Single-photon Properties Of Self-assembled Semiconductor Quantum Dots And Its Applications In Quantum Information

Since the second half of the20th century, with the rapid development of semicon-ductor nanofabrication technology, the limit of size of electronic chips changed from micron to nanometer scale. While energy consumption had been found would gener-ate heat in computer chips,this greatly influenced the development of chip integration and limited calculation speed of the classical computer. Therefore, the development of more faster and smaller physical carrier for classical information had encountered an unprecedented bottleneck. Quantum information came out due to the demand for scientific and technological development. As the Shor algorithm was proposed, people saw the advantages of quantum parallel algorithm. And this made people place high hopes on the quantum information. Three dimensional limiting makes the Semicon-ductor self-assembled quantum dot (SAQD)atom alike energy structure and discrete energy levels. So the energy level of the SAQD has limit lifetime and this makes it ra-diate single photons and be a potential system for the single photon sources.Moreover, the mature developed semiconductor Nonofabrication technology can be well applied on the SAQD, so the quantum dots (QDs) is easily to integrate with electronic chips. Therefore, I selected"Optical properties of self-assembled semiconductor quantum dots and its applications in quantum information"as the main topic of this thesis.Our primary works are as follow:1. SAQD is a potential system for the single photon sources which has atom alike structure.The semiconductor SAQD is a man-made solid system which has atom alike structure. It has discrete energy levels and emits single photons because current carriers in it are limited in three dimensions.Moreover, as semiconductor Nanofabrica-tion technology can be well used in it, SAQD is easily to integrate with electronic chips which makes the application prospect of it more vastity.2. We separated a single QD with method of sparse QD sample or making mask and mesa on the QD sample The QD samples fabricated in different conditions have different properties.We must isolate single photon to obtain the single photon source. One way is choosing appropriate temperature and other factors to grow sparse QD sample. Another useful method is making mask or mesa on the QD sample. We detected single photon emissions on the InAs/GaAs QD sample using methods men-tioned before.Moreover, we also obtained single QD in1550-nm telecom band by making mask on the InAs/InP QD sample.3. We measured correlation between exciton and biexciton emitted from SAQD. The QD transitions to biexciton state when it absorb two photons with opposite spin orientation. It is a cascade radiation progress when the electron decays from the biexciton state to ground state. First, the QD emits a photon (biexciton) and decays to the exciton state. Then it emits another photon (exciton) when decays to ground s-tate. We detected the exciton and biexciton emissions from QD in our experiment, then researched their correlation relationship and obtained conclusion that they had great correlation with each other.4. We realized quantum wheeler’s delayed-choice experiment Light is believed to exhibit wave-particle duality. The exhibition of light, wave or particle, is decided by the using detector in classical Young’s double-slit experiment, according to Bohr’s complementarity principle. We observed the wave-particle morphing phenomenon of a single photon by quantum wheeler’s delayed-choice experiment. More importantly, we also illustrated, for the first time, the behaviour of the quantum wave-particle su-perposition state of a single photon which revealed the deep relationship between the complementarity principle and the superposition principle. We got further understand-ing of the complementarity principle after the experiment.5. We realized Simpson’s paradox in quantum system Simpson’s paradox is a typical phenomenon in statistics. Some real-life examples of Simpson’s paradox always emerge in social-science statistics and medical-science statistics. Single photons emit-ted from the same QDs are independent of one another. Which makes them suitable for researching the Simpson’s paradox. We showed two kinds of Simpson’s paradoxes in our experiment.