On-chip encoder and method capable of realizing low power difference

Abstract

According to the on-chip encoder capable of realizing low power difference and the encoding method, the initial phase adjusting module used for adjusting the initial phase is introduced, so that different polarization state combinations are allowed to be obtained by scanning the initial phase, and the polarization state combination with low power difference is selected; therefore, the power difference of different polarization states obtained by the system is effectively reduced, and the tolerance to process deviation is improved.

Description

Technical Field

[0001] The present invention relates to the field of quantum information technology, and in particular to an on-chip encoder and method capable of achieving low power difference. Background Art

[0002] Quantum key distribution (QKD) is based on the principles of quantum mechanics. Due to the quantum non-cloning and uncertainty principle, it is a theoretically provable unconditionally secure key distribution system. With the development of quantum key distribution technology, providing small-volume, low-cost and highly stable quantum key distribution equipment will be more competitive. Quantum key distribution often involves more complex optical signal encoding and decoding. Currently, its encoding and decoding are often combined based on traditional optical fiber devices, which are large in size and high in cost. Realizing the encoding and decoding of optical signals on optical chips is one of the important solutions for small-volume, low-cost and highly stable quantum key distribution equipment.

[0003] The basic principle of high-speed polarization modulation is to generate two components of light with orthogonal polarization states, adjust the phase difference between the two components of light, and synthesize the polarization vector. The amplitudes of the two components of light are Ax and Ay, respectively, and the static phase difference (or initial phase) is The dynamic phase difference generated by the high-speed phase modulation device is

[0004]

[0005] Perform a Stokes vector solution:

[0006]

[0007] After simplification, we can get:

[0008]

[0009] From the above expression, we can see that theoretically, by adjusting the amplitudes Ax and Ay of the two components of light, or the dynamic phase difference Both can produce high-speed polarization modulation.

[0010] Figure 1 A polarization modulation scheme based on discrete devices in the prior art is shown, in which linear polarized light along the x-axis (horizontal direction) and linear polarized light along the y-axis (vertical direction) are generated through a fiber-optic optical circulator Cir, a polarization beam splitter PBS and a phase modulator PM, and then polarization synthesis is performed. Corresponding to the above principle formula, the amplitudes of the two components of light in this scheme are equal Ax = Ay, and the static phase difference The phase modulator is loaded with voltages corresponding to the four phases of 0, π / 2, π and 3π / 2, and a dynamic phase difference is generated accordingly. and 3π / 2, thus generating 45° linear polarized light, right-handed circularly polarized light, 135° linear polarized light, and left-handed circularly polarized light, respectively, which meet the requirements of quantum communication. Figure 1 The scheme shown mainly adjusts the dynamic phase difference

[0011] The current mainstream is to use the above-mentioned optical fiber devices and polarization-maintaining phase modulators to form polarization encoders, which are generally large in size and high in cost. Encoders based on optical chips will be the trend of the next generation of quantum communication equipment. Figure 2 A polarization modulation scheme based on an optical chip in the prior art is shown, which is adjusted by high speed and Realize high-speed polarization modulation. Corresponding to the above principle formula, the scheme adjusts Actually, it is to change Ax and Ay and adjust and is a change As listed in the coding example in Table 1, When , light is transmitted from path 3, i.e., Ax=1, Ay=0, and the |H> state is obtained; When , light is transmitted from path 4, i.e., Ax=0, Ay=1, and the |V> state is obtained; When Ax=Ay, adjust Get the |+> state; When Ax=Ay, adjust Get the |-> state. It can be seen that Figure 2 The scheme shown adjusts Ax, Ay and dynamic phase difference simultaneously

[0012]

