Week 26.05.2018 – 03.06.2018

Wednesday

Exotic Rational CFT and the Modular Bootstrap

Regular Seminar Sunil Mukhi (IISER, Pune)

at:
14:00 QMW
room G O Jones 610
abstract:

I will summarise old and recent developments on the classification and solution of Rational Conformal Field Theories in 2 dimensions using the method of Modular Differential Equations. Novel and exotic theories are found with small numbers of characters and simple fusion rules, one of these being the Baby Monster CFT. Correlation functions for many of these theories can be computed using crossing-symmetric differential equations.

Thursday

Perfect probabilistic storing and retrieving of unitary channels

Regular Seminar Michal Sedlak (Slovak Academy of Sciences)

at:
14:00 QMW
room G O Jones 610
abstract:

Any sequence of quantum gates on a set of qubits defines a multipartite unitary transformation. These sequences may correspond to some parts of a quantum computation or they may be used to encode classical/quantum information (e.g. in private quantum channels). If we have only limited access to such a unitary transformation, we may want to store it into a quantum memory and later perfectly retrieve it. Thus, once we cannot use the unitary transformation directly anymore, we could still apply it to any state with the help of the footprint kept in the quantum memory. This can be useful for speeding up some calculations or as an attack for process based quantum key distribution protocol or a communication scheme. We require the storing and retrieving protocol to perfectly reconstruct the unitary transformation, which implies non unit probability of success. We derive optimal probability of success for a d-dimensional unitary transformation used N-times. The optimal probability of success has a very simple form N/(N-1+d^2). This result implies that reliable storing of d^2 parameters of the unknown unitary transformation requires roughly d^2 uses of the transformation.