On-chip quantum state coding device and method based on multi-dimensional grating

Abstract

The invention provides an on-chip quantum state coding device and method based on a multi-dimensional grating, and relates to the technical field of quantum information, the on-chip quantum state coding device comprises a light path gating module, the light path gating module comprises a light path input end and a plurality of light path output ends, and the light path gating module is suitable for receiving a plurality of control signals at different moments according to the control signals at different moments; respectively gating a target light path output end in the plurality of light path output ends and closing other light path output ends; the multi-dimensional grating comprises a plurality of light beam input ends, and the plurality of light beam input ends are correspondingly connected with the plurality of light path output ends of the light path gating module; grating regions corresponding to different light beam input ends of the multi-dimensional grating have different preset angles. Based on different preset angles, the multi-dimensional grating can diffract light beams received by different light beam input ends to obtain different polarized light beams for the quantum key distribution system; and the coupling output end is arranged above the multi-dimensional grating and is suitable for coupling and outputting the plurality of diffracted beams to obtain a plurality of target quantum states so as to realize on-chip integrated quantum state coding.

Description

Technical Field

[0001] The present disclosure relates to the field of quantum information technology, and more specifically to an on-chip quantum state encoding device and method based on a multi-dimensional grating. Background Art

[0002] The quantum key distribution system is based on the quantum non-cloning and uncertainty principles, and can provide high-level information security protection to resist high-computing power cracking. Quantum key distribution often involves complex optical signal encoding. Currently, optical signal encoding is mainly achieved through the combined use of optical fiber devices, which usually have a large volume and high cost. Therefore, for small-volume, low-cost and highly stable quantum key distribution devices, the encoding of optical signals on optical chips is a technical problem that needs to be solved urgently. Summary of the invention

[0003] In view of this, the present disclosure provides an on-chip quantum state encoding device and method based on a multi-dimensional grating, which can realize quantum state encoding on an optical chip.

[0004] One aspect of the present disclosure provides an on-chip quantum state encoding device based on a multi-dimensional grating, the on-chip quantum state encoding device comprising: an optical path gating module, comprising an optical path input end and a plurality of optical path output ends, the optical path input end being adapted to obtain an initial light source, the optical path gating module being adapted to respectively select target optical path output ends among the plurality of optical path output ends and close other optical path output ends according to control signals at a plurality of different times, and based on the target optical path output ends selected at different times, converting the initial light source into a plurality of target light beams; wherein the control signal is a random number according to a quantum key distribution system. The obtained multidimensional grating comprises a plurality of beam input ends, and the plurality of beam input ends are correspondingly connected to the plurality of light path output ends of the light path gating module; the grating areas corresponding to different beam input ends of the multidimensional grating have different preset angles; based on the different preset angles, the multidimensional grating can diffract the beams received by the different beam input ends to obtain beams of different polarizations for a quantum key distribution system; a coupling output end is arranged above the multidimensional grating, and is suitable for coupling and outputting the plurality of diffracted beams to obtain a plurality of target quantum states, so as to realize on-chip integrated quantum state encoding.

[0005] According to an embodiment of the present disclosure, the above-mentioned optical path gating module includes silicon or lithium niobate photonic integrated materials.

[0006] According to an embodiment of the present disclosure, the multi-dimensional grating comprises silicon or lithium niobate photonic integrated material.

[0007] According to an embodiment of the present disclosure, the coupling output end includes a single-mode optical fiber.

[0008] According to an embodiment of the present disclosure, the multidimensional grating includes a four-dimensional grating; the four-dimensional grating includes four light beam input ends; and the on-chip quantum state encoding device obtains four target quantum states based on the four-dimensional grating.

[0009] According to an embodiment of the present disclosure, the grating areas corresponding to different light beam input ends of the above-mentioned four-dimensional grating have different preset angles; the included angle between the above-mentioned preset angles is 45 degrees; the polarization angles of the above-mentioned four target quantum states are 0 degrees, 45 degrees, 90 degrees and 135 degrees respectively.

