Wide-bandgap integrated photonics for quantum technologies

Abstract

Development of quantum networks is necessary for quantum communication and distributed quantum computing. This requires the distribution of entanglement across many stationary qubits in the network. Solid state defect quantum emitters (QEs) can function as light-matter interfaces for connecting the internal electron spin states acting as stationary qubits and quantum states of emitted photonic qubits. Entanglement can then be generated between distant spin qubits by heralded optical measurements of the emitted photons over fibers. Thus, a key challenge is the control of many QEs, as well as efficient routing and detection of the spin-state-dependent photons. With QEs being in solid-state, we can achieve the scaling needed through miniaturization of the control and routing components by using integrated electronics and photonics.

However, advanced and commonly-used integrated photonic platforms produced in foundries are based on silicon and silicon nitride, which are incompatible with the short wavelength emission of leading solid-state QEs. As such, there is a need for a wide-bandgap integrated photonics platform for quantum technologies. This thesis first develops photonic integrated circuits (PICs) based on aluminum nitride (AlN) on sapphire, which enables low-loss routing from the visible down to the ultraviolet spectrum. We will then show that thin film AlN is also host to bright, high-purity QEs compatible with monolithic PIC integration. As solid-state emitters in diamond are among the promising qubits for quantum networks due to their efficient optical interfaces and minute-scale spin coherence, we will then present on the large-scale heterogeneous assembly of diamond-waveguide-coupled QEs into AlN photonic circuits with in situ wavelength tuning.

To demonstrate the versatility of this photonics platform, we will lastly discuss the heterogeneous integration of QEs in 2D materials and detectors. These advances show that AlN is a promising and versatile wide-bandgap integrated photonics platform for quantum information processing.