[0013] Table 1 Coding table

[0014] Figure 3The polarization control device based on silicon-based phase change material in the prior art is shown, wherein the polarization rotation beam splitter 100 converts two optical signals of orthogonal polarization in the input optical fiber into a TE0 mode with the same phase and the same intensity. The optical beam splitter assembly 200 includes a first optical beam splitter 210 and a second optical beam splitter 220, and the phase shifter assembly 300 includes a first phase shifter 310, a second phase shifter 320, a third phase shifter 330 and a fourth phase shifter 340. Corresponding to the above principle formula, the optical beam splitters 210, 220 and the phase shifters 310, 320 in the scheme constitute a Mach-Zehnder interferometer, and the phase difference is generated by adjusting the phase shifters 310 and 320 to adjust the light intensity of the two ports after the output of 220 (i.e., the amplitudes of |H> and |V> used for polarization synthesis later, i.e., Ax and Ay in the formula); the optical beam splitter 220, the polarization rotation beam combiner 400 and the phase shifters 330 and 340 constitute a polarization vector synthesis unit, and the electrodes of the fourth phase shifter 340 are not externally applied with voltage, and no additional phase shift is generated except for the change in the optical path difference brought by the fourth phase shifter 340 itself, and the third phase shifter 330 is adjusted to generate It can be seen that in Figure 3 In the scheme shown, Ax, Ay and dynamic phase difference are adjusted simultaneously The phase shifter used is realized based on phase change thin film material.

[0015] In quantum key distribution, theoretically, except for the coding state, the remaining dimensions need to be indistinguishable, that is, theoretically the encoder should not introduce power differences. Although studies have reported that this can be achieved by modifying the coding rate formula, it will reduce system performance such as coding rate.

[0016] exist Figure 1 In the scheme shown, the modulation performance is good and the power difference in the coding state is small, but it has the problems of large device size and high cost.

[0017] exist Figure 2 In the scheme shown, polarization modulation is achieved by adjusting the amplitude and dynamic phase difference of the two polarization components. However, the current silicon-based high-speed phase modulation devices are based on the plasma dispersion effect. Although they have the advantage of high bandwidth, they generally have the problem of large modulation-related loss, that is, when different phases are modulated, their attenuation is also different accordingly. For this reason, the on-chip encoder of this type of scheme has different attenuation of photons when modulating different polarization states, resulting in power differences in different coding states.

[0018] Figure 3 The scheme shown also achieves polarization modulation by adjusting the amplitude and dynamic phase difference of the two components. In particular, phase change thin film materials are used to implement the phase shifter. It is not yet clear whether the problem of power difference in different polarization states can be solved, but it is known that the implementation of the phase shifter based on phase change materials is a new process, which is different from the current conventional wafer factory process and requires modification of the process and related processing equipment. Summary of the invention

[0019] In view of the above problems in the prior art, the present invention proposes an on-chip encoder and encoding method with low power difference, in which an initial phase adjustment module for adjusting the initial phase is introduced. Therefore, different polarization state combinations can be obtained by scanning the initial phase, and polarization state combinations with low power difference can be selected, thereby effectively reducing the power difference of different polarization states obtained by the system and improving the tolerance to process deviations.

[0020] Specifically, a first aspect of the present invention relates to an on-chip encoder capable of achieving low power difference, which comprises an optical power distribution module, an initial phase adjustment module, a dynamic phase difference adjustment module and a polarization rotation beam combining module;

[0021] The optical power distribution module is configured to split the input light into two components with the same mode;

[0022] The initial phase adjustment module is configured to modulate between the two components to form a static phase difference;

[0023] The dynamic phase difference adjustment module is configured to modulate between two components to form a dynamic phase difference;

[0024] The polarization rotation beam combining module is configured to perform polarization vector synthesis of two components with a static phase difference and a dynamic phase difference to obtain polarized signal light, thereby forming a quantum state for encoding.

[0025] Optionally, the optical power distribution module includes an optical beam splitter or a Mach-Zehnder interferometer.

[0026] Further, the initial phase adjustment module includes at least one of a first phase modulator and a second phase modulator, the first phase modulator is used to adjust the phase of one of the two components, and the second phase modulator is used to adjust the phase of the other of the two components.

[0027] Preferably, the first and second phase modulators are low-speed phase modulators.

[0028] Furthermore, the dynamic phase difference adjustment module includes at least one of a third phase modulator and a fourth phase modulator, the third phase modulator is used to adjust the phase of one of the two components, and the fourth phase modulator is used to adjust the phase of the other of the two components.

[0029] Preferably, the third and fourth phase modulators are high-speed phase modulators.

[0030] Furthermore, the polarization rotation and beam combining module is configured to make the two components form an orthogonal or certain angle light field and perform polarization vector synthesis.

