## Quantum Communication

## Broadcasting Of Correlations In Quantum World

In quantum information theory, entanglement and other measures of correlation plays a significant role in the computational and communicational processes like quantum key distribution, secret sharing, teleportation, super dense coding and in many other tasks. At least in that context, purer the entanglement more valuable is the given two qubit state. Therefore extraction and distillation of pure quantum entanglement from partially entangled states is considered to be an important task. The possibility of compression of quantum correlations naturally raises the question if the opposite, i.e decompression of quantum correlation is possible or not. Many researchers actually answered the query by using the process called “Broadcasting of Inseparability”. The question becomes important when there is exigency in increasing the number of available entangled pairs rather than purity of it.

## Charecterization Of Resource

One of the most important aspect of the quantum network is to understand the resources which will be useful as network. As we know that in a network we require entangled states to be connected between the nodes, so in a simplistic way we can think all entangled states as resource for the network. However the process of selection of resources are not straightforward and simple. There are in fact two possible ways of characterization of resources in a broad sense. The first case is the resources based on certain information processing tasks. These information processing tasks include 1) Teleportation 2) Super dense Coding 3) State merging and many others. It is not true if we comment that given an entangled state it will be useful for any kind of tasks. As an example if we want built a teleportation network, we know that not all entangled states will be useful for teleportation as long as we are expecting to have a quantum advantage. The second possible way is to select states which are not resource at the present moment but can be made useful for resource after quantum operations. As an example there are separable states which can be converted into an entangled state after global unitary operations.

## Quantum Secret Sharing

The basic idea of secret sharing is the process by which dealer shares secret with two parties in such a way that no body will be able to reveal the secret without invoking the other parties. This is a very useful technique if one of the party is dishonest. Quantum secret sharing generally deals with the problem of sharing of both classical as well as quantum secrets In general research was carried out mainly investigating the concept of quantum secret sharing using tripartite pure entangled states and multipartite states like graph states as resources. More precisely
when we talk about multiqubit secret sharing, we generally talk about a situation where the dealer wants to send multiple secrets; is a QSS scheme to various re constructors. Apart from classical and quantum secret sharing, protocols have been given to share semi-quantum secrets using entangled states as the resource.