We study non-Markovianity and information flow for qubits experiencing local dephasing with an Ohmic class spectrum. We demonstrate the existence of a temperature-dependent critical value of the Ohmicity parameter $s$ for the onset of non-Markovianity and give a physical interpretation of this phenomenon by linking it to the form of the reservoir spectrum. We demonstrate that this link holds also for more general spectra. We unveil a class of initial states for which discord is forever frozen at a positive value. We connect time-invariant discord to non-Markovianity and propose a physical system in which it could be observed.We study non-Markovianity and information flow for qubits experiencing local dephasing with an Ohmic class spectrum. We demonstrate the existence of a temperature-dependent critical value of the Ohmicity parameter $s$ for the onset of non-Markovianity and give a physical interpretation of this phenomenon by linking it to the form of the reservoir spectrum. We demonstrate that this link holds also for more general spectra. We unveil a class of initial states for which discord is forever frozen at a positive value. We connect time-invariant discord to non-Markovianity and propose a physical system in which it could be observed.

Physical Review AJan 24, 2013172 citations

Time-invariant discord in dynamically decoupled systems

Carole Addis, Göktuğ Karpat, Sabrina Maniscalco

Dynamical decoupling protocols are one of the most used tools for efficient quantum error corrections and for reservoir engineering. In this paper we study the effect of dynamical decoupling pulses on the preservation of both quantum and classical correlations, and their influence on the intriguing phenomenon of time-invariant discord. We study two qubits experiencing local dephasing with an Ohmic class spectrum and subject to dynamical decoupling protocols. We investigate the connection between the dynamics of both classical and quantum correlations and the behavior of information flow between system and environment. Finally, we establish a set of necessary conditions for which time-invariant discord can be created using dynamically decoupling techniques.Dynamical decoupling protocols are one of the most used tools for efficient quantum error corrections and for reservoir engineering. In this paper we study the effect of dynamical decoupling pulses on the preservation of both quantum and classical correlations, and their influence on the intriguing phenomenon of time-invariant discord. We study two qubits experiencing local dephasing with an Ohmic class spectrum and subject to dynamical decoupling protocols. We investigate the connection between the dynamics of both classical and quantum correlations and the behavior of information flow between system and environment. Finally, we establish a set of necessary conditions for which time-invariant discord can be created using dynamically decoupling techniques.

arXiv:1508.05790Physical Review ADec 7, 201515 citations

Frozen discord in stochastic dephasing environment

Bin Yi

Preserving quantum coherence is fundamental challenge in the field of quantum computation. Here, I investigate the frozen discord phenomenon and non-Markovianity for qubits experiencing local dephasing in a classical environment. The quantum discord of a certain initial bipartite state, independently interacting with stochastic Gaussian fields, can be frozen for a finite time. The preservation of discord is shown to be intimately related to the backflow of information from the environment. The relevant result for quantum dephasing environment is compared.Preserving quantum coherence is fundamental challenge in the field of quantum computation. Here, I investigate the frozen discord phenomenon and non-Markovianity for qubits experiencing local dephasing in a classical environment. The quantum discord of a certain initial bipartite state, independently interacting with stochastic Gaussian fields, can be frozen for a finite time. The preservation of discord is shown to be intimately related to the backflow of information from the environment. The relevant result for quantum dephasing environment is compared.

arXiv:2011.04180Nov 9, 20200 citations

FROZEN DISCORD IN NON-MARKOVIAN DEPHASING CHANNELS

LAURA MAZZOLA, Jyrki Piilo, Sabrina Maniscalco

We investigate the dynamics of quantum and classical correlations in a system of two qubits under local colored-noise dephasing channels. The time evolution of a single qubit interacting with its own environment is described by a memory kernel non-Markovian master equation. The memory effects of the non-Markovian reservoirs introduce new features in the dynamics of quantum and classical correlations compared to the white noise Markovian case. Depending on the geometry of the initial state, the system can exhibit frozen discord and multiple sudden transitions between classical and quantum decoherence [L. Mazzola, J. Piilo and S. Maniscalco, Phys. Rev. Lett. 104 (2010) 200401]. We provide a geometric interpretation of those phenomena in terms of the distance of the state under investigation to its closest classical state in the Hilbert space of the system.We investigate the dynamics of quantum and classical correlations in a system of two qubits under local colored-noise dephasing channels. The time evolution of a single qubit interacting with its own environment is described by a memory kernel non-Markovian master equation. The memory effects of the non-Markovian reservoirs introduce new features in the dynamics of quantum and classical correlations compared to the white noise Markovian case. Depending on the geometry of the initial state, the system can exhibit frozen discord and multiple sudden transitions between classical and quantum decoherence [L. Mazzola, J. Piilo and S. Maniscalco, Phys. Rev. Lett. 104 (2010) 200401]. We provide a geometric interpretation of those phenomena in terms of the distance of the state under investigation to its closest classical state in the Hilbert space of the system.

