Multi-protocol integrated chip

Abstract

This application discloses a multi-protocol integrated chip, relating to the fields of quantum secure communication and integrated optoelectronics. The chip includes an arrayed waveguide grating and a beam combiner output unit. The arrayed waveguide grating receives polarized quantum signals, time-bin quantum signals, and classical quantum signals transmitted through the same aperture and performs spectral convergence. It outputs two coherent orthogonal components of the polarized quantum signals through two ports, with one port combining and outputting the other component of the polarized quantum signal, the time-bin quantum signal, and the classical quantum signal. The beam combiner output unit restores the polarized quantum signal and outputs the combined signals to an optical fiber. This application is compatible with multiple encoding protocols, can be switched to adapt to different testing and packaging scenarios, and simultaneously improves the versatility and signal-to-noise ratio of the quantum key distribution system.

Description

Technical Field

[0001] This application relates to the fields of quantum secure communication and integrated optoelectronics, and in particular to a multi-protocol integrated chip. Background Technology

[0002] Quantum key distribution (QKD), based on the fundamental principles of quantum mechanics, achieves theoretically unconditionally secure information transmission and is the core technology of quantum secure communication systems. It is currently rapidly evolving from laboratory desktop systems towards large-scale commercialization and chip-based applications. Photonic integrated circuits (PICs), with their advantages of small size, low power consumption, and high stability, have become the core carrier for the engineering implementation of QKD systems. Among them, thin-film lithium niobate (TFLN) materials, due to their high electro-optic bandwidth, low transmission loss, and excellent nonlinear optical properties, have become the preferred platform for high-performance monolithic integrated QKD transmitter chips.

[0003] Currently, commercial QKD systems mainly employ two mainstream coding protocols: polarization coding and time-bin coding. Polarization coding offers a simple structure and concise encoding / decoding logic, but it is susceptible to interference from the birefringence effect of fiber optic links, limiting transmission stability. Time-bin coding, on the other hand, boasts strong resistance to channel interference and excellent robustness over long distances, but its encoding / decoding system structure is complex and integration is challenging. Existing integrated QKD transmitter chips are mostly designed and optimized for a single coding protocol, failing to achieve compatibility and dynamic switching between multiple coding protocols on a single chip architecture. This prevents QKD nodes from adaptively selecting the optimal coding strategy based on the fiber optic channel environment, severely limiting the versatility, network adaptability, and scenario coverage of QKD systems.

[0004] In QKD systems with multi-signal co-fiber transmission, on-chip beam combining and co-aperture transmission of weak quantum signals and strong classical optical signals are required. Existing on-chip beam combining schemes mostly employ Y-branching, multi-mode interferometers (MMIs), or cascaded directional coupler structures. Among these, Y-branching and MMIs inherently suffer from high insertion loss and poor wavelength adaptability, while cascaded directional couplers are lengthy and highly wavelength sensitive. None of these solutions can achieve low-loss beam combining of multiple wavelengths while providing high physical isolation between strong classical optical signals and single-photon-level weak quantum signals. This easily leads to broadband background noise and Raman scattering crosstalk, directly causing an increase in the system's quantum bit error rate (QBER) and a decrease in the key generation rate. Additional off-chip filtering devices are required, negating the advantages of chip integration.

[0005] Furthermore, polarization-encoded QKD chips need to achieve high-fidelity, efficient coupling output of polarization states. Existing solutions mostly employ a structure of polarization beam splitter rotator combined with edge coupler. This structure is extremely sensitive to chip fabrication process tolerances; even micron-level processing deviations can lead to a significant deterioration in polarization extinction ratio, making it impossible to balance high polarization fidelity with mass production yield. At the same time, a single coupling output structure cannot simultaneously meet the convenience of wafer-level automated testing and the low-loss requirements of packaging applications, further restricting the large-scale mass production and engineering application of QKD chips. Summary of the Invention

[0006] In view of this, this application provides a multi-protocol integrated chip that achieves multi-coding protocol compatibility, high-isolation multi-signal bundling, and flexible and configurable coupling output on a single-chip architecture, greatly improving the versatility, signal-to-noise ratio, and engineering feasibility of quantum key distribution systems.

[0007] This application provides a multi-protocol integrated chip, comprising: an arrayed waveguide grating having a first output port and a second output port, the arrayed waveguide grating being used to receive polarized quantum signals, time-cell quantum signals and classical quantum signals transmitted through the same aperture, and to perform spectral convergence on the polarized quantum signals, time-cell quantum signals and classical quantum signals to output one component of the polarized quantum signal through the first output port, and to combine the other component of the polarized quantum signal, the time-cell quantum signal and the classical quantum signal through the second output port, wherein the one component and the other component of the polarized quantum signal are coherent and orthogonal; and a beam combining output unit connected to the arrayed waveguide grating, the beam combining output unit being used to reconstruct the polarized quantum signal based on the one component and the other component of the polarized quantum signal, and to combine the reconstructed polarized quantum signal, time-cell quantum signal and classical quantum signal and output them to an optical fiber.