[0010] According to an embodiment of the present disclosure, the above-mentioned optical path gating module also includes an optical beam splitter and a plurality of first intensity modulators; the above-mentioned optical beam splitter includes a plurality of beam splitting ends, and the above-mentioned optical beam splitter is suitable for splitting the above-mentioned initial light source to obtain a plurality of initial light beams; the above-mentioned plurality of first intensity modulators are respectively connected to the plurality of beam splitting ends of the above-mentioned optical beam splitter and the plurality of optical path output ends of the above-mentioned optical path gating module, and are suitable for respectively enabling the above-mentioned target optical path output ends and closing other optical path output ends according to the above-mentioned plurality of control signals at different times, and based on the target optical path output ends enabled at different times, inputting the initial light beam of the corresponding beam splitting end into the above-mentioned corresponding light beam input end to obtain the corresponding target light beam.

[0011] According to an embodiment of the present disclosure, the above-mentioned optical path selection module also includes an optical beam splitter 1, an optical beam splitter 2, an optical beam splitter 3 and four second intensity modulators; the above-mentioned optical beam splitter 1 is suitable for splitting the above-mentioned initial light source to obtain a first light beam and a second light beam; the above-mentioned optical beam splitter 2 is suitable for splitting the above-mentioned first light beam to obtain a third light beam and a fourth light beam; the above-mentioned optical beam splitter 3 is suitable for splitting the above-mentioned second light beam to obtain a fifth light beam and a sixth light beam; the above-mentioned four second intensity modulators are suitable for receiving the above-mentioned third light beam, the above-mentioned fourth light beam, the above-mentioned fifth light beam and the above-mentioned sixth light beam respectively; it is also suitable for respectively selecting the target second intensity modulators in the above-mentioned four second intensity modulators and closing the other second intensity modulators according to the control signals at the above-mentioned multiple different times, and based on the target second intensity modulators selected at different times, inputting the light beam received by the above-mentioned target second intensity modulator into the above-mentioned corresponding light beam input end to obtain the corresponding target light beam.

[0012] According to an embodiment of the present disclosure, the above-mentioned optical path selection module includes an optical switch; the above-mentioned optical switch is connected to the above-mentioned multiple optical path output ends, and is suitable for selecting the above-mentioned target optical path output ends and closing other optical path output ends according to the above-mentioned multiple control signals at different times.

[0013] Another aspect of the present disclosure discloses an on-chip quantum state encoding method based on the above-mentioned on-chip quantum state encoding device based on a multidimensional grating, wherein the above-mentioned on-chip quantum state encoding device comprises an optical path gating module, a multidimensional grating and a coupling output end, wherein the above-mentioned optical path gating module comprises an optical path input end and a plurality of optical path output ends, wherein the above-mentioned multidimensional grating comprises a plurality of light beam input ends, wherein the plurality of light beam input ends are correspondingly connected to the plurality of light path output ends of the above-mentioned optical path gating module; wherein the above-mentioned coupling output end is arranged above the above-mentioned multidimensional grating; wherein the above-mentioned on-chip quantum state encoding method comprises: utilizing the above-mentioned optical path input end to obtain an initial light source; utilizing the above-mentioned optical path gating module to respectively select the above-mentioned light path input end according to control signals at a plurality of different times; wherein the above-mentioned light path gating module comprises a plurality of light beam input ends, wherein the plurality of light beam input ends are correspondingly connected to the plurality of light path output ends of the above-mentioned light path gating module ... The target optical path output end among the multiple optical path output ends is selected and other optical path output ends are closed, and based on the target optical path output ends that are selected at different times, the above-mentioned initial light source is converted into multiple target light beams; wherein the above-mentioned control signal is obtained according to the random number of the quantum key distribution system; using the above-mentioned multidimensional grating, based on the above-mentioned different preset angles, the light beams received by the above-mentioned different light beam input ends can be diffracted to obtain different polarized light beams for the quantum key distribution system; the grating areas corresponding to the different light beam input ends of the above-mentioned multidimensional grating have different preset angles; using the above-mentioned coupled output end, the above-mentioned multiple diffracted light beams are coupled out to obtain multiple target quantum states, so as to realize on-chip integrated quantum state encoding.

