Silica or Silica on Silicon is a established optical integration platform [1], while the integrated Laser-written circuits' technology [2] offers additionally high customizability, and flexibility for rapid prototyping. Such integrated circuits could provide certain advantages for the development of robust and customizable quantum computers, although a critical issue to their required scalability is the integration capability of multiple single photon sources. While the main class of single photon sources is based on quantum dots embedded in semiconductor nanowires (NWQD) [3] allowing their deterministic integration, such hybrid circuits have been demonstrated only in high refractive index platforms like silicon or silicon nitride, due the modal characteristics compatibility to NWQD. It was shown recently [1] the restricting limitations of coupling in silica waveguides due to the low refractive index contrast leading to coupling performance <5%. A new light coupling scheme [4] proposed here overcomes this limitation, providing means for light coupling >60%. The scheme is based on the incorporation of an optical microsphere between the nanowire and the waveguide, which can be properly optimized and arranged in terms of: size (d), refractive index (n), and the distance of the microsphere between the nanowire (L) and waveguide (D). Given a suitable optical arrangement, the illuminated by the NWQD microsphere produces a photonic nanojet which excites efficiently the guided eigenmodes of the input channel waveguide facilitating the light coupling by the nanowire. The feasibility of the proposed method (Fig. 1) is demonstrated by considering readily available Alumina or Barium Titanate microspheres with diameter range 4μm - 12μm, leading to coupling efficiencies higher than 60%. The method is adequately tolerant [5] in displacements, misalignments, and imperfections and is feasible, as we show here, by current state of the art techniques like Focussed Ion Beam (FIB) for enabling NWQD-microsphere-waveguide alignment. The proposed method could enable the on-chip integration of multiple single photon emitters' in silica, and is expected to have a high impact in scalable photonic integrated circuits for quantum computing or sensing applications.

Entangled photon pairs at telecom wavelengths are essential for quantum communication, distributed computing, and quantum-enhanced sensing. The telecom O-band offers low chromatic dispersion and fiber loss, which is ideal for long-distance networks. Site-controlled nanowire quantum dots have emerged as a promising platform for generating single and entangled photons, offering high extraction efficiency and scalability. However, their operation has largely been restricted to the visible and first near-infrared (NIR-I) windows. Here, we demonstrate a bright source of entangled photon pairs in the telecom O-band based on site-controlled nanowire quantum dots. We measure a fine-structure splitting of 4.6 μeV, confirming suitability for high-fidelity polarization entanglement. Quantum-state tomography of the biexciton-exciton cascade reveals a maximum fidelity of 85.8 ± 1.1% to the Φ⁺ Bell state and a maximum concurrence of 75.1 ± 2.1%. This work establishes nanowire quantum dots as viable entangled photon sources at telecom, advancing scalable quantum technologies for fiber-based networks.

Superconducting nanowire single-photon detectors (SNSPDs) have emerged as essential devices that push the boundaries of photon detection with unprecedented sensitivity, ultrahigh timing precision, and broad spectral response. Recent advancements in materials engineering, superconducting electronics integration, and cryogenic system design are enabling the evolution of SNSPDs from single-pixel detectors toward scalable arrays and large-format single-photon time tagging cameras. This perspective article surveys the rapidly evolving technological landscape underpinning this transition, focusing on innovative superconducting materials, advanced multiplexed read-out schemes, and emerging cryo-compatible electronics. We highlight how these developments are set to profoundly impact diverse applications, including quantum communication networks, deep-tissue biomedical imaging, single-molecule spectroscopy, remote sensing with unprecedented resolution, and the detection of elusive dark matter signals. By critically discussing both current challenges and promising solutions, we aim to articulate a clear, coherent vision for the next generation of SNSPD-based quantum imaging systems.

Amorphous silicon carbide (a-SiC) has emerged as a compelling candidate for applications in integrated photonics, known for its high refractive index, high optical quality, high thermo-optic coefficient, and strong third-order nonlinearities. Furthermore, a-SiC can be easily deposited via CMOS-compatible chemical vapor deposition (CVD) techniques, allowing for precise thickness control and adjustable material properties on arbitrary substrates. Silicon nitride (SiN) is an industrially well-established and well-matured platform, which exhibits ultra-low propagation loss, but it is suboptimal for high-density reconfigurable photonics due to the large minimum bending radius and constrained tunability. In this work, we monolithically combine the a-SiC with SiN photonics, leveraging the merits of both platforms, and achieve the a-SiC/SiN heterogeneous integration with an on-chip interconnection loss of ( 0.28^+0.44<inf>−0.28</inf>) dB and integration density increment exceeding 4444-fold. By implementing active devices on the a-SiC, we achieve 27 times higher thermo-optic tuning efficiency, with respect to the SiN photonic platform. In addition, the a-SiC/SiN platform gives the flexibility to choose the optimal fiber-to-chip coupling strategy depending on the interfacing platform, with efficient side-coupling on SiN and grating-coupling on the a-SiC platform. The proposed a-SiC/SiN photonic platform can foster versatile applications in programmable and quantum photonics, nonlinear optics, and beyond.

