Cryptography in a Quantum World
Stephanie Wehner
Abstract:
Quantum computing had a profound impact on cryptography. Shor's discovery of
an efficient quantum algorithm for factoring large integers implies that
many existing classical systems based on computational assumptions can be
broken, once a quantum computer is built. It is therefore imperative to find
other means of implementing secure protocols. This thesis aims to contribute
to the understanding of both the physical limitations, as well as the
possibilities of cryptography in the quantum setting. In particular, we
investigate several questions that are crucial to the security of quantum
protocols: How can we find good uncertainty relations for a large number of
measurement settings? How does the presence of entanglement affect classical
protocols? And, what limitations does entanglement impose on implementing
quantum protocols? Finally, can we circumvent some of those limitations
using realistic assumptions?
Keywords: Quantum Physics