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Spin manipulation in semiconductor quantum dots qubit

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Chinese Physics B 2018年第9期27卷 1-14页

作者： Ke Wang Hai-Ou L Ming Xiao Gang Cao and Guo-Ping Guo CAS Key Laboratory of quantum Information University of Science and Technology of ChinaHefei 230026China

Thirty years of effort in semiconductor quantum dots has resulted in significant developments in the control of spin quantum bits（qubits）. The natural two-energy level of spin states provides a path toward quantum information processing. In particular, the experimental implementation of spin control with high fidelity provides the possibility of realizing quantum computing. In this review, we will discuss the basic elements of spin qubits in semiconductor quantum dots and summarize some important experiments that have demonstrated the direct manipulation of spin states with an applied electric field and/or magnetic field. The results of recent experiments on spin qubits reveal a bright future for quantum information processing.

关键词： semiconductor quantum dot qubits spin manipulation

Qubits based on semiconductor quantum dots

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Chinese Physics B 2018年第2期27卷 127-139页

作者：张鑫李海欧王柯曹刚肖明郭国平 Key Laboratory of quantum Information Chinese Academy of Sciences University of Science and Technology of China

semiconductor quantum dots are promising hosts for qubits to build a quantum processor. In the last twenty years, in- tensive researches have been carried out and diverse kinds of qubits based on different types of semiconductor quantum dots were developed. Recent advances prove high fidelity single and two qubit gates, and even prototype quantum algorithms. These breakthroughs motivate further research on realizing a fault tolerant quantum computer. In this paper we review the main principles of various semiconductor quantum dot based qubits and the latest associated experimental results. Finally the future trends of those qubits will be discussed.

关键词： semiconductor quantum dot qubit quantum computing cavity quantum electrodynamics

semiconductor quantum computation

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National Science Review 2019年第1期6卷 32-54页

作者： Xin Zhang Hai-Ou Li Gang Cao Ming Xiao Guang-Can Guo Guo-Ping Guo Key Laboratory of quantum Information CAS University of Science and Technology of China Synergetic Innovation Center of quantum Information & quantum Physics University of Science and Technology of China

semiconductors, a significant type of material in the information era, are becoming more and more powerful in the field of quantum information. In recent decades, semiconductor quantum computation was investigated thoroughly across the world and developed with a dramatically fast speed. The research varied from initialization, control and readout of qubits, to the architecture of fault-tolerant quantum ***, we first introduce the basic ideas for quantum computing, and then discuss the developments of single-and two-qubit gate control in semiconductors. Up to now, the qubit initialization, control and readout can be realized with relatively high fidelity and a programmable two-qubit quantum processor has even been demonstrated. However, to further improve the qubit quality and scale it up, there are still some challenges to resolve such as the improvement of the readout method, material development and scalable designs. We discuss these issues and introduce the forefronts of progress. Finally, considering the positive trend of the research on semiconductor quantum devices and recent theoretical work on the applications of quantum computation, we anticipate that semiconductor quantum computation may develop fast and will have a huge impact on our lives in the near future.

关键词： semiconductor quantum dot qubit quantum computation spin manipulation

Circuit quantum electrodynamics with a quadruple quantum dot

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Chinese Physics B 2023年第7期32卷 150-155页

作者：林霆李海欧曹刚郭国平 CAS Key Laboratory of quantum Information University of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in quantum Information and quantum Physics University of Science and Technology of ChinaHefei 230026China Origin quantum Computing Company Limited Hefei 230088China

In this theoretical work,we describe a mechanism for the coupling between a plane structure consisting of four quantum dots and a *** systematically study the dependence of the quadruple coupling strength and the qubit decoherence rate and point out the optimized operating position of the hybrid *** to the transmission given by the input-output theory,the signatures in the resonator spectrum are ***,based on the parameters already achieved in previous works,we prove that the device described in this paper can achieve the strong coupling limit,i.e.,this approach can be used for system extension under the existing technical *** results show an effective and promotable approach to couple quantum dot structures in plane with the resonator and propose a meaningful extension method.

关键词： semiconductor qubit circuit quantum electrodynamics(QED) semiconductor quantum dot scalable semiconductor-based circuit QED architectures

Coherent manipulation of a tunable hybrid qubit via microwave control

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Chinese Physics B 2023年第8期32卷 409-414页

作者：顾思思王保传李海欧曹刚郭国平 CAS Key Laboratory of quantum Information University of Science and Technology of ChinaHefei 230026China CAS Center For Excellence in quantum Information and quantum Physics University of Science and Technology of ChinaHefei 230026China Origin quantum Computing Company Limited Hefei 230026China

Hybrid qubits enable the hybridization of charge and spin degrees of freedom,which provides a way to realize both a relatively long coherence time and rapid qubit ***,we use microwave driving to demonstrate the coherent operation of a tunable hybrid qubit,including X-rotation,Z-rotation,and rotation around an arbitrary axis in the X-Y panel of the Bloch ***,the coherence properties of the qubit and its tunability are *** measured coherence time of the X-rotation reaches~14.3 *** for the Z-rotation,the maximum decoherence time is~5.8 ns due to the larger sensitivity to *** employing the Hahn echo sequence to mitigate the influence of the low-frequency noise,we have improved the qubit coherence time from~5.8 ns to~15.0 *** results contribute to a further understanding of the hybrid qubit and a step towards achieving high-fidelity qubit gates in the hybrid qubit.

