Quantum transition and information properties of the Coulomb coupled trion (electron-electron-hole) in the double quantum dots under the influence of the time-dependent electric field have been studied. Tuning the Hubbard interaction strength amongst the states of electron-hole complexes and the parameters of the ac field, two strikingly different kinds of approximate qubit can be constructed within the eight trion states. The similarity and difference between the electron dynamic entanglement and overlapping of the wavefunction with the Bell state have been elucidated through analyzing these two kinds of qubit.
Trion quantum coherence in site-controlled pyramidal InGaAs quantum dots
Department of Physics, University of Strathclyde（斯特拉斯克莱德大学物理系）；Sussex Centre for Quantum Technologies, University of Sussex（苏塞克斯大学苏塞克斯量子技术中心）；Tyndall National Institute, University College Cork（科克大学学院廷德尔国家研究所）
Physical implementations of large-scale quantum processors based on solid-state platforms benefit from realizations of quantum bits positioned in regular arrays. Self-assembled quantum dots are well-established as promising candidates for quantum optics and quantum information processing, but they are randomly positioned. Site-controlled quantum dots, on the other hand, are grown in pre-defined locations, but have not yet been sufficiently developed to be used as a platform for quantum information processing. In this letter we demonstrate all-optical ultrafast complete coherent control of a qu…
We investigate the charging dynamics in epitaxially grown InAs quantum dots under resonant excitation with and without additional low-power above-band excitation. Time-resolved resonance fluorescence from a charged exciton (trion) transition is recorded as the above-band excitation is modulated on and off. The fluorescence intensity varies as the QD changes from charged to neutral and back due to the influence of the above-band excitation. We fit the transients of the time-resolved resonance fluorescence with models that represent the charging and neutralization processes. The time dependence …
Optical spin rotations and cycling transitions for measurement are normally incompatible in quantum dots, presenting a fundamental problem for quantum information applications. Here we show that for a hole spin this problem can be addressed using a trion with one hole in an excited orbital, where strong spin-orbit interaction tilts the spin. Then, a particular trion triplet forms a double $Λ$ system, even in a Faraday magnetic field, which we use to demonstrate fast hole spin initialization and coherent population trapping. The lowest trion transitions still strongly preserve spin, thus combin…
Spin entanglement using coherent light and cavity-QED
讨论了一种在高Q微腔中，通过探测与两个量子点发生色散相互作用并经历了自旋选择性三电子跃迁的法拉第旋转的强相干光，在两个相距较远的单电子掺杂量子点之间产生概率纠缠的方案.为了评估T. D. Ladd等人[New J.Phys.8，184（2006）]中描述的两个远距离量子点，需要理解由量子点自旋与材料的核自旋的超精细相互作用以及由不相同的量子点所施加的限制。通过在近似框架内解析计算贝尔态产生的保真度，证明了这种方法的可行性。的保真度进行了评估，为广泛的参数和不同的脉冲长度，产生信号和退相干之间的权衡，以及一组最佳的参数。研究了克服非全同量子点对保真度影响的策略，并讨论了核自旋所施加的时间尺度，表明利用远距离量子点可以有效地产生纠缠。在这种情况下，由于轻空穴过渡的影响变得重要，必须包括在内。该计划进行了讨论，以及为两侧腔，其中必须小心与反射光携带自旋信息。近似方法的有效性进行了检查一个更详细的半经典模拟，其中包括trion形成。
We describe the effects of the quantum back action under continuous optical measurement of electron spins in quantum dots. We consider the system excitation by elliptically polarized light close to the trion resonance, which allows for the simultaneous spin orientation and measurement. We microscopically demonstrate that the nuclei-induced spin relaxation can be both suppressed and accelerated by the continuous spin measurement due to the quantum Zeno and anti-Zeno effects, respectively. Our theoretical predictions can be directly compared with the future experimental results and straightforwa…
We study electric dipole spin resonance caused by sub-terahertz (THz) radiation in a multilevel finite-size quantum dot formed in a nanowire focusing on the range of driving electric fields amplitudes where a strong interplay between the Rabi spin oscillations and tunneling from the dot to continuum states can occur. A strong effect of the tunneling on the spin evolution in this regime occurs due to formation of mixed spin states. As a result, the tunneling strongly limits possible spin manipulations time. We demonstrate a backaction of the spin dynamics on the tunneling and position of the el…
Left-handedness with three zero-absorption windows tuned by the incoherent pumping field and inter-dot tunnelings in a GaAs/AlGaAs triple quantum dots system
Controlled Coherent Coupling in a Quantum Dot Molecule Revealed by Ultrafast Four-Wave Mixing Spectroscopy
Wrocław University of Science and Technology（弗罗茨瓦夫科技大学）；School of Physics, Trinity College Dublin（都柏林三一学院物理学院）；Technische Universität Berlin（柏林工业大学）；Ruhr-Universität Bochum（波鸿鲁尔大学）；Wrocław University of Technology（弗罗茨瓦夫理工大学）；Technische Universität München（慕尼黑工业大学）；Universität Paderborn（帕德博恩大学）；Université Grenoble Alpes（格勒诺布尔阿尔卑斯大学）
We demonstrate a fiber in-line single photon source based on a hybrid system of colloidal single quantum dots deposited on an optical nanofiber and cooled down to cryogenic temperature (3.7 K). We show that a charged state (trion) of the single quantum dot exhibits a photo-stable emission of single photons with high quantum efficiency, narrow linewidth (3 meV FWHM) and fast decay time ($10.0\pm0.5$ ns). The single photons are efficiently coupled to the guided modes of the nanofiber and eventually to a single mode optical fiber. The brightness (efficiency) of the single photon source is estimat…
