Modulation method suitable for optical signal and quantum key chip sending end device

Abstract

The disclosure provides a modulation method suitable for optical signals and a quantum key chip sending end device. The modulation method suitable for optical signals comprises: using binary digital to represent the level state of two electrical signals containing single-bit information; outputting the electrical signal as a modulated electrical signal according to the level state; and regulating the modulation component in the quantum key chip sending end device according to the modulated electrical signal, so as to modulate the degree of freedom of the optical signal applied to the modulation component, thereby realizing the encoding of single-bit information.

Description

Technical Field

[0001] At least one embodiment of this disclosure relates to the field of quantum communication technology, and more specifically to a quantum key chip transmitter device, a modulation method for optical signals, and a quantum key chip transmitter device. Background Technology

[0002] In quantum key distribution systems, single-photon sources are typically replaced by weakly coherent sources with diminished intensity. The photon number distribution of these weakly coherent sources follows a Poisson distribution, which can lead to two-photon scenarios. In such cases, Eve might employ a photon-number splitting (PNS) attack to eavesdrop, obtaining key information undetected. In 2003, Won Young Hwang first proposed the decoy state protocol to defend against PNS attacks. This method adds decoy states with different average photon numbers, making the phase-randomized weakly coherent state a mixture of different photon number states, thus detecting Eve's eavesdropping behavior.

[0003] To address security vulnerabilities at the device's probe end, in 2012, Hoi Kwong Lo's research group at the University of Toronto, Canada, proposed the Measurement Device Independent Quantum Key Distribution (MDIQKD) protocol. This protocol utilizes the idea of ​​entangled state distribution to make the system's security independent of the probe end. In 2018, AJ Shields et al. at Toshiba Research Europe proposed a novel phase encoding protocol, namely the dual-field quantum key distribution protocol, which improves the key generation rate through single-photon interference. In 2022, Xiongfeng Ma's research group at Tsinghua University proposed a novel measurement device independent quantum key distribution protocol, namely the Pattern Matching Quantum Key Distribution (MPQKD) protocol, which further improves the key generation rate by performing pulse pairing after probes occur.

[0004] With the continuous development and maturation of quantum communication technology, the widespread practical application of quantum key distribution has become a further requirement. However, common quantum key distribution terminals that rely on instrument modulation are large in size and expensive. Reducing cost and device size has become a pressing challenge, and the best solution is chip-based communication equipment. Currently, quantum key distribution based on optoelectronic devices and optical fibers does not require high repetition frequencies, and individual devices are expensive. Multi-bit modulation, which modulates multiple quantum states using a single pulse voltage output, can be used. However, as communication operating frequencies increase, multi-bit modulation suffers from noise interference and complex electronic systems, reducing modulation accuracy and communication quality. Multi-bit modulation cannot meet the ever-increasing operating frequency requirements in communication, and its complex electronics are not conducive to chip-based quantum key distribution communication equipment. Summary of the Invention

[0005] To address at least one of the technical problems mentioned above and others in the prior art, this disclosure provides a modulation method for optical signals and a quantum key chip transmitter device, which can improve the ability to resist noise interference and improve the accuracy and reliability of quantum communication.

[0006] According to a first aspect of this disclosure, a modulation method suitable for optical signals is provided, the method comprising:

[0007] The level states of two electrical signals containing single-bit information are represented using binary numbers;

[0008] Based on the above-mentioned level state, the above-mentioned electrical signal is output as the modulation electrical signal;

[0009] The modulation component in the quantum key chip transmitter device is controlled by the above-mentioned modulation electrical signal, thereby modulating the degree of freedom of the optical signal applied to the above-mentioned modulation component to realize the encoding of single-bit information.

[0010] According to a second aspect of this disclosure, a quantum key chip transmitter device is provided, comprising:

[0011] The light source module is suitable for outputting initial pulse light signals;

[0012] The controller is configured to use binary numbers to represent the level states of two electrical signals containing single-bit information, and output the electrical signals as modulated electrical signals according to the level states.

[0013] The modulation component is configured to modulate the degrees of freedom of the initial pulse optical signal under the control of the controller to achieve encoding of single-bit information.

[0014] According to embodiments of this disclosure, the modulation component includes:

[0015] A first intensity modulator is adapted to chop the initial pulsed optical signal based on the aforementioned modulated electrical signal to form a first pulsed optical signal containing different photon states; and

[0016] The second intensity modulator is adapted to modulate the first pulse optical signal based on the above-mentioned modulation electrical signal to form multiple second pulse optical signals with different intensities.