[0031] Optionally, the polarization rotation beam combiner module includes a two-dimensional grating and / or a polarization rotation beam combiner.

[0032] Furthermore, the optical power distribution module, the initial phase adjustment module, the dynamic phase difference adjustment module, and the polarization rotation beam combining module are connected through waveguides and integrated on the same chip.

[0033] A second aspect of the present invention relates to an encoding method capable of achieving low power difference, which comprises a quantum state preparation step, a power difference calculation step, a traversal step, an optimal value determination step and an encoding step;

[0034] In the quantum state preparation step, the input light is divided into two components with the same mode, and a static phase difference is first formed between the two components through phase modulation. Then, a dynamic phase difference is formed between the two components by phase modulation to generate a plurality of quantum states for encoding, wherein the plurality of quantum states are formed by synthesizing polarized signal light with two component polarization vectors having a static phase difference and a dynamic phase difference;

[0035] In the power difference calculation step, the power of the quantum state is measured, and the power difference of different quantum states is calculated;

[0036] In the traversal step, configure N+1 different static phase differences within the preset phase range i is a natural number from 0 to N; corresponding to each static phase difference The power difference PDL(i) is calculated through the quantum state preparation step and the power difference calculation step until a power difference PDL(i) less than or not exceeding a preset power difference threshold is obtained, or all N+1 power differences PDL(i) are obtained;

[0037] In the optimal value determination step, if a power difference PDL(i) less than or not exceeding a preset power difference threshold is obtained, the static phase difference and dynamic phase difference corresponding to the power difference PDL(i) are set as the optimal static phase difference and dynamic phase difference; if all N+1 power differences PDL(i) are obtained, the static phase difference and dynamic phase difference corresponding to the minimum value Min(PDL(i)) among the N+1 power differences PDL(i) are set as the optimal static phase difference and dynamic phase difference;

[0038] In the encoding step, the optimal static phase difference and the dynamic phase difference are utilized to generate a plurality of quantum states for encoding with the aid of the quantum state preparation step.

[0039] Preferably, the preset phase range has a size of 2π; and / or, the static phase difference N*△f=2π, f0 is the preset initial value.

[0040] Preferably, the encoding method of the present invention can be implemented by means of the above-mentioned on-chip encoder. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. It is obvious that the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1-3 Several polarization modulation schemes in the prior art are schematically shown respectively;

[0044] Figure 4 An example of a graph showing the relationship between the quantum state power difference, the angle deviation and the initial phase in the polarization modulation scheme is shown;

[0045] Figure 5 An embodiment of an on-chip encoder capable of achieving low power disparity according to the present invention is schematically shown;

[0046] Figure 6 Schematically illustrates an embodiment of an optical power distribution module used in the present invention;

[0047] Figure 7 Several embodiments of the phase difference adjustment module of the present invention are schematically shown;

[0048] Figure 8 Several implementations of the dynamic phase difference adjustment module of the present invention are schematically shown. DETAILED DESCRIPTION

[0049] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so as to fully convey the spirit of the present invention to those skilled in the art to which the present invention belongs. Therefore, the present invention is not limited to the embodiments disclosed herein.

[0050] As described in the background technology section, conventional polarization modulation (encoder) schemes often select Ax, Ay and dynamic phase difference As the adjustment amount, it is designed as Ax = Ay or Ax = 1 or Ay = 1 and other special cases, without paying attention to the initial phase (static phase difference) Usually it is The default is 0 or set to a constant value.

[0051] Breaking through the above conventional thinking, the inventors noticed that for fields such as quantum communication, only several polarization states that meet certain conditions need to be prepared, such as two sets of orthogonal polarization states. Therefore, in addition to the several polarization states given in the conventional solution that meet the requirements, there are still countless polarization state combinations that meet the requirements on the Poincaré sphere. Therefore, by adjusting the initial phase, a variety of polarization state combinations that meet the requirements can be generated. These polarization states are different, but meet specific angular relationships, such as the orthogonality of the two sets of polarization states required in quantum communication. In addition, in actual device implementation, chip lithography, doping and other processing inevitably have process deviations. For example, when using a two-dimensional grating to realize polarization rotation and beam combining, the orthogonality of the two components depends on the design and processing process deviations. In practice, there is a certain angle deviation θ, which may also affect the power difference between quantum states. Based on this, the inventors further derived and analyzed the theoretical formula of the above polarization modulation under the assumption that the angle deviation of the two components is θ:

