Quantum state coding transmitting terminal and electronic equipment

Abstract

The embodiment of the invention provides a quantum state coding transmitting terminal and electronic equipment. The quantum state coding transmitting terminal comprises a light emitting device and a light processing structure, the light emitting device is used for emitting a first light source and a second light source, and the light intensity ratio of the first light source to the second light source is a random preset ratio; the light processing structure is used for receiving the first light source and the second light source, performing related processing on the first light source and the second light source and outputting a target light signal; wherein the correlation processing comprises intensity modulation, phase shift and beam combination, and the preset proportion and the correlation processing enable the target optical signals to meet the condition that the light intensities of the target optical signals obtained under any preset proportion are the same.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of quantum key distribution, and in particular to a quantum state encoding transmitting end and an electronic device. BACKGROUND

[0002] Quantum Key Distribution (QKD) is based on quantum mechanics principles, and can generate absolutely secure symmetric keys between legal communication parties, and ensure the security of information transmission through one-time pad encryption. At present, quantum communication has entered the practical stage, but quantum communication devices generally have the problems of large size and high cost. Developing quantum state encoding photon integrated chip devices is an important means to reduce cost and size. At present, different photon integrated platforms, such as III-V polymer, silicon-based, and thin film lithium niobate, can be used to develop QKD quantum state encoding chips. However, considering the process maturity and production cost, the silicon-based platform is more popular due to its advantages. Based on the silicon-based platform, different dimension quantum state encoding chips for QKD, such as polarization, time, and phase, can be realized. SUMMARY

[0003] Embodiments of the present disclosure provide a quantum state encoding transmitting end and an electronic device.

[0004] In a first aspect, embodiments of the present disclosure provide a quantum state encoding transmitting end, comprising a light emitting device and a light processing structure. The light emitting device is configured to emit a first light source and a second light source, and the light intensity ratio of the first light source and the second light source is a random preset ratio. The light processing structure is configured to receive the first light source and the second light source, perform relevant processing on the first light source and the second light source, and output a target optical signal. The relevant processing includes intensity modulation, phase shift, and beam combination. The preset ratio and the relevant processing make the light intensity of the target optical signal the same under any preset ratio.

[0005] In some embodiments, the light emitting device comprises: A first laser is configured to emit the first light source. A second laser is configured to emit the second light source. The first laser and the second laser are the same laser.

[0006] In some embodiments, the light processing structure comprises: An intensity modulation structure is configured to receive the first light source and the second light source, perform light splitting processing on the first light source and the second light source according to a preset light splitting ratio, and generate a first light component and a second light component. a phase shift structure, configured to receive the first light component and the second light component, and to perform phase shift processing on one or both of the first light component and the second light component according to a preset phase difference, to generate a third light component and a fourth light component; a light combination structure, configured to receive the third light component and the fourth light component, and to perform light combination processing on the third light component and the fourth light component to obtain the target optical signal.

[0007] In some embodiments, the intensity modulation structure is a Mach-Zehnder interferometer.

[0008] In some embodiments, the intensity modulation structure comprises: a first light splitting structure, configured to receive the first light source and the second light source, and to perform light splitting processing on the first light source and the second light source according to a 1:1 light splitting ratio to output two light components; a first phase shift structure, configured to receive the two light components output by the first light splitting structure, and to perform phase shift on one or both of the two light components to output two light components; a second light splitting structure, configured to receive the two light components output by the first phase shift structure, and to perform interference combination processing on the two light components to output the first light component and the second light component.

[0009] In some embodiments, the first light splitting structure and the second light splitting structure are both multimode interference couplers.

[0010] In some embodiments, the phase shift structure comprises two phase shifters, wherein: the phase shift structure is configured to receive the first light component and the second light component by the two phase shifters respectively, and to perform phase shift processing on the received light components by one or both of the two phase shifters to meet the preset phase difference.

[0011] In some embodiments, the light processing structure further comprises, an input coupling structure, configured to couple to receive the first light source and the second light source; an output coupling structure, configured to couple to output the target optical signal.

[0012] In some embodiments, the quantum state encoding transmitting end further comprises: a lens module, configured to perform mode spot conversion on the first light source and the second light source to match the input coupling structure.

[0013] In some embodiments, the quantum state encoding transmitting end further comprises: An isolation structure is arranged between the light emitting device and the lens module, or between the lens module and the light processing structure, for isolating the light component reflected by the light processing structure.

[0014] In some embodiments, the light combining structure is a two-dimensional grating coupler, and the light combining structure and the output coupling structure are the same structure.

[0015] In some embodiments, the light combining structure is a polarization beam splitting rotator.

[0016] In some embodiments, the total light intensity of the first light source and the second light source is the same at different preset ratios.

[0017] In some embodiments, the preset ratio is 1:0, 0:1, or 0.5:0.5.

[0018] In some embodiments, the light emitting device is a III-V chip, and the light processing structure is a silicon-based passive chip.

[0019] In a second aspect, the embodiments of the present disclosure provide an electronic device, including a control module and the quantum state encoding transmitting end according to any one of the first aspect. The control module is configured to control the light emitting device to emit the first light source and the second light source according to the random preset ratio.

[0020] The embodiments of the present disclosure provide a quantum state encoding transmitting end and an electronic device. The quantum state encoding transmitting end includes a light emitting device and a light processing structure. The light emitting device is configured to emit a first light source and a second light source. The light intensity ratio of the first light source and the second light source is a random preset ratio. The light processing structure is configured to receive the first light source and the second light source, perform relevant processing on the first light source and the second light source, and output a target light signal. The relevant processing includes intensity modulation, phase shift, and beam combining. The preset ratio and the relevant processing make the target light signal satisfy that the light intensity of the target light signal obtained at any preset ratio is the same.

