# Appendix B — Glossary and laboratory directory {#glossary .unnumbered}

## Terms and where to study them

| Term | Meaning | Chapter |
|:--|:--|:--|
| Amplitude | Complex coordinate whose coherent sums determine probabilities | 2 |
| Ancilla | Additional subsystem used as workspace, a probe, or a resource | 1, 17 |
| Basis | Orthonormal coordinate set or measurement alternatives | 3 |
| Bloch vector | Three Pauli expectations of a qubit | 4, 6 |
| BQP | Bounded-error polynomial-time quantum decision complexity | 1 |
| Channel | Completely positive trace-preserving state transformation | 8 |
| Clifford | Gate mapping Pauli strings to Pauli strings by conjugation | 16, 19 |
| Code distance | Minimum weight of a nontrivial logical error in a stabilizer code | 17 |
| Concurrence | Here, $2|ad-bc|$ for a pure two-qubit state | 5 |
| Density matrix | Operator describing pure or mixed-state statistics | 6 |
| Detector | Parity of measurement records expected to be fixed absent faults | 18 |
| Eigenphase | Phase of a unitary eigenvalue, defined modulo one cycle | 12 |
| Entanglement | Joint-state nonseparability; pure-state factorization failure | 5, 6 |
| Erasure | Error with a known affected location | 17, 19 |
| Fidelity | State similarity; this book uses the squared convention | 6 |
| Gate depth | Sequential layers under an explicitly defined schedule | 1, 20 |
| Global phase | Common phase multiplying a whole state vector | 2 |
| Logical qubit | Encoded information-bearing subsystem or code-space factor | 17 |
| Magic state | Nonstabilizer ancillary resource for logical non-Clifford operations | 19 |
| Measurement instrument | Operations specifying both outcomes and conditioned states | 6 |
| Mitigation | Inference strategy estimating ideal quantities from noisy data | 8 |
| Oracle | Specified black-box operation counted as a resource | 9 |
| Partial trace | Reduction giving all statistics accessible to a subsystem | 6 |
| Pauli frame | Classical record used to interpret inferred Pauli corrections | 19 |
| Postselection | Restricting results to accepted observed events | 1, 19 |
| POVM | Positive measurement effects summing to identity | 6 |
| PQC | Classical cryptography designed to resist known quantum attacks | 22 |
| QEC | Quantum error correction | 17–19 |
| QKD | Quantum key distribution with classical authenticated processing | 22 |
| QFT | Unitary Fourier transform of quantum amplitudes | 12 |
| QPE | Quantum phase estimation | 12 |
| QSVT | Polynomial transformation of singular values through encoded access | 14 |
| Relative phase | Phase difference between coherent components | 2–4 |
| Schmidt rank | Number of nonzero Schmidt coefficients of a pure bipartite state | 6 |
| Shot | One execution yielding measurement data | 1, 23 |
| Stabilizer | Pauli constraint fixing a code space | 17 |
| Syndrome | Check outcomes used to infer errors | 17, 18 |
| T-count | Number of non-Clifford T resources in a specified circuit model | 19, 20 |
| Threshold | Noise boundary for a specified scalable correction protocol | 18 |
| Trace distance | Operational distinguishability measure based on trace norm | 6 |
| Uncomputation | Reversing coherent work to remove intermediate information | 1, 9 |
| Unitary | Inner-product-preserving linear transformation | 4 |

## Laboratory directory

All identifiers below are present in the web edition and linked from the corresponding PDF chapter.

| Lab | Experiment | Chapter |
|:--|:--|:--|
| L01 | Reversible logic and classical repetition | 1 |
| L02 | Complex state preparation | 2 |
| L03 | Full Z/X/Y projection workbench | 3 |
| L04 | Randomized measurement practice | 3 |
| L05 | Bloch sphere and single-qubit gates | 4 |
| L06 | Circuit builder and state evolution | 5 |
| L07 | Entanglement, density matrices, and partial trace | 6 |
| L08 | Bell/CHSH correlations and finite shots | 7 |
| L09 | Teleportation branches and corrections | 7 |
| L10 | Superdense coding | 7 |
| L11 | Exact single-qubit noise channels | 8 |
| L12 | Error-mitigation bias and variance | 8 |
| L13 | Deutsch, Deutsch–Jozsa, Bernstein–Vazirani | 9 |
| L14 | Simon constraints and row reduction | 10 |
| L15 | Grover and amplitude amplification | 11 |
| L16 | Quantum Fourier transform | 12 |
| L17 | Quantum phase estimation | 12 |
| L18 | Small-instance Shor order finding | 13 |
| L19 | Hamiltonian evolution and product formulas | 14 |
| L20 | Variational energy and gradient steps | 15 |
| L21 | One-layer QAOA on a triangle | 15 |
| L22 | Classical representation memory cost | 16 |
| L23 | Repetition-code syndromes and logical failures | 17 |
| L24 | Distance-three surface-code Pauli decoding | 18 |
| L25 | Illustrative logical and physical resources | 20 |
| L26 | BB84 transmission and intercept–resend | 22 |

## Limits that travel with the models

The generic circuit laboratory supports eight qubits and forty operations. Measurement branches are resampled for each shot. The phase and Fourier laboratories use exact small-register transforms. The Shor laboratory computes a modular-exponentiation Fourier marginal for N=15 or 21 and performs classical reconstruction; it does not compile a cryptographic modular arithmetic circuit.

The noise laboratory evolves one-qubit density operators with explicitly stated Kraus models. The surface-code laboratory uses nine data qubits, perfect stabilizer information, and minimum-weight Pauli recovery. It does not simulate faulty ancilla circuits or many-round spacetime decoding. The resource calculator uses an illustrative scaling relation, and the mitigation lab uses a specified exponential model.

BB84's classroom transcript exposes information for learning. It is not production cryptographic software and does not implement a composable finite-key proof or a secure authenticated network. These boundaries define what each tool actually computes; they are essential to interpreting its output.

