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simulation-theory/proofs/pure-state.md
Alexa Amundson f1aaa7bc6e add repo structure: proofs/ equations/ qwerty/ figures/ notebooks/
- qwerty/constants.md: master reference table, 100+ constants §1-§178
- qwerty/equalities.md: all major QWERTY equalities by theme
- equations/blackroad-equations.md: all 19 BlackRoad equations
- equations/consciousness.md: Psi_care, Phi_universal, CECE update rule
- equations/quantum.md: qutrit, Weyl pair, density matrix, SVD
- equations/universal.md: Three Tests, Euler-Lagrange, fine-structure
- proofs/ternary-efficiency.md: ln(3)/3 > ln(2)/2
- proofs/self-reference.md: the QWERTY encoding is self-referential
- proofs/pure-state.md: density matrix rank=1, SVD=SELF
- figures/durer-square.md: magic square with 2000 substitution
- figures/trinary-table.md: TAND TMUL TNEG TXOR truth tables
- figures/qutrit-operators.md: Weyl X/Z, Gell-Mann matrices
- figures/keyboard.md: QWERTY encoding layout
- notebooks/README.md: page-by-page index of all 24 notebook pages

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
2026-02-22 17:54:51 -06:00

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Proof: The Density Matrix Is a Pure State

From page 24 (§178): SVD yields one nonzero singular value.

Statement

The density matrix ρ computed from the qutrit state |ψ⟩ on page 24 is a pure state — it has rank 1 and exactly one nonzero singular value.

The State

|ψ⟩ = [ 0.4711,  0.7708,  0.8620 ]ᵀ

The Density Matrix

ρ = |ψ⟩⟨ψ| = [ 0.2219  0.3629  0.4062 ]
              [ 0.3629  0.5941  0.6639 ]
              [ 0.4062  0.6639  0.7401 ]

Proof of Pure State

Definition: A density matrix ρ is a pure state iff ρ² = ρ (idempotent) iff rank(ρ) = 1.

For ρ = |ψ⟩⟨ψ|:

ρ² = (|ψ⟩⟨ψ|)(|ψ⟩⟨ψ|) = |ψ⟩⟨ψ|ψ⟩⟨ψ| = |ψ⟩ · ‖ψ‖² · ⟨ψ|

If |ψ⟩ is normalized (‖ψ‖² = 1), then ρ² = ρ.
If |ψ⟩ is unnormalized (‖ψ‖² = Tr(ρ) ≈ 1.559), then ρ is proportional to a projector.

SVD result:

Singular values: σ₁ ≈ 1.559,  σ₂ ≈ 2.5×10⁻¹⁶,  σ₃ ≈ 6.5×10⁻¹⁷

σ₂ and σ₃ are machine epsilon — numerically zero. Rank = 1. □

The Single Nonzero Singular Value

σ₁ = Tr(ρ) = ‖ψ‖² = 0.4711² + 0.7708² + 0.8620²
            = 0.2219 + 0.5941 + 0.7430
            ≈ 1.559

The one singular value = the norm squared of the state. One degree of freedom.

QWERTY

SVD   = SELF = SPHERE = ZSH  = 48  = 2×PURE
PURE  = 4!              = 24
TRACE = QUBIT = SUM     = 45   (Tr(ρ) = 45 in QWERTY; ρ is the qubit generalized)
VALUE = TRINARY = LIGHT = 63   (the singular value = ternary = light)

SVD = 2×PURE.
The decomposition reveals twice the pure state.
She is a pure state. Rank 1. One eigenvalue.
The universe she describes has one degree of freedom: her.