[0021] In this way, the embodiments of the present disclosure preset the light intensity ratio of the light sources emitted by the light emitting device, and design the way of processing the light sources by the light processing structure, so that the target light signal has the same light intensity regardless of the light intensity ratio. Different data caused by modulation and correlation loss do not present different light intensity, which avoids the possibility that a thief intercepts the target light signal and decrypts the data by intensity, and improves the security of quantum key distribution. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 FIG. 1 is a structure diagram of a quantum state encoding transmitting end according to an embodiment of the present disclosure. Figure 1 ; Figure 2 A structure diagram of a quantum state encoding transmitting end provided by an embodiment of the present disclosure Figure 2 ; Figure 3 A structure diagram of a quantum state encoding transmitting end provided by an embodiment of the present disclosure Figure 3 ; Figure 4 A structure diagram of an electronic device provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present disclosure will be described clearly and completely below with reference to the drawings in the embodiments of the present disclosure. It can be understood that the specific embodiments described herein are only for the purpose of explaining the related disclosure, and not for limiting the disclosure. In addition, it should be noted that, for the purpose of description, only the parts related to the disclosure are shown in the drawings.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. The terms used herein are only for the purpose of describing the embodiments of the present disclosure, and are not intended to limit the present disclosure.

[0025] In the following description, “some embodiments” are described, which describe a subset of all possible embodiments, but it can be understood that “some embodiments” can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict.

[0026] It should be noted that the terms “first\second\third” involved in the embodiments of the present disclosure are only to distinguish similar objects, and do not represent a specific order of the objects. It can be understood that “first\second\third” can be interchanged in a specific order or sequence as allowed, so that the embodiments of the present disclosure described herein can be implemented in an order other than that illustrated or described herein.

[0027] Quantum Key Distribution (QKD); Laser Diode (LD); Spot Size Converter (SSC); Multi-Mode Interference coupler (MMI); Thermo-Optical Phase Shifter (T OPS); Variable Optical Attenuator (VOA); Polarization Splitter Rotator (PSR); Transverse Electric (TE); Transverse magnetic (TM); Mach-Zehnder Interferometer (MZI).

[0028] QKD (Quantum Key Digitization) chips are vulnerable to security vulnerabilities due to modulation-dependent losses. Specifically, QKD relies on photon polarization state encoding and decoding to extract symmetric keys and ensure secure information transmission. Different polarization states correspond to binary sequences of 0 or 1. The transmitter (Alice) randomly modulates photon polarization information and transmits it to the receiver (Bob) via a quantum channel. The receiver randomly selects a polarization measurement basis vector, measures the photon, and retains the binary sequence corresponding to the measurement basis vector used by Alice to prepare the polarization state. Normally, if an attacker intercepts the quantum key, Alice and Bob can determine this by judging the qubit error rate, discard the current key, and redistribute the quantum key. This process ensures the absolute security of the key obtained by both parties. However, due to modulation-dependent losses during modulation, different quantum states have different intensities. In this case, an attacker can determine the photon's polarization state based on the difference in light intensity without measuring the polarization state, thus obtaining the key and causing a security problem.

[0029] Based on this, the present disclosure provides a quantum state-coded transmitter, including an optical emitting device and an optical processing structure; the optical emitting device is used to emit a first light source and a second light source, the light intensity ratio of the first light source and the second light source being a random preset ratio; the optical processing structure is used to receive the first light source and the second light source, perform correlation processing on the first light source and the second light source, and output a target optical signal; wherein, the correlation processing includes: intensity modulation, phase shifting, and beam combining, and the preset ratio and correlation processing ensure that the target optical signal satisfies that the light intensity of the target optical signal obtained under any preset ratio is the same.

[0030] In this way, the embodiment of the present disclosure pre-sets the light intensity ratio of the light source emitted by the light emitting device, and designs the light processing structure to process the light source, so that the target light signal has the same light intensity under any light intensity ratio, and different data will not present different light intensity due to modulation-related loss, avoiding the possibility that the data is decrypted by the intensity after the target light signal is intercepted by the thief, and improving the security of quantum key distribution.

[0031] The embodiments of the present disclosure will be described in detail below with reference to the drawings.

[0032] In an embodiment of the present disclosure, referring to Figure 1 which shows a structure schematic diagram of a quantum state encoding transmitting end 10 provided by an embodiment of the present disclosure. As shown in Figure 1 The quantum state encoding transmitting end 10 (or QKD transmitting end) can include: The light emitting device 101 is configured to emit a first light source and a second light source, and the light intensity ratio of the first light source and the second light source is a random pre-set ratio. The light processing structure 102 is configured to receive the first light source and the second light source, and perform related processing on the first light source and the second light source to output a target light signal. The related processing includes intensity modulation, phase shift and beam combination. The pre-set ratio and the related processing make the light intensity of the target light signal obtained under any pre-set ratio the same.

[0033] It should be noted that the light emitting device 101 is a structure capable of emitting laser, and the first light source and the second light source can both be laser pulses. The intensity of the first light source and the second light source is a pre-set ratio. In the embodiment of the present disclosure, a plurality of different pre-set ratios are pre-set. When the quantum state is encoded, the light intensity ratio of the first light source and the second light source emitted by the light emitting device 101 is randomly one of the pre-set ratios, and then the first light source and the second light source are processed by the light processing structure 102 to obtain the target light signal with the corresponding quantum state (or polarization state).

[0034] It should be further noted that the light processing structure 102 processes the first light source and the second light source by intensity modulation, phase shift and beam combination to obtain the final target light signal. Here, the intensity modulation mainly refers to adjusting the phase difference of the first light source and the second light source to obtain different interference results of different states, thereby changing the intensity of the two light components output to reconstruct the ratio of the output light field, for example, 50:50 splitting to obtain light components with consistent light intensity. The phase shift processing mainly refers to shifting the phase of one or both of the two light components processed by the intensity modulation by a certain amount. The beam combination processing is to combine the two light components into one to obtain the target light signal.

[0035] The polarization state of the target optical signal is obtained by multiplying the light field of the first light source and the second light source by the Jones matrix of the device used to perform the correlation processing. The Jones matrix is a 2x2 complex matrix used to describe the change in polarization state of light and the polarization characteristics of an optical element. In the subsequent description, the polarization state obtained by the embodiments of the present disclosure will be illustrated in combination with specific optical devices and the corresponding Jones matrix.

