CrossTruncation

The Fock engine reduced to the Gaussian one, with convergence demonstrated

7/7 passed in 178ms

Test	What it does	Result
test_fock_channel	A number-basis beamsplitter with vacuum equals the thermal-loss map at $\xi =0$ to 1e-13 on displaced and thermal states.	✅ pass
test_fock_converges	The number basis reproduces the Gaussian layer's mean, covariance and Wigner function on a 31x31 window, each error falling at least 8x per cutoff doubling, a factor an hbar slip or a missing sqrt(2) fails.	✅ pass
test_fock_entropy	A thermal state's von Neumann entropy and purity in the number basis equal the symplectic ones.	✅ pass
test_fock_gaussianity	Relative-entropy non-Gaussianity and Wigner negativity vanish on every Gaussian twin at cutoff 96, converged 10x against 48, where a squeezed vacuum still reads 3e-4; negativity is bounded above only.	✅ pass
test_fock_physical	At every cutoff, including ones where the moments are 100% wrong, the number basis's second moments are bona fide and satisfy Heisenberg, and its Husimi grid stays inside $[0,1/(2\pi )]$.	✅ pass
test_fock_purity	A truncated pure state's density matrix reports purity 1 at every cutoff while its moments read $1/(2\sqrt{detV})$ = 0.650 at cutoff 6 and 0.99996 at 48, the pessimistic reading for a pure state.	✅ pass
test_trunc_underreports	trunc_error scores the lost population, not its effect on the moments: a squeezed vacuum's covariance error runs 15x to 140x above it, growing with the cutoff.	✅ pass