Abstract :

Quantum state discrimination is a fundamental problem in quantum mechanics underlying several applications in quantum information theory including quantum cryptography and quantum algorithms. The problem can be understood as follows: Suppose a quantum system has been prepared in one of several known quantum states. We do not know which state the system is in but wish to identify it as well as possible by performing a quantum measurement on the system. In other words, we want to reliably distinguish quantum states, in one of which a system has been prepared, from one another. For orthogonal states the solution is straightforward and the states can be distinguished perfectly, that is, without error. However, quantum mechanics forbids perfect discrimination if the states are not mutually orthogonal.

We will first state the problem with full generality, and give examples to illustrate the non-trivial nature of a seemingly innocuous problem. We will then introduce the paradigm of local operations and classical communication (LOCC) and define quantum state discrimination problem by LOCC. We will give a brief overview of this exciting field which gives rise to new kind of nonlocality and the concept of locally hidden information.

We will also briefly discuss applications in the field of quantum cryptography.

ABOUT THE SPEAKER:

Somshubhro Bandyopadhyay is an Associate Professor at Bose Institute, Kolkata. He obtained a Master's degree in Physics from Jadavpur University, Kolkata and Ph. D. in Physics from Bose Institute. After postdoctoral research at UCLA, University of Toronto and Universite de Montreal he has been at Bose Institute since 2008. His research interests concern quantum information theory and foundations of quantum mechanics.