[0017] According to embodiments of this disclosure, the modulation component includes:

[0018] The first intensity modulator is adapted to chop the initial pulse optical signal based on the above-mentioned modulated electrical signal to form a first pulse optical signal containing different photon states;

[0019] The second intensity modulator is adapted to modulate the first pulse optical signal based on the aforementioned modulation electrical signal to form multiple second pulse optical signals with different intensities; and

[0020] The polarization encoding module is suitable for modulating the second pulse optical signal into different polarization states based on the above-mentioned modulated electrical signal, so as to encode the transmitted key information into the second pulse optical signal with different polarization states;

[0021] The controller adjusts the first intensity modulator and the second intensity modulator to change the intensity of the first pulse light signal and the second pulse light signal, thereby achieving a decoy state.

[0022] The polarization encoding module is adjusted by the controller to control the different polarization states of the second pulse light signal, thereby realizing the decoy state polarization encoding.

[0023] According to embodiments of this disclosure, the polarization encoding module includes:

[0024] A beam splitter is suitable for dividing the aforementioned second pulse optical signal into two equal branches of optical signals.

[0025] Two parallel polarization coding branches, each polarization coding branch includes:

[0026] A phase modulator, suitable for modulating the phase of the aforementioned branch optical signal; and

[0027] An attenuator is used to attenuate the aforementioned branch optical signals to adjust their intensity and output a modulated optical signal; and

[0028] A polarization beam splitter is suitable for combining two modulated optical signals into a single beam signal and then splitting the combined beam signal into horizontally polarized light and vertically polarized light according to the polarization direction.

[0029] According to embodiments of this disclosure, the phase modulated by the first phase modulator of the two aforementioned phase modulators includes 0 and... Two, the second phase modulator in the two aforementioned phase modulators modulates a phase including 0 and two.

[0030] According to embodiments of this disclosure, if the modulation phase of the first phase modulator is 0 and the modulation phase of the second phase modulator is 0, a first polarization state is output. The first encoded information is 00; and / or

[0031] If the first phase modulator modulates the phase The second phase modulator modulates the phase to 0 and outputs the second polarization state. The second encoded information is 01; and / or

[0032] If the modulation phase of the first phase modulator is 0, the modulation phase of the second phase modulator is... Output the third polarization state The third encoding information is 10; and / or

[0033] If the first phase modulator modulates the phase The second phase modulator modulates the phase as follows: Output the fourth polarization state The fourth encoded information is 11;

[0034] in, For the above-mentioned horizontally polarized light, For the aforementioned vertically polarized light, The first polarization state and the second polarization state, as well as the second polarization state and the fourth polarization state, are two pairs of perpendicular basis vectors with an included angle of 45°.

[0035] According to embodiments of this disclosure, the beam splitter, the polarization-encoded branch, and the polarization beam splitter are optically connected to each other via polarization-maintaining optical fibers, so that the polarization state of the branch optical signals transmitted in the polarization-maintaining optical fibers remains unchanged.

[0036] According to a third aspect of this disclosure, a quantum key chip transmitter device is provided, the quantum key chip transmitter device comprising:

[0037] A continuous laser source, suitable for outputting an initial continuous optical signal;

[0038] The controller is configured to use binary numbers to represent the level states of two electrical signals containing single-bit information, and output the electrical signals as modulated electrical signals according to the level states.

[0039] Multiple intensity modulators connected in series are suitable for modulating the initial continuous optical signal based on the aforementioned modulation electrical signal to generate optical pulse signals of different intensities; and

[0040] The phase randomization module is suitable for modulating the phase of the optical pulse signal based on the aforementioned modulation electrical signal, so that the optical pulse signal has multiple different phase states; the phase randomization module includes multiple phase modulators connected in series, each of the aforementioned phase modulators being suitable for modulating the phase of the aforementioned initial continuous optical signal;

[0041] Specifically, the intensity modulator is adjusted by the controller to control the intensity of the initial pulse light signal, thereby achieving a decoy state; the phase randomization module is adjusted by the controller to modulate the phase of the light pulse signal, thereby achieving phase randomization.

[0042] According to embodiments of this disclosure, the plurality of the above-described intensity modulators include:

[0043] A first-level intensity modulator is suitable for chopping the aforementioned initial continuous optical signal, converting the continuous initial optical signal into an initial pulsed optical signal.

