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We present a quantum-analogous experimental demonstration of variational quantum process tomography using an optical processor. This approach leverages classical one-hot encoding and unitary decomposition to perform the variational quantum algorithm on a photonic platform. We create the first benchmark for variational quantum process tomography evaluating the performance of the quantum-analogous experiment on the optical processor against several publicly accessible quantum computing platforms, including IBM’s 127-qubit Sherbrooke processor, QuTech’s five-qubit Tuna-5 processor, and Quandela’s 12-mode Ascella quantum optical processor. We evaluate each method using process fidelity, cost function convergence, and processing time per iteration for variational quantum circuit depths of d = 3 and d = 6. Our results indicate that the optical processors outperform their superconducting counterparts in terms of fidelity and convergence behavior reaching fidelities of 0.8 after nine iterations, particularly at higher depths, where the noise of decoherence and dephasing affect the superconducting processors significantly. We further investigate the influence of any additional quantum optical effects in our platform relative to the classical one-hot encoding. From the process fidelity results it shows that the (classical) thermal noise in the phase-shifters dominates over other optical imperfections, such as mode mismatch and dark counts from single-photon sources. The benchmarking framework and experimental results demonstrate that photonic processors are strong contenders for near-term quantum algorithm deployment, particularly in hybrid variational contexts. This analysis is valuable not only for state and process tomography but also for a wide range of applications involving variational quantum circuit based algorithms.

A graphene-based photonics chip Graphene, the single-atom-thick form of carbon, holds promise for many applications, notably in electronics where it can complement or be integrated with silicon-based devices. Intense efforts have been devoted to develop a key enabling device, a broadband, fast optical modulator with a small device footprint. Now Liu et al . demonstrate an exciting new possibility for graphene in the area of on-chip optical communication: a graphene-based optical modulator integrated with a silicon chip. This new device relies on the electrical tuning of the Fermi level of the graphene sheet, and achieves modulation of guided light at frequencies over 1 gigahertz, together with a broad operating spectrum. At just 25 square micrometres in area, it is one of the smallest of its type. Integrated optical modulators with high modulation speed, small footprint and large optical bandwidth are poised to be the enabling devices for on-chip optical interconnects 1 , 2 . Semiconductor modulators have therefore been heavily researched over the past few years. However, the device footprint of silicon-based modulators is of the order of millimetres, owing to its weak electro-optical properties 3 . Germanium and compound semiconductors, on the other hand, face the major challenge of integration with existing silicon electronics and photonics platforms 4 , 5 , 6 . Integrating silicon modulators with high-quality-factor optical resonators increases the modulation strength, but these devices suffer from intrinsic narrow bandwidth and require sophisticated optical design; they also have stringent fabrication requirements and limited temperature tolerances 7 . Finding a complementary metal-oxide-semiconductor (CMOS)-compatible material with adequate modulation speed and strength has therefore become a task of not only scientific interest, but also industrial importance. Here we experimentally demonstrate a broadband, high-speed, waveguide-integrated electroabsorption modulator based on monolayer graphene. By electrically tuning the Fermi level of the graphene sheet, we demonstrate modulation of the guided light at frequencies over 1 GHz, together with a broad operation spectrum that ranges from 1.35 to 1.6 µm under ambient conditions. The high modulation efficiency of graphene results in an active device area of merely 25 µm 2 , which is among the smallest to date. This graphene-based optical modulation mechanism, with combined advantages of compact footprint, low operation voltage and ultrafast modulation speed across a broad range of wavelengths, can enable novel architectures for on-chip optical communications.

Artificial fish swarm algorithm (AFS) is used in the field of function optimization problems widely. The traditional AFS algorithm has some problems such as long time to find the optimal solution and easy to fall into local optimality at the later stage of the search. We investigate design solutions and methods to implement parallel AFS algorithms by taking advantage of the large number of TOC processor bits and the easy scalability of processor bits. Firstly, we find out the parallel part of the algorithm by analyzing the traditional AFS algorithm and carry out the parallel design. Then we performed a detailed design of the algorithm implementation flow and analyzed the clock cycle. Finally, the correctness of our proposed parallel algorithm is verified on SD11. Compared with the serial AFS and parallel AFS algorithms based on electronic computers, the TOC-based AFS algorithm (TOC-PAFS) proposed in this paper effectively reduces the search time and improves the search performance of complex multi-peaked function optimization problems.