arXiv:1006.1805International Journal of Quantum InformationApr 1, 201185 citations

Time-invariant discord and steady-state entanglement in engineered non-equilibrium dephasing environments

Abdul Basit, Hamad Ali, Xiaofei Yang +1 more

Abstract We study theoretically the dynamics of quantum and classical correlations in the two-qubit system, locally experiencing a one-sided engineered pure dephasing non-equilibrium environment with an Ohmic class spectrum. The environmental non-equilibrium nature is characterized by random perturbations with non-stationary statistics. Particularly, we investigate the influence of the non-equilibrium feature on the protection of these correlations and, more specifically, its effect on the non-trivial phenomenon of time-invariant discord. Remarkably, we show that in the presence of this engineered non-equilibrium environment, time-invariant discord with a significantly larger magnitude exists for all Ohmic spectral densities, i.e., sub-Ohmic, Ohmic, and super-Ohmic without zero-temperature restriction. Additionally, we also show that our engineered non-equilibrium model provides a promising tool for trapping entanglement in a steady-state with a higher magnitude. Moreover, our proposed model also renders new insights for controlling decoherence through engineering the relative initial phases of the bath modes without performing any artificial operations on the main quantum system.Abstract We study theoretically the dynamics of quantum and classical correlations in the two-qubit system, locally experiencing a one-sided engineered pure dephasing non-equilibrium environment with an Ohmic class spectrum. The environmental non-equilibrium nature is characterized by random perturbations with non-stationary statistics. Particularly, we investigate the influence of the non-equilibrium feature on the protection of these correlations and, more specifically, its effect on the non-trivial phenomenon of time-invariant discord. Remarkably, we show that in the presence of this engineered non-equilibrium environment, time-invariant discord with a significantly larger magnitude exists for all Ohmic spectral densities, i.e., sub-Ohmic, Ohmic, and super-Ohmic without zero-temperature restriction. Additionally, we also show that our engineered non-equilibrium model provides a promising tool for trapping entanglement in a steady-state with a higher magnitude. Moreover, our proposed model also renders new insights for controlling decoherence through engineering the relative initial phases of the bath modes without performing any artificial operations on the main quantum system.

Physica ScriptaApr 26, 20216 citations

Dynamics of Geometric Measure of Quantum Discord of Two Qubits in Independent Reservoirs

Longjiang Liu, Jiang Zhang, Song Cheng +1 more

We study the dynamics of geometric measure of quantum discord. The model under consideration is a physical system of two qubits coupled with two independent bosonic reservoirs described by Ohmic-like spectral densities. We aim to find how the system's geometric measure of quantum discord evolves, and whether and in what conditions it may remain constant for a time interval or be frozen forever. Our result shows that by properly choosing the system's initial states, geometric measure of quantum discord may hold a frozen phenomenon in a time interval for all the three types of reservoirs, sub-Ohmic, Ohmic, and super-Ohmic reservoirs, and it may also hold a time-invariant phenomenon for super-Ohmic reservoirs. The conditions satisfied by the coefficients of standard Bell-diagonal states, in which the frozen phenomenon in a time interval or the time-invariant phenomenon of geometric measure of quantum discord appears, are given.We study the dynamics of geometric measure of quantum discord. The model under consideration is a physical system of two qubits coupled with two independent bosonic reservoirs described by Ohmic-like spectral densities. We aim to find how the system's geometric measure of quantum discord evolves, and whether and in what conditions it may remain constant for a time interval or be frozen forever. Our result shows that by properly choosing the system's initial states, geometric measure of quantum discord may hold a frozen phenomenon in a time interval for all the three types of reservoirs, sub-Ohmic, Ohmic, and super-Ohmic reservoirs, and it may also hold a time-invariant phenomenon for super-Ohmic reservoirs. The conditions satisfied by the coefficients of standard Bell-diagonal states, in which the frozen phenomenon in a time interval or the time-invariant phenomenon of geometric measure of quantum discord appears, are given.

Journal of the Physical Society of JapanMay 20, 20131 citation

s

for the onset of non-Markovianity and give a physical interpretation of this phenomenon by linking it to the form of the reservoir spectrum. We demonstrate that this link holds also for more general spectra. We unveil a class of initial states for which discord is forever frozen at a positive value. We connect time-invariant discord to non-Markovianity and propose a physical system in which it could be observed.