Algorithmic cooling
A qubit (or quantum bit) is a unit of information that can be in a superposition of two states, denoted as formula_1 and formula_2. The general superposition can be written as formula_3where formula_4 and formula_5. If one measures the state of the qubit in the orthonormal basis composed of formula_1 and formula_2, one gets the result formula_1 with probability formula_9 and the result formula_2 with probability formula_11.
Flux qubit
The flux qubit is distinguished from other types of superconducting qubit such as the charge qubit or phase qubit by the coupling energy and charging energy of its junctions. In the charge qubit regime the charging energy of the junctions dominates the coupling energy, while in a flux qubit the situation is reversed and the coupling energy dominates. Typically in a flux qubit the coupling energy is 10-100 times greater than the charging energy. It is this ratio that allows the Cooper pairs to flow continuously around the loop, rather than tunnel discretely across the junctions as in a charge qubit.