In quantum mechanics, a doublet is a composite quantum state of a system with an effective spin of 1/2, such that there are two allowed values of the spin component, −1/2 and +1/2. Quantum systems with two possible states are sometimes called two-level systems.

What is singlet doublet and triplet state?

. As a result, there is only one spectral line of a singlet state. In contrast, a doublet state contains one unpaired electron and shows splitting of spectral lines into a doublet; and a triplet state has two unpaired electrons and shows threefold splitting of spectral lines.

Can the ground state be doublet?

The states |1, 1 and |0, 0 differ by flipping a spin of a single electron (marked by circles). We review the peculiarities of transport through a quantum dot caused by the spin transition in its ground state.