arXiv subjects

S. V. M. Satyanarayana

Publications and source records attributed to S. V. M. Satyanarayana.

9 recordsLinked to original sources

arXiv2025

Configurable controlled teleportation using multipartite GHZ states

We propose a controlled quantum teleportation protocol for securely transferring an unknown $n$-qubit state from a sender to a receiver, under the supervision of $m$ controller participants. The protocol uses $n$ copies of an $m$-qubit Greenberger-Horne-Zeilinger state as the quantum resource. Message qubits can be distributed among participants to enhance security against targeted external attacks. Each intermediate party may hold at most one resource qubit, reducing the total number of resource qubits required. The sender selects the end receiver during protocol execution, ensuring anonymity and minimizing the risk of interception by an external eavesdropper. We assess the protocol's performance by calculating teleportation fidelities for various $m$ and $n$ values and visualize the quantum states through Hinton diagrams. The results confirm the protocol's effectiveness for secure quantum communication in multi-party settings.

quant-ph↗

arXiv2019

Suppression of Chaos in Mutually Coupled Synchronized Generalized Lorenz Systems

In this work, the dynamics of a system of mutually coupled Generalized Lorenz systems (GLS) is investigated. The state variables of two Lorenz oscillators are coupled mutually via non-linear controls and synchronization is achieved between the state variables. We find that by suitably controlling a parameter having a bearing on the coupling coefficient between the two Lorenz oscillators, the GLS, while preserving synchronization is rendered to a state wherein chaotic nature of state variables is suppressed and state variables exhibit oscillatory character. The suppression of chaos is verified by power spectra, permutation entropy and Lyapunov exponent calculations. When operated in chaotic domain, we show the possibility of transition from the state of synchronization to the state of anti-synchronization.

nlin.CD↗

arXiv2017

Importance of phonon contribution to the free migration energy of the O vacancy in BaZrO3

BaZrO3 exhibits excellent proton conductivity and good high-temperature stability. It is therefore a promising electrolyte material for solid oxide fuel cells. The stability of BaZrO3 at high temperatures is generally explained by the low diffusivity of the O vacancy. Present first-principle Density-Functional-Theory calculations show that the slow migration of the doubly positively charged O vacancy at high temperature cannot be solely caused by the ground-state migration energy but by the contribution of phonon excitations to the free migration energy. With increasing temperature, the effective barrier for oxygen vacancy migration increases. At about 1000K, which is the operating temperature of fuel cells, the calculated O vacancy diffusivity is more than one order of magnitude lower than that determined using solely the ground-state migration barrier. The calculated diffusivity data agree well with experimental results from literature. The present work reveals that the high-temperature stability of BaZrO3 is mainly due to the phonon contribution to the free migration energy of the O vacancy.

cond-mat.mtrl-sci↗

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↗

arXiv2015

The THETA - temperature of Interacting Self Avoiding Walk on Face Centered Cubic Lattice

Interacting Self Avoiding Walk (ISAW) on a lattice is a simple model to study the Coil to Globule transition of linear homopolymers. The temperature at which the transition takes place is called the theta temperature. The value of theta temperature depends on the chosen lattices. The value of theta temperature for ISAW on FCC lattice is reported as $6.46$ in a simulation study [J. Chem. Phys. {\bf 135}, 204903 (2011)]. Latter it has been reported as $7.614$ [J. Chem. Phys. {\bf 138}, 024902 (2013)]. Simulations in these two studies involved long chains with over 2000 monomers. In this paper, we present a method that gives a reliable estimate of the theta temperature of ISAW on FCC lattice using chains of shorter walk lengths (less than 100 monomers). We compute density states of ISAW on FCC lattice by employing growth walk algorithm and then we use the recently introduced pseudo order parameter method to estimate the theta temperature. The value obtained from our method agrees very well with latter reported result of $7.614$. In order to corroborate our result we also estimate the theta temperature using the celebrated partition function zeroes method.

cond-mat.stat-mech↗

arXiv2014

Model for bidirectional movement of cytoplasmic dynein

Cytoplasmic dynein exhibits a directional processive movement on microtubule filaments and is known to move in steps of varying length based on the number of ATP molecules bound to it and the load that it carries. It is experimentally observed that dynein takes occasional backward steps and the frequency of such backward steps increases as the load approaches the stall force. Using a stochastic process model, we investigate the bidirectional movement of single head of a dynein motor. The probability for backward step is implemented based on Crook's fluctuation theorem of non-equilibrium statistical mechanics. We find that the movement of dynein motor is characterized with negative velocity implying backward motion beyond stall force. We observe that the motor moves backward for super stall forces by hydrolyzing the ATP exactly the same way as it does while moving forward for sub stall forces.

physics.bio-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↗

arXiv2013

Restriction on the rank of marginals of bipartite pure states

Consider a qubit-qutrit ($2 \times 3$) composite state space. Let $C(\{1}{2}I_2, \{1}{3}I_3)$ be a convex set of all possible states of composite system whose marginals are given by $\{1}{2}I_2$ and $\{1}{3}I_3$ in two and three dimensional spaces respectively. We prove that there exists no pure state in $C(\{1}{2}I_2, \{1}{3}I_3)$. Further we generalize this result to an arbitrary $m \times n$ bipartite systems. We prove that for $m < n$, no pure state exists in the convex set $C(ρ_A,ρ_B)$, for an arbitrary $ρ_A$ and rank of $ρ_B >m$.

quant-ph↗

arXiv1998

Chaos, Order Statistics and Unstable Periodic Orbits

We present a new method for locating unstable periodic points of one dimensional chaotic maps. This method is based on order statistics. The densities of various maxima of the iterates are discontinuous exactly at unstable periodic points of the map. This is illustrated using logistic map where densities corresponding to a small number of iterates have been obtained in closed form. This technique can be applied to the class of continuous time systems where the successive maxima of the time series behave as if they were generated from a unimodal map. This is demonstrated using Lorenz model.

chao-dyn↗