## Live-tweeting QCrypt 2015

今日は Konnichiwa!

The 5^{th} International conference on quantum cryptography (QCrypt) was held this year in beautiful Tokyo, Japan. QCrypt is the largest conference to focus entirely on quantum cryptography and it routinely gathers all the best researchers in the field from around the world.

## How to enhance separability and entanglement of quantum states

A quantum state \(\rho\) that is shared between two parties is called *separable* if it can be written as a convex combination of local quantum states \(\{\sigma_i\}\) and \(\{\tau_i\}\):

\[\rho = \sum_i p_i \sigma_i \otimes \tau_i.\]

States that are not separable are called entangled, and the distinction between these two types of states is important because there are many senses in which entangled states are exactly the "useful" ones in quantum information theory.