[0052]

[0053] After solving the Stokes vector and simplifying it, we can get:

[0054]

[0055] Using the above theoretical derivation results, numerical simulation can be used to obtain Figure 4 The power difference distribution of the four quantum states under different angle deviations and initial phases is shown in the figure. It can be seen that the four variables of the intensity ratio of the two components, angle deviation, dynamic phase difference and initial phase may affect the final polarization modulation result. Figure 4 Taking the four-state polarization modulation shown as an example, it can be found that when there is a deviation in the polarization combiner, the final state modulation result (polarization state and amplitude) is related to the initial phase, and the four-state power difference will change greatly with the initial phase.

[0056] Based on the above theoretical analysis results, the present invention proposes a polarization modulation scheme different from the conventional one, in which an initial phase adjustment module is introduced, so that the output polarization state combination can be adjusted by adjusting the initial phase, thereby allowing traversal selection to obtain the quantum state combination with the smallest power difference, thereby improving the tolerance to process deviations and optimizing the power differences of different quantum states.

[0057] Figure 5 An embodiment of an on-chip encoder capable of realizing low power difference according to the present invention is schematically shown, which allows a quantum state combination with reduced output power difference based on the above-mentioned low power difference working principle, thereby better meeting the encoding requirements.

[0058] like Figure 5As shown, the low power difference on-chip encoder of the present invention may include an optical power distribution module, an initial phase adjustment module, a dynamic phase difference adjustment module and a polarization rotation beam combining module.

[0059] The optical power distribution module may have an input end and two output ends, and is used to split the input light into two components with the same mode, thereby completing the distribution of the input optical power at the two output ends.

[0060] As an example, the optical power distribution module may be implemented by means of an optical beam splitter or a Mach-Zehnder interferometer.

[0061] The optical power distribution module implemented by means of an optical beam splitter can only achieve a specific beam splitting ratio, for example, its power ratio cannot be adjusted after tape-out. As an example, the optical power distribution module may include a multimode interferometer or a directional coupler.

[0062] Figure 6 An example of an optical power distribution module implemented by means of a Mach-Zehnder interferometer is schematically shown.

[0063] like Figure 6 As shown, the Mach-Zehnder interferometer can be composed of two optical beam splitters and a phase difference adjustment module, and the output beam splitting ratio can be adjusted as needed. Therefore, its power ratio can be adjusted even after tape-out.

[0064] Figure 7 Several implementations of the phase difference adjustment module are shown exemplarily. As shown in the figure, the phase difference adjustment module may include two waveguides and at least one phase modulator, wherein the phase modulator may be arranged on at least one of the two waveguides so as to perform phase modulation on at least one of the two components, thereby achieving phase difference adjustment between the two components. As an example, the phase modulator may be a thermal phase shifter, a plasma dispersion modulator, or a lithium niobate thin film modulator.

[0065] The initial phase adjustment module is similar in structure to the above-mentioned phase difference adjustment module, and includes two waveguides and at least one phase modulator, providing two input ends and two output ends. The two components output by the optical power distribution module can be transmitted along the two waveguides respectively, and the phase modulator is arranged on at least one of the two waveguides to perform phase modulation on at least one of the two components, thereby modulating the required static phase difference between the two components.

[0066] For example, the initial phase adjustment module may include a first phase modulator arranged on one of the two waveguides (for example, the first waveguide) for phase modulating the component transmitted along the waveguide; or a second phase modulator arranged on the other of the two waveguides (for example, the second waveguide) for phase modulating the component transmitted along the waveguide; or include the first and second phase modulators mentioned above at the same time for phase modulating the two components transmitted along the two waveguides respectively.

[0067] Those skilled in the art know that the phase modulation amount acting on the component can be controlled by adjusting the driving voltage of the first and / or second phase modulator. In addition, in the initial phase adjustment module, the number of the first and second phase modulators is not limited to one, but can be set as needed.

