Fig. 6: Experimental setup.
From: Self-normal and biorthogonal dynamical quantum phase transitions in non-Hermitian quantum walks
Photons are generated via spontaneous parametric down conversion in a Type-I non-linear β-barium-borate (BBO) crystal. The initial state is prepared by passing horizontally polarized photons, filtered by a polarizing beam splitter (PBS), through a half-wave plate (HWP) and a quarter-wave plate (QWP) with certain setting angles. The conditional shift operation \(\hat{T}\) is implemented using a beam displacer (BD), while the coin operator \(\hat{R}\) is realized by two HWPs. The non-unitary loss operator \(\hat{M}\) is implemented by introducing photon loss through a sandwich-type configuration consisting of two HWPs and a partially polarizing beam splitter (PPBS). Two types of measurements, projective and interference-based measurements, are performed to construct the evolved state before the photons are detected by avalanche photodiodes (APDs)