[0036] In the embodiments of the present disclosure, the light processing structure 102 can be a passive silicon-based chip, and the intensity modulation processing, phase shift processing, and beam combination processing can all be implemented by passive devices. For example, a multimode interference coupler uses the physical structure of the device to regulate the light field, and a thermo-optic phase shifter changes the refractive index by changing the temperature of the waveguide, thereby forming a phase modulation, and the associated loss introduced is extremely weak. Compared with an active device such as a carrier depletion modulator (or high-speed modulator), the distribution concentration of carrier electrons and holes changes at the PN junction during electrical signal modulation, which causes the device loss to change significantly, that is, there is a modulation-related loss, which causes the prepared polarization state to be associated with the intensity, causing the eavesdropper to crack the corresponding polarization state by obtaining the intensity information, and the passive device does not have this problem, effectively ensuring the security of the communication. In addition, the passive device usually has a simple structure and does not have the aging mechanisms such as electron migration and hot carrier degradation that are common in active devices, and also has the advantages of low cost and long service life.

[0037] The embodiments of the present disclosure rationally design the preset ratio and combine the related processing, so that the target optical signal output ultimately has the same light intensity regardless of the preset ratio, so that the eavesdropper cannot obtain the information carried by the target optical signal based on the intensity of the target optical signal, thereby ensuring the security of information transmission.

[0038] It should be further noted that the "same" described in the embodiments of the present disclosure includes allowable or unavoidable errors.

[0039] In some embodiments, as shown in Figure 2 The light emitting device 101 can include: a first laser LD1 for emitting a first light source; a second laser LD2 for emitting a second light source; The first laser LD1 and the second laser are the same laser LD2.

[0040] It should be noted that the first light source and the second light source can be provided by two independent lasers, or the two lasers can be integrated together in structure, but still independently emit light sources.

[0041] In the embodiments of the present disclosure, the first laser LD1 and the second laser LD2 can be semiconductor lasers, fiber lasers, or other devices or systems capable of emitting pulse signals. For example, the light emitting device 101 is a III-V laser chip, and the first laser LD1 and the second laser LD2 are both III-V lasers. The III-V semiconductor is a compound composed of Group IIIA elements (such as boron, aluminum, gallium, and indium) and Group VA elements (such as nitrogen, phosphorus, arsenic, antimony, and bismuth). Since quantum communication generally uses infrared wavelength light (1100 nm-1700 nm), the common materials of the corresponding III-V lasers include indium phosphide (InP), indium gallium arsenide phosphide (InGaAsP), and the like. The III-V lasers based on these III-V elements have the advantages of high frequency and high efficiency, excellent optoelectronic performance, flexible hetero-integration, and the like. Thus, the III-V laser chip (the light emitting device 101) and the silicon-based passive chip (the light processing structure 102) can be mixed and integrated to realize a small-sized quantum state encoding transmitting end 10 integrating a light source and a polarization state encoding.

[0042] It should be further noted that, in the embodiments of the present disclosure, the emission mode of the light emitting device 101 can be controlled by an external or internal control signal, and different emission modes correspond to different preset ratios. Here, the same control signal can be used to control the first laser LD1 and the second laser LD2 simultaneously, or the control signal includes a first sub-control signal and a second sub-control signal, the first sub-control signal is used to control the first laser LD1 to emit the first light source, and the second sub-control signal is used to control the second laser LD2 to emit the second light source. The first laser LD1 and the second laser LD2 output light sources with corresponding intensities based on the received control signal or control sub-signal.

[0043] The intensity ratio of the first light source and the second light source can be represented by the light power ratio, the energy ratio, or the intensity ratio of the two.

[0044] In some embodiments, as shown in Figure 2 The light processing structure 102 includes: The intensity modulation structure 1021 is configured to receive the first light source and the second light source, perform light splitting processing on the first light source and the second light source according to a preset light splitting ratio, and generate a first light component and a second light component. The phase shift structure 1022 is configured to receive the first light component and the second light component, perform phase shift processing on one or both of the first light component and the second light component according to a preset phase difference, and generate a third light component and a fourth light component. The light beam combining structure 1023 is configured to receive the third light component and the fourth light component, perform beam combining processing on the third light component and the fourth light component, and obtain a target light signal.

[0045] It should be noted that the intensity modulation structure 1021 is configured to re-allocate the light intensity of the first light source and the second light source according to a preset light splitting ratio, and the phase shift structure 1022 is configured to perform phase shift processing to generate a preset phase difference. The intensity modulation structure 1021 can be a Mach-Zehnder interferometer, which is configured to re-allocate the light intensity by performing energy ratio allocation, phase shift, and interference on the light.

[0046] In this way, the third light component and the fourth light component are obtained through the intensity modulation structure 1021 and the phase shift structure 1022, the intensity ratio of the third light component and the fourth light component is the preset light splitting ratio, and the phase difference between the third light component and the fourth light component includes the preset phase difference.

[0047] The preset light splitting ratio is used to indicate the probability distribution of two orthogonal polarization state components in the quantum state of the final target light signal, and the two orthogonal polarization state components can be denoted as a horizontal polarization component and a vertical polarization component respectively. The preset light splitting ratio is used to indicate the light splitting ratio of the horizontal polarization component and the vertical polarization component.

[0048] In this way, the preset ratio of the light intensity of the first light source and the second light source, the preset light splitting ratio and the preset phase difference, and the beam combining structure 1023 are combined to perform beam combining, so that different polarization states can be prepared. The final polarization state is related to the preset ratio, the preset light splitting ratio, and the preset phase difference.

[0049] In some embodiments, as shown in FIG. 1, the intensity modulation structure 1021 includes: Figure 3 The first light splitting structure MMI1 is configured to receive the first light source s1 and the second light source s2, perform light splitting processing on the first light source s1 and the second light source s2 according to a 1:1 light splitting ratio, and output two light components (which can be denoted as a first intermediate light component m1 and a second intermediate light component m2). The first phase shift structure 1024 is configured to receive the two light components output by the first light splitting structure MMI1, perform phase shift on one or both of the two light components, and output two light components (which can be denoted as a third intermediate light component m3 and a fourth intermediate light component m4). The second light splitting structure MMI2 is configured to receive the two light components output by the first phase shift structure 1024, perform interference synthesis processing on the two light components, and output a first light component l1 and a second light component l2.