[0068] As a preferred example, the first and / or second phase modulator used in the initial phase adjustment module is a low-speed phase modulator, such as a thermal phase shifter. Of course, the first and / or second phase modulator can also be a plasma dispersion modulator or a lithium niobate thin film modulator.

[0069] Figure 8 Several implementations of the dynamic phase difference adjustment module of the present invention are exemplarily shown, which are used to modulate between two components to form a dynamic phase difference so as to allow multiple quantum states required for subsequent polarization synthesis encoding.

[0070] like Figure 8 As shown, the dynamic phase difference adjustment module may include two waveguides and at least one phase modulator, providing two input ends and two output ends. The two components output by the initial phase adjustment module may be transmitted along the two waveguides respectively, and the phase modulator is arranged on at least one of the two waveguides to perform phase modulation on at least one of the two components, thereby modulating the dynamic phase difference required for forming the polarization synthesis quantum state between the two components.

[0071] For example, the dynamic phase difference adjustment module may include a third phase modulator arranged on one of the two waveguides (for example, the third waveguide) for phase modulating the component transmitted along the waveguide; or a fourth phase modulator arranged on the other of the two waveguides (for example, the fourth waveguide) for phase modulating the component transmitted along the waveguide; or include the above-mentioned third and fourth phase modulators at the same time, for phase modulating the two components transmitted along the two waveguides respectively.

[0072] Those skilled in the art know that the phase modulation amount acting on the component can be controlled by adjusting the driving voltage of the third and / or fourth phase modulator. In addition, in the dynamic phase difference adjustment module, the number of the third and fourth phase modulators is not limited to one, but can be set as needed.

[0073] As a preferred example, the third and / or fourth phase modulator used in the dynamic phase difference adjustment module is a high-speed phase modulator, such as a plasma dispersion modulator or a lithium niobate thin film modulator.

[0074] The polarization rotation beam combining module can have two input ends and one output end, wherein the two input ends respectively receive two components that have been phase modulated (for example, output by a dynamic phase difference adjustment module), so as to form an orthogonal or certain angle light field with the two components originally in the same mode in the polarization rotation beam combining module and perform vector synthesis of polarized signal light, and finally output the polarized signal light from the output end to generate a quantum state that meets the system (coding) requirements.

[0075] As an example, the polarization rotation beam combiner module may be a two-dimensional grating or a polarization rotation beam combiner.

[0076] Further, according to the present invention, the optical power allocation module, the initial phase adjustment module, the dynamic phase difference adjustment module and the polarization rotation beam combining module can be connected through waveguides and integrated into the same chip to form an on-chip encoder structure.

[0077] Continue to see Figure 5 When the input light reaches the on-chip encoder of the present invention, the input light is first input into the optical power distribution module and then divided into two components with the same mode and specific power ratio. These two components are input into the initial phase adjustment module, and then transmitted to the polarization rotation beam combining module through the dynamic phase difference adjustment module. After polarization synthesis is completed, it is output to form a quantum state for encoding. With this structure, multiple quantum states that meet the encoding requirements and have the smallest power difference can be found by adjusting the initial phase, thereby effectively reducing the power difference between quantum states.

[0078] In order to better understand the working principle of the present invention, Figure 5 The embodiment of the on-chip encoder is shown and the on-chip encoding method for realizing low power disparity of the present invention is specifically described.

[0079] The on-chip encoding method of the present invention may include a quantum state preparation step, a power difference calculation step, a traversal step, an optimal value determination step and an encoding step.

[0080] The quantum state preparation step is used to perform polarization modulation on the input light corresponding to the set static phase difference to form multiple quantum states required for encoding.

[0081] Specifically, in the quantum state preparation step, the input light can be first divided into two components of the same mode, and a static phase difference can be formed between the two components through phase modulation. In the present invention, this phase modulation related to the static phase difference can be achieved with the help of a low-speed phase modulator in the initial phase adjustment module. For example, the static phase difference (initial phase) between the two components can be set to a selected static phase difference (e.g., f0) by setting the driving voltage of the phase modulator in the initial phase adjustment module.

