Jiaying Yang, Quantum Technology

Opponent:
Christian Kraglund Andersen, TU Delft, Netherlands

Abstract

Distributed Quantum Computing (QC) is a system that interconnects multiple quantum processors through quantum communication channels. It enables scalable and robust quantum computations by leveraging the combined capabilities of each processor. This thesis explores key components of distributed QC, specifically focusing on the generation of propagating microwave photons and the emission of entanglement using superconducting systems. We present a series of experimental and theoretical demonstrations that establish essential foundations for high-fidelity quantum state transfer and remote entanglement generation via propagating microwave photons. First, we demonstrate deterministic quantum state transfer from a superconducting qubit to a propagating microwave mode by encoding the quantum state as a superposition of the vacuum state and the single-photon Fock state. We employ photon shaping techniques to emit photons with time-symmetric amplitude and constant phase, thereby ensuring efficient reabsorption by a receiver. However, photon loss remains the primary loss channel in distributed QC networks. To address this challenge, we further propose and experimentally generate frequency-bin-encoded photonic modes, that can serve as a heralding protocol for detecting photon losses. The protocol is achieved by deterministic encoding of qubit information into two simultaneous photonic modes with different frequencies. By excluding the vacuum as a logical state, frequency-bin-encoded photons enable effective error detection at the receiver processor. Finally, we explore the generation of entangled photonic modes through the continuous driving of a quantum emitter. We demonstrate that the temporally filtered modes, obtained from the two sidebands of the resonance fluorescence spectrum, exhibit entanglement and can be extracted to separate quantum processors. These works serve as foundational building blocks for quantum state transfer and remote entanglement in distributed QC networks, with potential applications in waveguide quantum electrodynamics and scalable quantum architectures.