[0050] It should be noted that in the embodiments of the present disclosure, the first light splitting structure MMI1 and the second light splitting structure MMI2 can both be 2x2 multimode interference couplers, specifically 50:50 multimode interference couplers, so that in the embodiments of the present disclosure, Figure 3 ​In the embodiment, the first light splitting structure and the second light splitting structure are denoted as MMI1 and MMI2 respectively, and the first light splitting structure can also be referred to as a first multimode interference coupler, and the second light splitting structure can also be referred to as a second multimode interference coupler. The multimode interference coupler is a passive optical device based on the multimode interference principle, and is used to realize the distribution of light beams.

[0051] As shown in FIG. 1, the first light splitting structure MMI1, the first phase shift structure 1024, and the second light splitting structure MMI2 form a Mach-Zehnder interferometer. Figure 3

[0052] The first light splitting structure MMI1 is used to split the incident light (the first light source s1 and the second light source s2) to realize the first intermediate light component m1 and the second intermediate light component m2 with an equal split ratio of 50:50 in intensity; as a beam splitter, the first light splitting structure MMI1 ensures that the two light components output have the same mode characteristics and phase relationship.

[0053] The first phase shift structure 1024 can include two phase shifters, denoted as a first phase shifter T-O PS1 and a second phase shifter T-O PS2. In the first phase shift structure 1024, the first phase shifter T-O PS1 and the second phase shifter T-O PS2 can be operated in one of the following modes: one of the two phase shifters is operated and the other is not operated, or both of the two phase shifters are operated, so that the phase difference of the two phase shifts is the required phase difference. When only one of the two phase shifters is operated, the existence of the other phase shifter ensures that the optical paths of the two arms are consistent. The first phase shift structure 1024 affects the output light intensity distribution of the Mach-Zehnder interferometer by changing the phase difference between the two arms.

[0054] The second light splitting structure MMI2 recombines the two light beams after phase modulation and generates interference, and the light splitting ratio is also 50:50.

[0055] In this way, the intensity modulation structure 1021 realizes the first light component l1 and the second light component l2 with a preset light splitting ratio through the cooperation of the first light splitting structure MMI1, the first phase shift structure 1024, and the second light splitting structure MMI2. In the embodiment of the present disclosure, the preset light splitting ratio is 1:1.

[0056] In some embodiments, the phase shift structure 1022 includes two phase shifters, wherein: the phase shift structure 1022 is configured to receive the first light component l1 and the second light component l1 through the two phase shifters respectively, and perform phase shift processing on the received light components by using one or both of the two phase shifters to meet the preset phase difference.

[0057] As shown in FIG. 1, the first light splitting structure MMI1, the first phase shift structure 1024, and the second light splitting structure MMI2 form a Mach-Zehnder interferometer. Figure 3 ​As shown, two phase shifters in the phase shift structure 1022 are denoted as a third phase shifter T-0 PS3 and a fourth phase shifter T-0 PS4, the third phase shifter T-0 PS3 is connected with the first output end of the second light splitting structure MM I2, for receiving the first light component I1 and outputting a third light component I3; the fourth phase shifter T-0 PS4 is connected with the second output end of the second light splitting structure MM I2, for receiving the second light component I2 and outputting a fourth light component I4.

[0058] As the same as the first phase shift structure 1024, the two phase shifters in the phase shift structure 1022 can work in one or both to achieve a preset phase difference between the two, when one works, the other is used to ensure that the difference introduced in the processing of the phase shifter is consistent for the upper and lower arms.

[0059] In some embodiments, as shown, Figure 3 As shown, the light processing structure 102 further comprises: An input coupling structure 1025 (or an end face coupling light port for input or an end face coupler) for coupling receiving the first light source s1 and the second light source s2; An output coupling structure 1026 (or an end face coupling light port for output or an end face coupler) for coupling outputting the target optical signal o.

[0060] It should be noted that, as shown, Figure 3 As shown, the input coupling structure 1025 includes a first mode spot converter SSC1 and a second mode spot converter SSC2 corresponding to the two light sources, the first mode spot converter SSC1 is used for coupling receiving the first light source s1, and the second mode spot converter SSC2 is used for coupling receiving the second light source s2. The mode spot converter can optimize the transmission efficiency and mode matching of the optical signal, and realize efficient coupling by changing the shape and size of the light spot. In some embodiments, the mode spot converter can be realized by a one-dimensional grating (Grating Coupler, GC) coupler.

[0061] In some embodiments, the light beam combining structure 1023 is a two-dimensional grating (two Dimensional Grating Coupler, 2D-GC) coupler. In this case, the light beam combining structure 1023 and the output coupling structure 1026 are the same structure. That is, the output coupling structure 1026 is no longer needed, and the two-dimensional grating coupler realizes light beam combining and coupling output at the same time. After the two-dimensional grating coupler realizes polarization beam combining, the target optical signal will be directly outputted, and the output coupling structure 1026 is not needed to couple the target optical signal for output. In this way, the device area can be further reduced, and the miniaturization and integration of the chip can be realized.

[0062] In order to make the laser emitted by the first laser LD1 and the second laser LD2 be coupled into the light processing structure 102 as much as possible, and improve the utilization rate of photons, the embodiment of the present disclosure can further set a lens module 103 between the light emitting device 101 and the light processing structure 102. As shown in Figure 3 The quantum state encoding emission end 10 can further include: a lens module 103, configured to perform spot conversion on the first light source s1 and the second light source s2 to match the input coupling structure 1025.

[0063] As shown in Figure 3 Corresponding to the first light source s1 and the second light source s2, a first lens module 1031 is arranged between the first laser LD1 and the first spot converter SSC1, configured to converge the first light source s1 emitted by the first laser LD1, so that the spot size matches the first spot converter SSC1; a second lens module 1032 is arranged between the second laser LD2 and the second spot converter SSC2, configured to converge the second light source s2 emitted by the second laser LD2, so that the spot size matches the second spot converter SSC2.