[0082] For the two components that already have the static phase difference, a dynamic phase difference will be formed between the two components again through phase modulation. At this time, in order to quickly obtain multiple quantum states that meet the encoding requirements, this phase modulation related to the dynamic phase difference can be achieved with the help of a high-speed phase modulator in the dynamic phase difference adjustment module. For example, the driving voltage of the high-speed phase modulator in the dynamic phase difference adjustment module can be adjusted to obtain multiple quantum states required by the system.

[0083] Subsequently, the two components with a static phase difference and a dynamic phase difference can be made to synthesize polarized signal light through polarization vectors, for example, through a polarization rotation beam combining module, to form a plurality of quantum states that meet the encoding requirements.

[0084] After multiple quantum states that can be used for encoding are prepared by the quantum state preparation step, the power difference between the different quantum states currently obtained can be obtained by the power difference calculation step. Thus, it is possible to find a quantum state combination (preparation parameter) that meets the encoding requirements and has the smallest power difference by means of a subsequent traversal process.

[0085] Specifically, in the power difference calculation step, the power of different quantum states can be measured at the output end, and the power difference of different quantum states in the multiple quantum states used for encoding can be calculated.

[0086] As mentioned above, the present invention adjusts the initial phase (static phase difference) for polarization modulation to find the initial phase value of the quantum state combination that can currently achieve the minimum power difference. To this end, N+1 different static phase differences can be configured within a preset phase range of, for example, 2π by means of a traversal step. i is a natural number from 0 to N. As an example, the initial phases can be configured as f0, f0+*Δf, f0+2*Δf, f0+3*Δf, f0+4*Δf, …, f0+N*Δf, where N*Δf=2π.

[0087] Then, corresponding to each static phase difference The corresponding power difference PDL(i) is calculated through the quantum state preparation step and the power difference calculation step.

[0088] According to the present invention, a power difference threshold can also be preset, so as to allow the traversal step to be performed when a certain static phase difference When the power difference PDL(i) obtained under the above conditions is less than or does not exceed the power difference threshold, the subsequent traversal process is stopped; otherwise, the traversal of all static phase differences is completed to obtain all N+1 power differences PDL(i).

[0089] According to the power difference PDL(i) obtained during the traversal process, the quantum state combination (preparation parameters) used for encoding can be finally determined in the optimal value determination step.

[0090] Specifically, in the optimal value determination step, if a static phase difference that makes its power difference PDL(i) less than or not exceeding the power difference threshold is directly found in the traversal step, The static phase difference and dynamic phase difference corresponding to the power difference PDL(i) are set as the optimal static phase difference and dynamic phase difference; if all N+1 power differences PDL(i) are obtained, the static phase difference and dynamic phase difference corresponding to the minimum value Min(PDL(i)) among the N+1 power differences PDL(i) are set as the optimal static phase difference and dynamic phase difference.

[0091] In the step of determining the optimal value, the optimal preparation parameters (such as static phase difference and dynamic phase difference) currently used for encoding are obtained. Then, in the encoding step, the optimal static phase difference and dynamic phase difference can be used to generate multiple quantum states for encoding by means of the quantum state preparation step. At this time, the output quantum state combination has the smallest power difference.

[0092] At this point, those skilled in the art can understand that the above-mentioned encoding method for realizing low power difference in polarization modulation scheme can be performed manually, or can be realized in a substantially automatic manner by setting a control module. For example, the control module can automatically configure the initial phase modulation amount of the initial phase adjustment module (for example, by controlling the driving voltage for the phase modulator), automatically obtain and configure the dynamic phase difference for forming multiple quantum states for encoding in the dynamic phase difference adjustment module (for example, by controlling the driving voltage for the phase modulator), and determine the optimal preparation parameters for encoding (static phase difference / dynamic phase difference) according to the measured power difference, etc.

[0093] In summary, compared with conventional schemes, the encoding scheme of the present invention introduces an initial phase adjustment module for adjusting the initial phase. Therefore, it allows different polarization state combinations to be obtained by scanning the initial phase, and polarization state combinations with low power differences are selected, thereby effectively reducing the power differences of different polarization states obtained by the system and improving the tolerance to process deviations.

