High Dynamic Range Quantum Optics

: Enabling bigger systems

Abstract

The development of a quantum optical quantum computer has three central aspects. These
are the generation of single photon photons, the manipulation of these photons and
detection. Due to the strict performance requirements across each of these domains, it is
desirable to have each of these elements monolithically integrated into a single photonic system.
One major challenge with integrating these systems is that the intense pump fields necessary to
generate single photons are at odds with the highly sensitive single photon detectors. To detect
the single photons that carry our quantum information, the pump must be extinguished to such
a degree as to not blind the detectors and prevent us from accessing the quantum state used for
computation.
In this thesis, we will describe our efforts in tackling this problem. We will come to understand
that high-extinction pump filtering comes in two parts, spectral and spatial filtering. On the
spectral side, we develop high-extinction coherency-broken Bragg filters that effectively remove
the pump from the waveguide. Despite the pump light being removed from the waveguide there
is still a problem with the residual scatter that persists inside the whole photonic chip. To this
end, we develop a spatial filter, a pattern of micro-machined holes through the entire chip height.
We demonstrate an additional extinction of -18.83 ± 0.36 dB that is provided by the spatial filter
device. Finally, we demonstrate tensor network methods for simulating nonlinear quantum optics
in time, with the goal being to provide a tool for designing more efficient sources, alleviating the
high-performance requirements required for high-extinction filtering.

Date of Award	19 Mar 2024
Original language	English
Awarding Institution	University of Bristol
Supervisor	Joshua W Silverstone (Supervisor)