[0014] The on-chip quantum state encoding device based on a multidimensional grating in the embodiment of the present disclosure has different preset angles for the grating areas corresponding to different beam input ends of the multidimensional grating. The multidimensional grating diffracts the light beams received at different beam input ends and outputs them from the coupled output end, which can directly generate two pairs of target quantum states of orthogonal polarization states. Compared with the conventional discrete device solution, the on-chip quantum state encoding device based on a multidimensional grating in the embodiment of the present disclosure can be processed on a mature photonic integration platform such as silicon-based or thin-film lithium niobate to achieve on-chip integration, significantly reducing the volume and cost of polarization encoding devices, so as to be applied to small-volume, low-cost and highly stable quantum key distribution devices. Compared with the conventional on-chip integration solution, the embodiment of the present disclosure does not rely on the adjustment of the phase difference in the two-component vector synthesis, and directly uses the grating area angle diffraction of the multidimensional grating to generate different polarization states, and the power consistency of different polarization states is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings.

[0016] Figure 1 The figure schematically shows a high-speed polarization control scheme of all-fiber in the related art.

[0017] Figure 2 The on-chip polarization coding structure in the related art is schematically shown.

[0018] Figure 3 A table schematically shows an example of polarization coding of an on-chip polarization coding structure in the related art.

[0019] Figure 4 A silicon-based polarization control device in the related art is schematically shown.

[0020] Figure 5 The structural diagram of an on-chip quantum state encoding device based on a multi-dimensional grating according to an embodiment of the present disclosure is schematically shown.

[0021] Figure 6 The structural diagram of the optical path gating module according to the embodiment of the present disclosure is schematically shown.

[0022] Figure 7 The structural diagram of an on-chip quantum state encoding device based on a multi-dimensional grating according to another embodiment of the present disclosure is schematically shown.

[0023] Figure 8 A coding table of an on-chip quantum state coding device based on a multi-dimensional grating according to another embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0025] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0026] 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 should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0027] When using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, and C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc. When using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, or C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.

[0028] It should also be noted that the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "back", "left", "right", etc., are only reference directions of the drawings and are not intended to limit the scope of protection of the present disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present disclosure.

[0029] The high-speed polarization modulation of a light beam is generally performed in the following manner: generating two components of light with orthogonal polarization states, adjusting the phase difference between the two components of light, and synthesizing the polarization vectors of the two components of light with adjusted phase difference. The amplitudes of the two components of light are expressed as and , the phases of the two components of light are expressed as and , the static phase difference is expressed as , the dynamic phase difference generated by the high-speed phase modulation device is expressed as ( and represents the phase modulation amount of the two-component light by the high-speed phase modulator), by adjusting the amplitude of the two-component light and , or dynamic phase difference , both can produce high-speed polarization modulation.

[0030] Figure 1 The figure schematically shows a high-speed polarization control scheme of all-fiber in the related art.

[0031] like Figure 1 As shown, in the related art, a fiber-optic optical circulator (Cir), a polarization beam splitter (PBS-A) and a phase modulator (PM) are used to generate linear polarized light in the horizontal direction and linear polarized light in the vertical direction, and then polarization synthesis is performed. Among them, the amplitudes of the two components of light are , static phase difference , the phase modulator is loaded with phases of 0, , and The corresponding voltage signals produce dynamic phase differences: , , and , respectively generating 45 degree linear polarized light, right-handed circularly polarized light, 135 degree linear polarized light and left-handed circularly polarized light, meeting the requirements of the quantum key distribution system. Specifically, a polarization beam splitter is used to generate two orthogonal polarization component lights, a phase modulator is used to adjust the phase difference, and a polarization beam splitter is used for vector synthesis.

[0032] Figure 2 The on-chip polarization coding structure in the related art is schematically shown.

[0033] Figure 3 A table schematically shows an example of polarization coding of an on-chip polarization coding structure in the related art.

[0034] like Figure 2 As shown, in the related art, by high-speed adjustment , and , achieving high-speed polarization modulation. , to change the amplitude of the two components of light and , by adjusting and , to change the dynamic phase difference of the two components of light .

[0035] like Figure 2 and Figure 3 As shown, when When , the light is transmitted from path 3, that is , ,get state; when When the light is transmitted from path 4, that is , ,get state; when When ,adjust ,get state; when When ,adjust ,get By adjusting the amplitude of the two components of light simultaneously and , and the dynamic phase difference between the two components , achieving high-speed polarization modulation.