[0044] A second-level intensity modulator is suitable for modulating the above-mentioned initial pulse optical signal to form a first pulse optical signal with a changed intensity;

[0045] A three-stage intensity modulator, suitable for modulating the intensity of the aforementioned first pulse optical signal to generate a reference photon and a working photon; and

[0046] A four-level intensity modulator is suitable for modulating the above-mentioned working photons to produce optical pulse signals containing signal states and optical pulse signals containing vacuum states;

[0047] Specifically, the controller adjusts the first-level intensity modulator and the second-level intensity modulator to control the intensity of the initial pulse light signal and the first pulse light signal, thereby achieving the decoy state; the signal state is a photon state containing key information, and the vacuum state is a state that does not contain any photons.

[0048] According to embodiments of this disclosure, the above-described working photons are suitable for carrying key information;

[0049] The aforementioned reference photon is used to adjust the phase of the signal photon based on the interference information of the aforementioned reference photon in the quantum communication process, so as to ensure the identity of the two optical pulse signals generated by the transmitting end and the measuring end respectively arriving at the measuring end.

[0050] According to embodiments of this disclosure, the plurality of the above-described phase modulators include Phase modulator, Phase modulator, Phase modulator and Phase modulator.

[0051] According to an embodiment of this disclosure, the phase randomization module includes four phase modulators, each of which has two states: a non-zero modulation voltage and a zero modulation voltage, so that the phase randomization module has 16 different phase states, thereby realizing 16 phase random modulations.

[0052] According to embodiments of this disclosure, the level states of two electrical signals containing single-bit information are represented using binary digits; an electrical signal is output as a modulation signal based on the level state; and the modulation component in the quantum key chip transmitter is controlled according to the modulation signal, thereby modulating the degrees of freedom of the optical signal applied to the modulation component to achieve encoding of single-bit information. This disclosure uses a single-bit binary encoding method in the modulation component of the quantum key chip transmitter, so that the set binary digital signal operates the chip in the form of digital level. Each device in the quantum key chip transmitter is controlled by 0 or 1 encoding, and the electronic complexity is also simplified, making it suitable for the widespread practical application of quantum key distribution. This improves the ability of the quantum key chip transmitter to resist noise interference, improves the accuracy and reliability of quantum communication, and improves the quality and confidentiality of quantum communication. Attached Figure Description

[0053] The foregoing contents, as well as other objects, features, and advantages of this disclosure, will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0054] Figure 1 A flowchart illustrating a modulation method for optical signals according to an embodiment of the present disclosure is shown schematically.

[0055] Figure 2 This schematic diagram illustrates the working principle of a quantum key chip transmitter device according to an embodiment of the present disclosure;

[0056] Figure 3 A schematic diagram illustrating the working principle of a quantum key chip transmitter device according to another embodiment of the present disclosure is shown; and

[0057] Figure 4 The schematic diagram illustrates the working principle of a quantum key chip transmitter device according to an embodiment of the present disclosure.

[0058] The meanings of the reference numerals in the above figures are as follows:

[0059] 1-Light source module;

[0060] 2-Modulation components;

[0061] 21-First intensity modulator;

[0062] 22 - Second intensity modulator;

[0063] 23-Polarization encoding module;

[0064] 231-Band splitter;

[0065] 232 - First polarization coding branch;

[0066] 2321 - First phase modulator;

[0067] 2322 - First Attenuator;

[0068] 233 - Second polarization coding branch;

[0069] 2331 - Second phase modulator;

[0070] 2332 - Second attenuator;

[0071] 234-Polarization beam splitter;

[0072] 3-Continuous laser source;

[0073] 4-First-level intensity modulator;

[0074] 5-Secondary intensity modulator;

[0075] 6-Three-level intensity modulator;

[0076] 7-Fourth-level intensity modulator;

[0077] 8-Phase randomization module;

[0078] 81- Phase modulator;

[0079] 82- Phase modulator;

[0080] 83- Phase modulator;

[0081] 84- Phase modulator. Detailed Implementation

[0082] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0083] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0084] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0085] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0086] In related technologies, quantum key distribution based on optoelectronic devices and optical fibers does not require high repetition frequencies, but individual devices are expensive. It can rely on multi-bit modulation, which modulates multiple quantum states using a single pulse voltage output, carrying multiple bits of information within a single pulse. This allows for the transmission of more data in the same amount of time, improving information transmission efficiency. However, as communication operating frequencies increase, multi-bit modulation suffers from noise interference and complex electronic systems, reducing modulation accuracy and communication quality. Multi-bit modulation cannot meet the demands of continuously increasing operating frequencies in communication, and its complex electronics are not conducive to chip-based quantum key distribution communication devices.

