How to preserve optimal measurements for state discrimination over any quantum channel

Staff - Faculty of Informatics

Date: / -

USI Lugano Campus, room A-34 Red Building (Via G. Buffi 13)


For practical quantum information applications one has to deal with the reality of non-perfect communication channels. We consider the problem of optimal quantum state discrimination, which consists in finding the best possible measurement that allows to distinguish two or more quantum states, over arbitrary quantum channels. We find sufficient conditions on the channels that guarantee the preservation of the optimality of the measurement. In addition, we show that under mild assumptions an optimal measurement can be preserved by a protocol requiring local operations and classical communication only, without the need to verify the quantum channel. 

The key idea is to perform a channel twirling to transform any noisy channel into a depolarization channel. We simulated the proposed protocol for two qubits discrimination on an IBM quantum computer and obtained a good agreement with the theoretical predictions.


Chahan M. Kropf is a Postdoc in physics at the Dept. of Mathematics and Physics, Università Cattolica del Sacro Cuore, Brescia, Italy. He received his Ph.D. in Physics from the Albert-Ludwigs university of Freiburg, Germany, in 2017 for his thesis on "Effective dynamics of disordered quantum systems" under the supervision of Prof. Andreas Buchleitner. Since October 2017, he holds a Post-Doc position from the INFN, section of Pavia , in the research focus DYNSYSMATH (Dynamical systems and non-equilibrium states of complex systems: Mathematical methods and physical concepts) working on diverse 'quantum technologies' problem, such as quantum communication, application of machine learning to quantum problems and quantum transport.


Prof. Stefan Wolf