[0036] Figure 4 A silicon-based polarization control device in the related art is schematically shown.

[0037] like Figure 4 As shown, in the related art, a phase shifter is prepared based on a phase change thin film material. The two orthogonally polarized light signals in the input optical fiber are converted into a TE0 mode with the same phase and intensity by a polarization rotation beam splitter 100. The first optical beam splitter 210, the second optical beam splitter 220, the first phase shifter 310 and the second phase shifter 320 constitute a Mach-Zehnder interferometer. The phase difference is generated by the first phase shifter 310 and the second phase shifter 320 to adjust the output light intensity of the second optical beam splitter 220, that is, the amplitude of the two components of light. and The second optical beam splitter 220, the polarization rotation beam combiner 400, the third phase shifter 330 and the fourth phase shifter 340 constitute a polarization vector synthesis unit. No voltage is applied to the electrodes of the fourth phase shifter 340, and no additional phase shift is generated except for the change in the optical path difference caused by the fourth phase shifter 340 itself. Dynamic phase difference is generated by adjusting the third phase shifter 330. By adjusting the amplitude of the two components of light simultaneously and , and the dynamic phase difference between the two components , achieving high-speed polarization modulation.

[0038] The quantum key distribution system is a secure communication protocol based on the principles of quantum mechanics, which uses properties such as quantum superposition and quantum entanglement to generate and distribute keys. The most commonly used quantum key distribution protocol is the BB84 protocol, which encodes information based on the polarization state of a single photon. The sender and receiver use different polarization bases to measure the polarization state of a single photon, and establish a secure key by comparing the measurement results. In the quantum key distribution system, in theory, except for the coding state, the remaining dimensions need to be indistinguishable, that is, in theory the encoder should not introduce power differences. For example, a polarization-encoded system, which encodes based on two pairs of orthogonal polarization states, requires that the power of the four polarization states be consistent.

[0039] In the related art, the power difference can be improved by modifying the coding rate formula, but the system performance such as the coding rate will be reduced.

[0040] In the related art, the polarization encoder in the form of a discrete device has good modulation performance and a small power difference between photons in different polarization states, but the device is large in size and high in cost.

[0041] In the related art, a polarization encoder in the form of a chip is used to achieve polarization modulation by adjusting the amplitude and dynamic phase difference of the two components of light. Silicon-based high-speed phase modulation devices are based on the plasma dispersion effect and have the advantage of high bandwidth, but they generally have the problem of large modulation-related losses, that is, when different phases are modulated, their attenuation is also different accordingly. Therefore, when silicon-based high-speed phase modulation devices modulate different polarization states, there are differences in the attenuation of photons, resulting in power differences in different polarization states. It is not clear whether the problem of power differences in different polarization states can be solved by realizing phase shifters based on phase change thin film materials, but it is known that the realization of phase shifters based on phase change thin film materials is a new process, which requires modification of the process and related processing equipment compared to conventional silicon photonic processes.

[0042] The present disclosure provides an on-chip quantum state encoding device and method based on a multi-dimensional grating, in order to solve at least one of the above technical problems.

[0043] Figure 5 The structural diagram of an on-chip quantum state encoding device based on a multi-dimensional grating according to an embodiment of the present disclosure is schematically shown.

[0044] like Figure 5 As shown, the on-chip quantum state encoding device based on a multi-dimensional grating includes an optical path gating module and a multi-dimensional grating.

[0045] According to an embodiment of the present disclosure, an optical path gating module includes an optical path input end and multiple optical path output ends, the optical path input end is suitable for obtaining an initial light source, and the optical path gating module is suitable for respectively selecting target optical path output ends among the multiple optical path output ends and closing other optical path output ends according to control signals at multiple different times, and converting the initial light source into multiple target light beams based on the target optical path output ends selected at different times; a multidimensional grating includes multiple beam input ends, and the multiple beam input ends are correspondingly connected to the multiple optical path output ends of the optical path gating module; the grating areas corresponding to different beam input ends of the multidimensional grating have different preset angles; based on different preset angles, the multidimensional grating can diffract the light beams received by different beam input ends to obtain different polarized light beams for a quantum key distribution system; the multidimensional grating is suitable for respectively diffracting the multiple target light beams based on the target optical path output ends selected at different times to obtain multiple diffracted light beams; a coupling output end is arranged above the multidimensional grating, and is suitable for coupling out the multiple diffracted light beams to obtain multiple target quantum states, so as to realize on-chip integrated quantum state encoding.

