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Laser Physics Letters

Quantum-memory-assisted entropic uncertainty and quantum correlation in structured reservoir

Bingbing Li, Feng Li, Jiadong Shi, Tao Wu

Published Jan 9, 2023• 4 citations
Publisher

Abstract

Abstract In this work, we investigate the dynamics of quantum-memory-assisted entropic uncertainty relation (EUR) and quantum correlation quantified by entropic discord and geometric discord within the Markovian reservoir and non-Markovian reservoir. Particularly, when the initial state is a pure sate or mixed state the EUR gradually increases during the evolution at first, but subsequently tends to stable in the long-time limit. On other hand, for the separable state the EUR almost keeps constant. In contrast, quantum discord decay asymptotically to zero for all types of initial states. As an application, we prove that both two quantum discords witnessed by the EUR are determined by the version of discord chosen, which regardless of the reservoir.

DOI
10.1088/1612-202x/acaea2

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Abstract In this work, we investigate the dynamics of quantum-memory-assisted entropic uncertainty relation (EUR) and quantum correlation quantified by entropic discord and geometric discord within the Markovian reservoir and non-Markovian reservoir. Particularly, when the initial state is a pure sate or mixed state the EUR gradually increases during the evolution at first, but subsequently tends to stable in the long-time limit. On other hand, for the separable state the EUR almost keeps constant. In contrast, quantum discord decay asymptotically to zero for all types of initial states. As an application, we prove that both two quantum discords witnessed by the EUR are determined by the version of discord chosen, which regardless of the reservoir.
Abstract We address the dynamics of the lower bound of geometric quantum discord and quantum-memory-assisted entropic uncertainty in a two-qutrit system when exposed to classical channels characterized by power-law (PL) and random telegraph (RT) noises. The system-channel coupling strategy is examined in two contexts: common qutrit-environment (CQE) and different qutrit-environment (DQE) configurations. We show that the geometric quantum discord functions remain anti-correlated with entropic uncertainty and decline as uncertainty appears in the system. The rate of entropic uncertainty appearance seems more prevalent than the decline rate of quantum discord function, suggesting that uncertainty causes the quantum correlations to fade in quantum systems. We find that non-local correlations estimated by the lower bound of geometric quantum discord are not destroyed even at the maximum entropic disorder and entropic uncertainty. In addition, the efficacy of entropic uncertainty and the lower bound is strongly influenced by the state’s purity factor, with the former being more robust at higher purity values and the latter at lower purity values. All the parameters impact entropic uncertainty, however, the mixedness of the state is noticed to greatly alter the generation of quantum memory. Besides, PL noise caused Markovian behavioral dynamics, and the RT noise allowed non-Markovian dynamics, while the latter remains more resourceful for the quantum correlations preservation and entropic uncertainty suppression. We also demonstrate how to model longer quantum correlations and provide optimal parameter settings for suppressing the dephasing and entropic uncertainty effects.
By using the quantum-memory-assisted entropic uncertainty relation (EUR), we derive a computable tight upper bound for quantum discord, which applies to an arbitrary bipartite state. Detailed examples show that this upper bound is tighter than other known bounds in a wide regime. Furthermore, we show that for any tripartite pure state, the quantum-memory-assisted EUR imposes a constraint on the shareability of quantum correlations among the constituent parties. This conclusion amends the well-accepted result that quantum discord is not monogamous.
The entropic uncertainty principle imposes a limit on how precisely two incompatible observables can be measured, which can be reduced when quantum memory is involved. We theoretically investigate the dynamics of the quantum-memory-assisted entropic uncertainty relation when either quantum memory alone or both the measured particle and the quantum memory interact with a squeezed-vacuum bath through energy-preserving interactions. We show that in both scenarios, the squeezing phase of the reservoir decreases the entropic uncertainty (EU), whereas the squeezing strength increases the EU. In addition, we find that EU can be significantly reduced when both the measured particle and quantum memory are subjected to a common squeezed-vacuum bath. Furthermore, we explore the key factors controlling the behavior of EU by exploring the competition between quantum discord and minimal missing information. Moreover, we examine the tightness of the entropic uncertainty bound (EUB) in both system-environment setups and observe that the EUB is less tight when both the measured particle and quantum memory are coupled to a common squeezed-vacuum bath.
Abstract The one-qubit teleportation protocol is one of the most well-known topics of quantum information theory. Indeed, the goal of this quantum protocol is to teleport an arbitrary quantum state. Herein, we investigate the entropic uncertainty relation in the presence of quantum memory (EUR-QM), quantum discord (QD), and fidelity of teleportation under dephasing, dissipative, and noisy environments. We relate the EUR-QM to QD and quantum teleportation and show analytically that there is a fully anti-correlated relation between QD and entropic uncertainty in a dephasing environment. In the process of our analysis, we also find an explicit relationship between the average fidelity of teleportation and the entropic uncertainty of the channel state. Significantly, the results report that the fidelity of teleportation and QD of the channel state are more stable and most efficiently under the influence of a dephasing environment than those under the influence of a dissipative or noisy environment. It turns out that under a dephasing environment, these results can be vital in practical goals where the maximum fidelity of teleportation and minimum uncertainty are required such as in quantum teleportation protocols and quantum computation.
Abstract By virtue of the quantum-memory-assisted entropic uncertainty relation (EUR), we analyze entanglement witness via the efficiencies of the estimates proposed by Berta (2010 Nat. Phys . 6 659) and Pati (2012 Phys. Rev . A 86 042105). The results show that, without a structured reservoir, the entanglement regions witnessed by these EUR estimates are only determined by the chosen estimated setup, and have no correlation with the explicit form of the initial state. On the other hand, with the structured reservoirs, the time regions during which the entanglement can be witnessed, and the corresponding entanglement regions closely depend on the choice of the estimated setup, the initial state and the state purity p . Concretely, for a pure state with p = 1 , the entanglement can be witnessed by both estimates, while for mixed states with p = 0.78 , it can only be witnessed using the Pati estimate. What is more, we find that the time regions incorporating the Pati estimate become discontinuous for the initial state with | ϕ ′ 〉 = ( | 01 〉 + | 10 〉 ) / 2 , and the corresponding entanglement regions remain the same; however the entanglement can only be witnessed once by utilizing the Berta estimate.
Abstract Using quantum discord (QD) and geometric quantum discord (GQD), quantum correlation dynamics is investigated for two coupled qubits within a multiqubit interacting system in the zero-temperature bosonic reservoir, under both weak and strong qubit-reservoir coupling regimes. The multiqubit system is connected with either a common bosonic reservoir (CBR) or multiple independent bosonic reservoirs (IBRs). In the CBR case, our findings indicate that both QD and GQD can be strengthened by increasing the number of qubits in the multiqubit system. Furthermore, we study the steady state QD and GQD in the strong coupling regime, and find that the stable value in the long-time limit is determined exclusively by the number of qubits. The evolution period of QD and GQD gets longer as the dipole–dipole interaction (DDI) strength increases, which helps prolong the correlation time and thus preserves the quantum correlation under the weak coupling regime. Further analysis reveals notable differences between the CBR and IBRs scenarios. In the IBRs case, the decay of QD and GQD becomes slower compared to the CBR case, with both measures tending to zero at a reduced rate. Moreover, GQD consistently exhibits lower values than QD in both scenarios. These findings provide valuable insights into the selection of appropriate correlation measurement techniques for quantifying quantum correlations.