Imperfect Quantum Photonic Integrated Circuits With Quantum Dot Phase Shifters

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McCaw, Adam
Quantum Nanophotonics , Quantum Computing
There has recently been a tremendous movement in research towards the field of quantum computing due to its potential to solve problems not possible with classical systems. Quantum computers can be implemented using on-chip quantum photonic circuits, which leverage photons as information for low-loss, high-speed processing. Integrating these circuits on-chip would allow for mass production with consistent performance and integration with electronic components. However, these circuits need to be cryogenically compatible to integrate single-photon detectors, and highly scalable for complex circuit implementation. In this thesis, we propose the use of quantum dots as phase shifters in quantum photonic circuits, which provide advantages over current phase shifter architecture through cryogenic compatibility, compactness, and fast reconfigurability. We show how chirally coupled quantum dots can achieve directional photon scattering with phase shifts of [−π, π], and how these can be used in Mach-Zehnder interferometer mesh architecture to implement any linear quantum circuit. We then go on to consider both nanophotonic and quantum dot imperfections, implementing a novel global phase shift optimization method to improve performance. By simulating random circuits with ranges of imperfections, we determine performance dependence for each imperfection independently. We then simulate state-of-the-art and typical imperfections to determine our architecture’s validity and scalability. From these results, we determine that fault-tolerant, highly scalable quantum computers are achievable with this architecture. Lastly, we consider this architecture for specific circuits, where we see near-perfect performance for state-of-the-art imperfections.
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