wai-quantum 0.3.39: the square's whole space group, a referee in each sector, and guided sampling #188

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dcharlot merged 6 commits from wai-quantum-nqs-pointgroup into main 2026-10-09 02:40:52 -04:00

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2026-10-08

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wai-quantum: guided sampling, and the 4 × 4 space group to rounding ...

VmcConfig::guide samples |ψ|² + guide·|ψ̄|² instead of |ψ|², |ψ̄| the
chains' typical amplitude when the batch starts, and weights each
sample back by |ψ|² over that; the error is then that of a weighted
mean. Near a node of the network the local energy is a large number
over a small one and |ψ|² visits too rarely for the variance to be
measured; the floor visits. Zero, the default, samples |ψ|² as before:
every pin and documented unguided figure is unchanged.

On the trained 4 × 4 J1-J2 networks, enumerated: the ±0.1 network's
guided variance came within 5 % of the exact one at every floor from
0.01 to 1, four seeds each (unguided seeds: 0.11 to 2.0 times it). The
±0.01 network's variance sits in two configurations of 12 870, which
no 8000 samples visit reliably; guided seeds still gave 0.1 to 2.3
times it.

Trained guided at 0.1 or 1, the same complex α = 1 space-group
network, start and 600 steps reach the ground energy to 1.7e-12 and
1.2e-12 (unguided: 1.27e-3), variance below 4e-11. The sector holds
107 configurations up to symmetry against 288 parameters; the docs say
so. Unprojected, the guide changes nothing (2.78e-2). Projected
networks in the CLI and nqs_ground now sample with a guide of 0.1.

A test holds guided estimates to enumeration on a projected 8-site
ring (energy within 5σ, variance within 20 %) and bit-identity across
thread counts.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

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2026-10-08 12:59:16 -04:00

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wai-quantum: no chain starts where the projection vanishes ...

A configuration fixed by a group element of character −1 has no
amplitude in the sector. Every move from it has ratio zero, so a chain
started there never left, and each of its samples fed the estimates
the diagonal energy alone. At momentum (π, π) in A1 a quarter of the
4 × 4 lattice's configurations are such; a test with 32 chains found
one stuck after burn-in. A chain now draws its start again until the
amplitude is finite. An unprojected network never redraws, and the
sector the documented 4 × 4 runs used has no such configurations.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

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2026-10-08 11:52:48 -04:00

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wai-quantum: the 4 × 4 space group after 2000 steps, and at α = 2 ...

From ±0.1 a complex α = 1 network reaches 4.60e-4 in 2000 steps, and
α = 2 reaches 6.91e-4 in 600; both energies over every configuration.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

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2026-10-08 11:39:38 -04:00

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wai-quantum: the sampled variance misses a tail near the nodes ...

Measured on the trained 4 × 4 networks with every configuration
enumerated: 89 % of the ±0.01 network's variance (0.55; sampled
1.4e-2) sits in two configurations of probability 2.6e-6 each, where
the local energy is 310 from the mean. Thinning tenfold does not find
it; 64 000 samples hit one and report 1.55. For the ±0.1 network 97 %
of the variance sits in configurations whose probabilities total
2.4e-3. Every sampled energy came out below the enumerated one, by at
most 4e-4 relative. The docs had put it down to the chains; it is the
tail.

Acceptance now counts proposals: a draw of two parallel spins
proposes nothing and was being counted as a rejection. Moves and
draws are unchanged, so every trajectory is the same bits.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

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2026-10-08 11:39:14 -04:00

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wai-quantum 0.3.39: a projected network starts off the ferromagnet ...

A projected network whose parameters start near zero is nearly the
projection of a constant: the uniform superposition, which at zero
magnetisation is the ferromagnet's member, an eigenstate whose energy
gradient vanishes. On the 8-site ring a ±0.01 start ends 2.8e-2 above
the ground state after 200 enumerated steps, ±0.1 ends 2.6e-4 above.
On the periodic 4 × 4 J1-J2 lattice at J2 = 0.5 the space group from
±0.01 ended at 2.09e-2 and from ±0.1 at 1.27e-3 (600 steps, energies
over every configuration); translations alone ended at 1.9e-2 from
either. Projected networks in the CLI and nqs_ground now start at
±0.1; --init sets it.

nqs_ground --exact-final evaluates the trained network over every
configuration. The sampled variance of the ±0.01 space-group run was
1.4e-2; its variance over every configuration is 0.55.

A test holds the trap: from ±0.01 the projected 8-site ring starts on
the ferromagnet and is still there after 40 steps; from ±0.1 it reaches
the ground state to 1e-3 in 200.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

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2026-10-08 10:33:03 -04:00

2026-10-07

Transaction Science

wai-quantum: the square's whole space group, and a referee in each sector ...

Symmetry::square projects onto the translations of an l × l torus with
the eight rotations and reflections, in one of their four
one-dimensional representations (PointIrrep), at momentum 0 or (π, π).
Symmetry::check proves a set of elements a group and its characters
multiplicative; ring and torus now refuse a momentum π their lengths
cannot carry.

SpinModel::exact_ground_energy_in is Lanczos on P H P, re-projected
after every product, so a projected network is held to its own
sector's ground energy. It refuses a set that is not a group, a model
the group does not preserve (commutes_with), and a flip out of a
nonzero magnetisation. Both referees now work on the magnetisation
sector's own amplitudes rather than all 2^n, with the same start and
the same order of sums.

The CLI and nqs_ground take --point-group a1|a2|b1|b2 and report the
exact energy in the projection's sector.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

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2026-10-07 15:03:39 -04:00