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arXiv:2410.04361 · Springer proceedings in mathematics & statistics

Geometry and Entanglement of Super-Qubit Quantum States

Oktay K. Pashaev, Aygül Koçak

Published Jan 1, 2025• 0 citations
arXivHTMLPDF
DOI
10.1007/978-3-031-84151-4_5

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This paper investigates the potential of utilizing super-space geometry as a framework for modeling quantum entanglement. Traditional entanglement theories primarily focus on particle interactions, while this work proposes a novel approach by embedding quantum entanglement within the structure of super-space geometry. We aim to develop a computational methodology that reveals the dynamic characteristics of entangled states through the lens of this geometric model. The core claim is that super-space geometry offers a unique and powerful means of capturing the non-local nature of quantum entanglement, providing a more precise and comprehensive understanding of its properties. This research explores the potential of this approach to address limitations in existing entanglement models.
The asymmetric three-qubit W-class state ∣W3L‾⟩|\overline{W_3^L}\rangle∣W3L​​⟩ defines an isosceles entanglement-network geometry, (a) two vertex-base (VB) links form stronger bipartite connections, (b) while the base-base (BB) link is weaker. This suggests that concentrating entanglement into a super-link may be advantageous for quantum-network tasks. Here, we show that this intuition is incomplete. We analytically compare the bipartite concurrence dynamics of the symmetric |W> state and the asymmetric ∣W3L‾⟩|\overline{W_3^L}\rangle∣W3L​​⟩ state, which differ both in entanglement-network geometry and excitation sector under standard noise models. In the absence of noise, the concurrence hierarchy is CVB>CW>CBBC_{VB} > C_W > C_{BB}CVB​>CW​>CBB​. Under phase damping, this hierarchy is preserved for all noise strengths and no entanglement sudden death occurs. Under amplitude damping, however, the hierarchy is reordered. The symmetric |W> state becomes the most robust, while the base-base concurrence of ∣W3L‾⟩|\overline{W_3^L}\rangle∣W3L​​⟩ vanishes at the finite threshold of parameter γγγ. We term this reordering as the \textit{Super-Link Fragility Effect}. The same structural asymmetry that produces a stronger vertex-base link also makes it more vulnerable to energy dissipation when coupled with multi-excitation amplitudes. Under depolarization, the asymmetry advantage is erased, with CWC_WCW​ and CVBC_{VB}CVB​ sharing the same sudden-death threshold for some value of the parameter p, while CBBC_{BB}CBB​ disappears earlier at some other value of the parameter p. The generalized amplitude damping channel continuously connects the damping-dominated regime to the pure-excitation limit, where the initial hierarchy is restored. These results show that entanglement robustness in WWW-class resources is controlled not by initial concurrence alone, but by the joint structure of entanglement-network geometry, excitation sector, and noise symmetry.
In this paper, the number-phase quantization scheme of the mesoscopic circuit, which consists of a single-qubit structure with superconducting quantum interference device coupled with a super-conducting resonator, is given. By introducing a unitary matrix and by means of spectral decomposition, the Hamiltonian operator of the system is exactly formulated in compact forms in spin-1/2 notation. The eigenvalues and the eigenstates of the system are investigated. It is found that using this system the entangled states can not only be prepared, but also be manipulated by tuning the magnetic flux through the super-conducting loop.