Singulettzustands

Singulettzustand refers to a quantum mechanical state of a system, typically a pair of particles, where their intrinsic angular momenta, or spins, are paired in such a way that their total spin angular momentum is zero. This means that the spins of the individual particles are antiparallel. For two spin-1/2 particles, such as electrons, a singlettzustand is one of the two possible composite spin states, the other being the triplettzustand. In the singlettzustand, the spin state is antisymmetric with respect to the exchange of the two particles. This property is a direct consequence of the Pauli exclusion principle, which states that identical fermions cannot occupy the same quantum state, and in the case of spin, requires that the overall wavefunction be antisymmetric.

The concept of the singlettzustand is crucial in various areas of quantum physics, including atomic physics, particle physics, and quantum information. For instance, the formation of chemical bonds often involves electrons in singlettzustands. In entanglement, a pair of particles can be created in a singlettzustand, meaning their spins are correlated even when separated by large distances. Measuring the spin of one particle instantaneously determines the spin of the other, irrespective of the distance between them, a phenomenon famously explored in Bell's theorem and experiments testing the foundations of quantum mechanics. The energy levels of molecules and atoms can also be influenced by the spin pairing in singlettzustands, leading to observable spectral differences compared to triplettzustands.