[0008] Furthermore, the multi-protocol integrated chip also includes a multi-source signal modulation module, comprising a polarization-coded modulation unit, a time-bin coded modulation unit, and a classical quantum signal modulation unit. The polarization-coded modulation unit, the time-bin coded modulation unit, and the classical quantum signal modulation unit are used to prepare polarization quantum signals, time-bin quantum signals, and classical quantum signals, respectively. The multi-source signal modulation module is also used to perform wavelength division multiplexing on the prepared polarization quantum signals, time-bin quantum signals, and classical quantum signals to output the polarization quantum signals, time-bin quantum signals, and classical quantum signals through the same aperture.

[0009] Furthermore, the polarization coding modulation unit includes: a beam splitting unit and two parallel modulation links; the beam splitting unit is used to split the first wavelength laser into two co-source optical signals and input them into the two modulation links respectively; each modulation link includes a decoy state modulation unit group, an intensity modulation unit group and a phase modulation unit group cascaded in sequence, used to sequentially perform decoy state modulation, intensity modulation and phase modulation on the optical signal to obtain two modulated optical signals, which serve as one component and the other component of the polarization quantum signal.

[0010] Furthermore, the time-bin coding modulation unit includes a beam splitting unit, two parallel modulation links, and a beam combining unit connected in sequence. The beam splitting unit splits the second wavelength laser into two optical signals of the same origin and inputs them into the two modulation links respectively. Each modulation link includes a decoy state modulation unit group, a time delay pulse pair generation unit group, an intensity modulation unit group, and a phase modulation unit group cascaded in sequence, used to sequentially perform decoy state modulation, time delay pulse pair generation, intensity modulation, and phase modulation on the optical signal to obtain two coherent pulse optical signals. The beam combining unit is used to combine the two coherent pulse optical signals to obtain the time-bin quantum signal.

[0011] Furthermore, the classical quantum signal modulation unit has a first input terminal and a second input terminal; wherein, the first input terminal is used to receive laser light of a third wavelength; the second input terminal is connected to an external electrical signal input terminal and is used to receive the cooperative control signal of the quantum transceiver system; the classical quantum signal modulation unit is used to perform on / off keying modulation on the laser light of the third wavelength according to the cooperative control signal to generate a classical quantum signal carrying the cooperative control signal.

[0012] Furthermore, the beam combining output unit includes a first output branch and a second output branch; the first output branch includes a two-dimensional grating coupler, and the second output branch includes a polarization rotation beam combiner; the beam combining output unit switches between the first output branch and the second output branch according to the testing requirements and packaging application scenarios of the multi-protocol integrated chip, so as to combine and output the restored polarization quantum signal, time chamber quantum signal and classical quantum signal.

[0013] Furthermore, the two-dimensional grating coupler has a first input arm and a second input arm that are orthogonal to each other; the first input arm receives one component of the polarization quantum signal, and the second input arm receives the other component of the polarization quantum signal, the time chamber quantum signal, and the classical quantum signal; the two-dimensional grating coupler is used to couple the signals received by the first input arm and the second input arm to two orthogonal polarization modes of a single-mode fiber, so that one component and the other component of the polarization quantum signal coherently superimpose in the grating radiation region to recover the polarization quantum signal, and then output the recovered polarization quantum signal, the time chamber quantum signal, and the classical quantum signal as a bundle.

[0014] Furthermore, the polarization rotation beam combiner has a first input port, a second input port, and a beam combining output port; the first input port is used to receive one component of the polarization quantum signal; the second input port is used to receive the other component of the polarization quantum signal, the time chamber quantum signal, and the classical quantum signal; the polarization rotation beam combiner is used to perform polarization rotation processing on one component of the polarization quantum signal, converting one component of the polarization quantum signal from a TE mode (Transverse Electric Mode) to a TM mode (Transverse Magnetic Mode) orthogonal to the other component of the polarization quantum signal, so that one component of the polarization quantum signal and the other component can be used to restore the polarization quantum signal; the beam combining output unit is used to combine the restored polarization quantum signal, the time chamber quantum signal, and the classical quantum signal in the same waveguide and output them.

[0015] Furthermore, the multi-source signal modulation module, the arrayed waveguide grating, and the beam combiner output unit are all integrated on the same thin-film lithium niobate waveguide; one component and the other component of the polarization quantum signal, the time chamber quantum signal, and the classical quantum signal are all transmitted in the form of the TE fundamental mode.

[0016] Furthermore, the multi-source signal modulation module is also electrically connected to a protocol switching control unit; the protocol switching control unit is used to acquire the transmission state of the classical quantum signal and generate control signals according to the transmission state to regulate the working state of the polarization coding modulation unit and the time-bin coding modulation unit.

[0017] The multi-protocol integrated chip provided in this application can achieve the following beneficial effects:

[0018] (1) Based on wavelength division multiplexing architecture, a modulation and transmission architecture with parallel polarization coding and time bin coding is constructed on a single thin-film lithium niobate chip to realize the common aperture preparation and transmission of three types of signals. The coding protocol can be dynamically switched according to the channel environment without changing the hardware, which solves the problem of single chip protocol and poor universality of traditional chips and significantly improves the network adaptability of quantum key distribution system.

