Somshubhro Bandyopadhyay                                                              
                                                                                      
When is teleportation 'quantum'?                                                      
                                                                                      
Quantum teleportation achieves transmission of quantum information through            
poor quantum channels by instead transmitting classical information                   
through the channel and consuming shared entanglement between the sender              
(A) and receiver (B). The figure of merit for quantum teleportation                   
performance is the fidelity, and low-fidelity teleportation is achievable             
classically, i.e. without entanglement shared between the sender and                  
receiver. We establish the quantum-classical threshold for teleportation              
by treating the relationship between the verifier (V), who tasks A and B              
with partial teleportation of his state, and A and B as adversarial: V                
fully tests the fidelity by employing partial teleportation (in contrast              
to the typical assumption of total teleportation) and A and B cannot                  
assume anything about the portion of the state that they do not teleport.             
We identify the fidelity threshold for which A and B definitely require               
entanglement, and we also establish the degree of entanglement required by            
A and B to prove to V that their teleportation is indeed 'quantum'.