Single-Photons, Entangled Photon Pairs & Optimal Quantum Cloning of Qubits

Abstract

Quantum physics has many applications today, many techniques have been developed and are now used in various fields. However, going back to the foundations, there are many interesting and still unresolved questions. This week, Nicolas Gisin will talk about the single photon, how to define it and how far it can travel if you want to use it to send information. He will also talk about quantum memories that can be used to extend this distance. This plays an important role in the transmission of entanglement, so the next part of the talk will be about pairs of photons, and we will consider quantum communication between two parties.

One of the most important concepts in quantum physics is the no-cloning theorem: It is impossible to make an exact copy of an unknown quantum state. However, there are schemes to approximate a quantum state using so-called quantum cloning machines. How this is achieved will also be discussed in the talk!