A Simplified Hierarchical Dynamic Quantum Secret Sharing Protocol with Added Features

Generalizing the notion of dynamic quantum secret sharing (DQSS), a simplified protocol for hierarchical dynamic quantum secret sharing (HDQSS) is proposed and it is shown that the protocol can be implemented using any existing protocol of quantum key distribution, quantum key agreement or secure direct quantum communication. The security of this proposed protocol against eavesdropping and collusion attacks is discussed with specific attention towards the issues related to the composability of the subprotocols that constitute the proposed protocol. The security and qubit efficiency of the proposed protocol is also compared with that of other existing protocols of DQSS. Further, it is shown that it is possible to design a semi-quantum protocol of HDQSS and in principle, the protocols of HDQSS can be implemented using any quantum state. It is also noted that the completely orthogonal-state-based realization of HDQSS protocol is possible and that HDQSS can be experimentally realized using a large number of alternative approaches.Comment: 9 pages, 1 figur

Competition between antiferromagnetism and superconductivity, electron-hole doping asymmetry and "Fermi Surface" topology in cuprates

We investigate the asymmetry between electron and hole doping in a 2D Mott insulator, and the resulting competition between antiferromagnetism (AF) and d-wave superconductivity (SC), using variational Monte Carlo for projected wave functions. We find that key features of the T = 0 phase diagram, such as critical doping for SC-AF coexistence and the maximum value of the SC order parameter, are determined by a single parameter which characterises the topology of the "Fermi surface" at half filling defined by the bare tight-binding parameters. Our results give insight into why AF wins for electron doping, while SC is dominant on the hole doped side. We also suggest using band structure engineering to control the parameter for enhancing SC.Comment: 4 pages, 4 figure

Open quantum system dynamics of XX-states: Entanglement sudden death and sudden birth

The origin of disentanglement for two specific sub-classes of $X$-states namely maximally nonlocal mixed states (MNMSs) and maximally entangled mixed states (MEMSs) is investigated analytically for a physical system consisting of two spatially separated qubits interacting with a common vacuum bath. The phenomena of entanglement sudden death (ESD) and the entanglement sudden birth (ESB) are observed, but the characteristics of ESD and ESB are found to be different for the case of two photon coherence and single photon coherence states. The role played by initial coherence for the underlying entanglement dynamics is investigated. Further, the entanglement dynamics of MNMSs and MEMSs under different environmental noises namely phase damping, amplitude damping and RTN noise with respect to the decay and revival of entanglement is analyzed. It's observed that the single photon coherence states are more robust against the sudden death of entanglement indicating the usability of such states in the development of technologies for the practical implementation of quantum information processing tasks.Comment: entanglement dynamics of some sub-classes of X-states are studie

Partial Loopholes Free Device Independent Quantum Random Number Generator Using IBM's Quantum Computers

Random numbers form an intrinsic part of modern day computing with applications in a wide variety of fields. But due to their limitations, the use of pseudo random number generators (PRNGs) is certainly not desirable for sensitive applications. Quantum systems due to their intrinsic randomness form a suitable candidate for generation of true random numbers that can also be certified. In this work, the violation of CHSH inequality has been used to propose a scheme by which one can generate device independent quantum random numbers by use of IBM quantum computers that are available on the cloud. The generated random numbers have been tested for their source of origin through experiments based on the testing of CHSH inequality through available IBM quantum computers. The performance of each quantum computer against the CHSH test has been plotted and characterized. Further, efforts have been made to close as many loopholes as possible to produce device independent quantum random number generators. This study will provide new directions for the development of self-testing and semi-self-testing random number generators using quantum computers.Comment: We present a scheme by which one can generate device independent quantum random numbers by use of IBM quantum computers that are available on the clou

Possibility of High Tc Superconductivity in doped Graphene

Graphene is at the forefront of condensed matter sciences, because of a variety of interesting phenomena it supports. If graphene could support high Tc superconductivity, after doping for example, it will make it even more valuable. Some authors have suggested possibility of superconductivity in graphite like systems. However, an early suggestion of one of us (Baskaran) was unique in the sense it combined Pauling's classic idea of resonating valence bond physics with band theory to obtain some exciting results for superconductivity. Black-Schaffer and Doniach took this approach further and found an unconventional d + id order parameter. To sharpen our theory and get more convincing and reliable results for superconductivity, we introduce a correlated variational BCS ground state wavefunction and perform extensive Monte Carlo study of the repulsive Hubbard model on the honeycomb lattice. We find that undoped graphene is not a superconductor, consistent with experiments and also mean field results. Interestingly, an appreciable superconducting order is obtained around an optimal doping. This result and a supportive slave particle analysis together suggest the possibility of high temperature superconductivity in doped graphene.Comment: 6 Pages, 3 Figure

Comparing coherence measures for X states: Can quantum states be ordered based on quantum coherence?

