Multichip multidimensional quantum networks with entanglement retrievability.

Quantum networks provide the framework for quantum communication, clock synchronization, distributed quantum computing, and sensing. Implementing large-scale and practical quantum networks relies on the development of scalable architecture and integrated hardware that can coherently interconnect many remote quantum nodes by sharing multidimensional entanglement through complex-medium quantum channels. We demonstrate a multichip multidimensional quantum entanglement network based on mass-manufacturable integrated-nanophotonic quantum node chips fabricated on a silicon wafer by means of complementary metal-oxide-semiconductor processes. Using hybrid multiplexing, we show that multiple multidimensional entangled states can be distributed across multiple chips connected by few-mode fibers. We developed a technique that can efficiently retrieve multidimensional entanglement in complex-medium quantum channels, which is important for practical uses. Our work demonstrates the enabling capabilities of realizing large-scale practical chip-based quantum entanglement networks.

High-performance lithium-niobate-on-insulator optical filter based on multimode waveguide gratings.

A high-performance optical filter is proposed and realized with multimode waveguide grating (MWG) and two-mode multiplexers on the x-cut lithium-niobate-on-insulator (LNOI) platform for the first time, to the best of our knowledge. The present optical filter is designed appropriately to avoid material anisotropy as well as mode hybridness, and has a low excess loss of 0.05 dB and a high sidelobe suppression ratio (SLSR) of 32 dB in theory with Gaussian apodization. The fabricated filters show a box-like response with 1-dB bandwidth of 6-23 nm, excess loss of ∼0.15 dB, sidelobe suppression ratio of >26 dB. The device performance is further improved with a sidelobe suppression ratio as high as 48 dB and a low excess loss of ∼0.25 dB by cascading two identical MWGs.

Silicon polarization beam splitter at the 2 µm wavelength band by using a bent directional coupler assisted with a nano-slot waveguide.

A silicon-based polarizing beam splitter (PBS) working at the 2 µm wavelength band is proposed and demonstrated experimentally by using a bent directional coupler assisted with a nano-slot waveguide. The nano-slot width is chosen as 180 nm so that the present PBS can be fabricated with MPW foundries. In theory, the designed PBS has extinction ratios (ERs) of >15 dB and >30 dB for TM- and TE- polarizations in the wavelength range of 1825-2020 nm, respectively. For the fabricated PBS, the excess losses (ELs) are low (∼0.5 dB) while the measured results show the ERs are >15 dB and >20 dB for TM- and TE-polarizations in the wavelength band of 1860-1980 nm.

Measurement of dilation pulses using a pulse-dilation framing camera.

A pulse-dilation framing camera (PFC) and its working principle are introduced. The influence of the dilation pulse on the exposure time is discussed. The measurement of the dilation pulse using the PFC are theoretically analyzed and experimentally verified. The waveform and the entire time history of the potential of the dilation pulse are simulated by the known dilation factors of the PFC in theory, with the potential deviation at the end of the dilation time of pulse being approximately 3.2%. In the experiment, the exposure time and dilation factors of the PFC are measured by using an array of fiber bundles and in taking many measurements, the waveform and the entire time history of the potential of dilation pulse are achieved by the dilation factors, with the potential deviation at the end of the dilation time of pulse being approximately 6.3%. The research results show that the experimental measurement is consistent with theoretical analysis, although there are some deviations, and it is feasible to measure the waveform and the entire time history of the potential of dilation pulse using the PFC. Moreover, the research may provide an idea for new applications of the framing camera.

Silicon-based polarization-insensitive optical filter with dual-gratings.

A silicon-based polarization-insensitive optical filter is proposed and demonstrated. For the present on-chip polarization-insensitive optical filter, there is a dual-polarization mode (de)multiplexer, a TE-type multimode waveguide grating (MWG) with triangular corrugations and a TM-type MWG with rectangular corrugations. Here the triangular corrugations are introduced to reduce the undesired reflection and suppress the Fabry-Parot resonance. Furthermore, lateral-shift apodization is introduced for both two types of MWGs to suppress the sidelobes. For the fabricated device, the measured 3 dB-bandwidth is as large as ∼11 nm and the excess loss is ∼1.5 dB for both polarizations, while the sidelobe suppression ratios are 23 dB and 17 dB for TE and TM polarizations, respectively.

Low-loss and low-crosstalk silicon triplexer based on cascaded multimode waveguide gratings.

A low-loss and low-crosstalk silicon triplexer is proposed and realized for wavelength-division-multiplexed optical systems with the wavelength channels of 1310, 1490, and 1550 nm. The proposed on-chip triplexer is composed of three cascaded multimode-waveguide-grating (MWG)-based filters, which consist of an MWG and a two-mode (de)multiplexer. For all three wavelength channels, flat-top spectral responses are achieved experimentally, and their 3 bandwidths are 89, 19, and 7 nm, respectively. The excess losses are less than 1 dB. The crosstalks are -36--27 and -32--28 dB for channels 1490 and 1550 nm, respectively.

Submicron-resonator-based add-drop optical filter with an ultra-large free spectral range.

A low-loss add-drop microring resonator (MRR) with an ultra-large free spectral range (FSR) is demonstrated by introducing an ultra-sharp multimode waveguide bend and bent asymmetrical directional couplers (ADCs). The multimode microring waveguide is introduced to achieve a low bent loss, even with a small radius (e.g., R = 0.8 µm). The bent ADCs are used to suppress the resonance of higher-order modes. For the fabricated device, the transmission at the drop port has a narrow 3 dB-bandwidth of 0.8 nm and a low excess loss of 1.8 dB. A record large FSR of 93 nm is achieved to the best of our knowledge.

Vis4Heritage: visual analytics approach on Grotto wall painting degradations.

For preserving the Grotto wall paintings and protecting these historic cultural icons from the damage and deterioration in nature environment, a visual analytics framework and a set of tools are proposed for the discovery of degradation patterns. In comparison with the traditional analysis methods that used restricted scales, our method provides users with multi-scale analytic support to study the problems on site, cave, wall and particular degradation area scales, through the application of multidimensional visualization techniques. Several case studies have been carried out using real-world wall painting data collected from a renowned World Heritage site, to verify the usability and effectiveness of the proposed method. User studies and expert reviews were also conducted through by domain experts ranging from scientists such as microenvironment researchers, archivists, geologists, chemists, to practitioners such as conservators, restorers and curators.