Institute of Physics Belgrade
University of Belgrade
Home
About the Institute
Welcome
Short history
Virtual tour
How to reach us
Audits
Structure
Management
People
Departments
Spin-offs
Policies
Research
Projects
Facilities
News
Activities
Seminars
Conferences
Publishing
Events
Graduate School
Links

search
search
:: home :: seminars
print

Seminars

28.05.2012. :: Seminar - Nikola Paunkovic



U ponedeljak 28.05. u 11h na Institutu za fiziku, u sali 300, odrzace se seminar pod naslovom

Quantum contract signing

dr Nikola Paunkovic

Instituto Superior Tecnico
Universidade Tecnica de Lisboa



Abstract:
We present a fair and optimistic quantum-contract-signing protocol between two clients that requires no communication with the third trusted party during the exchange phase. We discuss its fairness and show that it is possible to design such a protocol for which the probability of a dishonest client to cheat becomes negligible and scales as N−1/2, where N is the number of messages exchanged between the clients. Our protocol is not based on the exchange of signed messages: Its fairness is based on the laws of quantum mechanics. Thus, it is abuse free, and the clients do not have to generate new keys for each message during the exchange phase. We discuss a real-life scenario when measurement errors and qubit-state corruption due to noisy channels and imperfect quantum memories occur and argue that for a real, good-enough measurement apparatus, transmission channels, and quantum memories, our protocol would still be fair. Apart from stable quantum memories, the other segments of our protocol could be implemented by today`s technology, as they require in essence the same type of apparatus as the one needed for the Bennett-Brassard 1984 (BB84) cryptographic protocol. Finally, we briefly discuss two alternative versions of the protocol, one that uses only two states [based on the Bennett 1992 (B92) protocol] and the other that uses entangled pairs, and show that it is possible to generalize our protocol to an arbitrary number of clients.
Institute of Physics Belgrade - Pregrevica 118 - 11080 Belgrade - Serbia, Switchboard: +381 11 3713000, Fax: +381 11 3162190