shousheng. ”

"But I think it's time for such a new god-level figure to appear, we'll wait and see."

……