Preparation of non-classical photon states in laser-driven quantum-dot-cavity systems under the influence of acoustic phonons

在这个项目中，我们将探索理论上制备非经典光子态的可能性，例如，量子点腔系统中的薛定谔猫态、福克态或偏振纠缠两对态。这些态不仅可以用来检验量子力学的基础知识，而且也可以作为光子学、量子信息处理和量子密码学中可能应用的核心构件。我们将研究量子点腔系统中的光子态在多大程度上可以被不同的激光激发所操纵。特别感兴趣的是与晶格振荡（声子）的相互作用引起的新的物理效应，这在基于半导体的量子点系统中是无法避免的。 声子可能是制备的一个障碍，但也有可能，声子辅助的过程可能使新的制备protocols.We还将研究多远的光子对的产生，这产生于共振器中的双激子（即两个电子-空穴对的状态）的衰减，可以由外部激光场的影响和声子在这种情况下发挥什么作用。此外，到目前为止尚未探索的可能性之间切换不同类型的纠缠将被调查。两个时间相关函数应避免通常调用的量子回归定理，这是无效的系统与非马尔可夫环境（这里提供的声子）的评估。两时间相关函数直接与可测量的量相联系，包含了关于光子非经典性质的重要信息。通过模拟光子系统的关键物理量，如不可逆性、相干性、纠缠度以及记录N光子束的光子统计，我们有望发现新的物理见解，特别是对非马尔可夫效应的重要性的新的物理见解。本项目中的所有计算将使用数值完整的路径积分方法进行，而不需要对通常使用的模型进行任何近似。对于这里研究的量子耗散多能级系统，由于申请人小组取得的方法学进展，这种完整的处理最近才变得可用。第一次研究表明，即使是先进的完善的近似方法导致大偏差的数值完整的结果在实践相关的参数范围。特别是对于光子学性质，这是本项目的重点误差是很大的。因此，数值上完整的处理对于得出结论性的结果是决定性的。

In this project we shall explore theoretically possibilities to prepare non-classical photon states, such as, e.g., Schrödinger-cat states, Fock states or polarization entangled two-pair states, in quantum-dot-cavity systems. Such states can not only be used to test the basics of quantum mechanics but also serve as central building blocks for possible applications in photonics, quantum-information-processing and quantum-cryptography.We shall investigate in how far the photon state in a quantum-dot-cavity system can be manipulated by different laser excitations. Of particular interest are the new physical effects evoked by the interaction with lattice oscillations (phonons) which cannot be avoided in semiconductor based quantum dot systems. Phonons may be an obstacle for the preparation; but it is also possible that phonon-assisted processes may enable new preparation protocols.We shall also study how far the generation of photon-pairs, which arise from the decay of a biexciton (i.e. a state with two electron-hole pairs) in the resonator, can be influenced by external laser fields and what role phonons play in this case. Also the so far unexplored possibility to switch between different types of entanglement will be investigated.Two-time correlation functions shall be evaluated avoiding the usually invoked quantum regression theorem which is not valid for systems with a non-Markovian environment (here provided by the phonons). Two-time correlation functions are directly connected to measurable quantities and contain important information about the non-classical properties of photons. New physical insights in particular into the significance of non-Markovian effects are expected to be found by simulating key quantities of photonic systems such as the indistinguishability, the coherence, the degree of entanglement as well as by recording the photon statistics of N-photon bundles.All calculations within this project will be performed using numerically complete path-integral methods without any approximation to the usually used models. For the quantum-dissipative multi-level systems studied here, such a complete treatment has become available only recently due to a methodological progress reached by the group of the applicant. First studies reveal that even advanced well established approximate methods lead to large deviations from the numerically complete results in praxis-relevant parameter ranges. The errors are particularly large for photonic properties, which are the focus oft the present project. Thus, the numerically complete treatment is decisive for reaching conclusive results.