Coherent manipulation under resonant excitation of a single quantum dot state

Romain Melet, V. Voliotis, R. Grousson +3 more

N. H. Bonadeo, John Erland Østergaard, Dan Gammon +3 more

Jun Gao, Govind Krishna, Edith Yeung +6 more

Coherent control of single photon sources is a key requirement for the advancement of photonic quantum technologies. Among them, nanowire-based quantum dot sources are popular due to their potential for on-chip hybrid integration. Here, we demonstrate on-demand single-photon generation [g(2) (0) (X*) = 0.078] from resonantly excited InAsP/InP nanowire quantum dots and observe Rabi oscillations in the dot emission, indicating the successful coherent manipulation of the excitonic states in the nanowire. This work addresses the long-standing challenge of resonantly exciting nanowire-quantum dots. It paves the way for hybrid quantum photonic integration, enabling spin–photon entanglement and matter memories on-chip.

Harishankar Jayakumar, Ana Predojević, Tobias Huber +3 more

The strong confinement of semiconductor excitons in a quantum dot gives rise to atomlike behavior. The full benefit of such a structure is best observed in resonant excitation where the excited state can be deterministically populated and coherently manipulated. Because of the large refractive index and device geometry it remains challenging to observe resonantly excited emission that is free from laser scattering in III/V self-assembled quantum dots. Here we exploit the biexciton binding energy to create an extremely clean single photon source via two-photon resonant excitation of an InAs/GaAs quantum dot. We observe complete suppression of the excitation laser and multiphoton emissions. Additionally, we perform full coherent control of the ground-biexciton state qubit and observe an extended coherence time using an all-optical echo technique. The deterministic coherent photon pair creation makes this system suitable for the generation of time-bin entanglement and experiments on the interaction of photons from dissimilar sources.

利正 藤澤

Stefan Maximilian Strauß

Excitons in quantum dots represent a remarkably good two-level system with a large optical dipole transition moment. Although most research currently focuses on enhancing their already outstanding properties as single photon emitters they become also increasingly interesting for experimental fundamental research due to their large dipole transition moment. This thesis presents studies which explore fundamental phenomena in quantum dots using coherent spectrocopy methods. First, we will first examine the optical properties of site-controlled quantum dots which were grown using a buried stressor via resonance fluorescence. Subsequently, we will show results that were obtained using photocurrent spectroscopy to study single quantum dots that are embedded in micropillar resonators. This is followed by a study of the Wigner time delay induced by a single quantum dot and which shows that the maximum delay is larger than its dephasing time T2 which is the theoretical limit for coherently scattered fraction. The next section demonstrates that the response of a resonantly driven two-level system which in our case is represented by an exciton in a seminconductor quantum dot depends significantly on the photon statistics of the exciting light field. Most strikingly, the Mollow triplet which we observe under coherent excitation vanishes under thermal excitation. The second part presents results concerned with the resonantly driven biexciton cascade via two- photon excitation. The coherent interaction between light field and excitons gives rise to a complex five-level system. Here, we show for the first time two-photon Rabi oscillations in the temporal domain. Furthermore, we examine the correlations between the different transitions. The measurements show that we can manipulate the time-ordering of the emitted photons by changing for example the laser power. All these studies share the resonant excitation scheme which allows for a coherent manipulation of the states of the quantum dot and grants access to phenomena typical for resonance fluorescence such as the Mollow triplet and Rabi oscillations. In particular the experiments on photon excitation spectroscopy and the studies on the dressed biexciton cascade show that fundamental effects of quantum optics can be explored in a scalable and application oriented setting using quantum dots.