9 research outputs found
Coherent Eavesdropping Attacks in Quantum Cryptography: Nonequivalence of Quantum and Classical Key Distillation
The security of a cryptographic key that is generated by communication
through a noisy quantum channel relies on the ability to distill a shorter
secure key sequence from a longer insecure one. We show that -- for protocols
that use quantum channels of any dimension and completely characterize them by
state tomography -- the noise threshold for classical advantage distillation is
substantially lower than the threshold for quantum entanglement distillation
because the eavesdropper can perform powerful coherent attacks. The earlier
claims that the two noise thresholds are identical, which were based on
analyzing incoherent attacks only, are therefore invalid.Comment: 4 pages, 1 figure; this is the detailed account for the results
Reported in quant-ph/031015
Quantum Tomographic Cryptography with a Semiconductor Single Photon Source
In this paper we analyze the security of the so-called quantum tomographic
cryptography with the source producing entangled photons via an experimental
scheme proposed in Phys. Rev. Lett. 92, 37903 (2004). We determine the range of
the experimental parameters for which the protocol is secure against the most
general incoherent attacks
Quantum tomographic cryptography with Bell diagonal states: non-equivalence of classical and quantum distillation protocols
We present a generalized tomographic quantum key distribution protocol in
which the two parties share a Bell diagonal mixed state of two qubits. We show
that if an eavesdropper performs a coherent measurement on many quantum ancilla
states simultaneously, classical methods of secure key distillation are less
effective than quantum entanglement distillation protocols. We also show that
certain Bell diagonal states are resistant to any attempt of incoherent
eavesdropping.Comment: 9 pages. 2 figures There was an error in the formula 4
(transformation of Bell states). This error does not change the main result
of the paper, namely, that quantum distillation is more powerful than
classical advantage distillatio