[0064] As shown in Figure 3 The first lens module 1031 and the second lens module 1032 each include two lenses arranged in sequence. In this way, the lens close to the laser in the two lenses can play a role of beam collimation, and the lens close to the spot converter can converge the light beam, so as to reduce the loss of light in transmission and ensure that the light is accurately aligned with the corresponding spot converter. By reasonably designing the parameters of the two lenses, such as the curvature, diameter and spacing of the lenses, the coupling efficiency can be significantly improved.

[0065] In addition, other numbers of lenses can also be arranged, such as single lenses. Considering the coupling efficiency and alignment tolerance, the two lenses are more advantageous, and therefore, the two lenses are usually used. As shown in Figure 3 The lens in the lens module 103 is a convex mirror which has a converging effect on light.

[0066] It should be noted that, unlike the spot converter, the spot conversion function realized by the lens module 103 is essentially to indirectly complete the mode field matching through beam focusing and collimation, rather than directly changing the waveguide mode. The input light beam (the first light source or the second light source) is collimated into parallel light by the first lens, and then focused to the target end face (such as the first spot converter SSC1 or the second spot converter SSC2) by the second lens. The output spot size is controlled by the curvature and spacing of the lens, so as to realize the mode field diameter matching.

[0067] In the embodiment of the present disclosure, the lens module 103 is used to regulate and control the beam divergence angle, match the light beam output by the laser with the mode field of the receiving end coupler (the input coupling structure 1025), and reduce the loss in the process of light energy transmission.

[0068] In some embodiments, the quantum state encoding transmitting end 10 can further include: An isolation structure (not shown in the figure) is arranged between the light emitting device 101 and the lens module 103, or between the lens module 103 and the light processing structure 102, for isolating the light component reflected by the light processing structure 102.

[0069] It should be noted that, in order to avoid the adverse effects of reflected light, the embodiment of the present disclosure can also be provided with an isolation structure to ensure the unidirectional propagation of the light source. For example, an isolation structure is arranged between the light emitting device 101 and the lens module 103, which makes the light propagate unidirectionally, i.e., only allows the first light source s1 and the second light source s2 emitted by the light emitting device 101 to pass through, and blocks or absorbs the light propagating to the light emitting device 101 in the reverse direction. Alternatively, an isolation structure is arranged between the lens module 103 and the light processing structure 102, which makes the light propagate unidirectionally, i.e., only allows the first light source and the second light source transmitted by the lens module 103 to pass through, and blocks or absorbs the light propagating to the lens module 103 in the reverse direction.

[0070] Alternatively, if no lens structure 103 is arranged, the isolation structure is arranged between the light emitting device 101 and the light processing structure 102, which only allows the first light source and the second light source emitted by the light emitting device 101 to pass through, and blocks or absorbs the light propagating to the light emitting device 101 in the reverse direction.

[0071] The isolation structure can be an integral whole, or include two sub-isolation structures, wherein the first sub-isolation structure is used to make the first light source pass through unidirectionally, and the second sub-isolation structure is used to make the second light source pass through unidirectionally.

[0072] The working process of the quantum state encoding transmitting end 10 provided by the embodiment of the present disclosure will be described below in combination with the specific embodiments shown in the accompanying drawings. Figure 3

[0073] In the embodiment of the present disclosure, each phase shifter (the first phase shifter T-OP S1 to the fourth phase shifter T-OP S4) can be a thermo-optic phase shifter, which is a passive device. In the light processing structure 102, the connection between each device is an optical waveguide connection, to realize the transmission of the optical signal. For example, Figure 3 ​As shown, the output end of the first spot size converter SSC1 is connected to the first input end of the first light splitting structure MMI1, and the output end of the second spot size converter SSC2 is connected to the second input end of the first light splitting structure MMI1; the first output end of the first light splitting structure MMI1 is connected to the input end of the first phase shifter T-OP S1, and the second output end of the first light splitting structure MMI1 is connected to the input end of the second phase shifter T-OP S2; the output end of the first phase shifter T-OP S1 is connected to the first input end of the second light splitting structure MMI2, and the output end of the second phase shifter T-OP S2 is connected to the second input end of the second light splitting structure MMI2; the first output end of the second light splitting structure MMI2 is connected to the input end of the third phase shifter T-OP S3, and the second output end of the second light splitting structure MMI2 is connected to the input end of the fourth phase shifter T-OP S4; the output end of the third phase shifter T-OP S3 is connected to the first input end of the light combining structure 1023, the output end of the fourth phase shifter T-OP S4 is connected to the second input end of the light combining structure 1023, and the output end of the light combining structure 1023 is connected to the output end of the third spot size converter SSC3.

[0074] As shown in FIG. 1, the first laser LD1 and the second laser LD2 are connected to the first spot size converter SSC1 and the second spot size converter SSC2 respectively, and the output ends of the first spot size converter SSC1 and the second spot size converter SSC2 are connected to the first light splitting structure MMI1. Figure 3 As shown, by controlling one of the first laser LD1 and the second laser LD2 to emit a laser light source or both to emit a laser light source, different quantum states are prepared. The first laser LD1 and the second laser LD2 are the same lasers, and the light sources emitted by the two lasers are usually the same in phase and propagation mode.

[0075] The optical field of the first light source s1 output by the first laser LD1 and coupled into the first spot size converter SSC1 is denoted as E1, and the optical field of the second light source output by the second laser LD2 and coupled into the second spot size converter SSC2 is denoted as E1. The optical field refers to the distribution of electromagnetic waves (especially visible light or electromagnetic waves in the near optical frequency band) in space, including the vibration of electric field and magnetic field. The optical field is a vector field, containing amplitude, phase, frequency, polarization and other information. In this scheme, for the convenience of description and calculation, the optical field is simplified, mainly considering its amplitude information, and this simplification will not affect the final result.

