[[Quantum Information|Quantum information]] is unstable when left [[Quantum Error Correction|uncorrected]]. Smallest interactions between the environment or other particles will lead to a change in the [[Quantum State|quantum state]]. In addition to [[Dephasing|dephasing]], *energy relaxation* is a mechanism that contributes to the loss of [[Quantum Information|quantum information]], i.e. to the [[Decoherence|decoherence]] of [[Qubit|qubits]]. Energy relaxation describes jumps between [[Bohr Model|energy levels]] so that the system comes into (thermal) equilibrium with its environment. If we cool a system to a low enough temperature, energy relaxation will happen towards the [[Ground State|ground state]] of the system. Below, the process is displayed in two different illustrations: on the left, we see energy relaxation on the Bloch sphere: the states moves towards the North Pole of the [[Bloch Sphere|Bloch sphere]], the ground state of the [[Qubit|two-level system]]. On the right side, we displayed the relaxation towards the [[Ground State|ground state]] in terms of the energy. ![[energy_relaxation.excalidraw.light.svg]] >[!read]- Further Reading > - [[Dephasing]] > - [[Decoherence]] >[!ref]- References