[0046] According to an embodiment of the present disclosure, the control signal is obtained according to the random number of the quantum key distribution system. The sender selects the polarization direction of the quantum state according to the quantum random number generator, and the receiver also randomly selects the measurement basis vector for measurement.

[0047] The on-chip quantum state encoding device based on a multidimensional grating of the disclosed embodiment has different preset angles for the grating areas corresponding to different beam input ends of the multidimensional grating. The multidimensional grating diffracts the beams received at different beam input ends and outputs them from the coupled output end, which can directly generate two pairs of target quantum states of orthogonal polarization states. The on-chip quantum state encoding device based on a multidimensional grating of the disclosed embodiment can be processed on a mature photonic integration platform such as silicon-based or thin-film lithium niobate to achieve on-chip integration, reducing the volume and cost of polarization encoding devices, so as to be applied to small-volume, low-cost and highly stable quantum key distribution devices. The disclosed embodiment is different from the conventional solution of adjusting the phase difference of the two components (different polarization states require the phase modulator to load different phases, and the presence of different phases in carrier dispersion modulators such as silicon-based will also cause loss changes, thereby leading to power differences in different quantum states). The quantum state power of the disclosed embodiment has good consistency.

[0048] According to an embodiment of the present disclosure, the light beam input end is an on-chip waveguide. The multi-dimensional grating region is obtained by etching in the on-chip waveguide.

[0049] According to the embodiments of the present disclosure, quantum states with different polarization angles can be obtained through a multidimensional grating, and on-chip quantum state encoding can be achieved without relying on the two-component phase difference adjustment method, and there is no problem of phase modulation introducing quantum state power differences.

[0050] According to the embodiment of the present disclosure, the on-chip devices are connected in the form of on-chip waveguides, and according to a control signal, one beam input end is selected and the other beam input ends are closed. Each beam input end obtains a beam with the same mode.

[0051] According to an embodiment of the present disclosure, the optical path gating module may be a silicon or lithium niobate photonic integrated material.

[0052] According to an embodiment of the present disclosure, the multi-dimensional grating may be silicon or lithium niobate photonic integrated material.

[0053] According to an embodiment of the present disclosure, the coupling output end may be a single-mode optical fiber.

[0054] According to an embodiment of the present disclosure, the multidimensional grating may be a four-dimensional grating; the four-dimensional grating includes four light beam input ends; and the on-chip quantum state encoding device is based on the four-dimensional grating to obtain four target quantum states.

[0055] In one example, the four-dimensional grating includes a first beam input end, a second beam input end, a third beam input end, and a fourth beam input end. The grating areas corresponding to different beam input ends of the four-dimensional grating have different preset angles. Based on the first preset angle, the four-dimensional grating diffracts the first target beam received at the first beam input end to the coupling output end above, and outputs the first target quantum state. Based on the second preset angle, the four-dimensional grating diffracts the second target beam received at the second beam input end to the coupling output end above, and outputs the second target quantum state. Based on the third preset angle, the four-dimensional grating diffracts the third target beam received at the third beam input end to the coupling output end above, and outputs the third target quantum state. Based on the fourth preset angle, the four-dimensional grating diffracts the fourth target beam received at the fourth beam input end to the coupling output end above, and outputs the fourth target quantum state.

[0056] According to an embodiment of the present disclosure, the grating areas corresponding to different light beam input ends of the four-dimensional grating have different preset angles; the included angle between the preset angles is 45 degrees; the polarization angles of the four target quantum states are 0 degrees, 45 degrees, 90 degrees and 135 degrees respectively.

[0057] According to an embodiment of the present disclosure, different preset angles are designed by adjusting the process parameters of the four-dimensional grating. For example, the first preset angle can be designed to be 0 degrees, the second preset angle can be designed to be 45 degrees, the third preset angle can be designed to be 90 degrees, and the fourth preset angle can be designed to be 135 degrees. After the four-dimensional grating diffracts the target light beam to the optical fiber above the on-chip waveguide at the corresponding preset angle, the corresponding polarization angles of the first target quantum state are 0 degrees, the second target quantum state are 45 degrees, the third target quantum state are 90 degrees, and the fourth target quantum state are 135 degrees.