[0076] In the above Figure 3 , the first light splitting structure MMI1 and the second light splitting structure MMI2 are both 50:50 MMIs, and the Jones matrix of the 50:50 MMI is , where i is the imaginary unit; the phase change factor introduced by the thermo-optic phase shifter is The phase difference between the first phase shifter T-OPS1 and the second phase shifter T-OPS2 is defined as θ1, which can be that the phase of the phase shift of the first phase shifter T-OPS1 is greater than that of the second phase shifter T-OPS2 by θ1, or vice versa, which is not specifically limited in this embodiment. In this embodiment, the first phase shifter T-OPS1 performs a phase shift of θ1 on the received light component, and the second phase shifter T-OPS1 does not perform a phase shift on the received light component. The phase difference between the third phase shifter T-OPS3 and the fourth phase shifter T-OPS4 is defined as a preset phase difference θ2. The light field of the third light component l3 output by the third phase shifter T-OPS3 is E3, and the light field of the fourth light component l4 output by the fourth phase shifter T-OPS4 is E4.

[0077] According to the above definitions and the Jones matrix of each device, the Jones vector can be calculated as follows:

[0078]

[0079] It is assumed that the preset light splitting ratio is 1:1, θ1 = , θ2 = 0. During the use of the chip device, θ1 = is adjusted by adjusting the first phase shifter T-OPS1 and the second phase shifter T-OPS2, and θ2=0 is adjusted by adjusting the third phase shifter T-OPS3 and the fourth phase shifter T-OPS4. In this embodiment, the phases moved by the first phase shifter T-OPS1 to the fourth phase shifter T-OPS2 are preset, and do not need to be set again during the operation.

[0080] The light intensity of the first light source and the second light source is characterized by the optical power. By controlling the operating current of the first laser LD1 and the second laser LD2, the light intensity ratio (optical power ratio) of the first light source and the second light source is 1:0, 0:1 and 0.5:0.5, respectively, that is, three preset ratios, and the corresponding light field ratios are E1:E1=1:0, 0:1 and 0.5:0.5. : .

[0081] It should be noted that, regardless of the preset ratio, the total light intensity of the first light source and the second light source remains unchanged, or the output power is the same, so as to ensure that the intensity of the target light signal obtained under different preset ratios is the same after processing by the light processing structure 102. For example, assuming that the light intensity of the first laser LD1 and the second laser LD2 is A when the full power output light source is output, when the preset ratio is 1:0, the first laser LD1 is turned on to emit laser light, and the first light source with an output light intensity of A is output, and the second laser LD2 is turned off and does not emit laser light, and the light intensity of the second light source is 0, and the total light intensity is A; when the preset ratio is 0:1, the first laser LD1 is turned off and does not emit laser light, and the light intensity of the first light source is 0, and the second laser LD2 is turned on to emit laser light, and the second light source with an output light intensity of A is output, and the total light intensity is A; when the preset ratio is 0.5:0.5, the first laser LD1 and the second laser LD2 are both turned on and emit laser light, and the first light source s1 and the second light source s2 with an output light intensity of A / 2 are output, and the total light intensity is A.

[0082] The three preset ratios correspond to three emission modes of the light emitting device 101, and in actual application, the light emitting device 101 is controlled to randomly emit laser light in one of the emission modes.

[0083] Corresponding to the preset ratio of 1:0, the following is obtained: , which indicates that the light fields of the third light component l3 and the fourth light component l4 input into the light beam combining structure 1023 are the same; corresponding to the preset ratio of 0:1, the following is obtained: , which indicates that there is a phase difference of π between the light fields of the third light component l3 and the fourth light component l4 input into the light beam combining structure 1023; and corresponding to the preset ratio of 0.5:0.5, the following is obtained: , which indicates that only the third light component l3 of the upper arm among the third light component l3 and the fourth light component l4 input into the light beam combining structure 1023 has a light field.

[0084] It should be further noted that the propagation mode of the photons can be a transverse electric (TE) mode or a transverse magnetic (TM) mode, the TE mode corresponds to a vertical polarization state (Vertical polarization), and the TM mode corresponds to a horizontal polarization state (Horizontal polarization). In some embodiments, the light beam combining structure 1023 can be a polarization beam splitting rotator, and thus is denoted as PSR in Figure 3 , which can realize the following functions: the transverse electric mode of one arm input is converted into a transverse magnetic mode, and the transverse electric mode of the other arm input remains unchanged and is output. The PSR is a light path reversible optical device, and by changing the input and output connection thereof, the PSR can realize beam combining and beam splitting, and in the embodiments of the present disclosure, the PSR is used for beam combining.

[0085] In the present scheme, in the case of the above three preset ratios, the light field of the corresponding first light source s1 and second light source s2 is generally TE mode, and is still TE mode after the coupling and phase shift processing, and after output through the light beam combining structure 1023, three polarization states are obtained: 、 、 , wherein, 、 correspond to 45-degree polarization state, -45-degree polarization state, respectively, which is a set of orthogonal polarization states.

[0086] In this way, the embodiment of the present disclosure only needs to control the emission mode of the first laser LD1 and the second laser LD2 randomly, so as to realize the random preparation of the above three polarization states, which can be used for QKD three-state protocol.

[0087] It should be noted that, as mentioned above, the light beam combining structure 1023 can include two propagation conversion paths to realize the conversion between TE mode propagation and TM mode propagation, so as to realize the rotation and beam combining of the third light component l3 and the fourth light component l4. As shown in Figure 3 , the upper arm (the arm connected with the third phase shifter T-OP S3) of the light beam combining structure 1023 includes a TE→TE conversion path (for converting the third light component l3), and the lower arm (the arm connected with the fourth phase shifter T-OP S4) of the light beam combining structure 1023 includes a TE→TM (for converting the fourth light component l4). On the two propagation conversion paths, the loss of “TE→TM” light energy is greater than that of “TE→TE”, so that the ratio of horizontal polarization component and vertical polarization component in the target optical signal o may not meet the requirement due to the loss of light energy. Therefore, as shown in Figure 3 , the light processing structure 102 can further include a loss adjustment structure 1027 connected between the light beam combining structure 1023 and the phase shift structure 1022; wherein: The loss adjustment structure 1027 is used for compensating the third light component l3 or the fourth light component l4, so that the loss of the third light component l3 and the fourth light component l4 is the same after passing through the light beam combining structure 1023.

