Abstract The inherent association between real quantum systems and their surrounding environment invariably results in decoherence, leading to the loss of entanglement. This diminution in entanglement coincides with a decline in the fidelity of transmitted information using the entangled quantum resource. This study scrutinizes the impact of the squeezed generalized amplitude damping (SGAD) channel on quantum Fisher information (QFI) parameters. The SGAD channel model, a versatile framework, is also employed to simulate other dissipative channels, including amplitude damping (AD) and generalized amplitude damping (GAD). Kraus operators facilitate the modeling of noisy channels. The results reveal that, within the SGAD channel, the QFI remains impervious to the squeezing variables (r and
Φ Φ ). In the GAD channel,
FθGAD F θ GAD undergoes enhancement to a constant value with an upswing in temperature (T), while the
ϕ ϕ parameter in the GAD channel,
FϕGAD F ϕ GAD , akin to the SGAD channel, surges around T = 2 before complete loss ensues. Concerning the AD channel, the
θ θ component of the QFI initially experiences decoherence with an augmentation in the AD noise parameter (
λ λ ). Subsequently, it is restored to its initial value with a further escalation in
λ λ . Conversely, the
ϕ ϕ component of the QFI in the AD channel experiences decoherence with an elevation in the AD noise parameter (
λ λ ).
Abstract We explore the impact of channel correlations, resulting from consecutive uses of the channel, on the estimation of channel parameters. Specifically, we analyze the dynamics of quantum Fisher information (QFI) for correlation strength and coupling strength in a two-qubit system subjected to either a Random Telegraph (RT) noise channel or an Amplitude Damping (AD) noise channel. Our findings indicate that the correlation in the RT noise channel enhances the estimation precision of correlation strength but detracts from the precision of coupling strength estimation. However, the correlation in the AD noise channel exhibits a similar effect to that of the RT noise channel only in the initial stage of system’s evolution. In the long-term evolution, the correlation of the AD noise channel reduces the estimation precision of correlation strength but has no monotonic relationship with the estimation precision of coupling strength. Our study provides new insights into the effects of channel correlations on channel parameter estimation and has potential implications for controlling the precision of parameter estimation in quantum information processing.
Abstract The unavoidable interaction of a real quantum system with the environment leads to the degradation of quantum coherence. Consequently, this paper investigates how such interaction can influence the quantum Fisher information (QFI) with the Hawking effect in the Schwarzschild black hole. We have considered two models of quantum decoherence: amplitude damping and phase damping channels; both can be experimentally induced. We found that Quantum information F ϕ is more robust to phase flip channel than to the amplitude damping channel. It is observed that under the influence of phase damping channel, Quantum information F θ does not depend on Hawking temperature making the parameter estimation immune to the Hawking effect but susceptible to decoherence. We found that QFI dwindles with increasing Hawking temperature and becomes more attenuated with decoherence which implies that the parameter estimation can be achieved with higher precision when the black hole is not evaporating.
We introduce a quantum Fisher information based measurement-induced nonlocality (QFI-MIN), which quantifies the maximal statistical distinguishability induced by locally invariant unitary dynamics. The proposed measure inherits desirable properties including positivity, local unitary invariance, monotonicity under local operations, and immunity to the local ancilla problem. Analytical expressions are obtained for pure states, arbitrary two-qubit states, and two-qubit X states, revealing a direct connection with entanglement for pure systems. We further establish clear operational interpretations of QFI-MIN in quantum parameter estimation, local channel discrimination, and correlation-assisted communication. Its behavior under amplitude damping, depolarizing, and generalized amplitude damping channels demonstrates robustness against environmental noise. The proposed framework provides a physically consistent and operationally meaningful quantifier of quantum correlations, linking nonlocality, quantum metrology, and quantum information processing