Aconcagua University

Training quantum neural networks for Tl-limited hardware: what the qg symmetry filter does and does not do

A quantum neural network (QNN) built from gates that conserve the Hamming weight keeps its data in one weight sector, so the shots that left the sector can be discarded at readout. This is the qg filter of the qang library [1, 2]. We show that, with equal amplitude damping (T1) o...

Polarized light and geometric phase in qg units: Stokes parameters, Mueller matrices and Stokes' theorem

⟨ ⟩ The qang project describes qubits by measurement—level quantities, the qg values qgP = P [1]. This short note states two classical results in those units, implemented and checked in the qang library (pip install qang, version 0.6.0). First, a polarization state of light is a...

The local Bloch radius as an entanglement readout: what the qg symmetry filter restores and what it does not

Each qubit’s local qg values are a point in the Bloch ball. Its squared distance from the centre, , is the radius of the sphere on which the qubit lives (area ). For a pure register the deficit is the known one-tangle of the qubit with the rest; with noise it mixes entanglement a...