[0058] Figure 6 The structural diagram of the optical path gating module according to the embodiment of the present disclosure is schematically shown.

[0059] like Figure 6 As shown, the optical path gating module further includes an optical beam splitter and a plurality of first intensity modulators. In one example, the plurality of first intensity modulators may be high-speed intensity modulator 1, high-speed intensity modulator 2, high-speed intensity modulator 3 and high-speed intensity modulator 4.

[0060] According to an embodiment of the present disclosure, the optical beam splitter includes multiple beam splitting ends, and the optical beam splitter is suitable for splitting an initial light source to obtain multiple initial light beams; multiple first intensity modulators are respectively connected to the multiple beam splitting ends and the multiple light path output ends, and are suitable for selecting the target light path output end and closing other light path output ends according to a control signal, so as to input the initial light beam into the target light beam input end to obtain the target light beam.

[0061] According to an embodiment of the present disclosure, the optical beam splitter may be an on-chip multi-mode interferometer.

[0062] According to an embodiment of the present disclosure, the first intensity modulator may be an on-chip Mach-Zehnder interferometer.

[0063] According to the embodiments of the present disclosure, multiple initial light beams pass through multiple high-speed intensity modulators to obtain modulated light beams with the same pattern, so that the light beams obtained at the multiple light beam input ends have the same pattern.

[0064] Figure 7 The structural diagram of an on-chip quantum state encoding device based on a multi-dimensional grating according to another embodiment of the present disclosure is schematically shown.

[0065] like Figure 7 As shown, the optical path gating module also includes optical beam splitter 1, optical beam splitter 2 and optical beam splitter 3. In one example, the four second intensity modulators include high-speed intensity modulator 1, high-speed intensity modulator 2, high-speed intensity modulator 3 and high-speed intensity modulator 4. Optical beam splitter 1 is connected to the input waveguide to obtain the initial light source, and the coupled output end is the output optical fiber. All on-chip devices are connected in the form of on-chip waveguides.

[0066] According to an embodiment of the present disclosure, the optical beam splitter 1 is suitable for splitting the initial light source to obtain a first light beam and a second light beam; the optical beam splitter 2 is suitable for splitting the first light beam to obtain a third light beam and a fourth light beam; the optical beam splitter 3 is suitable for splitting the second light beam to obtain a fifth light beam and a sixth light beam; the four second intensity modulators are suitable for receiving the third light beam, the fourth light beam, the fifth light beam, and the sixth light beam, respectively; and are also suitable for selecting a target second intensity modulator among the four second intensity modulators and turning off other second intensity modulators according to a control signal, so as to input the light beam received by the target second intensity modulator into the target light beam input end to obtain the target light beam.

[0067] In one example, optical beam splitter 1 can be an on-chip multimode interferometer made of silicon, optical beam splitter 2 can be an on-chip multimode interferometer made of silicon, and optical beam splitter 3 can be an on-chip multimode interferometer made of silicon. High-speed intensity modulator 1 can be an on-chip Mach-Zehnder interferometer, high-speed intensity modulator 2 can be an on-chip Mach-Zehnder interferometer, high-speed intensity modulator can be an on-chip Mach-Zehnder interferometer, and high-speed intensity modulator 4 can be an on-chip Mach-Zehnder interferometer. The on-chip Mach-Zehnder interferometer can include a multimode interferometer, a low-speed phase shifter, and a high-speed phase shifter, and the material is silicon-based, wherein the low-speed phase shifter is a thermo-optical phase shifter, and the high-speed phase shifter is a carrier dispersion modulator.

[0068] In one example, the multidimensional grating can be a four-dimensional grating, including a first beam input end, a second beam input end, a third beam input end, and a fourth beam input end, which are respectively connected to four second intensity modulators. Each beam input end includes an on-chip waveguide, the material of which is silicon, and a grating region is etched on the on-chip waveguide. The ports of adjacent beam input ends have a 45-degree angle with the grating region, and the ports of the four beam input ends have a 0-degree, 45-degree, 90-degree, and 135-degree angle with the grating region, respectively.