[0087] In view of this, this disclosure provides a modulation method for optical signals and a quantum key chip transmitter device. It utilizes binary digits to represent the level states of two electrical signals containing single-bit information; outputs an electrical signal as a modulation signal based on the level states; and modulates the modulation component in the quantum key chip transmitter device according to the modulation signal, thereby modulating the degrees of freedom of the optical signal applied to the modulation component to achieve single-bit information encoding. This disclosure uses single-bit binary encoding in the modulation component of the quantum key chip transmitter device, enabling the set binary digital signal to operate the chip in the form of digital levels. Each device in the quantum key chip transmitter device is controlled by 0 or 1 encoding, simplifying the electronic complexity. This method is suitable for the widespread practical application of quantum key distribution, improves the quantum key chip transmitter device's resistance to noise interference, enhances the accuracy and reliability of quantum communication, and improves the quality and confidentiality of quantum communication.

[0088] Figure 1 A flowchart illustrating a modulation method for optical signals according to an embodiment of the present disclosure is shown schematically.

[0089] According to some embodiments of this disclosure, such as Figure 1As shown, the modulation method applicable to optical signals includes operations S101 to S103.

[0090] In operation S101, binary numbers are used to represent the level states of two electrical signals containing single-bit information.

[0091] In operation S102, an electrical signal is output as a modulation signal according to the level state.

[0092] In operation S103, the modulation component in the quantum key chip transmitter device is controlled according to the modulation electrical signal, thereby modulating the degree of freedom of the optical signal applied to the modulation component to realize the encoding of single-bit information.

[0093] According to some embodiments of this disclosure, the level states of two electrical signals containing single-bit information are represented by binary numbers; an electrical signal is output as a modulation signal according to the level state; and the modulation component in the quantum key chip transmitter device is controlled according to the modulation signal, thereby modulating the degrees of freedom of the optical signal applied to the modulation component to achieve single-bit information encoding. This disclosure uses a single-bit binary encoding method in the modulation component of the quantum key chip transmitter device, so that the set binary digital signal operates the chip in the form of digital level. Each device in the quantum key chip transmitter device is controlled by 0 or 1 encoding, and the electronic complexity is also simplified, which is suitable for the widespread practical application of quantum key distribution, improves the ability of the quantum key chip transmitter device to resist noise interference, improves the accuracy and reliability of quantum communication, and improves the quality and confidentiality of quantum communication.

[0094] According to some embodiments of this disclosure, binary numbers are typically 0 and 1, and binary numbers can be used to represent the level state of an electrical signal. A single bit of information can be represented as a high or low level state of an electrical signal. If the electrical signal is in a high level state, it is typically interpreted as the binary number "1"; if the electrical signal is in a low level state, it is typically interpreted as the binary number "0".

[0095] According to some embodiments of this disclosure, the level state of an electrical signal refers to the stable potential state of the electrical signal within a certain time range.

[0096] Figure 2 The schematic diagram illustrates the working principle of a quantum key chip transmitter device according to an embodiment of the present disclosure.

[0097] According to some embodiments of this disclosure, such as Figure 2As shown, the quantum key chip transmitter device includes: a light source module 1, a controller, and a modulation component 2. The light source module 1 is suitable for outputting an initial pulse light signal; the controller is configured to use binary numbers to represent the level states of two electrical signals containing single-bit information, and output electrical signals as modulation signals according to the level states; the modulation component 2 is configured to modulate the degrees of freedom of the initial pulse light signal under the control of the controller to realize the encoding of single-bit information.

[0098] According to some embodiments of this disclosure, the quantum key chip transmitter device is configured to output an initial pulse light signal by setting a light source module 1; the controller is configured to represent the level states of two electrical signals containing single-bit information using binary numbers, and output electrical signals as modulation signals according to the level states; the modulation component 2 is used to modulate the degrees of freedom of the initial pulse light signal under the control of the controller to realize the encoding of single-bit information. By using the single-bit binary encoding method in the modulation component 2 of the quantum key chip transmitter device, the set binary digital signal is used to operate the chip in the form of digital level. Each device in the quantum key chip transmitter device is controlled by 0 or 1 encoding, and the electronic complexity is also simplified, which is suitable for the widespread practical application of quantum key distribution, improves the resistance to noise interference, reduces the probability of eavesdropping in quantum communication, improves the accuracy and reliability of quantum communication, and further improves the quality and confidentiality of quantum communication.

[0099] According to some embodiments of this disclosure, the quantum key chip transmitter uses the BB84 protocol, which utilizes the four polarization states of a single photon to encode random key information. All components of the quantum key chip transmitter, including the light source module 1, controller, and modulation component 2, are integrated onto a lithium niobate optical chip. Lithium niobate is an excellent optical material with good optical properties, thermal stability, and mechanical stability. Integrating all components of the quantum key chip transmitter onto a lithium niobate optical chip enables the entire system to operate stably under various environmental conditions, reducing performance fluctuations caused by changes in the external environment. Furthermore, the optical signal maintains high efficiency and stability during transmission within the chip, thereby improving the overall performance of the quantum key chip transmitter.