In order to utilize the advantages of optical computing and promote the application and popularization of Ternary Optical Computer (TOC), this paper proposes a dual-center programming model consisting of electronic processor and optical processor, presents the theory and technologies of the dual-center model in detail, and for the first time explains the SAN ZHI GUANG (SZG) file chain technology, gives the implementation method of the dual-center model. The model tries to effectively manage the resources of optical processor and solve the problem of the distance and network connection mode of using the TOC. Experimental results show that the dual-center model is correct and the implementation method is feasible. It can improve the usability of the TOC and further simplify the TOC programming process, and makes common users apply the TOC and electronic computer to work cooperatively for the same task.

Waveguide-integrated photonic modulators are crucial devices when encoding optical signals for electronic–photonic integration on silicon 1 , 2 . Silicon photonic modulators based on the free carrier plasma dispersion effect 3 have undergone significant development in recent years 4 , 5 , 6 , 7 , 8 , 9 , 10 , reaching speeds of 40 Gbit s –1 (ref.  7 ). Some issues yet to be resolved include the large size and the relatively high energy consumption of silicon Mach–Zehnder interferometer modulators, and the susceptibility to fabrication errors as well as a limited operation wavelength range of ∼1 nm for silicon microring modulators. We demonstrate the first waveguide-integrated GeSi electro-absorption modulator on silicon with a small active device area of 30 µm 2 , a 10-dB extinction ratio at 1,540 nm, an operating spectrum range of 1,539–1,553 nm, ultralow energy consumption of 50 fJ per bit, and a 3-dB bandwidth of 1.2 GHz. This device offers unique advantages for use in high-performance electronic–photonic integration with complementary metal oxide semiconductor circuits. A waveguide–integrated GeSi electro-absorption modulator on silicon with an ultra-low energy consumption of 50 fJ –1 bit is presented. Operating in the spectral range of 1539—1553 nm, the CMOS–compatible device has an active area of 30 µm 2 and is anticipated to be useful for future communication systems based on large–scale electronic–photonic integration on silicon.

Significant progress has been made recently in demonstrating that silicon photonics is a promising technology for low-cost optical detectors, modulators and light sources 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 . It has often been assumed, however, that their performance is inferior to InP-based devices. Although this is true in most cases, one of the exceptions is the area of avalanche photodetectors, where silicon's material properties allow for high gain with less excess noise than InP-based avalanche photodetectors and a theoretical sensitivity improvement of 3 dB or more. Here, we report a monolithically grown germanium/silicon avalanche photodetector with a gain–bandwidth product of 340 GHz, a k eff of 0.09 and a sensitivity of −28 dB m at 10 Gb s −1 . This is the highest reported gain–bandwidth product for any avalanche photodetector operating at 1,300 nm and a sensitivity that is equivalent to mature, commercially available III–V compound avalanche photodetectors. This work paves the way for the future development of low-cost, CMOS-based germanium/silicon avalanche photodetectors operating at data rates of 40 Gb s −1 or higher. A monolithically grown Ge/Si avalanche photodetectors (APD) with a gain–bandwidth product of 340 GHz, the highest value for any APDs operating at 1,300 nm, and a sensitivity equivalent to commercially available III-V compound APDs is reported. The excellent performance paves the way to achieving low-cost, CMOS-based, Ge/Si APDs operating at data rates of 40 Gb s −1 or higher, where the performance of III-V APDs is severely limited.

Every holographic video display is built on a spatial light modulator, which directs light by diffraction to form points in three-dimensional space. The modulators currently used for holographic video displays are challenging to use for several reasons: they have relatively low bandwidth, high cost, low diffraction angle, poor scalability, and the presence of quantization noise, unwanted diffractive orders and zero-order light. Here we present modulators for holographic video displays based on anisotropic leaky-mode couplers, which have the potential to address all of these challenges. These modulators can be fabricated simply, monolithically and at low cost. Additionally, these modulators are capable of new functionalities, such as wavelength division multiplexing for colour display. We demonstrate three enabling properties of particular interest—polarization rotation, enlarged angular diffraction, and frequency domain colour filtering—and suggest that this technology can be used as a platform for low-cost, high-performance holographic video displays. Realizing holographic video displays is proving far from straightforward, but it is shown here that it may be possible to overcome the limitations of present displays by harnessing the desirable optical manipulation properties of anisotropic leaky-mode spatial light modulators. Displays of success Holographic video displays suitable for everyday use are still the stuff of science fiction: current implementations tend to be slow, small and costly and suffer from restricted viewing angles. Here Daniel Smalley et al . harness the desirable optical manipulation properties of anisotropic leaky-mode spatial light modulators to produce devices with the potential to address all of these obstacles. The authors calculate that this technology could reduce the cost of a holographic video monitor to under $500 excluding light sources. Other possible applications include lithography, microscopy, optogenetics and micromanipulation.