[0069] Figure 8 A coding table of an on-chip quantum state coding device based on a multi-dimensional grating according to another embodiment of the present disclosure is schematically shown.

[0070] like Figure 8 As shown, in one example, the four second intensity modulators are respectively selected according to the control signal. When the high-speed intensity modulator 1 is light-transmitted, the other modulators are extinguished, and the first target quantum state with a polarization angle of 0 degrees is obtained; when the high-speed intensity modulator 2 is light-transmitted, the other modulators are extinguished, and the second target quantum state with a polarization angle of 45 degrees is obtained; when the high-speed intensity modulator 3 is light-transmitted, the other modulators are extinguished, and the third target quantum state with a polarization angle of 90 degrees is obtained; when the high-speed intensity modulator 4 is light-transmitted, the other modulators are extinguished, and the fourth target quantum state with a polarization angle of 135 degrees is obtained. According to at least four random numbers, two pairs of target quantum states with orthogonal polarization states can be obtained, which meets the BB84 protocol requirements of the quantum key distribution system.

[0071] According to an embodiment of the present disclosure, the optical path gating module includes an optical switch; the optical switch connects multiple optical path output ends and is suitable for gating a target optical path output end and closing other optical path output ends according to a control signal.

[0072] The present disclosure also provides an on-chip quantum state encoding method based on the above-mentioned on-chip quantum state encoding device.

[0073] According to an embodiment of the present disclosure, an on-chip quantum state encoding device includes an optical path gating module, a multidimensional grating and a coupled output end, the optical path gating module includes an optical path input end and multiple optical path output ends, the multidimensional grating includes multiple light beam input ends, and the multiple light beam input ends are correspondingly connected to the multiple light path output ends of the optical path gating module; the coupled output end is arranged above the multidimensional grating. The on-chip quantum state encoding method includes: using an optical path input end to obtain an initial light source; using an optical path selection module, according to control signals at multiple different times, respectively selecting target optical path output ends among multiple optical path output ends and closing other optical path output ends, and based on the target optical path output ends selected at different times, converting the initial light source into multiple target light beams; wherein the control signal is obtained according to the random number of the quantum key distribution system; using a multidimensional grating, based on different preset angles, the light beams received at different light beam input ends can be diffracted to obtain different polarized light beams for the quantum key distribution system; the grating areas corresponding to different light beam input ends of the multidimensional grating have different preset angles; using a coupled output end, multiple diffracted light beams are coupled out to obtain multiple target quantum states, so as to realize on-chip integrated quantum state encoding.

[0074] The on-chip quantum state encoding device based on a multidimensional grating of the disclosed embodiment can be processed on a mature photonic integration platform such as silicon-based or thin-film lithium niobate, achieving on-chip integration and reducing the volume and cost of polarization encoding devices. The light beam is diffracted through different beam input ends of the multidimensional grating and coupled out by a single-mode optical fiber to directly generate two pairs of orthogonal polarization states of the target quantum state.

[0075] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. An on-chip quantum state encoding device based on a multidimensional grating, characterized in that: The on-chip quantum state encoding device comprises: An optical path gating module, comprising an optical path input end and a plurality of optical path output ends, wherein the optical path input end is adapted to obtain an initial light source, and the optical path gating module is adapted to respectively select a target optical path output end among the plurality of optical path output ends and close other optical path output ends according to control signals at a plurality of different times, and based on the target optical path output ends selected at different times, convert the initial light source into a plurality of target light beams; wherein the control signal is obtained according to a random number of a quantum key distribution system; A multidimensional grating, comprising a plurality of beam input ends, wherein the plurality of beam input ends are correspondingly connected to the plurality of light path output ends of the light path gating module; the grating areas corresponding to different beam input ends of the multidimensional grating have different preset angles; based on the different preset angles, the multidimensional grating can diffract the beams received by the different beam input ends to obtain different polarized beams for a quantum key distribution system; The coupling output end is arranged above the multi-dimensional grating and is suitable for coupling out the multiple diffracted light beams to obtain multiple target quantum states to realize on-chip integrated quantum state encoding.