[0100] According to some embodiments of this disclosure, the light source module 1 is a pulsed laser source that outputs an initial continuous optical signal. In the field of quantum communication, decoy state technology introduces light pulses of different intensities, making it impossible for eavesdroppers in the quantum communication process to accurately determine which states contain key information, thereby detecting the eavesdropper's measurement behavior and reducing the probability of information being eavesdropped on during quantum communication. In implementing the decoy state, the initial continuous optical signal needs to be modulated to emit three light pulses of different intensities: a signal state, a strong light state, and a vacuum state. The signal state is a pulse state used to transmit actual information. The signal state carries the original information of the key, and the intensity of the light pulse in the signal state needs to be controlled within a certain range to ensure effective information transmission without introducing excessive noise or interference due to excessive intensity. The intensity of the light pulse in the strong light state is higher than that in the signal state. Because the strong light state has a larger number of photons, any changes in the channel can be detected. By measuring the strong light state, the potential impact on the signal state during transmission can be estimated, allowing for appropriate corrective measures. The vacuum state is a state without photons, i.e., no light pulses are emitted. In decoy state technology, the introduction of a vacuum state is intended to contrast with the signal state and the strong light state, thereby more accurately evaluating the performance of the quantum communication channel. Measurements of the vacuum state can further verify the stability and reliability of the quantum communication channel. Decoy state technology modulates three states—signal, strong light, and vacuum—with different light pulse intensities to ensure communication security and improve communication efficiency and stability.

[0101] According to some embodiments of this disclosure, such as Figure 2 As shown, the modulation component 2 includes a first intensity modulator 21 and a second intensity modulator 22. The first intensity modulator 21 is adapted to chop the initial pulse optical signal based on the modulation electrical signal to form a first pulse optical signal containing different photon states; the second intensity modulator 22 is adapted to modulate the first pulse optical signal based on the modulation electrical signal to form multiple second pulse optical signals with different intensities.

[0102] According to some embodiments of this disclosure, such as Figure 2As shown, the quantum key chip transmitter device is configured to output an initial pulsed light signal by setting the light source module 1; the controller is configured to represent the level states of two electrical signals containing single-bit information using binary numbers, and outputs an electrical signal as a modulation signal according to the level states; the initial pulsed light signal is chopping-processed by a first intensity modulator 21 based on the modulation signal to form a first pulsed light signal containing different photon states; the first pulsed light signal is modulated by a second intensity modulator 22 based on the modulation signal to form multiple second pulsed light signals with different intensities. The first intensity modulator 21 and the second intensity modulator 22 modulate the initial pulsed light signal under the control of the controller. The degrees of freedom are modulated to encode single-bit information and change the intensity of the initial pulse light signal, thereby realizing a decoy state. The modulation component 2 in the quantum key chip transmitter device is used through single-bit binary encoding so that the set binary digital signal operates the chip in the form of digital level. Each device in the quantum key chip transmitter device is controlled by 0 or 1 encoding. At the same time, the electronic complexity is also simplified, which is suitable for the widespread practical application of quantum key distribution, improves the ability to resist noise interference, reduces the probability of being eavesdropped in quantum communication, improves the accuracy and reliability of quantum communication, and further improves the quality and confidentiality of quantum communication.

[0103] According to some embodiments of this disclosure, the first intensity modulator 21 and the second intensity modulator 22 precisely control the intensity of the light pulse based on the modulation electrical signal, realizing the generation of the decoy state and providing a sufficient extinction ratio for the experiment. The controller applies two modulation electrical signals to the first intensity modulator 2 and the second intensity modulator 3, respectively, including a first modulation electrical signal and a second modulation electrical signal. The first modulation electrical signal and the second modulation electrical signal can be the same or different, and the consistency or inconsistency of the first modulation electrical signal and the second modulation electrical signal can be adjusted accordingly according to actual needs. By connecting the first intensity modulator 2 and the second intensity modulator 3 in series and modulating the first modulation electrical signal and the second modulation electrical signal, the accuracy of controlling the light pulse intensity is improved.

[0104] According to some embodiments of this disclosure, the initial pulsed optical signal first passes through a first intensity modulator 21, where it is chopped according to encoding requirements to generate a vacuum state or a photonic state. Then, the chopped initial pulsed optical signal enters a second intensity modulator 22, where it is further modulated into a signal state or a decoy state according to encoding requirements. These two modulators work together to ensure that the optical pulse signal has the correct intensity and encoding state during transmission.

