Gaussian boson sampling with 1,024 squeezed states in 8,176 modes

To achieve the precise phase control required for efficient filtering, a mirror on the longer arm is mounted to a piezoelectric transducer (PZT) for tuning and active stabilization. Two counter-propagating probe beams are used for phase setting and locking, which are detected at the secondary output port of each MZI. Phase setting and locking utilize two counter-propagating probe beams, detected at the secondary output port of each MZI. A probe beam at 1064 nm, coupled into the single-mode squeezed state (SMSS) path at the third MZI, is partially extracted for photodiode-based feedback monitoring, with the remainder propagating to subsequent MZIs for recursive probing. For phase tuning, a back-propagating probe beam, matched in path, frequency, and polarization to the squeezed light (thus marked with the same color), is injected. The phase is adjusted by modulating the active lock setpoint to minimize the probe intensity detected by the corresponding photodiode. Dichroic mirrors separate the probe laser from the squeezed light before detection to prevent crosstalk. The phase setting and stabilization precision are estimated to be within ± λ/1200 at 1550 nm.