[0019] (2) The arrayed waveguide grating is innovatively used as the core device for beam combining. By utilizing its excellent spectral filtering and wavelength selection characteristics, it can achieve low-loss convergence of multiple wavelengths while providing high physical isolation between classical strong light and weak quantum signals, effectively suppressing noise and crosstalk. It can significantly reduce the quantum error rate of the system and improve the secure code generation rate without the need for additional off-chip filtering devices.

[0020] (3) The design of a switchable dual-branch output structure allows for flexible selection of two-dimensional grating vertical output or polarization rotation beam combining edge output according to test requirements and packaging scenarios. This solves the problems of traditional structures being sensitive to process tolerance and easily deteriorating polarization extinction ratio, ensuring high-fidelity output of polarization state, while also taking into account test convenience and low packaging loss requirements, greatly improving chip mass production yield and engineering adaptability.

[0021] (4) The multi-source signal modulation, wavelength division multiplexing beam combining, polarization state restoration and coupling output are fully integrated into the same thin-film lithium niobate waveguide. All signals are transmitted in TE fundamental mode, giving full play to the advantages of thin-film lithium niobate in high bandwidth, low loss and high modulation efficiency, compressing device size, reducing system power consumption and cost, and making it suitable for large-scale commercial quantum secure communication networks. Attached Figure Description

[0022] The embodiments of this application are described below with reference to the accompanying drawings, in which:

[0023] Figure 1 This schematic diagram illustrates the overall structure of a multi-protocol integrated chip according to an embodiment of this application.

[0024] Figure 2 A schematic diagram of the structure of a polarization-coded modulation unit according to an embodiment of this application is shown.

[0025] Figure 3 A schematic diagram of the structure of a time-bin coding modulation unit according to an embodiment of this application is shown. Detailed Implementation

[0026] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this application for ease of explanation. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0027] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The terms “comprising,” “including,” etc., as used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0028] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0029] Secondly, this application provides a detailed description in conjunction with schematic diagrams. When detailing the embodiments of this application, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of this application. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0030] Figure 1 The schematic diagram illustrates the overall structure of a multi-protocol integrated chip according to an embodiment of this application.

[0031] like Figure 1 As shown, the multi-protocol integrated chip of this application includes: an arrayed waveguide grating having a first output port and a second output port, the arrayed waveguide grating being used to receive polarized quantum signals, time-cell quantum signals and classical quantum signals transmitted through the same aperture, and to perform spectral convergence on the polarized quantum signals, time-cell quantum signals and classical quantum signals to output one component of the polarized quantum signal through the first output port, and to combine the other component of the polarized quantum signal, the time-cell quantum signal and the classical quantum signal through the second output port, wherein the one component and the other component of the polarized quantum signal are coherent and orthogonal; a beam combining output unit connected to the arrayed waveguide grating, the beam combining output unit being used to reconstruct the polarized quantum signal based on the one component and the other component of the polarized quantum signal, and to combine the reconstructed polarized quantum signal, time-cell quantum signal and classical quantum signal and output them to an optical fiber.

[0032] Specifically, the arrayed waveguide grating of this application is an on-chip integrated 1×2-port planar arrayed waveguide grating structure with an operating wavelength range of 1545nm-1555nm, a channel spacing of 0.8nm, a channel isolation of ≥35dB, and an insertion loss of ≤1.2dB. It has one signal input terminal and two independent output ports, namely the first output port and the second output port. This arrayed waveguide grating serves as the core of the chip's spectral convergence and signal routing. Its input terminal is connected to the output terminal of the multi-source signal modulation module via a single-mode waveguide. It is used to receive polarization quantum signals, time-bin quantum signals, and classical quantum signals transmitted by the multi-source signal modulation module through the same aperture. These three types of signals are optical signals of different wavelengths based on a wavelength division multiplexing architecture, each carried in a mutually isolated wavelength channel, ensuring no spectral crosstalk at the input stage. For example, in this embodiment, the first wavelength is 1550.12nm, the second wavelength is 1550.92nm, and the third wavelength of the classical cooperative optical signal is 1552.52nm, all within the C-band of optical fiber communication, with a wavelength spacing of ≥0.8nm.

[0033] The arrayed waveguide grating utilizes its excellent wavelength selection and grating diffraction characteristics to achieve low-loss spectral convergence of three types of input multi-wavelength signals. At the same time, it achieves port allocation of the signal through precise wavelength routing: one component of the polarization quantum signal is output separately through the first output port, and the other component of the polarization quantum signal, the time chamber quantum signal, and the classical quantum signal are pre-bundled and output through the second output port. Among them, one component and the other component of the polarization quantum signal are homogeneous optical signals originating from the same laser source, and they maintain strict coherence and orthogonality, providing a physical basis for the high-fidelity reconstruction of the subsequent polarization quantum signal.

[0034] In this embodiment, an adjustable optical path delay line can also be provided between the first output port of the arrayed waveguide grating and the beam combining output unit to compensate for the transmission optical path difference of the two polarization components, ensuring that the two reach the polarization restoration structure in phase synchronization and avoiding polarization state restoration distortion.

