
Robustness of high-dimensional quantum cryptography on quantum hacking - zenonian
http://advances.sciencemag.org/content/3/2/e1601915.full
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zenonian
Abstract

Attempts at cloning a quantum system result in the introduction of
imperfections in the state of the copies. This is a consequence of the no-
cloning theorem, which is a fundamental law of quantum physics and the
backbone of security for quantum communications. Although perfect copies are
prohibited, a quantum state may be copied with maximal accuracy via various
optimal cloning schemes. Optimal quantum cloning, which lies at the border of
the physical limit imposed by the no-signaling theorem and the Heisenberg
uncertainty principle, has been experimentally realized for low-dimensional
photonic states. However, an increase in the dimensionality of quantum systems
is greatly beneficial to quantum computation and communication protocols.
Nonetheless, no experimental demonstration of optimal cloning machines has
hitherto been shown for high-dimensional quantum systems. We perform optimal
cloning of high-dimensional photonic states by means of the symmetrization
method. We show the universality of our technique by conducting cloning of
numerous arbitrary input states and fully characterize our cloning machine by
performing quantum state tomography on cloned photons. In addition, a cloning
attack on a Bennett and Brassard (BB84) quantum key distribution protocol is
experimentally demonstrated to reveal the robustness of high-dimensional
states in quantum cryptography.