[0105] According to some embodiments of this disclosure, the first pulsed optical signal may include a signal state and a decoy state. In the above-described quantum key chip transmitter device, the decoy state can be generated by continuously changing the modulation of an intensity modulator. In a single-bit binary encoded optical chip, when the initial pulsed optical signal is sequentially sent to two cascaded two-stage intensity modulators, the first intensity modulator 21 is used to chop to generate a vacuum state. Whether chopping is performed corresponds to the first bit of the code 0 or 1, respectively, to realize a non-emitting state (i.e., a vacuum state) and an emitting state. The second intensity modulator 22 is used to modulate a signal state and a decoy state with different intensities, corresponding to the second bit of the code 0 or 1. When the first intensity modulator 21 is modulated into a vacuum state, the second intensity modulator 22 can simultaneously be in decoy state mode, increasing the extinction ratio of the vacuum state. In this way, by setting the binary language 01 encoding to control the decoy state, the phases of the decoy states generated at this time are also independent of each other.

[0106] According to embodiments of this disclosure, the process of encoding single-bit information in a quantum key distribution chip transmitter includes: converting the information to be controlled into binary code. Binary code has only two states: "1" and "0"; converting the encoded binary information into an electrical signal; and inputting the electrical signal into a modulation component, such as an intensity modulator. The intensity modulator, based on the input electrical signal, modulates the intensity of the initial pulsed light signal by changing its internal physical states (such as refractive index, electric field, etc.). In representing the level states of two electrical signals containing single-bit information using binary numbers, the binary numbers correspond to a specific state of the intensity modulator; for example, "1" may represent high intensity, and "0" may represent low intensity. By changing the sequence of the binary code, continuous control of the intensity modulator's state can be achieved, thereby realizing precise control of the initial pulsed light signal intensity.

[0107] Figure 3 The schematic diagram illustrates the working principle of a quantum key chip transmitter device according to another embodiment of the present disclosure.

[0108] According to some embodiments of this disclosure, such as Figure 3 As shown, the modulation component 2 includes a first intensity modulator 21, a second intensity modulator 22, and a polarization encoding module 23. The first intensity modulator 21 is adapted to chop the initial pulse optical signal based on the modulation electrical signal to form a first pulse optical signal containing different photon states; the second intensity modulator 22 is adapted to modulate the first pulse optical signal based on the modulation electrical signal to form multiple second pulse optical signals with different intensities; the polarization encoding module 23 is adapted to adjust the second pulse optical signals to have different polarization states based on the modulation electrical signal to encode the transmitted key information into the second pulse optical signals with different polarization states.

[0109] According to some embodiments of this disclosure, the controller regulates the first intensity modulator 21 and the second intensity modulator 22 to change the intensity of the first pulse light signal and the second pulse light signal, thereby realizing the decoy state; the controller regulates the polarization encoding module 4 to control the different polarization states of the second pulse light signal, thereby realizing the polarization encoding of the decoy state.

[0110] According to some embodiments of this disclosure, the controller applies three modulation electrical signals to the first intensity modulator 2, the second intensity modulator 3, and the polarization encoding module 23, respectively. These signals include a first modulation electrical signal, a second modulation electrical signal, and a third modulation electrical signal. The first, second, and third modulation electrical signals may or may not be consistent, and adjustments can be made to their consistency or inconsistency as needed. By modulating the first, second, and third modulation electrical signals, the accuracy of controlling the intensity of the output optical pulses, including the first and second pulse optical signals, can be improved.

[0111] According to some embodiments of this disclosure, such as Figure 3 As shown, the quantum key chip transmitter device is configured to output an initial pulse light signal by setting a light source module 1; the controller is configured to use binary numbers to represent the level states of two electrical signals containing single-bit information, and output electrical signals as modulation signals according to the level states; the initial pulse light signal is chopped by a first intensity modulator 21 based on the modulation signal to form a first pulse light signal containing different photon states; the first pulse light signal is modulated by a second intensity modulator 22 based on the modulation signal to form multiple second pulse light signals with different intensities; the second pulse light signal is modulated by a polarization encoding module 23 based on the modulation signal to form second pulse light signals with different polarization states, so as to encode the transmitted key information into the second pulse light signals with different polarization states; the first intensity modulator 21, the second intensity modulator 22 and the polarization encoding module 23 modulate the degrees of freedom of the initial pulse light signal under the control of the controller to realize the encoding of single-bit information and change the intensity of the initial pulse light signal, thereby realizing a decoy state, improving the resistance to noise interference, reducing the probability of eavesdropping in quantum communication, improving the accuracy and reliability of quantum communication, and further improving the quality and confidentiality of quantum communication.

