Wieck, Arne Ludwig, Yun Meng, Xiaolong Hu, Huali Duan, Wenchao Chen, Wei Fang, Moritz Cygorek, Xing Lin, Da-Wei Wang, Chao-Yuan Jin and Feng Liu, 24 July 2023, Nature Nanotechnology. Reference: “Coherent control of a high-orbital hole in a semiconductor quantum dot” by Jun-Yong Yan, Chen Chen, Xiao-Dong Zhang, Yu-Tong Wang, Hans-Georg Babin, Andreas D. These measures facilitated the performance of the experiments by the Chinese partners working with Jun-Yong Yan and Feng Liu.

In the process, the researchers increased the ensemble homogeneity of the quantum dots and ensured the high purity of the structures produced. Arne Ludwig at the Chair for Applied Solid State Physics headed by Professor Andreas Wieck. Hans-Georg Babin produced the high-purity semiconductor samples for the experiment at Ruhr University Bochum under the supervision of Dr. Such superpositions are the basis for quantum bits, which, unlike conventional bits, exist not only in the states “0” and “1,” but also in superpositions of both. The hole thus existed in both states simultaneously. The researchers used finely tuned laser pulses to create a superposition between the hole ground state and the higher energy state. With a second laser, they triggered the radiative Auger process to elevate one hole to a series of higher energy states.

With the first laser, they excited an electron-hole pair in the quantum dot to create a quasiparticle consisting of two holes and an electron. In the current project, the researchers showed that the radiative Auger process can be coherently driven: they used two different laser beams with intensities in a specific ratio to each other. In 2021, a team of researchers succeeded for the first time in specifically stimulating the radiative Auger transition in a semiconductor. The same process can be witnessed with electron holes – in other words, missing electrons. In this process, an electron recombines with a hole, partially releasing its energy as a photon and partially transferring it to another electron. To achieve this superposition state, the researchers utilized the radiative Auger transition. (The Bochum research team: Hans-Georg Babin (left) and Arne Ludwig.) Credit: RUB, Marquard Harnessing the Radiative Auger Process

The trick: two optical laser pulses that act as a single terahertz laser pulse. Researchers have successfully created a quantum superposition state within a semiconductor nanostructure that might serve as a basis for quantum computing. This team, however, achieved the excitation with two carefully calibrated, short-wavelength optical laser pulses.

Unfortunately, this wavelength was too long to accurately focus the beam on the quantum dot. Previously, the induction of such a state necessitated a large-scale, free-electron laser capable of emitting light in the terahertz range. Such superposition states are fundamental for quantum computing. Using a special energy transition, the researchers created a superposition state in a quantum dot – a tiny area of the semiconductor – in which an electron hole simultaneously possessed two different energy levels. Achieved through the use of two specifically calibrated short-wavelength optical laser pulses, the team was able to generate a quantum bit, or qubit, in a semiconductor nanostructure.Ī German-Chinese research team has successfully created a quantum bit in a semiconductor nanostructure. (Artist’s concept.)Ī German-Chinese research team has successfully created a quantum superposition state in a semiconductor nanostructure, marking a significant breakthrough for quantum computing. By using two carefully calibrated optical laser pulses, they facilitated a unique energy transition, forming a quantum bit within a semiconductor nanostructure. Scientists have created a quantum superposition state within a semiconductor nanostructure, a significant advancement for quantum computing.

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