[0035] The beam combining output unit, which is connected one-to-one with the two output ports of the arrayed waveguide grating, is the core functional unit of the chip for polarization state restoration and final beam combining of multiple signals. It is also the key interface connecting the on-chip optical system and the external fiber optic link. After receiving the optical signal output from the dual ports of the arrayed waveguide grating, the beam combining output unit first uses the two coherent orthogonal components of the polarized quantum signal to accurately restore the polarization state based on the principle of coherent light superposition, thus recovering the complete polarized quantum signal carrying quantum information. Then, the restored polarized quantum signal is finally combined with the pre-bundled time chamber quantum signal and classical quantum signal from the second output port of the arrayed waveguide grating, coupling the three types of signals to the same transmission link and finally outputting them to the external single-mode fiber. This achieves common-aperture transmission of all signals, greatly simplifying the fiber optic link architecture of the quantum key distribution system.

[0036] In this embodiment, the multi-protocol integrated chip further includes a multi-source signal modulation module, comprising a polarization-coded modulation unit, a time-bin coded modulation unit, and a classical quantum signal modulation unit. The polarization-coded modulation unit, the time-bin coded modulation unit, and the classical quantum signal modulation unit are used to prepare polarization quantum signals, time-bin quantum signals, and classical quantum signals, respectively. The multi-source signal modulation module is also used to perform wavelength division multiplexing on the prepared polarization quantum signals, time-bin quantum signals, and classical quantum signals to output the polarization quantum signals, time-bin quantum signals, and classical quantum signals through the same aperture.

[0037] Specifically, the multi-source signal modulation module serves as the on-chip parallel preparation source for three types of signals. The multi-source signal modulation module includes mutually independent and wavelength-isolated polarization-coded modulation units, time-bin-coded modulation units, and classical quantum signal modulation units. The three modulation units are responsible for the independent preparation of polarization quantum signals, time-bin-coded quantum signals, and classical quantum signals, respectively: the polarization-coded modulation unit generates polarization quantum signals that meet the quantum key distribution protocol through beam splitting and multi-level modulation; the time-bin-coded modulation unit prepares time-bin-coded quantum signals resistant to channel interference through processes such as time delay pulse pair generation and phase encoding; and the classical quantum signal modulation unit loads the collaborative control signal of the quantum transceiver system onto the optical carrier to generate classical quantum signals for timing synchronization and parameter negotiation. The three types of signals prepared by the three modulation units are combined by the multi-source signal modulation module through the on-chip wavelength division multiplexing structure. The three signals of different wavelengths are coupled to the same output waveguide, realizing the same aperture output of the three types of signals. This provides a unified and continuous input signal for the spectral convergence and signal routing of the back-end arrayed waveguide grating, completing the full-link on-chip integration of multi-protocol signals from preparation to transmission, and ensuring the overall integration and operational stability of the chip.

[0038] In this embodiment, the classical quantum signal modulation unit has a first input terminal and a second input terminal; wherein, the first input terminal is used to receive laser light of a third wavelength; the second input terminal is connected to an external electrical signal input terminal and is used to receive the cooperative control signal of the quantum transceiver system; the classical quantum signal modulation unit is used to perform on / off keying modulation on the laser light of the third wavelength according to the cooperative control signal to generate a classical quantum signal carrying the cooperative control signal.

[0039] Specifically, the classical quantum signal modulation unit is a high-speed electro-optic modulation structure with a modulation bandwidth ≥10GHz. It is equipped with independent first and second input terminals, which respectively realize optical carrier reception and electrical control signal access. The specific working logic and structural characteristics are as follows:

[0040] The first input terminal of the classical quantum signal modulation unit is an optical signal input terminal, which is connected to an external laser source through an on-chip single-mode waveguide. It is specifically used to receive continuous laser light of a third wavelength. This wavelength of laser light serves as the optical carrier of the classical quantum signal and is isolated from the working wavelengths of the polarization quantum signal and the time-bin quantum signal to avoid spectral crosstalk with the quantum signal. The second input terminal is an electrical signal input terminal, which is connected to an external electrical signal input terminal through an on-chip coplanar waveguide. It is specifically used to receive the collaborative control signal of the quantum transceiver system. This collaborative control signal contains key information required in the quantum key distribution process, such as the global synchronization clock, channel parameter negotiation data, basis vector comparison information, and link status feedback data. It is the core command signal to ensure the stable and orderly operation of the quantum communication link. The classical quantum signal modulation unit is based on the on-off keying (OOK) modulation principle. It loads the electrical domain cooperative control signal received at the second input terminal onto the third wavelength optical carrier input at the first input terminal. By high-speed on-off modulation of the optical carrier, the conversion from electrical signal to optical signal is completed, and finally a classical quantum signal carrying complete cooperative control information is generated. This signal not only provides precise timing synchronization for the quantum transceiver, ensuring that quantum state preparation and detection are strictly aligned on the time axis, but also realizes real-time protocol interaction between the transceiver and the transceiver, providing comprehensive logical support for the stable operation of the quantum communication link.

[0041] In this embodiment, the beam combining output unit includes a first output branch and a second output branch; the first output branch includes a two-dimensional grating coupler, and the second output branch includes a polarization rotation beam combiner; the beam combining output unit switches between the first output branch and the second output branch according to the testing requirements and packaging application scenarios of the multi-protocol integrated chip, so as to combine and output the restored polarization quantum signal, time chamber quantum signal and classical quantum signal.

