arXiv subjects

K. G. Paulson

Publications and source records attributed to K. G. Paulson.

8 recordsLinked to original sources

arXiv2023

Quantum speed of evolution of neutral mesons

We investigate the quantum-mechanical time-evolution speed limit for neutral $K$ and $B$ mesons, both single as well as correlated, within the framework of open quantum systems. The role of coherence--mixing, a crucial feature of the open system evolution of the underlying quantum systems (here, the mesons), on the quantum-mechanical time-evolution speed limit is studied. The impact of decoherence and CP (charge conjugation parity) symmetry violation on quantum-mechanical time-evolution speed limit is also investigated. The quantum-mechanical time-evolution speed limit increases with the evolution time for the single mesons, a signature of the underlying open system dynamics of the evolution being semi-group in nature. The evolution of the correlated mesons slows down for an evolution time of approximately one-fourth of the lifetime, after which it is sped up. An overall pattern that emerges is that correlated mesons evolve faster as compared to their uncorrelated counterparts, suggesting that quantum correlations can speed up evolution.

hep-ph↗

arXiv2023

Harnessing quantumness of states using discrete Wigner functions under (non)-Markovian quantum channels

The negativity of the discrete Wigner functions (DWFs) is a measure of non-classicality and is often used to quantify the degree of quantum coherence in a system. The study of Wigner negativity and its evolution under different quantum channels can provide insight into the stability and robustness of quantum states under their interaction with the environment, which is essential for developing practical quantum computing systems. We investigate the variation of DWF negativity of qubit, qutrit, and two-qubit systems under the action of (non)-Markovian random telegraph noise (RTN) and amplitude damping (AD) quantum channels. We construct different negative quantum states which can be used as a resource for quantum computation and quantum teleportation. The success of quantum computation and teleportation is estimated for these states under (non)-Markovian evolutions.

quant-ph↗

arXiv2023

Quantum correlations and speed limit of central spin system

In this article, we consider single, and two-qubit central spin systems interacting with spin baths and discuss their dynamical properties. We consider the cases of interacting and non-interacting spin baths and investigate the quantum speed limit (QSL) time of evolution. The impact of the size of the spin bath on the quantum speed limit for a single qubit central spin model is analyzed. We estimate the quantum correlations for (non-)interacting two central spin qubits and compare their dynamical behaviour with that of QSL time under various conditions. We show how QSL time could be availed to analyze the dynamics of quantum correlations.

quant-ph↗

arXiv2022

Quantum speed limit time: role of coherence

The minimum evolution time between multi-qubit quantum states is estimated for non-Markovian quantum channels. We consider the maximally coherent pure and mixed states as well as multi-qubit $X$ states as initial states and discuss the impact of initial coherence and the behaviour of coherence on their speed of evolution for both dephasing and dissipative processes. The role of the non-zero value of initial coherence under information backflow conditions for the non-unital dissipative process is revealed by the flow of quantum speed limit time ($τ_{QSL}$). The trade-off between mixedness and coherence on the speed limit time reveals the nature of the quantum process the states undergo. The complementarity effect between mixedness and coherence is more prominent in the quantum non-unital dissipation process. The parametric trajectory of speed limit time vividly depicts the difference in the evolution of pure and mixed initial states, and this could be used to distinguish between the unital and non-unital channels studied in this work. Our investigation of quantum speed limit time on multi-qubit entangled $X$ states reveals that $τ_{QSL}$ can be identified as a potential dynamical witness to distinguish multi-qubit states in the course of evolution.

quant-ph↗

arXiv2022

Phase covariant channel: Quantum speed limit of evolution

The quantum speed of evolution for the phase covariant map is investigated. This involves absorption, emission and dephasing processes. We consider the maps under various combinations of the above processes to investigate the effect of phase covariant maps on quantum speed limit time. For absorption-free phase covariant maps, combinations of dissipative and CP-(in)divisible (non)-Markovian dephasing noises are considered. The role of coherence-mixedness balance on the speed limit time is checked in the presence of both vacuum and finite temperature effects. We also investigate the rate at which Holevo's information changes and the action quantum speed of evolution for specific cases of the phase covariant map.

quant-ph↗

arXiv2019

Tri-partite non-maximally entangled mixed states as a resource for optimum controlled quantum teleportation fidelity

Three-qubit mixed states are used as a channel for controlled quantum teleportation (CQT) of single-qubit states. The connection between different channel parameters to achieve maximum controlled teleportation fidelity is investigated. We show that for a given multipartite entanglement and mixedness, a class of non-maximally entangled mixed $X$ states ($X-$NMEMS) achieves optimum controlled quantum teleportation fidelity, interestingly a class of maximally entangled mixed $X$ states ($X-$MEMS) fails to do so. This demonstrates, for a given spectrum and mixedness, that $X-$MEMS are not sufficient to attain optimum controlled quantum teleportation fidelity, which is in contradiction with the traditional quantum teleportation of single qubits. In addition, we show that biseparable $X-$NMEMS, for a certain range of mixedness, are useful as a resource to attain high controlled quantum teleportation fidelity, which essentially lowers the requirements of quantum channels for CQT.

quant-ph↗

arXiv2015

Dilapidation of nonlocal correlations of two qubit states in noisy environment

Composite quantum systems exhibit non-local correlations. These counter intuitive correlations form a resource for quantum information processing and quantum computation. In our previous work on two qubit maximally entangled mixed states, we observed that entangled states, states that can be used for quantum teleportaion, states that violate Bell-CHSH inequality and states that do not admit local hidden variable description is the hierarchy in terms of the order of nonlocal correlations. In order to establish this hierarchy, in the present work, we investigate the effect of noise on two quibt states that exhibit higher order nonlocal correlations. We find that dilapidation of nonlocal correlations in the presence of noise follow the same hierarchy, that is, higher order nonlocal correlation disappears for small strength of noise, where as lower order nonlocal correlations survive strong noisy environment. We show the results for decoherence due to amplitude damping channel on various quantum states. However, we observe that same hierarchy is followed by states undergoing decoherence due to phase damping as well as depolarizing channels.

quant-ph↗

arXiv2013

Relevance of rank for a mixed state quantum teleportation resource

Mixed entangled states are generic resource for quantum teleportation. Optimal teleportation fidelity measures the success of quantum teleportation. The relevance of rank in the teleportation process is investigated by constructing three new maximally entangled mixed states (MEMS) of different ranks. Linear entropy, concurrence, optimal teleportation fidelity and Bell function are obtained for each of the state analytically. It is found that mixed states with higher rank are better resource for teleportation. In order to achieve a fixed value of optimal teleportation fidelity, we find that low rank states must have high concurrence. Further, for each of ranks 2, 3 and 4, we numerically generate 30000 maximally entangled mixed states. The analysis of these states reveals the existence of a rank dependent upper bound on optimal teleportation fidelity for a fixed purity. In order to achieve a fixed optimal teleportation fidelity, we find MEMS exhibit a rank dependent lower bound on concurrence. MEMS are classified in terms of their degree of nonlocality.

quant-ph↗