A quantum emitter called a lead-vacancy (PbV) center has been created in diamond by scientists. This unique color center produces photons with specific frequencies and has a sharp zero-phonon-line. Unlike other diamond color centers, the PbV color center can maintain its optical properties at high temperatures of 16 K, making it ideal for transmitting quantum information in large-scale quantum networks.
Similar to how electric circuits use components to regulate electronic signals, quantum networks depend on specialized components and technology. rnrn
The nodes play a key role in transferring quantum information between different points, laying the groundwork for the development of quantum systems. In quantum networks, the intentional defects known as color centers in diamond crystals are essential for creating and preserving stable quantum states over significant distances.
When exposed to external light, these color centers in diamond release photons that contain details about their internal electronic states, particularly the spin states. The interaction between the emitted photons and the spin states of the color centers allows for the transfer of quantum information.
The ability to create a stable and reliable quantum network is essential for the transmission of quantum information between different nodes. One common example of color centers in diamond is the nitrogen-vacancy (NV) center, where a nitrogen atom is placed next to missing carbon atoms in the diamond lattice. However, the photons emitted from NV color centers do not have well-defined frequencies and are influenced by interactions with the surrounding environment, making it difficult to maintain a dependable quantum system.
To combat this issue, an international team of researchers, led by Associate Professor Takayuki Iwasaki from Tokyo Institute of Technology, has developed a single negatively charged lead-vacancy (PbV) cIn diamond, a lead atom is inserted between neighboring vacancies in a diamond crystal. A study in the journal Physical Review Letters on February 15, 2024, shows that the PbV center emits photons of specific frequencies that are not affected by the crystal’s vibrational energy. These features make the photons reliable carriers of quantum information for large-scale quantum networks.
For stable and coherent quantum states, the emitted photon must be transform-limited, meaning it should have the minimum possible spread in its frequency. Additionally, it should haveemission into zero-phonon-line (ZPL) refers to the energy from the emission of photons only being used to change the electronic configuration of the quantum system, rather than being exchanged with the vibrational lattice modes (phonons) in the crystal lattice.
In order to create the PbV center, lead ions were introduced beneath the diamond surface using ion implantation. Afterward, an annealing process was conducted to repair any damage caused by the lead ion implantation. The resulting PbV center shows a spin 1/2 system, with four distinct energy states where the ground and excited state are split into two energy levels. On p rnrnThe PbV center was the focus of the study, and the researchers observed electron transitions between energy levels that resulted in four distinct ZPLs, labeled A, B, C, and D based on the decreasing energy of the associated transitions. Among these, the C transition was found to have a transform-limited linewidth of 36 MHz.
“Our research involved examining the optical properties of individual PbV centers under resonant excitation, and we found that the C-transition, one of the ZPLs, approaches the nearly transform-limited state at 6.2 K without significant phonon-induced relaxation and spectral diffusion,” explained Dr. Iwasaki.
The PbV center is unique in its ability to maintain its properties under these conditions.The linewidth is approximately 1.2 times the transform-limit at temperatures as high as 16 K, which is crucial for achieving around 80% visibility in two-photon interference. In comparison, color centers like SiV, GeV, and SnV require cooling to much lower temperatures (4 K to 6 K) to meet similar conditions. By producing well-defined photons at relatively high temperatures compared to other color centers, the PbV center can serve as an efficient quantum light-matter interface, allowing quantum information to be transmitted over long distances by photons through optical fibers.
“These findings could lead the way for the PbV center to become a foundationalDr. Iwasaki concludes that the research opens the door to building large-scale quantum networks. The study is referenced in the journal article titled “Transform-Limited Photon Emission from a Lead-Vacancy Center in Diamond above 10 K” by Peng Wang, Lev Kazak, Katharina Senkalla, and others, published in Physical Review Letters in 2024. The DOI for the article is 10.1103/PhysRevLett.132.073601.Based on the HTML code provided, it appears to be a list within an article or document. The specific content of the list is not clear from the code alone.