Abstract
We construct a practically implementable classical processing for the Bennett-Brassard 1984 (BB84) protocol and the six-state protocol that fully utilizes the accurate channel estimation method, which is also known as the quantum tomography. Our proposed processing yields at least as high a key rate as the standard processing by Shor and Preskill. We show two examples of quantum channels over which the key rate of our proposed processing is strictly higher than the standard processing. In the second example, the BB84 protocol with our proposed processing yields a positive key rate even though the so-called error rate is higher than the 25% limit.
Highlights
Quantum key distributionQKDhas attracted great attention as an unconditionally secure key distribution scheme
We construct a practically implementable classical processing for the Bennett-Brassard 1984 ͑BB84͒ protocol and the six-state protocol that fully utilizes the accurate channel estimation method, which is known as the quantum tomography
We show two examples of quantum channels over which the key rate of our proposed processing is strictly higher than the standard processing
Summary
Quantum key distributionQKDhas attracted great attention as an unconditionally secure key distribution scheme. A classical processing consists of a procedure to determine a key rate from a channel estimate and a procedure for the information reconciliation and the privacy amplification. Their proof techniques can be used to prove the security of the QKD protocols with a classical processing that fully utilizes the accurate estimation method They only considered Pauli channels or partial twirled channels.. We present a practically implementable procedure for the information reconciliation and the privacy amplification in which we can share a secret key at the determined key rate. By combining our proposed procedure to determine a key rate based on the accurate channel estimate and Devetak and Winter’s procedure for the information reconciliation and the privacy amplification, we can obtain the same key rate as in this paper. Our results in this paper can be extended to procedures with the noisy preprocessing and twoway classical communicationsee Remark 11͒
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