The top of the scholar

Chapter 131 We succeeded!
After switching to micro-nano structure materials, the collection efficiency has improved a lot compared to before, but it is only maintained at about 12%.

Moreover, the collection efficiency fluctuates seriously and is very unstable, and the quality of the light source has also declined.

The practical significance of such experimental results is very small.

And this new experiment, everyone also very much hopes that it can achieve higher collection efficiency and at the same time ensure the quality of the light source.

After the preparations are in place, the experiment is about to begin.

"We first use a picosecond laser with a repetition rate of 79 MHz to perform two-photon resonance excitation." Wang Xiangwu said.

Wu Hong used the instrument to adjust the parameters of the laser to ensure that the wavelength of the laser was between the exciton line and the biexciton line.

At the π pulse, photons are counted using an avalanche photodiode.

As the experiment progresses, the real-time absorption efficiency value is also reflected in the instrument.

And when everyone saw the data, they all had excited expressions on their faces.

"Is it so high? The collection efficiency has reached about 90%!"

Compared with the previous 12%, this increase is undoubtedly a qualitative change.

Of course, the current collection efficiency is only a rough one without any corrections.

The actual collection efficiency should be even lower.

After completing several sets of data, Wang Xiangwu decided to conduct further analysis on these sets of data.

After all, the 90% collection efficiency just now still has a certain amount of water.

Only through the revised collection efficiency is it more convincing.

Wu Hong opened the software, and after completing the data synchronization, he processed the several sets of data just now.

In the actual data processing process, it is necessary to deduct the loss of the optical path and correct the APD efficiency to obtain the final and more accurate collection efficiency.

After the processing of the data is completed, the final collection efficiency appears.

"85.3%? That's pretty good!"

Although it has not yet reached the ultra-high efficiency of 90%.

But compared with the previous 12%, this is undoubtedly a very big improvement.

"Although this is only the collection efficiency of single photons, it has indeed far exceeded our expectations. Such a high collection efficiency can be said to be practical!"

Seeing the final result, Wang Xiangwu was very excited.

This proves that the new light source structure designed by Xu You is indeed very successful!

Wu Hong was also very excited about this.

Although when Wu Hong saw Xu You's design, he had a premonition that this would definitely be a breakthrough design.

But after all, theory and reality are not completely equal. Only when the ideal experimental results are really produced can the theory be proved to be correct.

In the past few months, Wu Hong has been waiting for the day when the experiment will start.

Today's experimental results finally prove that this new light source structure is successful.

"Next, let's start experiments with entangled photon pairs."

Entangled photon pairs are less efficient to collect than single photons.

But as long as it can reach more than 50%, it is considered a relatively good efficiency.

After completing several sets of experiments, Wu Hong revised the efficiency value again.

Unlike single photons, this time, corrections for biexciton state preparation efficiency and purity are required.

And when they saw the revised collection efficiency, everyone's mood lifted again.

"75.4%! It's already much more than 50%!"

It is already a very shocking data to be able to achieve such a level of collection efficiency of entangled photon pairs.

At this moment, the scientific researchers in the entire laboratory can finally release their suppressed mood for several months.

This project about China's new generation of quantum computers is of great significance to everyone.

Even if the scientific research results cannot be published in the short term, everyone will not ignore this project.

As China's top scientific researchers, they all want to make a little contribution to the development of the country's cutting-edge technology.

"Okay, calm down, the experiment is not over yet. We still have a lot of work to do."

Wang Xiangwu tried his best to suppress the joy in his heart, and urged everyone to calm down and continue the next experiment.

Only high collection efficiency does not fully represent the practicability of the light source structure.

In addition, measurements of photon entanglement fidelity and indistinguishability are also required.

After several days of experiments, all data were measured and corrected.

In addition to very high collection efficiency.

The entanglement fidelity of photons, as well as the indistinguishability of photons, are also in the very high range.

"By splitting the light with a grating and sending the exciton photon and the biexciton photon to one end, we finally got an entanglement fidelity of 88.6%. By interferometry of the two exciton photons, the exciton and biexciton photons The indistinguishability also reached 90.1% and 90.3% respectively.”

For such a result, the experimental group no longer had any extravagant expectations.

No matter from which point of view, the new light source structure designed by Xu You can be said to be very successful.

Such breakthrough results are not only to the extent that papers can be published in top journals, but also breakthrough technologies that can be directly used on optical quantum computers.

This time, Xu You became the key to the project again, contributing the most important light source structure design.

And the other members of the experimental group, even if they did not have as outstanding contributions as Xu You, all made their own efforts for this project.

After a brief celebration, Wang Xiangwu also quickly decided to inform Academician Han Shubin of this achievement.

"Because it's an internal project, you don't need to pay too much attention to the format, just express the key theories, images, and experimental data. When the project paper is officially submitted later, it will not be too late for us to provide a standard paper."

Wang Xiangwu knew that on the other side of the ocean, the United States must also be researching and developing a new generation of quantum computers.

At this critical moment, every new technological breakthrough is very important.

After all, if you are not submitting a paper to a journal, you don't need to pay so much attention to the format.

After Han Shubin heard the news, he immediately invited Wang Xiangwu's experimental group to the Chinese Academy of Sciences.

After all, there are some things that cannot be fully reflected only through papers, and more detailed communication is required.

On the appointed day, Wang Xiangwu brought the core members of the project to the Chinese Academy of Sciences.

As the designer of the new light source structure, Xu You is naturally among them.

In the office, Han Shubin was drinking tea while waiting for the arrival of Wang Xiangwu's experimental group.

"The scientific research team of Ji University has performed really well recently. Last time, Qiao Sen's experimental group made good experimental results in the field of superconducting quantum. This time, Wang Xiangwu's experimental group has made a breakthrough in the field of optical quantum."

(End of this chapter)