[0094] Although the present invention has been described above through specific embodiments in conjunction with the accompanying drawings, those skilled in the art will readily recognize that the above embodiments are merely exemplary and are used to illustrate the principles of the present invention, and do not limit the scope of the present invention. Those skilled in the art may make various combinations, modifications and equivalent substitutions to the above embodiments without departing from the spirit and scope of the present invention.

Claims

1. An on-chip encoder capable of achieving low power difference, comprising an optical power distribution module, an initial phase adjustment module, a dynamic phase difference adjustment module and a polarization rotation beam combining module; The optical power distribution module is configured to split the input light into two components with the same mode; The initial phase adjustment module is configured to modulate between the two components to form a static phase difference; The dynamic phase difference adjustment module is configured to modulate between two components to form a dynamic phase difference; The polarization rotation beam combining module is configured to synthesize polarized signal light by combining two component polarization vectors with a static phase difference and a dynamic phase difference to form a quantum state for encoding.

2. The on-chip encoder according to claim 1, wherein: The optical power distribution module includes an optical beam splitter or a Mach-Zehnder interferometer.

3. The on-chip encoder according to claim 1, wherein: The initial phase adjustment module includes at least one of a first phase modulator and a second phase modulator, wherein the first phase modulator is used to adjust the phase of one of the two components and the second phase modulator is used to adjust the phase of the other of the two components.

4. The on-chip encoder according to claim 3, wherein: The first and second phase modulators are low-speed phase modulators.

5. The on-chip encoder according to claim 1, wherein: The dynamic phase difference adjustment module includes at least one of a third phase modulator and a fourth phase modulator, wherein the third phase modulator is used to adjust the phase of one of the two components, and the fourth phase modulator is used to adjust the phase of the other of the two components.

6. The on-chip encoder according to claim 5, wherein: The third and fourth phase modulators are high-speed phase modulators.

7. The on-chip encoder according to claim 1, wherein: The polarization rotation and beam combining module is configured to make two components form an orthogonal or certain angle light field and perform polarization vector synthesis.

8. The on-chip encoder according to claim 7, wherein: The polarization rotation beam combiner module includes a two-dimensional grating and / or a polarization rotation beam combiner.

9. The on-chip encoder according to any one of claims 1 to 8, wherein: The optical power distribution module, the initial phase adjustment module, the dynamic phase difference adjustment module and the polarization rotation beam combining module are connected through waveguides and integrated on the same chip.

10. A coding method capable of achieving low power difference, comprising a quantum state preparation step, a power difference calculation step, a traversal step, an optimal value determination step and a coding step; In the quantum state preparation step, the input light is divided into two components with the same mode, a static phase difference is first formed between the two components by phase modulation, and then a dynamic phase difference is formed between the two components by phase modulation to generate multiple quantum states for encoding, wherein, The plurality of quantum states are formed by synthesizing two component polarization vectors having a static phase difference and a dynamic phase difference into polarized signal light; In the power difference calculation step, the power of the quantum state is measured, and the power difference of different quantum states is calculated; In the traversal step, N+1 different static phase differences are configured within the preset phase range. i is a natural number from 0 to N; corresponding to each static phase difference The power difference PDL(i) is calculated through the quantum state preparation step and the power difference calculation step until a power difference PDL(i) less than or not exceeding a preset power difference threshold is obtained, or all N+1 power differences PDL(i) are obtained; In the optimal value determination step, if a power difference PDL(i) less than or not exceeding a preset power difference threshold is obtained, the static phase difference and dynamic phase difference corresponding to the power difference PDL(i) are set as the optimal static phase difference and dynamic phase difference; if all N+1 power differences PDL(i) are obtained, the static phase difference and dynamic phase difference corresponding to the minimum value Min(PDL(i)) among the N+1 power differences PDL(i) are set as the optimal static phase difference and dynamic phase difference; In the encoding step, the optimal static phase difference and the dynamic phase difference are utilized to generate a plurality of quantum states for encoding with the aid of a quantum state preparation step.

11. The encoding method according to claim 10, wherein: The preset phase range has a size of 2π; and / or the static phase difference N*△f=2π, f0 is the preset initial value.

12. The encoding method according to claim 10, which is implemented by means of an on-chip encoder according to any one of claims 1-9.

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