Robert Spekkens

Finding the consequences of symmetries in dynamics is a subject with broad applications in physics. We are interested to find tools to study the consequences of symmetry which apply to open as well as closed quantum systems. We introduce a different point of view for thinking about asymmetry which is not based on symmetric dynamics; instead it is based on the intuition that a state which breaks symmetry can be thought as a signal which carries information about the group element. Using this point of view we use information measures to build asymmetry measures via the Holevo quantity. We show that for pure states Noether's theorem includes all the possible implications of the symmetry of dynamics, but for mixed states conservation of asymmetry measures imply more constraints than those prescribed by Noether's theorem.