[0042] Specifically, the beam combining output unit can flexibly switch between the first output branch and the second output branch to work independently according to the actual application requirements of the multi-protocol integrated chip. Without changing the core architecture of the chip's front-end, it can achieve efficient beam combining output of the restored polarization quantum signal, time chamber quantum signal and classical quantum signal, taking into account both the chip's wafer-level testing requirements and device packaging application scenarios, and greatly improving the chip's engineering adaptability.

[0043] In this embodiment, the two-dimensional grating coupler has a first input arm and a second input arm that are orthogonal to each other. The first input arm receives one component of the polarization quantum signal, and the second input arm receives the other component of the polarization quantum signal, the time chamber quantum signal, and the classical quantum signal. The two-dimensional grating coupler is used to couple the signals received by the first input arm and the second input arm to two orthogonal polarization modes of a single-mode fiber, so that one component and the other component of the polarization quantum signal coherently superimpose in the grating radiation region to recover the polarization quantum signal, and then output the recovered polarization quantum signal, the time chamber quantum signal, and the classical quantum signal as a bundle.

[0044] Specifically, the two-dimensional grating coupler is an on-chip integrated polarization-sensitive grating coupling structure. It is configured with a first input arm and a second input arm that are orthogonal to each other. The two input arms correspond to the two orthogonal polarization coupling modes of the grating, respectively, enabling independent reception and coupling of signals with different polarization states. When the two-dimensional grating coupler is working, it utilizes its own polarization-sensitive coupling characteristics to couple the signal received by the first input arm to the first orthogonal polarization mode of the external single-mode fiber, and the signal received by the second input arm to the second orthogonal polarization mode of the external single-mode fiber. The two polarization modes are free from crosstalk and the transmission is stable. At the same time, one component of the polarization quantum signal and the other component undergo spatial coherent superposition in the grating radiation region. Based on the principle of coherent light superposition, the complete polarization quantum signal is accurately restored. The restored polarization quantum signal, along with the time chamber quantum signal and the classical quantum signal, are synchronously coupled to the same single-mode fiber, realizing the common-aperture bundled output of the three types of signals and completing the vertical coupling and docking between the chip and the fiber optic link.

[0045] In this embodiment, the polarization rotation beam combiner has a first input port, a second input port, and a beam combining output port. The first input port is used to receive one component of the polarization quantum signal. The second input port is used to receive the other component of the polarization quantum signal, the time chamber quantum signal, and the classical quantum signal. The polarization rotation beam combiner is used to perform polarization rotation processing on one component of the polarization quantum signal, converting it from a TE mode (Transverse Electric Mode) to a TM mode (Transverse Magnetic Mode) orthogonal to the other component of the polarization quantum signal, so that the polarization quantum signal can be restored from the other component. The beam combining output unit is used to combine the restored polarization quantum signal, the time chamber quantum signal, and the classical quantum signal in the same waveguide and output them.

[0046] Specifically, the polarization rotation beam combiner is an on-chip integrated structure combining polarization conversion and beam combining. It is equipped with a first input port, a second input port, and a beam combining output port. All three ports are on-chip single-mode waveguide interfaces, adapted to the signal transmission links within the chip. The first input port is connected to the first output port of the arrayed waveguide grating and is specifically used to receive one component of the polarization quantum signal. The second input port is connected to the second output port of the arrayed waveguide grating and is specifically used to receive the other component of the polarization quantum signal, the time-bin quantum signal, and the classical quantum signal. The beam combining output port is the only signal output terminal of the device, used to achieve the final beam combining output of multiple signals. When the polarization rotation combiner is working, it first performs polarization rotation processing on one component of the polarization quantum signal received at the first input port. Through the gradual design of the waveguide geometry, this component is efficiently converted from the TE mode common in the chip to a TM mode orthogonal to the other component of the polarization quantum signal, ensuring the coherent orthogonality of the two polarization components. Subsequently, the converted TM mode polarization quantum signal component coherently superimposes with the other component of the polarization quantum signal that maintains the TE mode in the second input port, accurately restoring the complete polarization quantum signal. Finally, the beam combining output unit combines the restored polarization quantum signal with the time chamber quantum signal and the classical quantum signal transmitted along the same path in the same on-chip single-mode waveguide. The beam combining output port of the polarization rotation combiner realizes the common aperture edge output of the three types of signals, which can be directly connected to the end-face coupling structure of the external optical fiber link.

[0047] The dual-branch switchable design of the beam output unit caters to both chip testing and packaging needs. The first output branch is adapted to wafer-level automated probe testing, which can complete performance testing without chip disassembly, greatly improving the efficiency of chip R&D and mass production screening. The second output branch is adapted to commercial packaging of devices, achieving low-loss edge coupling, meeting the engineering deployment requirements of quantum key distribution systems, and improving the chip's full life cycle adaptability.

[0048] In this embodiment, the multi-source signal modulation module, the arrayed waveguide grating, and the beam combining output unit are all integrated on the same thin-film lithium niobate waveguide; one component and the other component of the polarization quantum signal, the time chamber quantum signal, and the classical quantum signal are all transmitted in the form of the TE fundamental mode.

