The study demonstrates quantum-memory-assisted interferometry across a two-station network, achieving an end-to-end protocol that entangles nuclear qubits, collects signal photons through SMSPG, and performs non-local heralding to extract differential phase from nuclear XX parity measurements.

Background: Optical interferometry faces baseline-related attenuation from photon loss and fibre connections, and incorporating quantum memories and entanglement offers a path to extend baselines and boost sensitivity.

The report adopts a technical, objective tone, detailing experimental procedures, data, figures, and methods while outlining practical advances and ongoing challenges.

Each station uses silicon-vacancy centers in diamond nanophotonic cavities with a two-qubit register (electron spin as communication qubit and 29Si nuclear spin as memory) and reads signal fields reflected from fibre-coupled cavities through an optical network.

Differential phase φ between stations is inferred via non-local measurements; entangled memories enable optimal non-local sensing by heralding photon arrivals without revealing station identities, improving signal-to-noise.

Event-ready entanglement is demonstrated with Bell-state preparation (Ψ−) and fidelities around 0.83, yielding practical entanglement rates suitable for sensing experiments (about 13 Hz at F≥0.5, 1.9 Hz at F≥0.79).

Key innovations include an improved parallel entanglement scheme and non-local, non-destructive photon heralding that filters vacuum fluctuations to boost interferometer visibility while preserving differential phase information.

Baseline extension is achieved by inserting fibre between stations up to about 1.55 km, attaining nuclear Bell-pair fidelity around 0.63 and showing φ-dependent nuclear parity oscillations that indicate preserved local-phase processing over longer links.

The work presents a concise introductory summary of quantum-memory-assisted, entanglement-enabled non-local interferometry across two stations using SiV centers in diamond to enable long-baseline, memory-enabled measurements.

Broader implications point to a practical route for long-baseline quantum interferometry with memories, with potential impact on astronomical imaging, high-resolution sensing, and networked metrology through scalable, memory-assisted non-local measurements.

The protocol employs both local and non-local photon heralding via parity measurements on electron spins, and uses photon-mode erasure by interfering signal light with a local oscillator to erase which-path information while preserving nuclear-spin phase data.

Limitations include finite Bell-state fidelity, mis-heralding, photon loss, detector dark counts, and microwave errors; addressing these would extend optimal performance to weaker signal regimes and advance practical quantum-enhanced sensing.