[0112] According to some embodiments of this disclosure, polarization coding utilizes the polarization state of an optical signal to carry and transmit information. During the encoding process, different polarization states are used to represent different information or data bits. This polarization coding method relies on the polarization characteristics of light, i.e., the change in the direction of electric field vibration in the light wave. Therefore, by precisely controlling the polarization state of light, efficient and stable information transmission can be achieved.

[0113] According to some embodiments of this disclosure, the polarization encoding module 23 includes a beam splitter 231, two parallel polarization encoding branches 232 and 233, and a polarization beam splitter 234. The beam splitter 231 is adapted to divide the second pulse optical signal into two equal branches; each polarization encoding branch includes a phase modulator and an attenuator. The phase modulator is adapted to modulate the phase of the branch optical signal; the attenuator is adapted to attenuate the branch optical signal to adjust the intensity of the branch optical signal and output a modulated optical signal. The polarization beam splitter 234 is adapted to combine the two modulated optical signals into a single beam signal and then divide the combined beam signal into horizontally polarized light and vertically polarized light according to the polarization direction.

[0114] According to some embodiments of this disclosure, the second pulse optical signal is divided into two branches by a beam splitter 231, and the phase and intensity of the two branches are modulated by two parallel polarization coding branches 232 and 233 respectively, and two modulated optical signals are output. The two modulated optical signals are combined into a combined optical signal by a polarization beam splitter 234, and the combined optical signal is divided into horizontally polarized light and vertically polarized light according to the polarization direction.

[0115] According to some embodiments of this disclosure, each polarization-coded branch is provided with a phase modulator and an attenuator. The phase modulator transmits information by changing the phase of the signal, thereby improving the efficiency and reliability of signal transmission; while the attenuator ensures the stability and accuracy of the signal during transmission by adjusting the signal strength.

[0116] According to some embodiments of this disclosure, the beam splitter 231, polarization-encoded branches 232 and 233, and polarization beam splitter 234 are optically connected in pairs through polarization-maintaining optical fibers so that the polarization state of the branch optical signals transmitted in the polarization-maintaining optical fibers remains unchanged.

[0117] According to some embodiments of this disclosure, by using polarization-maintaining optical fibers to optically connect beam splitter 231, polarization coding branches 232 and 233 and polarization beam splitter 234 respectively, the polarization state of the branch optical signal transmitted in the polarization-maintaining optical fiber can remain unchanged.

[0118] According to some embodiments of this disclosure, polarization-maintaining fiber is an optical fiber communication or sensing line with special properties. By increasing the inherent birefringence properties of the optical fiber, polarization-maintaining fiber overcomes the influence of environmental factors on the polarization state of light transmitted in the optical fiber, thereby ensuring the stable transmission of the polarization state of the light wave and improving the performance of the communication and sensing system.

[0119] According to some embodiments of this disclosure, the phase modulated by the first phase modulator 2321 of the two phase modulators includes 0 and 1. Two, the second phase modulator 2331 in the two phase modulators modulates a phase including 0 and two.

[0120] According to some embodiments of this disclosure, the first phase modulator 2321 is... A phase modulator is capable of modulating 0 and 1. Two phases; the second phase modulator 2331 is A phase modulator is capable of modulating 0 and 1. Two phases.

[0121] According to some embodiments of this disclosure, if the modulation phase of the first phase modulator 2321 is 0 and the modulation phase of the second phase modulator 2331 is 0, a first polarization state is output. The first encoded information is 00; and / or if the first phase modulator 2321 modulates the phase as... The second phase modulator 2331 modulates the phase to 0 and outputs the second polarization state. The second encoded information is 01; and / or if the modulation phase of the first phase modulator 2321 is 0, the modulation phase of the second phase modulator 2331 is... Output the third polarization state The third encoded information is 10; and / or if the first phase modulator 2321 modulates the phase as... The second phase modulator 2331 modulates the phase as follows: Output the fourth polarization state The fourth encoded information is 11.

[0122] According to some embodiments of this disclosure It is horizontally polarized light. It is vertically polarized light. It is a complex number; there are two pairs of perpendicular basis vectors with an included angle of 45° between the first polarization state and the second polarization state, and between the second polarization state and the fourth polarization state.

[0123] According to some embodiments of this disclosure The first polarization state, This is the second polarization state; both the first and second polarization states are linear polarization states. This is the third polarization state, also known as the left-handed polarization state. It is the fourth polarization state, also known as the right-handed polarization state. The third and fourth polarization states are both circular polarization states.

