Reconfiguration of Quantum Photonic Integrated Circuits Using Auxiliary Fields

Manipulating photons in quantum photonic integrated circuits (QPICs) is essential for quantum communications and computation, demanding precise control over phase shifts and photon coupling. Despite the challenges arising from the low electro-optic and thermo-optic coefficients of glass waveguides, femtosecond laser direct writing (FsLDW) technology offers a rapid method for QPIC preparation. In this work, the use of auxiliary fields is proposed to reconfigure QPICs with FsLDW. Through adiabatic elimination, modulations of inter-waveguide coupling are achieved, allowing for arbitrary, controllable beam-splitting ratios and error correction in discrete quantum walking networks. The experiments also demonstrate full-period phase shift modulation over 2π in a Mach-Zehnder interferometer by employing an adjustable auxiliary field. Particularly, high-quality two-photon quantum interference and high-fidelity quantum logic function conversion between a controlled-NOT gate and a controlled-PHASE gate are exhibited. This novel approach provides a promising mechanism for modulating the phase and coupling between photons in 3D and large-scale QPICs.