Frequency-entangled photon pairs play a vital role in various quantum technologies, including quantum computing, quantum communication, and quantum sensing. Broadening the bandwidth of frequency-entangled photon pairs enhances the performance of these technologies. Here, we report the experimental demonstration of the generation of ultra-broadband frequency-correlated photon pairs using a high-index contrast doped glass microring resonator fabricated on a silicon chip. The generated photon pairs exhibit frequency correlation between 106 mode pairs and 212 frequency combs in total, ranging from 1394.0 to 1745.9 nm with the bandwidth of 351.9 nm and covering the telecom E-, S-, C-, L-, and U-bands. The bandwidth of the photon pairs is more than three times larger than the record so far achieved with an on-chip microring resonator. This result will be useful for secure quantum communications and high-resolution quantum optical coherence tomography.
Frequency-entangled photon pairs play a vital role in various quantum technologies, including quantum computing, quantum communication, and quantum sensing. Broadening the bandwidth of frequency-entangled photon pairs enhances the performance of these technologies. Here, we report the experimental demonstration of the generation of ultra-broadband frequency-correlated photon pairs using a high-index contrast doped glass microring resonator fabricated on a silicon chip. The generated photon pairs exhibit frequency correlation between 106 mode pairs and 212 frequency combs in total, ranging from 1394.0 to 1745.9 nm with the bandwidth of 351.9 nm and covering the telecom E-, S-, C-, L-, and U-bands. The bandwidth of the photon pairs is more than three times larger than the record so far achieved with an on-chip microring resonator. This result will be useful for secure quantum communications and high-resolution quantum optical coherence tomography.
The on-chip generation of optical quantum states will enable accessible advances for quantum technologies. We demonstrate that integrated quantum frequency combs (based on high-Q microring resonators made from a CMOS-compatible, high refractive-index doped-glass platform) can enable the generation of pure heralded single photons, cross-polarized photon pairs, as well as bi- and multi-photon entangled qubit states over a broad frequency comb covering the S, C, L telecommunications band, with photon frequencies corresponding to standard telecommunication channels spaced by 200 GHz. Exploiting a self-locked, intra-cavity excitation configuration, a highly-stable source of multiplexed heralded single photons is demonstrated, operating continuously for several weeks with less than 5% fluctuations. The photon bandwidth of 110 MHz is compatible with quantum memories, and high photon purity was confirmed through single-photon auto-correlation measurements. In turn, by simultaneously exciting two orthogonal polarization mode resonances, we demonstrate the first realization of type-II spontaneous FWM (in analogy to type-II spontaneous parametric down-conversion), allowing the direct generation of orthogonally-polarized photon pairs on a chip. By using a double-pulse excitation, we demonstrate the generation of time-bin entangled photon pairs. We measure qubit entanglement with visibilities above 90%, enabling the implementation of quantum information processing protocols. Finally, the excitation field and the generated photons are intrinsically bandwidth-matched due to the resonant characteristics of the ring cavity, enabling the multiplication of Bell states and the generation of a four-photon time-bin entangled state. We confirm the generation of this four-photon entangled state through four-photon quantum interference.
Entangled photon-pair sources are essential components for emerging quantum information-processing technologies. Among various platforms, on-chip microresonators offer strong potential due to their resonant enhancement and suitability for wafer-scale integration. In this study, we demonstrate ultrabright entangled photon-pair generation from high- Q silicon microring resonators. By optimizing the device geometry and coupling configuration to suppress sidewall scattering and selectively excite the fundamental mode, we achieve single-mode resonance with an intrinsic Q -factor of 1.26 × 10 6 using only standard fabrication processes available in CMOS foundries. The resulting high- Q resonator yields a record-high brightness coefficient of 3.9 × 10 9 Hz/GHz/mW 2 . At an on-chip pump power of 240 μW, we obtain a maximum brightness of 22.0 MHz/GHz and a maximum photon-pair generation rate of 9.19 MHz. At a low-pump power of 10 μW, Franson-type two-photon interference exhibits a visibility of 98.0 ± 0.2%, confirming high-quality time–energy entanglement. These results show that narrow bandwidth and high generation rate can be achieved simultaneously in CMOS-compatible silicon photonic sources, thereby advancing their use in quantum repeaters and scalable quantum networks.
The generation of optical quantum states on an integrated platform will enable low cost and accessible advances for quantum technologies such as secure communications and quantum computation. We demonstrate that integrated quantum frequency combs (based on high-Q microring resonators made from a CMOS-compatible, high refractive-index glass platform) can enable, among others, the generation of heralded single photons, cross-polarized photon pairs, as well as bi- and multi-photon entangled qubit states over a broad frequency comb covering the S, C, L telecommunications band, constituting an important cornerstone for future practical implementations of photonic quantum information processing.
Frequency entangled photon sources are in high demand in a variety of optical quantum technologies, including quantum key distribution, cluster state quantum computation and quantum metrology. In the recent decade, chip-scale entangled photon sources have been developed using silicon platforms, offering robustness, large scalability and CMOS technology compatibility. Here, we report the generation of frequency correlated photon pairs using a 150-GHz silicon nitride ring cavity. First, the device is characterized for studying the phase matching condition during spontaneous four-wave mixing. Next, we evaluate the joint spectrum intensity of the generated photons and confirm the photon pair generation in a total of 42 correlated frequency mode pairs, corresponding to a bandwidth of 51.25 nm. Finally, the experimental results are analyzed and the joint spectral intensity is quantified in terms of the phase matching condition.
Frequency entangled photons have potential for various quantum applications. Recently, on-chip photon-pair sources made by CMOS compatible processes have attracted attention. In this paper, we report broadband generation of photon-pairs via a spontaneous four-wave mixing process using a CMOS compatible ring resonator. We performed frequency-correlation between the signal and idler photons by frequency-resolved coincidence detection and confirmed that the signal and idler photons are correlated over 59 frequency modes, a bandwidth of 23.6 nm, which are the largest numbers achieved to date. Furthermore, we reproduced the experimentally observed joint spectral intensity from the obtained transmission spectrum of the resonator involving the information of the dispersion of the device.
Photon pair sources with the capability to tune the wavelength and correlation properties of the generated photons can be useful for quantum applications such as communication, sensing, and computing. Silicon devices based on the SOI (silicon-on-insulator) platform benefits from both tight modal confinement, due to high index contrast between core and cladding, and CMOS compatible manufacturing process, making it a suitable platform for such sources. In the present work, we discuss the possibility of using planar resonant silicon devices with bend radii of a few tens of microns as photon pair sources. We discuss that a silicon nanophotonic chip consisting of either a single microring or coupled microrings can be used to generate photon pairs around 1.55 um. We discuss that the photons are generated in multiple pairs of wavelengths and can be tuned over several nanometers, demonstrating the capability to generate wavelength division multiplexed photon pairs at freely chosen telecommunication-band wavelengths. Further on, we discuss the ease of control over the bi-photon spectrum of the generated photon pairs and its implication in controlling their correlation properties. Uncorrelated photon pairs can be used to herald a single photon, and correlated photon pairs can be used in various quantum applications such as communication and sensing. In the end, we discuss the design parameters of a single microring resonator based sources.