Measurement Device Independent Quantum Digital Signature (MDI-QDS): Difference between revisions

The MDI-QKD protocol requires an untrusted third party sitting in the middle of the participating parties, arbitrator. The following steps are performed with Seller and each recipient, pairwise. Seller and recipient each prepare a state in a randomly chosen basis (of the two chosen bases, say rectilinear ([[Glossary#X basis |X]]) and diagonal ([[Glossary#Z basis|Z]]) basis), and send it to the arbitrator. The arbitrator performs [[Glossary#Bell State Measurement|Bell State Measurement]] on the two incoming states. A successful BSM entangles the two states and the outcome of the measurement is one of the four [[Glossary#Bell State|Bell States]], which is declared by the arbitrator over public channel. This process is repeated until sifting condition is met. In '''sifting''', Seller and recipient then exchange the information regarding their basis for each event, which is neglected if their chosen basis is mismatched. If matched then, depending on the basis chosen for preparation, data (classical information of their states/ classical bits) corresponding to each event is classified into two sets. This is repeated unless cardinality of the two sets is above a certain threshold number of elements. The recipient flips his bits (set elements) for each event according to the table shown in [[Measurement Device Independent Quantum Digital Signature (MDI-QDS)#Pseudo Code|Pseudo Code]]. This step is done to finally correlate seller's bits with recipient's bits. This marks the end of Sifting. Finally, one of sets is used for error correction in MDI-QKD (not the concern of this protocol), while the other set is divided into two parts, one to be used as the shared common key and the other, to calculate the error rate. If error rate is greater than the tolerance value decided, the protocol is aborted by both parties.