Quantum coherence is an essential resource for quantum information processing and various quantitative measures of it have been introduced. However, the interconnections between these measures are not yet understood properly. Here, using a large set of randomly prepared $X$ states and analytically obtained expressions of various measures of coherence (e.g., relative entropy of coherence, $l1$ norm of coherence, coherence via skew information, and first-order coherence), it is established that these measures of quantum coherence cannot be used to perform ordering of a set of quantum states based on the amount of coherence present in a state. Further, it is shown that for a given value of quantum coherence measured by the relative entropy of coherence, maximally nonlocal mixed states of $X$ type (which are characterized by maximal violation of the CHSH inequality) have maximum quantum coherence as measured by $l1$ norm of coherence. In addition, the amount of coherence measured by $l1$ norm of coherence for a Werner state is found to be always less than that for a maximally nonlocal mixed state even when they possess an equal amount of coherence measured by the relative entropy of coherence. These resource theory based measures of coherence are not observed to show any relation with the first-order coherence, while its maximum (hidden coherence) is found to be more connected to concurrence both being basis independent quantities. These observations could be of use in obtaining a deeper understanding of the interconnections between various measures of quantum coherence.Comment: Interconnections between various measures of quantum coherence is investigated using $X$ state

A study of fasting lipid profile in chronic kidney disease patients

Background: Dyslipidemia is very much common in chronic kidney disease patients and is responsible for cardiovascular disease (CKD) which is most common cause of mortality in them. So, it is necessary to study the lipid profile in CKD patients to prevent morbidity and mortality.Methods: Subjects each of 50 in number are grouped into healthy controls (group-1), CKD patients without hemodialysis (group-2), CKD patients with hemodialysis (group-3). After fasting of 12 hours, lipid profile is assessed in all cases.Results: In this study, there is increase in Total cholesterol (TC), Low Density lipoprotein (LDL), very Low-Density lipoprotein (VLDL) and Triglycerides (TG) and decrease in High Density Lipoprotein (HDL) in all CKD patients compared to healthy controls (p-value for each parameter <0.001). There is increase in TC, TG and VLDL in diabetic CKD patients compare to non-diabetic CKD patients and p-value for each parameter is <0.05. It was found that TG and VLDL increase and HDL decrease in group-3 compare to group-2 is statistically significant (p-value for each <0.05) and no significant variation in TC and LDL in these groups.Conclusions: Present study demonstrated that there is dyslipidemia in CKD patients irrespective of mode of management, but the derangement is much more common and significant in CKD with hemodialysis group and they are at risk of cardiovascular disease. It is better to start lipid lowering drugs which decreases disease progression and dyslipidemia

Solar has greater techno-economic resource suitability than wind for replacing coal mining jobs

Coal mining directly employs over 7 million workers and benefits millions more through indirect jobs. However, to meet the 1.5 °C global climate target, coal's share in global energy supply should decline between 73% and 97% by 2050. But what will happen to coal miners as coal jobs disappear ?Answering this question is necessary to ensure a just transition and to ensure that politically powerful coal mining interests do not impede energy transitions. Some suggest that coal miners can transition to renewable jobs. However, prior research has not investigated the potential for renewable jobs to replace 'local' coal mining jobs. Historic analyses of coal industry declines show that coal miners do not migrate when they lose their jobs. By focusing on China, India, the US, and Australia, which represent 70% of global coal production, we investigate: (1) the local solar and wind capacity required in each coal mining area to enable all coal miners to transition to solar/wind jobs; (2) whether there are suitable solar and wind power resources in coal mining areas in order to install solar/wind plants and create those jobs; and (3) the scale of renewables deployment required to transition coal miners in areas suitable for solar/wind power. We find that with the exception of the US, several GWs of solar or wind capacity would be required in each coal mining area to transition all coal miners to solar/wind jobs. Moreover, while solar has more resource suitability than wind in coal mining areas, these resources are not available everywhere. In China, the country with the largest coal mining workforce, only 29% of coal mining areas are suitable for solar power. In all four countries, less than 7% of coal mining areas have suitable wind resources. Further, countries would have to scale-up their current solar capacity significantly to transition coal miners who work in areas suitable for solar development.publishedVersio

Experimental implementation of distributed phase reference quantum key distribution protocols

Quantum cryptography is now considered as a promising technology due to its promise of unconditional security. In recent years, rigorous work is being done for the experimental realization of quantum key distribution (QKD) protocols to realize secure networks. Among various QKD protocols, coherent one way and differential phase shift QKD protocols have undergone rapid experimental developments due to the ease of experimental implementations with the present available technology. In this work, we have experimentally realized optical fiber based coherent one way and differential phase shift QKD protocols at telecom wavelength. Both protocols belong to a class of protocols named as distributed phase reference protocol in which weak coherent pulses are used to encode the information. Further, we have analyzed the key rates with respect to different parameters such distance, disclose rate, compression ratio and detector dead time.Comment: DPS and COW protocols for QKD are experimentally implemente