(Foreword)

New research, new panels.

(Text)

September 7, 2021 at 2:45 p.m.

Professor Wu carefully wrote a large number of explanations of physical terms on the blackboard. The students in the classroom were struggling to write and copy the contents of the blackboard. Every time Professor Wu picked up the blackboard eraser, there was a noise in the classroom.

Cui Li also kept copying the content on the blackboard: "Cheng Yin, why don't you copy it?" Don't expect to copy my notebook. ”

I glanced at Cui Li: "Look at your stingy appearance, if you don't copy it, you won't copy it." ”

"Don't you know, it is said that many people can't pass Professor Wu's quantum physics course, and they can't pass the make-up exam, and in the end they can only make up for other credits!" Cui Li lowered his voice.

While speaking, Professor Wu picked up the blackboard eraser again, and Cui Li continued to write in his notebook: "I can't tell you anymore, I finally caught up with it before, and now it's going to be slow again." ”

Indeed, Professor Wu's class is different from other professors' classes, he doesn't say anything before class, first write all the content of today's class on the blackboard, regardless of whether the students below have copied it or not, and use the blackboard eraser to clear it word for word.

Professor Wu turned around and looked at us: "Students, can anyone tell me what is the main difference between quantum mechanics and classical mechanics that we talked about in the last class?" ”

Professor Wu's gaze scanned the entire classroom, and most of the students began to rummage through their previous notes.

"Can any student answer this question quickly?" Professor Wu's gaze finally fell on me.

Hey, I can't hide from it.

I slowly stood up, and the eyes of the class suddenly converged on me. I looked at Professor Wu and explained: "[1] One of the main differences between quantum mechanics and classical mechanics is the place of measurement processes in theory. In classical mechanics, the position and momentum of a physical system can be determined and predicted with infinite precision. At least theoretically, the measurement has no effect on the system itself, and can be carried out with infinite precision. In quantum mechanics, the measurement process itself has an impact on the system.

To describe the measurement of an observable quantity, it is necessary to linearly decompose the state of a system into a linear combination of a set of eigenstates of the observable quantity. The measurement process can be seen as a projection on these eigenstates, and the measurement result is the eigenvalue corresponding to the eigenstate being projected. If, for an infinite number of copies of the system, each copy is measured once, we can obtain a probability distribution of all possible measurements, each equal to the absolute square of the coefficients of the corresponding eigenstate.

It can be seen that the measurement sequence of two different physical quantities A and B may directly affect their measurement results. In fact, such is the case with incompatible observables. 【1】”

"Yes, that's very clear." Professor Wu looked very happy.

"Didn't you take notes in class? How do you remember? Cui Li looked at me with a surprised expression.

I didn't answer, just smiled.

September 7, 2021 at 3:10 p.m.

The bell rang for the end of class. I was about to pack up the books on the table. However, Professor Wu walked straight in my direction.

"Cheng Yin, do you remember the last time Mr. Jack asked me to ask you about scientific research?"

"You mean the scientific research team? Could it be that I can join Mr. Jack's research group now? "I feel a joy that I can't put into words. Since the last scientific research session came back. I've been looking forward to being part of Mr. Jack's research group.

"Research group? What kind of research group? Cui Li asked curiously on the side.

"AEF has set up a scientific research team to recruit members from various schools, and I recommend Cheng Yin and you, Cui Li, on behalf of our physics department."

"Great, AEF is a well-known company in the scientific research community, and it's really rare to have such an opportunity." Cui Li was actually happier than me after listening to Professor Wu's words.

"It's great that you can all agree." As he spoke, Professor Wu gave two pieces of letter to Cui Li and me. "There is specific information on it, this time you are participating in the research group in the name of the school, but you must behave well.

I opened the letter in my hand, as if the doors of AEF were opening to me.

September 16, 2021 at 8:59 a.m.

I hurried to the 5th floor of the first teaching building before 10 o'clock. I opened the letter that Professor Wu gave me last time:

Members of the AEF scientific research team report to work.

Time: 10 a.m., September 16, 2021.

Location: 5th Floor, First Teaching Building, China University of Science and Technology Development.

I pushed open the door to the classroom, and there was no one. I looked at my watch and I was leaning on it, and the hands of the watch clearly pointed to 8:59. I actually misread the time, and it was an hour early.

I put down the backpack on my shoulder. He sat in a corner of the classroom and waited quietly for the other members to arrive.

September 16, 2021 at 9:30 a.m.

Half an hour passed, and the door to the classroom was finally opened by someone.

"Cheng Yin, you actually arrived a long time ago, I thought you must have arrived last. Hey~~ I still want to win the first place! "The person who spoke was none other than Cui Li.

I glanced at him, "Morning." ”

"Cheng Yin, you don't know, I didn't sleep all night last night, I'm so happy, I am so happy that I can study a topic with high-talented students from various schools, I am so happy that I am almost speechless." Cui Li sat down next to me excitedly.

I always felt familiar with all this, and sure enough, Cui Li began to chatter again: "What kind of people do you say the people who participate in the research team will be, are they all the same as me, talented and intelligent, and extraordinary." ”

I watched Cui Liyi talk to himself there, and I sometimes really wondered how he could be a physics student.

Just as Cui Li was speaking, I heard footsteps at the door of the classroom. The teacher's door was opened again. Looking at the figure walking in front of me, I was so shocked that I couldn't close my mouth. How is this possible?

Cui Li stepped forward and said hello: "Hello, classmate, are you here to report to the research group?" The man looked at Cui Li and nodded. "I'm also part of the research team, my name is Cui Li. What's your name? Which school? ”

"Hello, my name is Li Ruina." The blonde woman briefly returned to Cui Li's question. I found an empty seat and sat down.

"Li Ruina, I thought you were a foreigner when I looked at you? By the way, what kind of school are you? Cui Li asked.

"Cui Li, you can't let people rest for a while?" I walked up to them: "Hello, Li Ruina, I didn't expect to meet you here."

"Hello, sincerity. Me too. ”

Cui Li didn't wait for me to finish saying hello, pulled me to the side and whispered, "Do you know her?" Who is she? ”

I glanced at Li Ruina, who was sitting in the front row, and said, "Li Ruina, chief engineer of AEF. ”

[1] ——Excerpt from Baidu Encyclopedia "Quantum Mechanics"