On-demand single-photon sources operating at telecom wavelengths are crucial for quantum communication and photonic quantum technologies. In this work, we demonstrate high-purity, indistinguishable single-photon generation in the telecom O-band from an InAsP/ InP nanowire quantum dot. We measured a single-photon purity of g²ð0Þ ¼ 0:006 6 0:003 under above-band excitation. Furthermore, we characterize two-photon interference via Hong–Ou–Mandel measurements and achieve a photon indistinguishability of 81:1% 6 3:7% with a temporal postselection of a 300 ps time window and 5:6% 6 1:5% without temporal postselection. We estimate a first-lens source efficiency of ～28%. These results highlight the potential of nanowire quantum dots as a promising source of telecom single photons for photonic quantum applications, offering deterministic positioning, efficient photon extraction, and scalable production.

We demonstrate a frequency modulated continuous-wave (FMCW) light detection and ranging (LIDAR) system utilizing a superconducting nanowire single-photon detector (SNSPD) to measure vibrational spectra using reflected signals at the single-photon level. By determining the time-variant Doppler shift of the reflected probe signal, this system successfully reconstructs various audio signals, including pure sinusoidal, multi-tonal, and musical signals, up to 200 Hz, limited by the laser frequency modulation rate and the Nyquist sampling theorem. Additionally, we employ scanning galvo mirrors to perform 3D measurements and map audio signals from different regions in the scanned field of view. The integration of an SNSPD provides significant advantages such as near-unity detection efficiency, low dark count rates, and picosecond timing jitter, enabling measurements of vibrational spectra with as few as 100 detected reflected photons per laser sweep.

Coherent control of single-photon sources is crucial for the advancement of many photonic quantum technologies. In this work, we demonstrate on-demand single-photon generation and coherent manipulation of excitons in InAsP/InP nanowire quantum dots (NW QDs) (Fig. 1 (a)) under resonant excitation. Nanowire quantum dots are promising candidates for hybrid photonic integration due to their deterministic growth[1], high extraction efficiency[2], and precise spatial positioning capabilities[3].

The mobility edge (ME) is a crucial concept in understanding localization physics, marking the critical transition between extended and localized states in the energy spectrum. Anderson localization scaling theory predicts the absence of ME in lower dimensional systems. Hence, the search for exact MEs, particularly for single particles in lower dimensions, has recently garnered significant interest in both theoretical and experimental studies, resulting in notable progress. However, several open questions remain, including the possibility of a single system exhibiting multiple MEs and the continual existence of extended states, even within the strong disorder domain. Here, we provide experimental evidence to address these questions by utilizing a quasiperiodic mosaic lattice with meticulously designed nanophotonic circuits. Our observations demonstrate the coexistence of both extended and localized states in lattices with broken duality symmetry and varying modulation periods. By single-site injection and scanning the disorder level, we could approximately probe the ME of the modulated lattice. These results corroborate recent theoretical predictions, introduce a new avenue for investigating ME physics, and offer inspiration for further exploration of ME physics in the quantum regime using hybrid integrated photonic devices.

Surface acoustic waves are a powerful tool for controlling quantum systems, including quantum dots (QDs), where the oscillating strain field can modulate the emission wavelengths. We integrate InAsP/InP nanowire QDs onto a thin-film lithium niobate platform and embed them within Si₃N₄-loaded waveguides. We achieve a 0.70 nm peak-to-peak wavelength modulation at 13 dBm using a single focused interdigital transducer (FIDT) operating at 400 MHz, and we double this amplitude to 1.4 nm by using two FIDTs as an acoustic cavity. Additionally, we independently modulate two QDs with an initial wavelength difference of 0.5 nm, both integrated on the same chip. We show that their modulated emissions overlap, demonstrating the potential to bring them to a common emission wavelength after spectral filtering. This local strain-tuning represents a significant step toward generating indistinguishable single photons from remote emitters heterogeneously integrated on a single chip, advancing on-chip quantum information processing with multiple QDs.

Silica-on-silicon is a major optical integration platform, while the emergent class of the integrated laser-written circuits’ platform offers additionally high customizability and flexibility for rapid prototyping. However, the inherent waveguides’ low core/cladding refractive index contrast characteristic, compared to other photonic platforms in silicon or silicon nitride, sets serious limitations for on-chip efficient coupling with single photon emitters, like semiconductor nanowires with quantum dots, limiting the applications in quantum computing. A new light coupling scheme proposed here overcomes this limitation, providing means for light coupling >50%. The scheme is based on the incorporation of an optical microsphere between the nanowire and the waveguide, which is properly optimized and arranged in terms of size, refractive index, and the distance of the microsphere between the nanowire and waveguide. Upon suitable design of the optical arrangement, the photonic nanojet emitted by the illuminated microsphere excites efficiently the guided eigenmodes of the input channel waveguide, thus launching light with high-coupling efficiency. The method is tolerant in displacements, misalignments, and imperfections and is fabricationally feasible by the current state of art techniques. The proposed method enables the on-chip multiple single photon emitters’ integration, thus allowing for the development of highly customizable and scalable quantum photonic-integrated circuits for quantum computing and communications.