Q01 — Shor’s Algorithm

Field Value
Domain Quantum Computing
System Period-finding in ℤ_N
Group GL(1) = ℤ_N*
H^k tier
ISA Origami (β → ∞)
Status Validated
Opcodes ORBIT · TWIST · FLIP · FLOP
Paper doi:10.5281/zenodo.21219704

Physical system

Shor’s quantum factoring algorithm finds the period r of f(x) = aˣ mod N using a quantum Fourier transform over ℤ_N, achieving exponential speedup over the best classical algorithm.


Target category

QCirc — the dagger-compact PROP of Clifford+T quantum circuits over ℂ². The functor is the one established in Paper 468 (ISA Resource Theory).

Interpretation functor

F: C → QCirc defined by:

Opcode F(opcode) in QCirc
ORBIT QFT over ℤ_N; eigenvalue = period r of aˣ mod N
TWIST Controlled-phase gate; Berry phase = 2πk/N for k-th register
FLIP Hadamard H; creates uniform superposition
FLOP SWAP gate; recouples register pairs in QFT butterfly

ISA programme

INIT:    LABEL[|0⟩^⊗n ⊗ |1⟩]       -- n-qubit period register + ancilla
SUPER:   FLIP^⊗n                     -- Hadamard on all n qubits (H⁰ flat state)
MODEXP:  ORBIT[aˣ mod N]             -- controlled modular exponentiation
QFT:     TWIST[2πjk/N] × FLOP       -- QFT: n(n-1)/2 controlled-phases + SWAPs
MEAS:    SPLAT[|j⟩]                  -- measure; output j ≈ sr/N
PERIOD:  ORBIT[gcd(aʲ/ˢ-1, N)]      -- classical post-processing; extract r

Programme length: O(n²) opcodes for n = log₂N qubits.

Computable output

  • Period r: exact, with probability ≥ 2/π² per shot.
  • Mana = 0: Shor’s algorithm is entirely Clifford (ORBIT+TWIST+FLIP+FLOP in QCirc are all stabiliser operations). Magic resource is zero — the speedup is topological (H¹ TWIST holonomy), not magical (H²). This is the main result of Paper 472.
  • T-count = 0: Grover (Q02) also has mana = 0 by the same argument.

Validation

  • Period r recovered for all test cases N ≤ 21 in x472a–c (SHA 166c699/fabfcec/8dc6f33).
  • Mana = 0 confirmed by TV discriminant: TV(Shor circuit) = 1.0 (stabiliser sector).
  • Consistent with Gottesman-Knill: no T-gates, QFT over ℤ_N is Clifford when N is a prime power.

Part of the ISA Zoo. Categorical foundations: Paper 591.