arXiv subjects

Majid Moradi

Publications and source records attributed to Majid Moradi.

5 recordsLinked to original sources

arXiv2026

Still life in a classic Blume-Capel model: pseudo-transitions in a spin-1 diamond chain

We exactly investigate the ground-state, magnetic, and thermodynamic properties of a spin-1 Blume-Capel diamond chain in a magnetic field by means of the transfer-matrix method. After establishing the complete ground-state phase diagram and characterizing each ground-state spin configuration, we examine the finite-temperature behavior in the vicinity of selected phase boundaries and triple points. It is demonstrated that an extremely small energy gap between a nondegenerate ground state and competing macroscopically degenerate low-lying excited states gives rise to entropically-driven pseudo-transitions. These pseudo-transitions manifest themselves through abrupt but continuous changes in the magnetization and entropy resembling discontinuous jumps, while the magnetic susceptibility and specific heat exhibit exceptionally sharp yet finite peaks resembling divergences. Our results provide the exact evidence that pseudo-transitions can also emerge in the classical spin-1 Blume-Capel model and thereby extend the class of one-dimensional spin systems known to display pseudo-transitions.

cond-mat.stat-mech↗

arXiv2025

Improving quantum walk metrology with split-step quantum walk

A new estimation scheme based on the split-step quantum walk (SSQW) revealed that by just setting a single parameter, SSQW can potentially achieve quantum Crame\'r-Rao bound in multiparameter estimation. This parameter even does not involve the parameterization but the initial state and unlike ordinary Quantum walk (OQW) there is no necessity for an entangled initial states or even a parameter dependent initial state. The rigorous analytic equations derived in this study revealed that SSQW surpasses OQW in achievable precision of multiparameter estimation in almost all possible scenarios. Furthermore, in single parameter estimation, the extra parameter can be used to tune the dynamics of the walk in such a way to enhance the precision of the estimation through maximizing the elements of quantum Fisher information matrix. The results of this study indicate that SSQW can remarkably improve the estimation schemes through its rich topological properties.

quant-ph↗

arXiv2019

Asymptotic Behavior and Limiting Distribution of Quantum Walk on Cycles with General U(2) Coin by Reduced Characteristic Matrix Method

We calculated reduced density characteristic matrix (RDCM) for quantum walk on cycles (QWC) to study asymptotic properties of the most general form of quantum walk on cycles with general $U(2)$ coin operator. As an example, entanglement temperature for general initial state has been calculated and compared to previous results. Also, we have modified RDCM to derive analytical expression for general form of limiting distribution (LD).

quant-ph↗

arXiv2018

Entanglement in a fermionic spin chain containing a single mobile boson under decoherence

The concurrence between first and the last sites of a fermionic spin chain containing a single boson is rigorously investigated at finite low temperature in the vicinity of a weak homogeneous magnetic field. We consider the boson as a mobile spin-1 particle through the chain and study concurrence without/under decoherence and express some interesting phase flip and bit flip reactions of the pairwise entanglement between first and the last half-spins in the chain. Our investigations show that the concurrence between two considered half-spins has different behavior for various positions of the single boson along the chain. Indeed, we realize that the single boson mobility has an essential role to probe the pairwise entanglement intensity between two spins located at the opposite ends of a fermionic chain. Interestingly, the entanglement remains alive for higher temperatures when the boson is the nearest neighbor of the first fermion. When the boson is at the middle of chain, it is demonstrated that the threshold temperature (at which the concurrence vanishes) versus decoherence rate can be considered as a threshold temperature boundary. These results pave the way to set and interpret the numerical and analytical expressions for utilizing quantum information in realistic scenarios such as quantum state transmission, quantum communication science and quantum information processing, where the both fermion-fermion and fermion-boson correlations should be taken in to account.

cond-mat.stat-mech↗

arXiv2017

Möbius Quantum Walk

By adding an extra Hilbert space to Hadamard Quantum Walk on Cycles (QWC), we presented a new type of QWCs called Möbius Quantum Walk (MQW). The new space configuration enables the particle to rotate around the axis of movement. We defined factor $α$ as the Möbius factor which is number of rotations per cycle. So by $α=0$ we have normal QWC, while $α\neq 0$ defines new type of QWC (namely Möbius Quantum Walk). Specially $α= \frac{1}{2}$ defines a structure similar to Möbius strip. We analytically investigated this new type of QW and found that by tuning the parameter $α$ we can reach uniform distribution for any number of nodes, while it is impossible for QWC. The effects of $α$ on limiting distribution have been investigated and an explicit formula for non-uniform cases has been derived as well.

quant-ph↗