  Silicon photonics has been studied as an integratable optical platform where
numerous applicable devices and systems are created based on modern physics and
state-of-the-art nanotechnologies. The implementation of quantum mechanics has
been the driving force of the most intriguing design of photonic structures,
since the optical systems are found of great capability and potential in
realizing the analogues of quantum concepts and phenomena. Non-Hermitian
physics, which breaks the conventional scope of quantum mechanics based on
Hermitian Hamiltonian, has been widely explored in the platform of silicon
photonics, with promising design of optical refractive index, modal coupling
and gain-loss distribution. As we will discuss in this chapter, the
unconventional properties of exceptional points and parity-time symmetry
realized in silicon photonics have created new opportunities for ultrasensitive
sensors, laser engineering, control of light propagation, topological mode
conversion, etc. The marriage between the quantum non-Hermiticity and classical
silicon platforms not only spurs numerous studies on the fundamental physics,
but also enriches the potential functionalities of the integrated photonic
systems.
