Chapter 539

It has long been no secret that Gu Lu teaches at the School of Mathematics of Yan University.

However, before this, Gu Lu's fame in Yanda was only spread among a group of little girls.

It wasn't until Gu Lu's name appeared on the hot search list of the scarf that many students of Yan University knew that they still had such a hidden dragon and crouching tiger in Yan University.

Therefore, in today's Yan University, Gu Lu's name can be called an existence that everyone knows and everyone knows.

And according to Gu Lu's appearance, he also belongs to the kind that will never notice it when he glances over.

Since Gu Lu became famous on the Internet, the students of Yan University thought that they could easily meet Gu Lu on campus.

But to everyone's surprise, Gu Lu has completely become an elusive existence in the past month or so.

Except for the time period of six or seven o'clock in the morning and eleven or twelve o'clock in the middle of the night, someone met Gu Lu at the school gate, and few people saw Gu Lu at Yan University in the rest of the time.

It seems that Gu Lu has been busy with other things outside of school.

Gradually, everyone has forgotten about it.

But everyone didn't expect that in the library today, they happened to meet Gu Lu by accident.

Listening to the sound of flipping through the book just now, everyone thought that someone was deliberately pretending to be like this.

But if that person is Gu Lu, then there is no element of pretending, because Gu Lu's own strength is like this.

Flipping the book so fast is just a manifestation of Gu Lu's strength.

Everyone was obviously surprised by Gu Lu's sudden appearance in the library.

Although everyone and Gu Lu are in the same Yenching University, to be honest, they think that they and Gu Lu are completely two worlds, and it is a rare opportunity to be so close.

So the students who noticed Gu Lu's existence in the library began to run around the dormitory group or class group one by one to tell each other.

"Uncle Gu is in the library, everyone hurry up and come and watch!!"

"Who is Uncle Gu?" [look confused] .jpg"

"Qingqing, you read the book and look stupid, Uncle Gu is Gu Lu, didn't you say you liked Uncle Gu's appearance before?"

"Get up right away and wait for me for three minutes!"

"Hey, I'm at home, and I can't get over at all. If only I had been in school like you, I was preparing for graduate school. ”

"Don't talk about you, the big guy of Baoyan. ”

"Help me get an autograph of Uncle Gu, of course, it would be better if there was a handsome photo of Uncle Gu!"

"I'm rushing over from the cafeteria, Sisi, stop Uncle Gu, don't let him run!"

"Before you come, let me let you appreciate Uncle Gu's appearance. [A candid photo of Gu Lu's side face] .jpg"

"Lick the screen!"

............

Although it is the summer vacation, there are still many students staying in school.

Therefore, as soon as the news of 'Uncle Gu appeared in the library' spread, many people responded to go to watch Gu Lu and meet the 'man of the hour' who he was studying.

On Gu Lu's side, he didn't know that a large number of people were gathering for the library.

He was immersed in the knowledge of the book and couldn't extricate himself.

In fact, after so many years of development and research, qubit coding has been gradually divided into two forms of encoding.

One is qubit coding based on the spin state of electrons, or spin qubit coding for short.

The other is qubit coding based on charge distribution, which is referred to as charge qubit coding.

Spin qubit coding and charge qubit encoding, which are the two mainstream forms of qubit encoding.

Spin qubit encoding is the use of the spin up and spin down of a single or multiple electrons as the ground state of the qubit. In the absence of an external magnetic field, the two spin states of the electron are energetically degenerate and cannot serve as the two orthogonal bases required to constitute the qubits.

However, in the presence of an external magnetic field tomb, due to the Zeeman split, the two spin degenerate states of the electrons are split into non-degenerate states with a certain energy difference, forming an effective two-level system, and then the two non-degenerate white spin states are used as the ground states of the qubits, so as to further realize the quantum coherence operations required for quantum computing.

Charge qubit encoding, on the other hand, is very different.

The principle of charge qubit encoding is to make use of an interaction in two quantum dots called 'tunneling coupling'.

The so-called tunneling coupling refers to the fact that electrons in one quantum dot can tunnel into another quantum dot, and this tunneling effect is derived from the distribution of the electron wave function.

Two weakly coupled quantum dots in which the distribution overlap of the electron wave function is small, and the probability of electrons tunneling from one quantum dot to another is also small.

In the two highly coupled quantum dots, the distribution overlap region of the electron wave function is large, and the probability of electrons tunneling from one quantum dot to the other is very high.

Charge qubits are encoded by adjusting the charge distribution of electrons by using 'tunneling coupling'.

Spin qubit encoding and charge qubit encoding are two completely different ways of encoding qubits.

But both approaches have their advantages and disadvantages.

It can be summarized simply as the coherence time of spin qubits is long, but the manipulation is complex and slow. Charge qubits have a short coherence time, but they are simple to manipulate and fast.

To be clear, while qubit coding can affect the speed and coherence time of a quantum computer, coherence and speed are mutually opposed.

Good coherence requires isolating the quantum system from the outside world as much as possible and weakening the interaction between the system and the outside world, which will inevitably increase the complexity and speed of manipulating the quantum system from the outside.

However, on the other hand, the fast manipulation speed requires a strong interaction between the outside world and the quantum system, which will inevitably increase the influence of external noise on the quantum system and cause the decoherence of the quantum system.

To put it simply, the speed at which a quantum computer operates and the coherence time are two contradictory points.

The faster the operation is of course the better, and the longer the coherence time is of course the better.

But in most cases, only one or the other.

The hard task set by Academician Guo for Gu Lu is to control the operation speed of the quantum computer at the order of a few picoseconds through qubit coding, but there is no too hard requirement for the parameter of coherence time.

But coherence time is closely related to the performance of quantum computers.

It is clear without thinking about it, although Academician Guo did not set too hard requirements, if it is just to blindly improve the speed of operation and thus reduce the coherence time, that method is categorically undesirable.

Because that's the equivalent of picking up sesame seeds and throwing watermelon.