Photonic quantum technologies leverage quantum mechanical effects to enable secure communication, enhanced measurement, and quantum information processing. These technologies rely on photons for their high-speed transmission and low noise, making them essential for future quantum networks and processors. Quantum information science has shown that quantum mechanical effects can be harnessed to achieve new functionalities, such as quantum key distribution (QKD), which uses quantum states to ensure secure communication. Future applications include quantum computers, quantum metrology, and quantum lithography, which could offer exponential improvements in computation and precision. Quantum mechanics, developed in the early 20th century, describes the probabilistic nature of quantum systems, including superposition and entanglement. These principles underpin photonic quantum technologies, which use single photons or quantum states of light for information processing. Photonic quantum technologies originate from quantum optics and have been tested in experiments such as quantum teleportation and entanglement. Single photons are a leading approach for quantum information processing, but challenges remain in achieving high-fidelity deterministic operations. Quantum metrology aims to achieve the highest precision by using quantum states, while quantum lithography uses quantum states to define features smaller than the wavelength. Bright laser beams can also be used to create quantum states, such as squeezed states, which have reduced noise and are useful for quantum communication and metrology. Squeezed states and entangled states are key for quantum information processing, enabling tasks like quantum teleportation and quantum computing. Integrated photonic circuits are crucial for scaling up quantum technologies. These circuits use waveguides and other components to manipulate photons on a chip, enabling high-performance quantum devices. Challenges include achieving strong nonlinear interactions, high-efficiency single-photon sources, and detectors. Semiconductor-based single-photon sources, such as quantum dots in cavities, are promising for generating indistinguishable photons. Solid-state cavity quantum electrodynamics (QED) has shown progress in achieving strong nonlinear interactions, which are essential for quantum computing. Future developments in photonic quantum technologies will depend on advances in integrated photonics, quantum sources, and detectors. These technologies have the potential to revolutionize secure communication, quantum computing, and precision measurement. The integration of quantum mechanics with photonics is key to realizing the full potential of quantum technologies.Photonic quantum technologies leverage quantum mechanical effects to enable secure communication, enhanced measurement, and quantum information processing. These technologies rely on photons for their high-speed transmission and low noise, making them essential for future quantum networks and processors. Quantum information science has shown that quantum mechanical effects can be harnessed to achieve new functionalities, such as quantum key distribution (QKD), which uses quantum states to ensure secure communication. Future applications include quantum computers, quantum metrology, and quantum lithography, which could offer exponential improvements in computation and precision. Quantum mechanics, developed in the early 20th century, describes the probabilistic nature of quantum systems, including superposition and entanglement. These principles underpin photonic quantum technologies, which use single photons or quantum states of light for information processing. Photonic quantum technologies originate from quantum optics and have been tested in experiments such as quantum teleportation and entanglement. Single photons are a leading approach for quantum information processing, but challenges remain in achieving high-fidelity deterministic operations. Quantum metrology aims to achieve the highest precision by using quantum states, while quantum lithography uses quantum states to define features smaller than the wavelength. Bright laser beams can also be used to create quantum states, such as squeezed states, which have reduced noise and are useful for quantum communication and metrology. Squeezed states and entangled states are key for quantum information processing, enabling tasks like quantum teleportation and quantum computing. Integrated photonic circuits are crucial for scaling up quantum technologies. These circuits use waveguides and other components to manipulate photons on a chip, enabling high-performance quantum devices. Challenges include achieving strong nonlinear interactions, high-efficiency single-photon sources, and detectors. Semiconductor-based single-photon sources, such as quantum dots in cavities, are promising for generating indistinguishable photons. Solid-state cavity quantum electrodynamics (QED) has shown progress in achieving strong nonlinear interactions, which are essential for quantum computing. Future developments in photonic quantum technologies will depend on advances in integrated photonics, quantum sources, and detectors. These technologies have the potential to revolutionize secure communication, quantum computing, and precision measurement. The integration of quantum mechanics with photonics is key to realizing the full potential of quantum technologies.