Real State Security Clause Samples

Real State Security. The QCKA protocol (and, indeed, most if not all QKD protocols) may be broken into three distinct modules or CPTP maps: first is a sampling module which takes as input a quantum state ρTABE where the T register represents the sampling subset t used and B represents all p Bobs. Here, this module measures the T register which chooses a subset t; from this, all qudits indexed by t are measured in the Fourier basis, producing outcome q ∈ Am·(p+1). The output of this process is the subset chosen t, the observed q, and also the post-measured state ρABE(t, q). Following this, the raw-key generation module is run, denoted , which takes as input the previous post measured state and measures the remaining systems in the Z basis resulting in raw keys for all parties. The output of this module is the raw key produced along with a post-measured state for Eve. Finally, a post-processing module is run, denoted , which will run an error correction protocol and privacy amplification, yielding the final secret key. The output of this last CPTP map is the actual secret key produced along with Eve’s final quantum ancilla. This module requires as input the raw keys along with q (needed to determine the final secret key size). We want to show, with high probability over the choice of sampling subset and test measurement outcome, that the final secret key is ϵPA-close to the ideal secret key as defined by Equation 3. Recall, ψ AB1···BpE is the actual state produced by the adversary and sent to each of the parties. We may assume this is a pure state as a mixed state would lead to greater uncertainty for Eve. Of course, in the real case, the choice of subset is independent of the Σ