2. The on-chip quantum state encoding device according to claim 1, characterized in that: The optical path gating module comprises silicon or lithium niobate photonic integrated material.

3. The on-chip quantum state encoding device according to claim 1, characterized in that: The multi-dimensional grating comprises silicon or lithium niobate photonic integrated material.

4. The on-chip quantum state encoding device according to claim 1, characterized in that: The coupled output end includes a single-mode optical fiber.

5. The on-chip quantum state encoding device according to claim 1, characterized in that: The multi-dimensional grating includes a four-dimensional grating; the four-dimensional grating includes four light beam input ends; the on-chip quantum state encoding device obtains four target quantum states based on the four-dimensional grating.

6. The on-chip quantum state encoding device according to claim 5, characterized in that: The grating areas corresponding to different light beam input ends of the four-dimensional grating have different preset angles; the included angle between the preset angles is 45 degrees; the polarization angles of the four target quantum states are 0 degrees, 45 degrees, 90 degrees and 135 degrees respectively.

7. The on-chip quantum state encoding device according to claim 1, characterized in that: The optical path gating module also includes an optical beam splitter and a plurality of first intensity modulators; The optical beam splitter comprises a plurality of beam splitting ends, and the optical beam splitter is adapted to split the initial light source to obtain a plurality of initial light beams; The multiple first intensity modulators are respectively connected to the multiple beam splitting ends of the optical beam splitter and the multiple optical path output ends of the optical path selection module, and are suitable for respectively selecting the target optical path output ends and closing other optical path output ends according to the multiple control signals at different times, and based on the target optical path output ends selected at different times, inputting the initial light beam of the corresponding beam splitting end into the corresponding light beam input end to obtain the corresponding target light beam.

8. The on-chip quantum state encoding device according to claim 5, characterized in that: The optical path gating module further includes optical beam splitter 1, optical beam splitter 2, optical beam splitter 3 and four second intensity modulators; The optical beam splitter 1 is adapted to split the initial light source into a first light beam and a second light beam; The optical beam splitter 2 is adapted to split the first light beam into a third light beam and a fourth light beam; The optical beam splitter 3 is adapted to split the second light beam into a fifth light beam and a sixth light beam; The four second intensity modulators are adapted to receive the third light beam, the fourth light beam, the fifth light beam, and the sixth light beam respectively; It is also suitable for respectively selecting the target second intensity modulators among the four second intensity modulators and turning off the other second intensity modulators according to the control signals at different times, and based on the target second intensity modulators selected at different times, inputting the light beam received by the target second intensity modulator into the corresponding light beam input end to obtain the corresponding target light beam.

9. The on-chip quantum state encoding device according to claim 1, characterized in that: The optical path gating module includes an optical switch; The optical switch is connected to the multiple optical path output ends, and is suitable for respectively switching on the target optical path output ends and closing other optical path output ends according to the multiple control signals at different times.

10. An on-chip quantum state encoding method based on the on-chip quantum state encoding device based on a multi-dimensional grating as claimed in any one of claims 1 to 9, characterized in that: The on-chip quantum state encoding device comprises an optical path gating module, a multidimensional grating and a coupling output end, wherein the optical path gating module comprises an optical path input end and a plurality of optical path output ends, and the multidimensional grating comprises a plurality of light beam input ends, and the plurality of light beam input ends are correspondingly connected to the plurality of light path output ends of the optical path gating module; The coupling output end is arranged above the multi-dimensional grating; The on-chip quantum state encoding method comprises: Using the optical path input end, obtaining an initial light source; Using the optical path gating module, according to control signals at multiple different times, target optical path output ends among the multiple optical path output ends are respectively selected and other optical path output ends are closed, and based on the target optical path output ends selected at different times, the initial light source is converted into multiple target light beams; wherein the control signal is obtained according to a random number of a quantum key distribution system; By using the multidimensional grating, based on the different preset angles, the light beams received by the different light beam input ends can be diffracted to obtain light beams with different polarizations for a quantum key distribution system; the grating areas corresponding to the different light beam input ends of the multidimensional grating have different preset angles; The multiple diffracted light beams are coupled out using the coupled output end to obtain multiple target quantum states, so as to realize on-chip integrated quantum state encoding.

Images