arXiv subjects

C. G. Feyisa

Publications and source records attributed to C. G. Feyisa.

3 recordsLinked to original sources

arXiv2026

Informational Mpemba Effect for Fast State Purification in Non-Hermitian System

Quantum systems are inherently fragile to environmental fluctuations or decoherence, limiting their advantages in applications of quantum information and quantum computation. State purification offers a route to recover the purity of system under noisy conditions. Here, we demonstrate a rapid purification of initially mixed states by harnessing collective reservoir engineering in driven non-Hermitian qubit systems, together with multipartite entanglement generation in larger systems. We show that the onset of efficient purification-assisted entanglement generation is dictated by the degeneracy of collective subradiant modes, rather than by exceptional points. Moreover, the system dynamics manifests an informational Mpemba effect, i.e., a more mixed initial state reaches its steady state with unit purity at a faster rate, resembling the conventional Mpemba effect where a hotter system cools more rapidly. These results reveal a unique advantage of driven non-Hermitian quantum systems with engineered collective dissipation, enabling enhanced purification efficiency and offering new opportunities for relaxation control of non-Hermitian systems and quantum state preparations.

quant-ph↗

arXiv2024

High-fidelity multipartite entanglement creation in non-Hermitian qubits

Non-Hermitian quantum systems showcase many distinct and intriguing features with no Hermitian counterparts. One of them is the exceptional point which marks the PT (parity and time) symmetry phase transition, where an enhanced spectral sensitivity arises and leads to novel quantum engineering. Here we theoretically study the multipartite entanglement properties in non-Hermitian superconducting qubits, where high-fidelity entangled states can be created under strong driving fields or strong couplings among the qubits. Under an interplay between driving fields, couplings, and non-Hermiticity, we focus on generations of GHZ states or GHZ classes in three and four qubits with all-to-all couplings, which allows a fidelity approaching unity when relatively low non-Hermitian decay rates are considered. This presents an ultimate capability of non-Hermitian qubits to host a genuine and maximal multipartite entanglement. Our results can shed light on novel quantum engineering of multipartite entanglement generations in non-Hermitian qubit systems.

quant-ph↗

arXiv2024

Robustness of tripartite entangled states in passive PT-symmetric qubits

Non-Hermitian quantum systems have attracted significant interest in recent years due to the presence of unique spectral singularities known as exceptional points (EPs), where eigenvalues and eigenvectors coalesce. The drastic changes in these systems around their EPs have led to unique entanglement dynamics, which remained elusive until quite recently. In this work, we theoretically investigate the robustness of tripartite entanglement induced by EPs of the passive PT-symmetric non-Hermitian superconducting qubits, both in stand-alone configurations and hybrid setups with Hermitian qubits. In particular, we consider the qubits with both all-to-all and nearest-neighbour couplings under uniform and non-uniform coupling strengths. Our results reveal that non-Hermitian qubits with all-to-all coupling generate GHZ states, while those with nearest-neighbour interactions produce W states. These entangled states are resilient to non-uniform couplings and off-resonant driving fields. Moreover, the hybrid configurations combining Hermitian and non-Hermitian qubits suggest the importance of EPs for generating and maintaining genuine tripartite entanglement in our system. Additionally, driving the PT-symmetric qubits with a strong Rabi frequency can help sustain tripartite entanglement over time by countering losses, while strong inter-qubit coupling can benefit these entangled states in the low dissipation regime. These findings suggest that exploiting non-Hermitian systems and their associated EPs can create robust entangled states which are useful for both fundamental studies and quantum technologies.

quant-ph↗