Quantumness of hybrid systems under quantum noise

TL;DR

This paper studies how quantum correlations in a hybrid qubit-qutrit system are affected by different types of noise, revealing that quantum discord persists longer than entanglement under decoherence.

Contribution

It introduces a model for hybrid qubit-qutrit systems under noise and compares the effects of dephasing and phase-flip channels on quantum correlations.

Findings

Quantum correlations degrade monotonically with temperature and noise.

Entanglement experiences sudden death under strong noise, while discord persists longer.

Asymmetric noise can enhance the robustness of quantum correlations.

Abstract

We investigate the quantum correlations in an axially symmetric hybrid qubit-qutrit system subjected to different noisy environments. We first introduce a physical model and analyze its Hamiltonian structure, emphasizing the role of hybrid dimensionality and axial symmetry. The effects of decoherence are then examined under two local noise mechanisms, namely dephasing and phase-flip channels, acting on the qubit and qutrit subsystems in both symmetric and asymmetric configurations. Quantum correlations are quantified using negativity to capture entanglement and quantum discord based on linear entropy to characterize more general nonclassical correlations. Our results show that both thermal fluctuations and phase noise lead to a monotonic degradation of quantum correlations, with increasing temperature accelerating coherence loss and inducing entanglement sudden death at finite temperatures. While negativity vanishes abruptly under sufficiently strong noise, quantum discord persists beyond the entanglement threshold, revealing residual quantum correlations in mixed states. We further demonstrate that asymmetric noise configurations significantly enhance the robustness of both entanglement and discord by partially shielding coherence in the less affected subsystem. A comparative analysis reveals that phase-flip noise is more destructive than pure dephasing, leading to faster suppression of quantum correlations.