Planck’s constant is a fundamental physical constant that is utterly important in quantum mechanics. It is named after the father of quantum theory, Max Planck. When you multiply the Planck constant by a photon’s frequency, you get the photon‘s energy. We use the letter “h” to denote it. If the quantum computer becomes a reality, it could have a significant impact on the world.
The fundamental constant of physics, the Boltzmann constant, is one of the seven "defining constants" that have been given exact definitions.