Developing Quantum-Optical Measurements of Excitonic Coherence for Quantum Entanglement in Single Organic Molecules

有机半导体是碳基材料，已发现其广泛用于有机发光二极管、太阳能电池、激光器和场效应晶体管。有机半导体中的激发电子态是离域电子空穴对，称为激子。最初，这些激子形成时，它们的部分分子轨道贡献都完全同相，是一个量子力学相干的物体。随后与环境的相互作用使组分退相，使激子波函数坍缩成经典物体。这种崩溃的测量和识别的化学结构，可以保持足够长的时间来利用它的量子纠缠相干是非常具有挑战性的。在这个建议新颖的量子光学测量激子相干有机半导体将开发。这将通过测量作为能量和时间的函数的单分子的Hanbury Brown和Twiss几何中的二阶光致发光强度互相关来实现。在这样做的过程中，状态耦合和状态相干性将被测量，并确定可以保持它们的化学结构。两个系统将被探讨，共轭分子二对强耦合之间存在的状态，和共价连接的二聚体激子离域发生在更大的距离。通过在单分子水平上使用新的量子光学技术获得的有价值的新知识将实现对激子性质的基本理解的进步，并突出了它们的性质可以被化学工程用于量子应用的有利方式。

Organic semiconductors are carbon-based materials that have found widespread use in organic light emitting diodes, solar cells, lasers, and field effect transistors. Excited electronic states in organic semiconductors are delocalised electron hole pairs, called excitons. Very initially these excitons are formed with their partial molecular orbital contributions all perfectly in phase, a quantum mechanically coherent object. Subsequent interactions with the environment dephase the components, collapsing the exciton wavefunction into a classical object. Measurement of this collapse and identifying chemical structures that can preserve coherence long enough for it to be harnessed for quantum entanglement are very challenging.In this proposal novel quantum-optical measurements of excitonic coherence in organic semiconductors will be developed. This will be achieved by measuring the second order photoluminescence intensity cross-correlations in a Hanbury Brown and Twiss geometry of single molecules as a function of energy and time. In doing so, state coupling and state coherences will be measured and chemical structures that can preserve them identified. Two systems will be explored, conjugated molecular dyads where strong coupling exists between the states, and covalently linked dimers where exciton delocalisation occurs over larger distances. The valuable new knowledge that is obtained by working at the single molecule level with novel quantum-optical techniques will realise advances in the fundamental understanding of the nature of excitons, and highlight advantageous ways their properties can be chemically engineered for quantum applications.