Protecting Quantum Fisher Information in Correlated Quantum Channels

• Published in: Annalen der Physik Vol. 532; no. 1
• Main Authors: Hu, Ming‐Liang, Wang, Hui‐Fang
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.01.2020
• Subjects: Channels; correlated quantum channel; Correlation; decoherence; Depolarization; Fisher information; Parameterization; quantum Fisher information; Qubits (quantum computing)
• ISSN: 0003-3804; 1521-3889
• DOI: 10.1002/andp.201900378

Quantum Fisher information (QFI) has potential applications in quantum metrology tasks. QFI is investigated when the consecutive actions of a quantum channel on the sequence of qubits have partial classical correlations. The results showed that while the decoherence effect is detrimental to QFI, effects of such classical correlations on QFI are channel‐dependent. For the Bell‐type probe states, the classical correlations on consecutive actions of the depolarizing and phase flip channels can be harnessed to improve QFI, while the classical correlations in the bit flip and bit‐phase flip channels induce a slight decrease of QFI. For a more general parameterization form of the probe states, the advantage of using the initial correlated system on improving QFI can also remain in a wide regime of the correlated quantum channels. The control of quantum Fisher information (QFI) in correlated quantum channels is explored. It is shown that while the decoherence effect is detrimental to QFI, the classical correlations between consecutive actions of the quantum channel can be harnessed to improve QFI in a wide regime of the quantum channel, and such an improvement applies to very general probe states.