Curator's Take
This article shows that a single‑photon detector can be made intrinsically polarization‑selective by embedding gold nanowire metamaterials directly on a NbTiN superconducting nanowire, eliminating the need for external waveplates or metasurfaces. By arranging four such pixels into an array the authors achieve full Stokes tomography with >98 % fidelity while retaining the high count rates and low dark‑count performance of conventional SNSPDs, a step forward from recent on‑chip polarimetry demonstrations that still relied on separate optics. The monolithic design promises truly scalable photonic quantum processors, imaging systems and spectroscopy platforms, although large‑scale fabrication and uniformity will need to be proven before commercial deployment.
— Mark Eatherly
Summary
Light polarization is a primary degree of freedom for encoding quantum information. The scaling up of photonic quantum networks and computer architecture depends crucially on its precise characterization. This is typically achieved by placing external waveplates, polarizers, moving mounts, and recently metasurfaces, on top of the detectors. All these solutions complicate integration and scaling. Here we break convention with traditional architecture and present a monolithic, self-aligned metal-superconductor nanowire single photon detector (M-SNSPD) possessing intrinsic full polarization selectivity. Gold nanowires, co-fabricated atop NbTiN superconducting nanowires within the same lithographic footprint, act as polarization-selective plasmonic metamaterials inducing resonant absorption in the NbTiN. U-shaped wires provide linear polarization selectivity, while S-shaped meanders distinguish circular polarization, while retaining the high-count rates and low dark count rates of conventional SNSPDs. By arranging them into a four-pixel array we realize simultaneous projection onto four polarizations and demonstrate continuous polarization state tomography with an ensemble average fidelity exceeding 98%. Our approach opens new avenues towards scalable detector arrays with integrated plasmonic functionalities, for single photon polarimetry, imaging and spectroscopy.