Beihang University Finds Purification Rate Constant at Unit Efficiency

Researchers at Beihang University have identified a boundary on how effectively quantum bits, or qubits, can be purified, revealing that for a qubit, the decay rate of the determinant presents a sharp null test at unit efficiency. The team reports deriving three distinct speed limits governing quantum state purification, and these limits consistently appear in a ratio of two to four to eight. This precise mathematical relationship suggests an underlying structure to the purification process. The maximal decay rate is a state-independent constant, at which point purification effectively stops, implying a hard boundary on achievable improvement. These…