[0049] For example, to fully leverage the miniaturization, high stability, and low loss advantages of photonic integrated devices, this application integrates three core functional modules—a multi-source signal modulation module, an arrayed waveguide grating, and a beam combiner output unit—all monolithically onto the same thin-film lithium niobate waveguide substrate. This is achieved using a planar waveguide integrated process, with each module directly connected via an on-chip single-mode waveguide, eliminating the need for any external discrete optical components or additional fiber optic coupling. Thin-film lithium niobate material possesses inherent characteristics such as ultra-high electro-optic modulation efficiency, ultra-wide operating bandwidth, and ultra-low waveguide transmission loss. Integrating all core modules onto this single waveguide substrate significantly reduces the chip's physical size and overall system power consumption, while completely avoiding coupling losses between discrete components, optical path alignment errors, and interference from the external environment. This significantly improves the chip's long-term stability and reliability, while also being compatible with mature CMOS (Complementary Metal-Oxide-Semiconductor) fabrication technology, enabling large-scale, low-cost mass production.

[0050] In this embodiment, the multi-source signal modulation module is also electrically connected to a protocol switching control unit; the protocol switching control unit is used to acquire the transmission state of the classical quantum signal and generate control signals according to the transmission state to regulate the working state of the polarization coding modulation unit and the time-bin coding modulation unit.

[0051] Specifically, in order to enable the chip to adapt to different optical fiber channel environments and break the limitations of the single coding protocol of traditional quantum integrated chips, the multi-source signal modulation module is also electrically connected to a protocol switching control unit. This unit is the core of the chip's protocol control. It is electrically connected to the polarization coding modulation unit, time-bin coding modulation unit, and classical quantum signal modulation unit in the multi-source signal modulation module through on-chip coplanar waveguides, forming a closed-loop channel state feedback and coding protocol control system.

[0052] For example, firstly, the transmission status of the classical quantum signal in the optical fiber transmission process is acquired in real time through the signal feedback link of the classical quantum signal modulation unit. This transmission status includes key parameters such as the degree of birefringence interference in the optical fiber channel, link transmission loss, signal-to-noise ratio, quantum bit error rate, and real-time channel stability, which are important bases for judging the adaptability of the current channel environment. Secondly, the protocol switching control unit has a built-in preset protocol switching strategy. Based on the acquired real-time transmission status, it analyzes and judges to generate corresponding electrical control signals. These control signals include start / stop instructions for the modulation unit and operating parameter calibration instructions. For example, when the channel interference is lower than a preset threshold, the polarization-coded modulation unit is activated first; when the channel birefringence interference is higher than the preset threshold, it automatically switches to the time-binding-coded modulation unit.

[0053] Finally, the generated control signals are transmitted to the drive control terminals of the polarization coding modulation unit and the time chamber coding modulation unit respectively, so as to precisely regulate the working state of the two modulation units and flexibly realize the switching between single protocol independent operation and dual protocol parallel operation.

[0054] Figure 2 A schematic diagram of the structure of a polarization-coded modulation unit according to an embodiment of this application is shown.

[0055] like Figure 2 As shown, the polarization coding modulation unit includes: a beam splitting unit and two parallel modulation links; the beam splitting unit is used to split the first wavelength laser into two co-source optical signals and input them into the two modulation links respectively; each modulation link includes a decoy state modulation unit group, an intensity modulation unit group and a phase modulation unit group cascaded in sequence, which are used to sequentially perform decoy state modulation, intensity modulation and phase modulation on the optical signal to obtain two modulated optical signals, which serve as one component and the other component of the polarization quantum signal.

[0056] The beam splitter unit is a low-loss optical power beam splitting structure with a splitting ratio of 50:50 and an insertion loss of ≤0.3dB. It is specifically used to receive the first wavelength continuous laser input from the outside. This laser is a narrow-linewidth, high-coherence single-frequency laser, which is the optical carrier of the polarization quantum signal. The beam splitter unit splits the input first wavelength laser into two co-source optical signals with equal power and without deflection. The two optical signals originate from the same laser source, maintain strict coherence, and have initially consistent optical power and transmission phase. Subsequently, the two co-source optical signals are input into two parallel modulation links, laying the physical foundation for subsequent synchronous modulation.

[0057] The two modulation links are designed with a symmetrical or asymmetrical structure. Each modulation link contains a decoy state modulation unit group, an intensity modulation unit group, and a phase modulation unit group cascaded in sequence. The three modulation units work in sequence according to the signal transmission order to perform staged and refined electro-optic modulation on the input homogeneous optical signal. The modulation process of the two modulation links is carried out synchronously, and finally outputs two optical signals that have completed the full process modulation, which serve as one component and the other component of the polarization quantum signal, respectively.

[0058] The decoy state modulation unit group rapidly and dynamically modulates the amplitude of the optical signal, quickly switching between three different intensities of optical pulses—signal state, decoy state, and vacuum state—in the time domain. This ensures high consistency in the statistical characteristics of pulses of different intensities, effectively resisting photon number sorting attacks and guaranteeing the security of the quantum key distribution process from the ground up. The intensity modulation unit group is used to precisely calibrate the intensity of the decoy-modulated optical signal. By independently controlling the optical power of the two optical signals, it ensures that the intensity ratio of the two output optical signals precisely matches the polarization state synthesis requirements, avoiding polarization state reconstruction distortion caused by intensity deviation. The phase modulation unit applies a precise phase shift to the two optical signals, controlling the relative phase difference between them. This phase difference is a key parameter for constructing different polarization quantum states. By precisely controlling the phase difference, the subsequently synthesized polarization quantum signal can meet the polarization state requirements of the BB84 quantum key distribution protocol.

