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design and simulation using microring resonators (Master thesis)

Παπακώστας, Γεράσιμος/ Papakostas, Gerasimos/ Quantum Computing and Quantum Technologies/ Κβαντική Υπολογιστική και Κβαντικές Τεχνολογίες

Quantum computing leverages the fundamental principles of quantum mechanics, namely superposition, entanglement, and interference, to perform computations that are practically intractable for classical computing systems. Among the various technological platforms proposed for quantum information processing, photonics stands out due to its intrinsic high-speed operation, robustness against environmental noise, and scalability. This thesis presents the design and simulation of all-optical single-qubit quantum gates based on Micro-Ring Resonator (MRR) technology, utilizing silicon nitride (Si₃N₄) as the core material platform. A seven-resonator architecture is employed to implement the fundamental Pauli gates (X, Y, and Z), while a novel two-qubit architecture is proposed for realizing the Controlled-Z gate through purely optical means. Optical pumping is used to control the effective refractive index of each resonator via the Kerr nonlinearity, enabling dynamic modulation of phase and amplitude without the need for electronic control. Analytical modeling, supported by Coupled-Mode Theory (CMT), establishes the relationships among resonance wavelength, phase shift, and optical power. Extensive simulations are carried out using Python to evaluate the performance of the proposed architectures. The optical model validates the resonance and phase characteristics predicted by theory, while quantum-level verification confirms that the resulting optical field transformations correspond to the desired Pauli unitary operators. The calculated gate fidelities approach 0.99, with simulated insertion losses below 1 dB and switching times on the order of picoseconds. The results demonstrate that all-optical control of quantum logic operations is feasible within the capabilities of current photonic fabrication technologies. The proposed system offers a scalable, low-power, and ultrafast platform for quantum photonic computing, bridging the gap between integrated photonics and quantum information processing.