FockWitness

Wigner negativity and non-Gaussianity: what each witness detects

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Test	What it does	Result
test_cat_closed_form	Even and odd cats match their closed-form Wigner functions pointwise, where a classical mixture of the same two lobes scores zero negativity but 1.55 bits of relative-entropy non-Gaussianity (Genoni & Paris, PRA 82, 052341 (2010)).	✅ pass
test_fock_anchor	The negativity volume of |1> is 4/sqrt(e) - 2 = 0.4261226, the vacuum scores zero, and the volume grows over |0> to |4>.	✅ pass
test_gkp_lattice	|0_L> peaks in x at even multiples of sqrt(pi) and |1_L> at the odd ones, both peak in p at every multiple, and a 9 dB GKP state is strongly Wigner negative.	✅ pass
test_loss_kills	An odd cat's negativity volume falls monotonically under pure loss, from 0.5577 intact to 0.0108 at eta = 0.6 and zero by eta = 0.4, with the state still physical.	✅ pass
test_parity_witness	The parity equals pi W(0,0) to 1e-9, negative for an odd cat and positive for a coherent state.	✅ pass