The behaviors of quantum Fisher information (QFI) and quantum signal to noise ratio (QSNR) of a qutrit interacting with random telegraphic noise (RTN) are studied. Analytical relations for both quantities are obtained for the ground and first excited states of qutrit as initial states and numerical procedure is followed for the superposition of these states. Every choice of the initial state leads to considerably larger values of QFI. The ground initial state can be favorable for precise estimation of the smaller values of unknown parameter of RTN for all choices of the time of interaction. Depending on the time of interaction, the excited initial state of qutrit could do better for both smaller and larger values in the slow regime of RTN. Different choices of the initial superposition state could serve better for precise estimation purposes. Our results suggest that a qutrit may perform better than a qubit as a probe for precise estimation of unknown parameters.
The behaviors of quantum Fisher information (QFI) and quantum signal to noise ratio (QSNR) of a qutrit interacting with random telegraphic noise (RTN) are studied. Analytical relations for both quantities are obtained for the ground and first excited states of qutrit as initial states and numerical procedure is followed for the superposition of these states. Every choice of the initial state leads to considerably larger values of QFI. The ground initial state can be favorable for precise estimation of the smaller values of unknown parameter of RTN for all choices of the time of interaction. Depending on the time of interaction, the excited initial state of qutrit could do better for both smaller and larger values in the slow regime of RTN. Different choices of the initial superposition state could serve better for precise estimation purposes. Our results suggest that a qutrit may perform better than a qubit as a probe for precise estimation of unknown parameters.
We address the use of simple quantum probes for the spectral characterization of classical noisy environments. In our scheme a qubit interacts with a classical stochastic field describing environmental noise and is then measured after a given interaction time in order to estimate the characteristic parameters of the noise. In particular, we address estimation of the spectral parameters of two relevant kinds of non-Gaussian noise: random telegraph noise with a Lorentzian spectrum and colored noise with a $1/{f}^{\ensuremath{\alpha}}$ spectrum. We analyze in detail the estimation precision achievable by quantum probes and prove that population measurement on the qubit is optimal for noise estimation in both cases. We also evaluate the optimal interaction times for the quantum probe, i.e., the values maximizing the quantum Fisher information (QFI) and the quantum signal-to-noise ratio. For random telegraph noise the QFI is inversely proportional to the square of the switching rate, meaning that the quantum signal-to-noise ratio is constant and thus the switching rate may be uniformly estimated with the same precision in its whole range of variation. For colored noise, the precision achievable in the estimation of ``color,'' i.e., of the exponent $\ensuremath{\alpha}$, strongly depends on the structure of the environment, i.e., on the number of fluctuators describing the classical environment. For an environment modeled by a single random fluctuator estimation is more precise for pink noise, i.e., for $\ensuremath{\alpha}=1$, whereas by increasing the number of fluctuators, the quantum signal-to-noise ratio has two local maxima, with the largest one drifting towards $\ensuremath{\alpha}=2$, i.e., brown noise.
In the present paper, the joint effects of two kinds of classical environmental noises, without direct interaction among each other, on the dynamics of quantum correlations (QCs) of a three-qubit system coupled in independent environments is investigated. More precisely, we join the random telegraph noise (RTN) and the static noise (SN) and focus on the dynamics of entanglement and quantum discord (QD) when the qubits are initially prepared in the GHZ- and W-type states. The overall noise affecting the qubits is obtained by combining the RTN and SN in two different setups. The results show that the disorder of the environmental noise as well as its memory qualities and the purity of the initial state considered play a crucial role in the time evolution of the system in such a way that the dynamics of QCs can be controlled by varying them. In fact, we show that, depending on the initial state and noise regime considered, the rate of collapse of QCs may either decrease or increase with the increase of the degree of disorder of the SN, the switching rate of the RTN and the purity of the initial state.
We study the evolution of entanglement and nonlocality of a non-interacting qubit-qutrit system under the effect of random telegraph noise (RTN) in independent and common environments in Markovian and non-Markovian regimes. We investigate the dynamics of qubit-qutrit system for different initial states. These systems could be existed in far astronomical objects. A monotone decay of the nonlocality (entanglement) is found in the Markov regime, while for non-Markovian noise, phenomena of sudden change (death) and revival occurs. We find that the preserving nonlocality (entanglement) depends on initial state of the system in common and independent environments; so, we can not strictly conclude that independent or common environments are more robust against the noise.
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.
Time evolution of the quantum correlation of the hybrid qubit-qutrit system in multilocal and global dephasing under the effect of a classical noises environment is presented. We considered the qutrit in z direction and the qubit x direction. In addition, our system presents two configurations: the different and the common environment and our discussion involves three types of noises: A Static Noise (SN), Random Telegraph Noise (RTN) and Ornstein- Uhlenbeck noise (OU). By using the density matrix approach to determine the evolution of the state of the system, the found that the static noise is fatal for the quantum entanglement, the quantum correlation and for RTN and OU noises the quantum entanglement, the quantum correlation decreases monotonically with a sufficiently long time. Therefore, we can say that, entanglement and the quantum correlation are more robust to the noise precisely those Random telegraph noise and Ornstein-Uhlenbeck noise.
We investigate the dynamics of entanglement, quantum discord (QD) and state coherence in a bipartite and noninteracting spin-qutrits system under mixed classical noises. Specifically, the collective effects of static noise (SN) and random telegraphic noise (RTN) each being coupled with a marginal system, are analyzed. While the static noise models a non-Markovian environment, the dynamic noise can model both a Markovian or a non-Markovian environment, and both dynamics are studied. We show that quantum correlations and coherence may survive the noise degrading effects at sufficiently long time when the Markovian regime of the RTN is considered. Meanwhile, the opposite is found in the non-Markovian regime, wherein the nonmonotonic dynamics of quantum features avoid sudden death phenomena. However, the static noise is more fatal to the survival of quantum correlations and quantum state coherence as compared to the RTN.