The construction of a device that consists of a semiconductor substrate with an array of split-ring gold resonators demonstrates that metamaterials (objects with properties based on their structure instead of the materials they are composed of) can be designed to efficiently control terahertz waves in real time. The development of artificially structured electromagnetic materials, termed metamaterials, has led to the realization of phenomena that cannot be obtained with natural materials 1 . This is especially important for the technologically relevant terahertz (1 THz = 10 12  Hz) frequency regime; many materials inherently do not respond to THz radiation, and the tools that are necessary to construct devices operating within this range—sources, lenses, switches, modulators and detectors—largely do not exist. Considerable efforts are underway to fill this ‘THz gap’ in view of the useful potential applications of THz radiation 2 , 3 , 4 , 5 , 6 , 7 . Moderate progress has been made in THz generation and detection 8 ; THz quantum cascade lasers are a recent example 9 . However, techniques to control and manipulate THz waves are lagging behind. Here we demonstrate an active metamaterial device capable of efficient real-time control and manipulation of THz radiation. The device consists of an array of gold electric resonator elements (the metamaterial) fabricated on a semiconductor substrate. The metamaterial array and substrate together effectively form a Schottky diode, which enables modulation of THz transmission by 50 per cent, an order of magnitude improvement over existing devices 10 .

Silicon has long been the optimal material for electronics, but it is only relatively recently that it has been considered as a material option for photonics 1 . One of the key limitations for using silicon as a photonic material has been the relatively low speed of silicon optical modulators compared to those fabricated from III–V semiconductor compounds 2 , 3 , 4 , 5 , 6 and/or electro-optic materials such as lithium niobate 7 , 8 , 9 . To date, the fastest silicon-waveguide-based optical modulator that has been demonstrated experimentally has a modulation frequency of only ∼20 MHz (refs 10 , 11 ), although it has been predicted theoretically that a ∼1-GHz modulation frequency might be achievable in some device structures 12 , 13 . Here we describe an approach based on a metal–oxide–semiconductor (MOS) capacitor structure embedded in a silicon waveguide that can produce high-speed optical phase modulation: we demonstrate an all-silicon optical modulator with a modulation bandwidth exceeding 1 GHz. As this technology is compatible with conventional complementary MOS (CMOS) processing, monolithic integration of the silicon modulator with advanced electronics on a single silicon substrate becomes possible.

As a label‐free imaging technique, quantitative phase imaging (QPI) provides optical path length information of transparent specimens for various applications in biology, materials science, and engineering. Multispectral QPI measures quantitative phase information across multiple spectral bands, permitting the examination of wavelength‐specific phase and dispersion characteristics of samples. Herein, the design of a diffractive processor is presented that can all‐optically perform multispectral quantitative phase imaging of transparent phase‐only objects within a snapshot. The design utilizes spatially engineered diffractive layers, optimized through deep learning, to encode the phase profile of the input object at a predetermined set of wavelengths into spatial intensity variations at the output plane, allowing multispectral QPI using a monochrome focal plane array. Through numerical simulations, diffractive multispectral processors are demonstrated to simultaneously perform quantitative phase imaging at 9 and 16 target spectral bands in the visible spectrum. The generalization of these diffractive processor designs is validated through numerical tests on unseen objects, including thin Pap smear images. Due to its all‐optical processing capability using passive dielectric diffractive materials, this diffractive multispectral QPI processor offers a compact and power‐efficient solution for high‐throughput quantitative phase microscopy and spectroscopy. Leveraging deep learning‐designed diffractive layers, an all‐optical diffractive processor can rapidly obtain multispectral quantitative phase images (QPI) of transparent objects by transforming their phase profiles at target spectral bands into spatial intensity variations measured by a monochrome image sensor. This compact diffractive QPI framework can work at different parts of the spectrum through integration with various image sensors.