INTEGRATED QUANTUM PHOTONIC CIRCUITS WITH QUANTUM DOTS
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Scalable quantum photonics require efficient single-photon emitters as well as low-loss reconfigurable photonic platforms that connect and manipulate these single photons. Quantum dots are excellent sources of on-demand single photons and can act as stable quantum memories. Therefore, integration of quantum dots with photonic platforms is crucial for many applications in quantum information processing.
In this thesis, we first describe hybrid integration of InAs quantum dots hosted in InP to silicon photonic waveguides. We demonstrate an efficient transition of quantum emission to silicon. Quantum nature of the emission is confirmed through photon correlation measurements. Secondly, we present a micro-disk resonator device based on silicon photonics that enables on-chip filtering and routing of single photons generated by quantum dots. The tunability of silicon photonics decreases at low temperatures due to “carrier freeze-out”. Because of a strong electro-optic effect in lithium niobate, this material is the ideal platform for reconfigurable photonics, even at
cryogenic temperatures. To this end, we demonstrate integration of quantum dots with thin-film lithium niobate photonics promising for active switching and modulating of single photons.
More complex quantum photonic devices require multiple identical single-photon emitters on the chip. However, the transition wavelength of quantum dots varies because of the slightly different shape and size of each dot. To address this hurdle, we propose and characterize a quantum dot device located in an electrostatic field. The resonance wavelength of the quantum dot emission is tuned up to 8 nm, more than one order of magnitude greater than the transition linewidth, opening the possibility of tuning multiple quantum dots in resonance with each other.
Finally, we discuss the application of a single quantum dot strongly coupled to a nanophotonic cavity as an efficient medium for non-linear phenomenon of optical amplification. Presence of a strong pump laser inverses the population of the quantum dot and leads to stimulated emission from the cavity-coupled quantum dot. Using this platform, we observe an optical gain of ~ 16%, significantly increased compared to previous demonstrations of gain in single solid-state quantum emitters without cavities or weakly coupled to cavities. These demonstrations are significant steps toward robust control of single photons using linear and non-linear photonic platforms.