Charged excitons and biexcitons in laterally coupled InGaAs quantum dots

Dissipative preparation of the exciton and biexciton in a self-assembled quantum dot on picosecond timescales

Pulsed resonant fluorescence is used to probe ultrafast phonon-assisted exciton and biexciton preparation in individual self-assembled InGaAs quantum dots. By driving the system using large area ($\geq10π$) near resonant optical pulses, we experimentally demonstrate how phonon mediated dissipation within the manifold of dressed excitonic states can be used to prepare the neutral exciton with a fidelity $\geq 70\%$. By comparing the phonon-assisted preparation with resonant Rabi oscillations we show that the phonon-mediated process provides the higher fidelity preparation for large pulse areas …

Coherent and robust high-fidelity generation of a biexciton in a quantum dot by rapid adiabatic passage

A biexciton in a semiconductor quantum dot is a source of polarization-entangled photons with high potential for implementation in scalable systems. Several approaches for non-resonant, resonant and quasi-resonant biexciton preparation exist, but all have their own disadvantages, for instance low fidelity, timing jitter, incoherence or sensitivity to experimental parameters. We demonstrate a coherent and robust technique to generate a biexciton in an InGaAs quantum dot with a fidelity close to one. The main concept is the application of rapid adiabatic passage to the ground state-exciton-biexc…

Excitation intensity dependence of photoluminescence spectra of SiGe quantum dots grown on prepatterned Si substrates: Evidence for biexcitonic transition

The pumping intensity (I) dependence of the photoluminescence (PL) spectra of perfectly laterally two-dimensionally ordered SiGe quantum dots on Si(001) substrates was studied. The PL results from recombinations of holes localized in the SiGe quantum dots and electrons localized due to the strain field in the surrounding Si matrix. The analysis of the spectra revealed several distinct bands, attributed to phonon-assisted recombination and no-phonon recombination of the excitonic ground state and of the excited excitonic states, which all exhibit a linear I dependence of the PL intensity. At ap…

Two qubit conditional quantum logic operation in a single self-assembled quantum dot

The four-level exciton/biexciton system of a single semiconductor quantum dot acts as a two qubit register. We experimentally demonstrate an exciton-biexciton Rabi rotation conditional on the initial exciton spin in a single InGaAs/GaAs dot. This forms the basis of an optically gated two-qubit controlled-rotation (CROT) quantum logic operation where an arbitrary exciton spin is selected as the target qubit using the polarization of the control laser.

Charged exciton emission at 1.3 $μ$m from single InAs quantum dots grown by metalorganic chemical vapor deposition

We have studied the emission properties of self-organized InAs quantum dots (QDs) grown in an InGaAs quantum well by metalorganic chemical vapor deposition. Low-temperature photoluminescence spectroscopy shows emission from single QDs around 1300 nm; we clearly observe the formation of neutral and charged exciton and biexciton states, and we obtain a biexciton binding energy of 3.1 meV. The dots exhibit an s-p shell splitting of approximately 100 meV, indicating strong confinement.

Single-Gate Accumulation-Mode InGaAs Quantum Dot with a Vertically Integrated Charge Sensor

We report on the fabrication and characterization of a few-electron quantum dot controlled by a single gate electrode. Our device has a double-quantum-well design, in which the doping controls the occupancy of the lower well while the upper well remains empty under the free surface. A small air-bridged gate contacts the surface, and is positively biased to draw laterally confined electrons into the upper well. Electrons tunneling between this accumulation-mode dot and the lower well are detected using a quantum point contact (QPC), located slightly offset from the dot gate. The charge state of…

电可调轨道耦合与O波段量子点分子的量子光发射

Electrically tunable orbital coupling and quantum light emission from O-band quantum dot molecules

研究通过调节电场实现量子点分子中轨道耦合的可调性，并观察到O波段量子点分子的量子光发射特性，探讨了轨道耦合对二阶相关函数的影响。

Coherence and indistinguishability of highly pure single photons from non-resonantly and resonantly excited telecom C-band quantum dots

In the present work, the effect of resonant pumping schemes in improving the photon coherence is investigated on InAs/InGaAs/GaAs quantum dots emitting in the telecom C-band. The linewidths of transitions of multiple exemplary quantum dots are determined under above-band pumping and resonance fluorescence via Fourier-transform spectroscopy and resonance scans, respectively. The average linewidth is reduced from $9.74\,\mathrm{GHz}$ in above-band excitation to $3.50\,\mathrm{GHz}$ in resonance fluorescence underlining its superior coherence properties. Furthermore, the feasibility of coherent s…

MBE生长的用于发射电信O波段和C波段量子点的虚拟衬底

MBE-grown virtual substrates for quantum dots emitting in the telecom O- and C-bands

本研究针对电信窗口高性能量子光子器件制备难题，设计了基于组分渐变InGaAs虚拟衬底的MBE生长异质结构，实现了1200-1600 nm可调谐的O/C波段量子点发光，为未来量子网络光子器件提供了灵活平台。