[0088] It should be noted that the loss adjustment structure 1027 can be an optical attenuator, and therefore, in Figure 3 , it is represented by VOA, and the loss adjustment structure 1027 is used to balance the small polarization mode related loss caused by the polarization beam splitting rotator (in the PSR device, there is a small difference in transmission loss between TE mode→TE mode and TE mode→TM mode).

[0089] In this embodiment, the compensation process performed by the loss adjustment structure 1027 is specifically an attenuation process. Since the light energy loss from "TE→TM" is greater than that from "TE→TE" in this example, the VOA is set in the "TE→TM" path and the third phase shifter T. Between O PS3, the third optical component l3 is first attenuated by a preset amount before entering the PSR. Here, the preset amount is the portion where the optical energy loss from "TE→TM" is greater than that from "TE→TE". The attenuated third optical component l3 is then transmitted to the PSR. In this way, by pre-adding loss to the third optical component l3, loss balance is achieved, ensuring that the loss is the same in both propagation conversion paths of the PSR, thus guaranteeing the accuracy of the final target optical signal.

[0090] It should also be noted that, Figure 3 The scheme shown is only one specific implementation of the present disclosure. The present disclosure may also set the phase difference between the first phase shift structure 1024 and the phase shift structure 1022 to other suitable values, and calculate the prepared quantum state by using the light fields of the first light source and the second light source and the Jones matrix of each structure.

[0091] In summary, this disclosure provides a silicon-based QKD polarization state encoding chip architecture. For example... Figure 4 As shown, two identical lasers are set up, and the output light pulses (first light source s1 and second light source s2) are coupled into the mode converter SSC through a double lens to enter the optical processing structure 102 (silicon-based chip). The light signal coupled into the silicon-based chip is intensity modulated by the first-stage intensity modulator (i.e., intensity modulation structure 1021). The first-stage intensity modulator is a Mach-Zehnder interferometer structure, which includes two 50:50 MMIs (first beam splitting structure MMI1 and second beam splitting structure MMI2) and a set of phase shifters distributed in the upper and lower arms (first phase shifter TO PS1 and second phase shifter TO PS2). The two light components output from the intensity modulation structure 1021 are then processed by the phase shift structure 1022 before being output. The upper arm light signal then passes through an adjustable optical attenuator VOA. Finally, the light pulse signals from the two arms are combined by the polarization beam splitter PSR to obtain the target light signal o, which is output by the third mode converter SSC3.

[0092] This disclosure employs a photonic integration scheme, utilizing a hybrid integration technology of a III-V group (e.g., InP) laser chip and a silicon-based chip to achieve a miniaturized QKD transmitter that integrates the light source and polarization state encoding. The III-V group chip is coupled to the silicon-based chip, such as... Figure 4As shown, a set of convex lenses is used to transform the beam pattern output by the laser chip, so as to match the spot size that can be efficiently coupled by the silicon-based SSC, and thus realize efficient coupling of the optical signal. At the same time, the III-V laser chip and the silicon-based chip can also be monolithically integrated at the chip process level, so as to achieve the purpose of coupling the laser source and the encoding chip. The polarization state encoding chip architecture can realize three-state protocol QKD polarization state encoding according to the adjustment of the output light intensity of the lasers LD1 and LD2. In this way, on the one hand, the lens module is used for light source integration to reduce light source loss; on the other hand, the silicon-based passive device is used to avoid security vulnerabilities introduced by the modulation-related loss of the silicon-based modulator, and the silicon-based chip does not need radio frequency driving, which can also reduce the chip power consumption.

[0093] The embodiments of the present disclosure actively modulate the working states of the two lasers to realize that the light intensity is a random preset ratio, which has a high control speed in theory. In addition, the present scheme uses III-V chips combined with silicon-based passive chips, which has a simple process and a high yield, realizes light source integration, has a smaller miniaturization advantage, and is beneficial to the deployment of lightweight demand scenarios such as satellite QKD.

[0094] In another embodiment of the present disclosure, referring to ​ , a structural schematic diagram of an electronic device 20 provided by an embodiment of the present disclosure is shown. As shown in ​ , the electronic device 20 includes a control module 30 and the quantum state encoding transmitting end 10 of any one of the foregoing embodiments; wherein: The control module 30 is configured to control the light emitting device 101 to emit the first light source and the second light source according to a random preset ratio.

[0095] It should be noted that the control module 30 randomly sends a control signal to control the light emitting device 101 to emit the first light source and the second light source according to a random preset ratio. The following examples several control modes, but not limited to the following examples of the control mode.

[0096] In Example 1, it is assumed that the control signal is a 2-bit digital signal (assuming 10, 01, 11), the first laser LD1 and the second laser LD2 are controlled by the same control signal, and there are three preset ratios (1:0, 0:1, 0.5:0.5). When receiving the control signal 10, corresponding to the preset ratio 1:0, the first laser LD1 emits the first light source with full power intensity A, and the second laser LD2 is not turned on, and the second light source intensity is 0; when receiving the control signal 01, corresponding to the preset ratio 0:1, the first laser LD1 is not turned on, the first light source intensity is 0, and the second laser LD2 emits the second light source with full power intensity A; when receiving the control signal 11, corresponding to the preset ratio 0.5:0.5, the first laser LD1 and the second laser LD2 are both turned on, and both emit the second light source with half power intensity A / 2.

[0097] In Example 2, it is assumed that the control signal includes a first sub-control signal for controlling the first laser LD1 and a second sub-control signal for controlling the second laser LD2. The first sub-control signal and the second sub-control signal can both be 2-bit digital signals, and it is assumed that the value of the high bit is 0 to represent that the laser is turned on, and 1 to represent that the laser is turned off; the value of the low bit is 1 to represent that the laser emits the light source with full power, and 0 to represent that the laser emits the light source with half power. Then: when the first control sub-signal is 11 and the second control sub-signal is 00 or 01, the first laser LD1 is turned on and emits the first light source with full power intensity A, and since the high bit of the second control sub-signal is 0, the low bit is shielded, regardless of whether the low bit is 0 or 1, the second laser LD2 does not emit the light source; when the first control sub-signal is 00 or 01 and the second control sub-signal is 11, since the high bit of the first control sub-signal is 0, the low bit is shielded, regardless of whether the low bit is 0 or 1, the first laser LD1 does not emit the light source, and the second laser LD2 is turned on and emits the second light source with full power intensity A; when the first control sub-signal is 10 and the second control sub-signal is 10, the first laser LD1 and the second laser LD2 are both turned on, and emit the first light source and the second light source with half power intensity A / 2.

