The second lecture in this series starts by providing a definition of quantum technology, quantum metrology, and quantum-based measurements along with a short summary of the properties required of the devices and underlying technology. These properties include that the devices must be deployable, usable, flexible, and manufacturable. The lecture then provides a brief introduction to single-photon technologies including their potential application as a source of certifiable random numbers. The lecture continues with an explanation of how this technology may be the basis for a future redefinition of the candela. This is followed by an overview of photon pressure and its use for calibrating small mass and force. The lecture then presents new concepts for measuring ultra-high vacuum and how atom-based sensors provide a means for measuring electric and magnetic fields in addition to chip-scale atomic clocks. The lecture concludes with a brief description of the dissemination of the quantum SI including the development of embedded “chip-scale” metrology in the broader infrastructure.