Spontaneous emission increases the entropy of the subsystem, specifically the atom and emitted photon, when described with a mixed state. In contrast, the total closed system's von Neumann entropy remains unchanged, as information is encoded through entanglement with the environment. Achieving laser cooling requires both spontaneous and stimulated emission, highlighting the necessity of spontaneous emission in quantum processes.
PREREQUISITESPhysicists, quantum mechanics students, and researchers interested in the thermodynamic implications of quantum processes and the role of entropy in spontaneous emission.
Yes. And the corollary is that you cannot achieve laser cooling of atoms with stimulated emission alone, you need spontaneous emission.Khashishi said:Does entropy increase during spontaneous emission?
The answer depends on what kind of entropy do you have in mind. Do you mean entropy of the total closed system, or entropy of the subsystem (e.g. atom and photon, but without environment)? If you mean the former, then von Neumann entropy does not change, and information is encoded in the entanglement with environment. If you mean the latter, then von Neumann entropy increases, provided that you describe the system with the mixed state without a projection to the measured state.Khashishi said:Does entropy increase during spontaneous emission?
If not, how is the information about the emitted photon mode encoded into the initial state of the atom (and/or environment)? If so, where does the extra information come from?