Alphabeta Math
Pipeline-generated
How statement and proof provenance work

The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.

  • Literature-sourced: the exact statement appears in a cited source; only wording and notation differ.
  • AI-adapted: a semantically identical restatement of literature-sourced material, modulo indexing, notation, and boundary cases adopted by the library.
  • AI-generated: a genuinely novel statement formulated by AI, with no source for the claim itself.

These labels describe origin, not correctness: citations and verification chips remain separate evidence.

Quantum Key Distribution and Composable Secrecy — Examples

1 · Prerequisites

2 · Summary

The first calculation keeps a 1/4 abort probability and shows that the real-ideal trace distance and secrecy error are both 3/8 when the accepted key is always 0 but the parties agree. The second compares a uniformly secret but always mismatched key with a perfectly matched but deterministic key, showing that secrecy and correctness are distinct conditions.

3 · Logical flowchart

4 · Definitions, theorems and proofs

None yet.

5 · Examples, counterexamples and false statements

ExampleConstruction: AI-generatedVerification: AI-generatedOpen item page →

Acceptance probability weights an otherwise imperfect one-bit key

Example

Take K={0,1}, a one-element transcript alphabet T={t}, and a one-dimensional adversary system HE=C. A finite protocol aborts with probability 1/4 and, on acceptance, both parties always output key 0. Then the correctness error is 0, the secrecy error is 3/8, and the abort-aware real-ideal trace distance is exactly 3/8.

Facts & Assumptions

Given: The key alphabet, transcript, adversary space, and output law in the Example.

[F1]

Finite authenticated key-distribution protocol: the output has a normalized classical state on keys, transcript and adversary; the abort flag is shared.

[F2]

Abort-aware real and ideal QKD outputs and security errors: the ideal accepted key is uniform and shared; the secrecy error is the acceptance probability times the normalized accepted secrecy distance.

[F3]

Trace Distance: for density operators, D(ρ,σ)=12∥ρ−σ∥1.

[F4]

Trace Norm Spectral Formula and Trace Norm Unitary Invariance And Positive Formula: for a self-adjoint diagonal matrix, the trace norm is the sum of the absolute diagonal entries.

[F5]

QKD composable secrecy is bounded by correctness plus secrecy: the real-ideal trace-distance error is bounded by the sum of correctness and secrecy errors.

Verification

Given: ρreal=14∣⊥,⊥,t⟩⟨⊥,⊥,t∣+34∣0,0,t⟩⟨0,0,t∣, with the one-dimensional Eve factor suppressed.

1.1givenF1F2construct

The ideal state keeps the abort block and replaces the accepted block by 34τAB, so ρideal=14∣⊥,⊥,t⟩⟨⊥,⊥,t∣+38∣0,0,t⟩⟨0,0,t∣+38∣1,1,t⟩⟨1,1,t∣.

1.2givenF1F3F4algebra

Their difference is 38∣0,0,t⟩⟨0,0,t∣−38∣1,1,t⟩⟨1,1,t∣. The two basis vectors are orthogonal by [F1], so its nonzero eigenvalues are 3/8 and −3/8; [F3]–[F4] give δid=12(3/8+3/8)=3/8.

2.1givenF2F3F4F5step 1.2algebra∎

The accepted keys always agree, so εcor=0. The accepted Alice state is ∣0⟩⟨0∣, whose difference from τA=12(∣0⟩⟨0∣+∣1⟩⟨1∣) has nonzero diagonal entries 1/2,−1/2 and trace distance 1/2. Thus εsec=(3/4)(1/2)=3/8. The theorem's sum bound [F5] holds with equality.

ExampleConstruction: AI-generatedVerification: AI-generatedOpen item page →

Secrecy and correctness are separate requirements

Example

For K={0,1}, no abort, a one-element transcript, and a one-dimensional adversary system, consider two finite output laws. In the first, Alice's key is uniform but Bob always outputs its complement: secrecy error is 0 and correctness error is 1. In the second, both parties always output 0: correctness error is 0 and secrecy error is 1/2. Thus neither condition implies the other.

Facts & Assumptions

Given: The two normalized classical output states described in the Example.

[F1]

Abort-aware real and ideal QKD outputs and security errors: the correctness error is the probability of unequal accepted outputs, and secrecy compares Alice's accepted key with a uniform key independent of transcript and Eve.

[F2]

Trace Distance: trace distance of density operators is half the trace norm of their difference.

[F3]

Trace Norm Spectral Formula: for an orthogonal diagonal decomposition, the trace norm is the sum of absolute eigenvalues.

[F4]

QKD composable secrecy is bounded by correctness plus secrecy: the real-ideal distance is at most the sum of the correctness and secrecy errors.

Verification

Given: Let ρ(1)=12∣0,1,t⟩⟨0,1,t∣+12∣1,0,t⟩⟨1,0,t∣ and ρ(2)=∣0,0,t⟩⟨0,0,t∣, with Eve's one-dimensional factor suppressed.

1.1givenF1F2F3algebra

For ρ(1), Alice's marginal is I/2, so it is already uniform and independent of the trivial transcript-adversary state; hence εsec=0. Every output pair differs, so εcor=1. The real state is supported on {∣0,1,t⟩,∣1,0,t⟩} while the ideal state is supported on the orthogonal set {∣0,0,t⟩,∣1,1,t⟩}. Their difference therefore has positive and negative parts each of trace one, giving δid=1 by [F2]–[F3].

2.1givenF1F2F3F4algebra∎

For ρ(2), the parties always agree, so εcor=0. Alice's accepted state is ∣0⟩⟨0∣, and ∣0⟩⟨0∣−I/2 has eigenvalues 1/2,−1/2; hence εsec=1/2. The real-ideal output difference has the same two eigenvalues, so δid=1/2. Both cases satisfy [F4] with equality, while each has exactly one of the two component errors zero.

Sources