关键词： semiconductor quantum dot hybrid qubit qubit operation microwave control

Modification of the spontaneous emission of quantum dots near the surface of a three-dimensional colloidal photonic crystal

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Chinese Physics B 2010年第11期19卷 441-447页

作者：刘正奇冯天华戴峭峰吴立军兰胜丁才蓉汪河洲 Gopal Achanta Venu Laboratory of Photonic Information Technology School for Information and Optoelectronic Science and EngineeringSouth China Normal University State Key Laboratory of Optoelectronic Materials and Technologies Zhongshan (Sun Yat-Sen) University Department of Condensed Matter Physics and Material Science Tata Institute of Fundamental ResearchHomi Bhabha RoadMumbai 400005India

This paper demonstrates experimentally and numerically that a significant modification of spontaneous emission rate can be achieved near the surface of a three-dimensional photonic crystal. In experiments, semiconductor coreshell quantum dots are intentionally confined in a thin polymer film on which a three-dimensional colloidal photonic crystal is fabricated. The spontaneous emission rate of quantum dots is characterised by conventional and time-resolved photoluminescence （PL） measurements. The modification of the spontaneous emission rate, which is reflected in the change of spectral shape and PL lifetime, is clearly observed. While an obvious increase in the PL lifetime is found at most wavelengths in the band gap, a significant reduction in the PL lifetime by one order of magnitude is observed at the short-wavelength band edge. Numerical simulation reveals a periodic modulation of spontaneous emission rate with decreasing modulation strength when an emitter is moved away from the surface of the photonic crystal. It is supported by the fact that the modification of spontaneous emission rate is not pronounced for quantum dots distributed in a thick polymer film where both enhancement and suppression are present simultaneously. This finding provides a simple and effective way for improving the performance of light emitting devices.

关键词： spontaneous emission colloidal photonic crystal semiconductor quantum dot time-resolved photoluminescence

Steady-state linear optical properties and Kerr nonlinear optical response of a four-level quantum dot with phonon-assisted transition

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Chinese Physics B 2016年第1期25卷 589-594页

作者：佘彦超罗婷婷张蔚曦冉茂武王登龙 College of Physics and Electronic Engineering Tongren University School of Physics and Optoelectronices Xiangtan University

The linear optical properties and Kerr nonlinear optical response in a four-level loop configuration GaAs/A1GaAs semiconductor quantum dot are analytically studied with the phonon-assisted transition （PAT）. It is shown that the changes among a single electromagnetically induced transparency （EIT） window, a double EIT window and the amplification of the probe field in the absorption curves can be controlled by varying the strength of PAT to. Meanwhile, double switching from the anomalous dispersion regime to the normal dispersion regime can likely be achieved by increasing the Rabi energy of the external optical control field. Furthermore, we demonstrate that the group velocity of the probe field can be practically regulated by varying the PAT and the intensity of the optical control field. In the nonlinear case, it is shown that the large SPM and XPM can be achieved as linear absorption vanishes simultaneously, and the PAT can suppress both third-order self-Kerr and the cross-Kerr nonlinear effect of the QD. Our study is much more practical than its atomic counterpart due to its flexible design and the controllable interference strength, and may provide some new possibilities for technological applications.

关键词： electromagnetically induced transparency phonon-assisted transition semiconductor quantum dot

Pure spin-current diode based on interacting quantum dot tunneling junction

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Chinese Physics B 2021年第11期30卷 545-550页

作者： Zhengzhong Zhang Min Yu Rui Bo Chao Wang Hao Liu Faculty of Mathematics and Physics Huaiyin Institute of TechnologyHuaian 223003China The Affiliated Drum Tower Hospital of Nanjing University Medical School Nanjing 210093China

A magnetic field-controlled spin-current diode is theoretically proposed,which consists of a junction with an interacting quantum dot sandwiched between a pair of nonmagnetic *** applying a spin bias VS across the junction,a pure spin current can be obtained in a certain gate voltage regime,regardless of whether the Coulomb repulsion energy *** interestingly,if we applied an external magnetic field on the quantum dot,we observed a clear asymmetry in the spectrum of spin current IS as a function of spin bias,while the charge current always decays to zero in the Coulomb blockade *** asymmetry in the current profile suggests a spin diode-like behavior with respect to the spin bias,while the net charge through the device is almost *** from the traditional charge current diode,this design can change the polarity direction and rectifying ability by adjusting the external magnetic field,which is very *** device scheme can be compatible with current technologies and has potential applications in spintronics or quantum processing.

关键词： pure spin current semiconductor quantum dot spin diode

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Science Bulletin 2021年第4期66卷 332-338,M0004页

作者： Baochuan Wang Ting Lin Haiou Li Sisi Gu Mingbo Chen Guangcan Guo Hongwen Jiang Xuedong Hu Gang Cao Guoping Guo CAS Key Laboratory of quantum Information University of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in quantum Information and quantum Physics University of Science and Technology of China.Hefei 230026China Department of Physics and Astronomy University of California at Los AngelesLos AngelesCA 90095USA Department of Physics University at BuffaloSUNYBuffaloNY 14260-1500USA Origin quantum Computing Company Limited Hefei 230026China

We develop a new spectroscopic method to quickly and intuitively characterize the coupling of two microwave-photon-coupled semiconductor qubits via a high-impedance *** distinctive and unique geometric patterns are revealed as we tune the qubit tunnel couplings relative to the frequency of the mediating *** patterns are in excellent agreement with a simulation using the Tavis-Cummings model,and allow us to readily identify different parameter regimes for both qubits in the detuning *** method could potentially be an important component in the overall spectroscopic toolbox for quickly characterizing certain collective properties of multiple cavity quantum electrodynamics(QED)coupled qubits.

关键词： quantum computation semiconductor qubit Cavity quantum electrodynamics Strong coupling semiconductor quantum dot