[0059] Optionally, the decoy state modulation unit group includes several decoy state modulation units; the intensity modulation unit group includes several intensity modulation units; and the phase modulation unit group includes several phase modulation units. The number of units in each unit group in the two modulation links may be the same or different.

[0060] Optionally, the decoy modulation unit group, intensity modulation unit group, and phase modulation unit group in the two modulation links may also be absent.

[0061] Optionally, in the two modulation links, each pair of decoy state modulation unit groups and each pair of intensity modulation unit groups can also be connected via a 2×2 multi-mode inferometer (MMI) or other devices with beam combining and splitting functions; each pair of intensity modulation unit groups and each pair of phase modulation unit groups can also be connected via a 2×2 multi-mode inferometer or other devices with beam combining and splitting functions. For example, in the two modulation links, the optical signals output from the two decoy state modulation unit groups in the upper and lower paths are combined by a 2×2 multi-mode inferometer and then split into two beams, which are then processed in the upper and lower intensity modulation unit groups respectively.

[0062] Figure 3 A schematic diagram of the structure of a time-bin coding modulation unit according to an embodiment of this application is shown.

[0063] like Figure 3The time-bin coding modulation unit shown includes a beam splitting unit, two parallel modulation links, and a beam combining unit connected in sequence. The beam splitting unit splits the second wavelength laser into two optical signals of the same origin and inputs them into the two modulation links respectively. Each modulation link includes a decoy state modulation unit group, a time delay pulse pair generation unit group, an intensity modulation unit group, and a phase modulation unit group cascaded in sequence, which are used to sequentially perform decoy state modulation, time delay pulse pair generation, intensity modulation, and phase modulation on the optical signal to obtain two coherent pulse optical signals. The beam combining unit is used to combine the two coherent pulse optical signals to obtain the time-bin quantum signal.

[0064] Among them, the time delay pulse pair generation unit group adopts the structure of unbalanced Mach-Zehnder interferometer (UMZI) with fixed-length optical delay line. The two arms of the unbalanced interferometer are set with a fixed optical path difference, and the corresponding time delay difference can be customized according to the system pulse repetition frequency (e.g., 2.5GHz repetition frequency corresponds to 400ps time delay difference), and the time delay control accuracy is less than 1ps.

[0065] The delay pulse pair generation unit group splits the decoy-modulated single optical pulse into an "early-late" coherent double pulse state with a fixed delay difference, forming two time-domain basis vectors for time-bin encoding, providing a time-domain carrier for subsequent quantum information loading. The two arms of the unbalanced interferometer adopt a symmetrical bent waveguide design to ensure that the transmission loss of the two arms is completely consistent, avoiding optical power deviation in the double pulse; the delay pulse pair generation unit groups of the two modulation links adopt completely identical structural parameters to ensure strict synchronization of the timing of the two output double pulses.

[0066] The two parallel modulation links are arranged in a symmetrical or asymmetrical waveguide layout. Each modulation link includes a decoy state modulation unit group, a time delay pulse pair generation unit group, an intensity modulation unit group, and a phase modulation unit group cascaded sequentially along the optical transmission direction. The four unit groups sequentially modulate the input homogeneous optical signals, and finally output two coherent pulse optical signals that meet the requirements of the quantum key distribution protocol.

[0067] Optionally, the decoy state modulation unit group includes several decoy state modulation units; the time delay pulse pair generation unit group includes several time delay pulse pair generation units; the intensity modulation unit group includes several intensity modulation units; and the phase modulation unit group includes several phase modulation units. The number of units in each unit group in the two modulation links may be the same or different.

[0068] Optionally, the decoy state modulation unit group, the time delay pulse pair generation unit group, the intensity modulation unit group, and the phase modulation unit group in the two modulation links may also be absent.

[0069] Optionally, in the two modulation links, each pair of identical unit groups can also be connected by a 2×2 multimode interferometer or other devices with beam combining and splitting functions; for example, the optical signals output by the upper and lower decoy modulation unit groups are combined by the 2×2 multimode interferometer and then split into two optical signals, which are respectively entered into the upper and lower time delay pulse generation unit groups for processing.

[0070] Those skilled in the art will understand that the features described in the various embodiments of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments of this disclosure can be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0071] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A multi-protocol integrated chip, characterized in that, include: An arrayed waveguide grating has a first output port and a second output port. The arrayed waveguide grating is used to receive polarized quantum signals, time-cell quantum signals, and classical quantum signals transmitted through the same aperture, and to perform spectral convergence on the polarized quantum signals, time-cell quantum signals, and classical quantum signals to output one component of the polarized quantum signal through the first output port, and to output the other component of the polarized quantum signal, the time-cell quantum signal, and the classical quantum signal by combining them through the second output port. The one component and the other component of the polarized quantum signal are coherent and orthogonal. A beam combining output unit is connected to the arrayed waveguide grating. The beam combining output unit is used to reconstruct the polarization quantum signal based on one component and another component of the polarization quantum signal, and to combine the reconstructed polarization quantum signal, the time chamber quantum signal and the classical quantum signal into an optical fiber.