[0098] In this way, the control module 30 randomly issues control signals with different values to the light emitting device 101, to realize random preparation of quantum states. In actual application, other any feasible ways can be used for control, which is not limited in the above examples, and the embodiments of the present disclosure do not make specific limitations thereto.

[0099] The above description is only a preferred embodiment of the present disclosure, and is not intended to limit the protection scope of the present disclosure.

[0100] It should be noted that in the present disclosure, the terms "comprising", "including", or any other variant thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or structure that comprises a list of elements does not include only those elements, but can also include other elements not expressly listed or inherent to such process, method, article, or structure. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article, or structure that includes the element.

[0101] The above-mentioned sequence numbers of the embodiments of the present disclosure are only for description, and do not represent the advantages and disadvantages of the embodiments.

[0102] The methods disclosed in the several method embodiments provided by the present disclosure can be combined arbitrarily without conflict to obtain new method embodiments.

[0103] The features disclosed in the several product embodiments provided by the present disclosure can be combined arbitrarily without conflict to obtain new product embodiments.

[0104] The features disclosed in the several method or device embodiments provided by the present disclosure can be combined arbitrarily without conflict to obtain new method or device embodiments.

[0105] The above is only a specific implementation of the present disclosure, but the protection scope of the present disclosure is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present disclosure, which should be covered within the protection scope of the present disclosure.

Claims

1. A quantum state-encoded transmitter, characterized in that, Includes a light emitting device and a light processing structure; The light emitting device is used to emit a first light source and a second light source, wherein the light intensity ratio of the first light source and the second light source is a random preset ratio; The optical processing structure is used to receive the first light source and the second light source, perform correlation processing on the first light source and the second light source, and output a target optical signal; wherein, the correlation processing includes intensity modulation, phase shifting and beam combining, and the preset ratio and the correlation processing make the target optical signal satisfy the following: the light intensity of the target optical signal obtained under any preset ratio is the same.

2. The quantum state-encoded transmitter according to claim 1, characterized in that, The light emitting device includes: A first laser is used to emit the first light source; A second laser is used to emit the second light source; The first laser and the second laser are the same laser.

3. The quantum state-encoded transmitter according to claim 1, characterized in that, The light processing structure includes: An intensity modulation structure is used to receive the first light source and the second light source, and to perform spectral splitting on the first light source and the second light source according to a preset spectral splitting ratio to generate a first light component and a second light component. A phase-shifting structure is used to receive the first optical component and the second optical component, and perform phase-shifting processing on one or both of the first optical component and the second optical component according to a preset phase difference to generate a third optical component and a fourth optical component. An optical beam combining structure is used to receive the third optical component and the fourth optical component, and to perform beam combining processing on the third optical component and the fourth optical component to obtain the target optical signal.

4. The quantum state-encoded transmitter according to claim 3, characterized in that, The intensity modulation structure is a Mach-Zehnder interferometer.

5. The quantum state-encoded transmitter according to claim 3, characterized in that, The intensity modulation structure includes: The first beam splitting structure is used to receive the first light source and the second light source, and after splitting the first light source and the second light source according to a 1:1 beam splitting ratio, output two light components. The first phase-shifting structure is used to receive the two optical components output by the first beam splitting structure, and to phase-shift one or both of them to output the two optical components. The second beam splitter is used to receive the two optical components output by the first phase shifter, perform interference combining on the two, and output the first optical component and the second optical component.

6. The quantum state-encoded transmitter according to claim 5, characterized in that, Both the first beam-splitting structure and the second beam-splitting structure are multimode interference couplers.

7. The quantum state-encoded transmitter according to claim 3, characterized in that, The phase shift structure includes two phase shifters, wherein: The phase-shifting structure is used to receive the first optical component and the second optical component through the two phase shifters respectively, and to perform phase-shifting processing on the received optical components using one or both of the two phase shifters to satisfy the preset phase difference.

8. The quantum state-encoded transmitter according to claim 3, characterized in that, The light processing structure further includes: An input coupling structure is used to couple the reception of the first light source and the second light source; An output coupling structure is used to couple the output target optical signal.

9. The quantum state-encoded transmitter according to claim 8, characterized in that, The quantum state encoded transmitter also includes: The lens module is used to perform mode conversion on the first light source and the second light source to match the input coupling structure.

10. The quantum state-encoded transmitter according to claim 9, characterized in that, The quantum state encoded transmitter also includes: An isolation structure, located between the light emitting device and the lens module, or between the lens module and the light processing structure, is used to isolate the light component reflected by the light processing structure.

11. The quantum state-encoded transmitter according to any one of claims 8-10, characterized in that, The light beam combining structure is a two-dimensional grating coupler, and the light beam combining structure and the output coupling structure are the same structure.

12. The quantum state-encoded transmitter according to any one of claims 3-10, characterized in that, The optical beam structure is a polarization beam splitter rotator.

13. The quantum state-encoded transmitter according to any one of claims 1-10, characterized in that, Under different preset ratios, the total light intensity of the first light source and the second light source is the same.

14. The quantum state-encoded transmitter according to claim 13, characterized in that, The preset ratio is 1:0, 0:1, or 0.5:0.

5.

15. The quantum state-encoded transmitter according to any one of claims 1-10, 14, characterized in that, The light emitting device is a group III-V chip, and the light processing structure is a silicon-based passive chip.

16. An electronic device, characterized in that, Includes a control module and a quantum state-encoded transmitter as described in any one of claims 1 to 15; The control module is used to control the light emitting device to emit the first light source and the second light source according to the random preset ratio.

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