This work explores the dynamics of quantum Fisher information (QFI) in open quantum systems coupled to squeezed reservoirs, providing a mathematical framework for analyzing parameter estimation precision under decoherence. We analyze QFI in two-qubit systems undergoing pure dephasing, considering the effects of squeezing parameter, phase difference, and coupling strength within an Ohmic spectral density model. The decoherence factor shows how reservoir engineering influences coherence loss. Numerical results demonstrate that optimal squeezing and local bath configurations enhance QFI preservation, while collective couplings accelerate decay. We also examine the interplay with von Neumann entropy, highlighting their inverse correlation, where increased mixedness reduces metrological sensitivity.
High-precision quantum parameter estimation is fundamental to the advancement of quantum metrology. Although reservoir engineering provides a powerful approach to improve estimation by tailoring system-environment interactions, the role of the squeezing phase and correlations arising from the sequential utilization of the same squeezed reservoir remains inadequately explored. In this work, we employ a correlated squeezed-thermal reservoir to enhance the precision of estimating the phase parameter
φ and the correlation factor
μ, both individually and simultaneously. We show that the squeezing phase
Φ is crucial for achieving quantum-enhanced precision, with optimal phase-matching conditions that depend strongly on
μ. Specifically, we derive the near-optimal phase-matching relations aimed at maximizing the quantum Fisher information (QFI) for both
φ and
μ, as well as minimizing the total variance
Δsim in joint estimation. Furthermore, we show that the joint estimation variance is dominated by
Fφ, which motivates our search for the phase-matching conditions that minimize
Δsim. Through the ratio
R of variances, we demonstrate that joint estimation conserves quantum resources and maintains high precision when the squeezing phase is optimized for
Fφ, despite the inherent incompatibility of the parameters. These findings provide practical insights into reservoir engineering strategies for high-precision quantum sensing and information processing.
Quantum Fisher information (QFI) quantifies the sensitivity of a quantum state to a parameter change and plays a key role in quantum metrology. Meanwhile, quantum coherence is a crucial resource for quantum information processing. However, despite extensive studies on various aspects of quantum metrology, the interplay between the dynamics of the QFI and quantum coherence remains unexplored. Here, we explore the factorization relationship between the QFI and quantum coherence, both theoretically and experimentally. We prepare pure states in qubit and qutrit systems and apply unitary evolution to investigate this relationship. Our results confirm the factorization law, offering strong evidence for this relationship. Furthermore, we establish a lower bound on the variance of the estimated parameter that does not require the final state information. This approach reveals a deep connection between the QFI and quantum coherence, providing insights into quantum parameter estimation. These findings have potential applications in quantum sensing and quantum metrology.
Abstract We have investigated the teleportation of quantum Fisher information (QFI) for a single-qubit system by using two different maximally entangled pure states as resources influenced by a Davies-type Markovian environment. According to the definition of QFI, we first derive the explicit analytical results of QFI with respect to the weight parameter and phase parameter under decoherence. Our analytical results show that the teleportation of QFI is seriously affected by two classes of environment, including dissipative and pure dephasing, depending on the parameter of the teleported state during the teleportation process. In particular, for the optimal precision of estimating the weight parameter is only affected by a dissipative environment with temperature, while the precision of estimating the phase parameter is merely influenced by the dephasing environment.
We investigate the simultaneous control of quantum parameter-estimation precision and non-Markovian memory effects in a driven two-qubit system that is collectively coupled to a leaky cavity. Using a dressed-state formalism, we derive analytical solutions for identical and non-identical qubits and analyze how classical driving and detuning affect metrological performance. Classical driving enhances the quantum Fisher information (QFI) by sustaining coherence and shifting effective transitions away from cavity resonance, thereby suppressing decoherence in both weak- and strong-coupling regimes. The steady-state QFI is further improved by positive classical-field detuning, which reduces spectral overlap with the lossy reservoir. To characterize memory effects, we examine the QFI-flow and the Breuer–Laine–Piilo (BLP) trace-distance measure. Our results reveal a nontrivial control trade-off: increasing the Rabi frequency suppresses non-Markovian information backflow, whereas increasing qubit detuning enhances memory effects by promoting system–environment correlations. Despite their different definitions, the QFI-flow and BLP measures yield consistent qualitative behavior in this system. These findings demonstrate that classical-field parameter tuning empowers researchers to optimize estimation precision and non-Markovianity in dissipative cavity-QED, with direct applicability to superconducting circuit platforms.
We consider the optimal parameter estimation for a two-level system coupled to multiple bosonic reservoirs. By using quantum Fisher information (QFI), we investigate the effect of the Markovian reservoirs’ number N on QFI in both weak and strong coupling regimes for a two-level system surrounded by N zero-temperature reservoirs of field modes initially in the vacua. The results show that the dynamics of QFI non-monotonically decays to zero with revival oscillations at some time in the weak coupling regime depending on the reservoirs’ parameters. Furthermore, we also present the relations between the QFI flow, the flows of energy and information, and the sign of the decay rate to gain insight into the physical processes characterizing the dynamics.
Accurately characterizing the properties of structured reservoirs is a key challenge in quantum systems and is of great importance for advances in quantum metrology and sensing. In this work, we employ a two-level system (qubit) as a probe, which is coupled to a structured reservoir consisting of an ancilla qubit and a Markovian environment modeled as a thermal bath. By exploiting non-Markovian dynamics, we systematically investigate the effectiveness of different interaction types between the probe and ancilla for estimating critical parameters, including temperature, ancilla frequency, and system-bath coupling strength. We quantify the precision of parameter estimation using quantum Fisher information (QFI) and analyze the system dynamics in both transient and steady-state regimes. Our findings demonstrate that non-Markovianity substantially enhances parameter estimation in the transient regime, with specific interactions facilitating sustained information backflow and yielding higher QFI values. However, the performance of these interactions is contingent on the parameter under estimation and the operational regime. For instance, certain interactions become prominent in the transient regime but exhibit diminished utility in the steady state, whereas others maintain their effectiveness even at equilibrium. These results stress the importance of judiciously selecting interactions adapted to specific estimation objectives and operational regimes.