Chapter 129 We succeeded!
After replacing the micro-nano structure material, the collection efficiency has been greatly improved compared to before, but it only remains at around 12%.
Moreover, the collection efficiency fluctuates severely and is very unstable, and the quality of the light source has also declined.
Such experimental results have very little practical significance.
In this new experiment, everyone very much hopes to achieve higher collection efficiency while ensuring the quality of the light source.
After the preparations are completed, the experiment is about to begin.
"We first use a picosecond laser with a repetition rate of 79 MHz to perform two-photon resonant excitation," said Wang Xiangwu.
Wu Hong used instruments 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, an avalanche photodiode is used to count the photons.
As the experiment progresses, the real-time absorption efficiency values are also reflected in the instrument.
And when everyone saw the data, they all looked excited.
"Is it so high? The collection efficiency has reached about 90%!"
Compared with the last 12%, this increase is undoubtedly a qualitative change.
Of course, the current collection efficiency is only rough and has not been corrected in any way.
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 some water in it.
Only through the corrected collection efficiency can it be more convincing.
Wu Hong opened the software, completed the data synchronization, and then processed the previous sets of data.
In the actual data processing process, it is necessary to deduct the loss of the optical path and perform APD efficiency correction to obtain the final more accurate collection efficiency.
After completing the processing of the data, the final collection efficiency appeared.
“85.3%? That’s pretty good!”
Although it has not yet reached the ultra-high efficiency of 90%.
But compared to the previous 12%, this is undoubtedly a huge improvement.
"Although this is only the collection efficiency of a single photon, 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 drawing, he had a hunch that this would definitely be a groundbreaking design.
But after all, theory and practice are not completely equal. Only when ideal experimental results are achieved can the theory be proved to be correct.
Over the past few months, Wu Hong has been waiting for the day when the experiment would begin.
Today's experimental results finally proved that this new light source structure is successful.
"Next, let's start the experiment on entangled photon pairs."
Compared with single photons, the collection efficiency of entangled photon pairs is lower.
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 once again revised the efficiency value.
Unlike single photons, this time, the efficiency and purity of the biexciton state preparation need to be corrected.
And when everyone saw the revised collection efficiency, their mood was lifted again.
"75.4%! This is already much higher than 50%!"
Being able to achieve such a level of collection efficiency for entangled photon pairs is already a very shocking data.
All of a sudden, the researchers in the entire laboratory can finally relieve themselves from the depressed mood they have been feeling for the past few months.
This research project on 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 their own contribution to the development of the country's cutting-edge science and technology.
"Okay, calm down, the experiment is not over yet. We still have a lot of work to do next."
Wang Xiangwu tried hard to suppress his inner joy and urged everyone to calm down and continue with the next experiment.
High collection efficiency alone cannot fully represent the practicality of the light source structure.
In addition, it is also necessary to measure the entanglement fidelity and indistinguishability of photons.
After several days of experiments, all the data were measured and corrected.
In addition to very high collection efficiency.
The fidelity of the photons' entanglement, and the photons' indistinguishability, is also in a very high range.
"By splitting the light using a grating, we sent the exciton photons and biexciton photons to one end respectively, and we finally obtained an entanglement fidelity of 88.6%. Through the interference measurement of the two exciton photons, the indistinguishability of the exciton and biexciton photons also reached 90.1% and 90.3%, respectively."
With such a result, the experimental group no longer had any extravagant expectations.
From any perspective, the new light source structure designed by Xu You can be said to be very successful.
Such breakthrough results are not only worthy of being published in top journals, but are also breakthrough technologies that can be directly used in optical quantum computers.
This time, Xu You once again became the key to the project and contributed the most important light source structure design.
Even though the other members of the experimental group did not make as outstanding contributions as Xu You, they all contributed their efforts to this project.
After a brief celebration, Wang Xiangwu quickly decided to inform Academician Han Shubin of this achievement.
"Because this is an internal project, you don't have to pay too much attention to the format. Just put the key theories, images, and experimental data. When the project paper is officially submitted, it won't 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 conducting research and development of a new generation of quantum computers.
At this critical moment, every breakthrough in new technology is very important.
After all, since you are not submitting a paper to a journal, you don't need to pay so much attention to the format.
After learning the news, Han Shubin immediately invited Wang Xiangwu's experimental group to come to HUST.
After all, some things cannot be fully reflected through papers alone, and more detailed communication is required.
On the agreed day, Wang Xiangwu brought the core members of the project to HUST.
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 research team of Jida 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."