2. The multi-protocol integrated chip according to claim 1, characterized in that, The multi-protocol integrated chip also includes: A multi-source signal modulation module includes a polarization-coded modulation unit, a time-bin coded modulation unit, and a classical quantum signal modulation unit. The polarization-coded modulation unit, the time-bin coded modulation unit, and the classical quantum signal modulation unit are used to prepare the polarization quantum signal, the time-bin quantum signal, and the classical quantum signal, respectively. The multi-source signal modulation module is also used to perform wavelength division multiplexing on the generated polarization quantum signal, time chamber quantum signal and classical quantum signal so as to output the polarization quantum signal, time chamber quantum signal and classical quantum signal through the same aperture.

3. The multi-protocol integrated chip according to claim 2, characterized in that, The polarization coding modulation unit includes: a beam splitter and two parallel modulation links; The beam splitting unit is used to split the laser of the first wavelength into two optical signals of the same origin, and input them into the two modulation links respectively; Each modulation link includes a decoy state modulation unit group, an intensity modulation unit group, and a phase modulation unit group cascaded in sequence, used to sequentially perform decoy state modulation, intensity modulation, and phase modulation on the optical signal to obtain two modulated optical signals, which serve as one component and the other component of the polarization quantum signal.

4. The multi-protocol integrated chip according to claim 2, characterized in that, The time-bin coding and modulation unit includes a beam splitting unit, two parallel modulation links, and a beam combining unit connected in sequence. The beam splitting unit splits the second wavelength laser into two optical signals of the same origin and inputs them into the two modulation links respectively; Each modulation link includes a decoy state modulation unit group, a time delay pulse pair generation unit group, an intensity modulation unit group, and a phase modulation unit group cascaded in sequence, used to sequentially perform decoy state modulation, time delay pulse pair generation, intensity modulation, and phase modulation on the optical signal to obtain two coherent pulse optical signals; The beam combining unit is used to combine the two coherent pulse optical signals to obtain the time chamber quantum signal.

5. The multi-protocol integrated chip according to claim 2, characterized in that, The classical quantum signal modulation unit has a first input terminal and a second input terminal; The first input terminal is used to receive laser light of a third wavelength; The second input terminal is connected to an external electrical signal input terminal and is used to receive the collaborative control signal of the quantum transceiver system; The classical quantum signal modulation unit is used to perform on / off key modulation of the third wavelength laser according to the cooperative control signal, thereby generating a classical quantum signal carrying the cooperative control signal.

6. The multi-protocol integrated chip according to claim 1, characterized in that, The beam combining output unit includes a first output branch and a second output branch; The first output branch includes a two-dimensional grating coupler, and the second output branch includes a polarization rotation beam combiner; The beam combining output unit switches between the first output branch and the second output branch according to the testing requirements and packaging application scenarios of the multi-protocol integrated chip, so as to combine and output the restored polarization quantum signal, the time chamber quantum signal and the classical quantum signal.

7. The multi-protocol integrated chip according to claim 6, characterized in that, The two-dimensional grating coupler has a first input arm and a second input arm that are orthogonal to each other; The first input arm receives one component of the polarization quantum signal, and the second input arm receives the other component of the polarization quantum signal, the time chamber quantum signal, and the classical quantum signal. The two-dimensional grating coupler is used to couple the signals received by the first input arm and the second input arm to two orthogonal polarization modes of a single-mode fiber, so that one component of the polarization quantum signal and the other component coherently superimpose in the grating radiation region to recover the polarization quantum signal, and then output the recovered polarization quantum signal, the time chamber quantum signal and the classical quantum signal together.

8. The multi-protocol integrated chip according to claim 6, characterized in that, The polarization rotating beam combiner has a first input port, a second input port, and a beam combining output port; The first input port is used to receive one component of the polarization quantum signal; the second input port is used to receive the other component of the polarization quantum signal, the time chamber quantum signal, and the classical quantum signal. The polarization rotation beam combiner is used to perform polarization rotation processing on one component of the polarization quantum signal, converting one component of the polarization quantum signal from a TE mode to a TM mode orthogonal to the other component of the polarization quantum signal, so that one component and the other component of the polarization quantum signal can be used to reconstruct the polarization quantum signal. The beam combining output unit is used to combine the restored polarization quantum signal, the time chamber quantum signal, and the classical quantum signal in the same waveguide and output them.

9. The multi-protocol integrated chip according to claim 2, characterized in that, The multi-source signal modulation module, the arrayed waveguide grating, and the beam combining output unit are all integrated on the same thin-film lithium niobate waveguide. One component and the other component of the polarization quantum signal, the time chamber quantum signal, and the classical quantum signal are all transmitted in the form of the TE fundamental mode.

10. The multi-protocol integrated chip according to claim 2, characterized in that, The multi-source signal modulation module is also electrically connected to a protocol switching control unit; the protocol switching control unit is used to acquire the transmission state of the classical quantum signal and generate a control signal according to the transmission state to regulate the working state of the polarization coding modulation unit and the time chamber coding modulation unit.

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