2,467 research outputs found
Complete elimination of information leakage in continuous-variable quantum communication channels
In all lossy communication channels realized to date, information is
inevitably leaked to a potential eavesdropper. Here we present a communication
protocol that does not allow for any information leakage to a potential
eavesdropper in a purely lossy channel. By encoding information into a
restricted Gaussian alphabet of squeezed states we show, both theoretically and
experimentally, that the Holevo information between the eavesdropper and the
intended recipient can be exactly zero in a purely lossy channel while
minimized in a noisy channel. This result is of fundamental interest, but might
also have practical implications in extending the distance of secure quantum
key distribution.Comment: 9 pages, 5 figure
Composable security proof for continuous-variable quantum key distribution with coherent states
We give the first composable security proof for continuous-variable quantum
key distribution with coherent states against collective attacks. Crucially, in
the limit of large blocks the secret key rate converges to the usual value
computed from the Holevo bound. Combining our proof with either the de Finetti
theorem or the Postselection technique then shows the security of the protocol
against general attacks, thereby confirming the long-standing conjecture that
Gaussian attacks are optimal asymptotically in the composable security
framework.
We expect that our parameter estimation procedure, which does not rely on any
assumption, will find applications elsewhere, for instance for the reliable
quantification of continuous-variable entanglement in finite-size settings.Comment: 27 pages, 1 figure. v2: added a version of the AEP valid for
conditional state
Continuous Variable Quantum Key Distribution: Finite-Key Analysis of Composable Security against Coherent Attacks
We provide a security analysis for continuous variable quantum key
distribution protocols based on the transmission of squeezed vacuum states
measured via homodyne detection. We employ a version of the entropic
uncertainty relation for smooth entropies to give a lower bound on the number
of secret bits which can be extracted from a finite number of runs of the
protocol. This bound is valid under general coherent attacks, and gives rise to
keys which are composably secure. For comparison, we also give a lower bound
valid under the assumption of collective attacks. For both scenarios, we find
positive key rates using experimental parameters reachable today.Comment: v2: new author, technical inaccuracy corrected, new plots, v3:
substantially improved key rates against coherent attacks (due to correction
of an error in the numerical computation
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