[0124] Figure 4 The schematic diagram illustrates the working principle of a quantum key chip transmitter device according to an embodiment of the present disclosure.

[0125] According to some embodiments of this disclosure, such as Figure 4As shown, the quantum key distribution chip transmitter includes a continuous laser source 3, a controller, multiple intensity modulators 4-7 connected in series, and a phase randomization module 8. The continuous laser source 3 is used to output an initial continuous optical signal; the controller is configured to use binary numbers to represent the level states of two electrical signals containing single-bit information, and outputs an electrical signal as a modulation signal according to the level states; the multiple intensity modulators 4-7 connected in series are used to modulate the initial continuous optical signal based on the modulation electrical signal to generate optical pulse signals with different intensities; the phase randomization module 8 is used to modulate the phase of the optical pulse signal based on the modulation electrical signal, so that the optical pulse signal has multiple different phase states; the phase randomization module includes multiple phase modulators connected in series, each of which is used to modulate the phase of the initial continuous optical signal.

[0126] According to some embodiments of this disclosure, the intensity modulator is controlled by a controller to control the intensity of the initial pulse light signal, thereby achieving a decoy state; the phase randomization module is controlled by a controller to modulate the phase of the light pulse signal, thereby achieving phase randomization.

[0127] According to some embodiments of this disclosure, such as Figure 4 As shown, the quantum key chip transmitter device outputs an initial continuous optical signal through a continuous laser source 3. The controller is configured to represent the level states of two electrical signals containing single-bit information using binary digits, and outputs an electrical signal as a modulation signal based on the level states. Multiple intensity modulators 4-7 connected in series are used to modulate the initial continuous optical signal based on the modulation signal to generate optical pulse signals of different intensities. A phase randomization module 8 modulates the phase of the optical pulse signal based on the modulation signal, giving the optical pulse signal multiple different phase states. Because of the continuous laser source 3, controller, multiple intensity modulators 4-7 connected in series, and phase randomization module 8, this quantum key chip transmitter device can achieve decoy states and phase randomization. Phase randomization enhances security by randomizing the phase of the optical signal, improves resistance to noise interference, increases the accuracy and reliability of quantum communication, and further improves the quality and confidentiality of quantum communication.

[0128] According to some embodiments of this disclosure, each device in the quantum key distribution chip transmitter includes a plurality of intensity modulators 4-7 connected in series and a phase randomization module 8. The method of using single-bit binary encoding for each device in the quantum key distribution chip transmitter allows the chip to be operated by a set binary digital signal in the form of a digital level. Each device in the quantum key distribution chip transmitter is controlled by 0 or 1 encoding, which simplifies the electronic complexity and is suitable for the widespread practical application of quantum key distribution.

[0129] According to some embodiments of this disclosure, the protocol of the aforementioned quantum key chip transmitter is a dual-field protocol. The quantum key chip transmitter integrates all components, including a continuous laser source 3, a controller, multiple intensity modulators 4-7 connected in series, and a phase randomization module 8, onto a lithium niobate optical chip. Lithium niobate is an excellent optical material with good optical properties, thermal stability, and mechanical stability. Integrating all components of the aforementioned quantum key chip transmitter onto a lithium niobate optical chip enables the entire system to operate stably under various environmental conditions, reducing performance fluctuations caused by changes in the external environment. Furthermore, the optical signal maintains high efficiency and stability during transmission within the chip, thereby improving the overall performance of the quantum key chip transmitter.

[0130] According to some embodiments of this disclosure, the controller applies multiple modulation electrical signals to the multiple intensity modulators 4-7 and the phase randomization module 8 connected in series. These signals may be the same or different, and each modulation electrical signal is modulated accordingly based on actual needs. By modulating each modulation electrical signal, the intensity of the optical pulse signal, including the initial continuous optical signal, is changed, thereby improving the accuracy of the control over the optical pulse intensity.

[0131] According to some embodiments of this disclosure, the multiple intensity modulators include a first-level intensity modulator 4, a second-level intensity modulator 5, a third-level intensity modulator 6, and a fourth-level intensity modulator 7. The first-level intensity modulator 4 is suitable for chopping the initial continuous optical signal, converting the continuous initial optical signal into an initial pulsed optical signal; the second-level intensity modulator 5 is suitable for modulating the initial pulsed optical signal to form a first pulsed optical signal with a changed intensity; the third-level intensity modulator 6 is suitable for modulating the intensity of the first pulsed optical signal to generate a reference photon and a working photon; the fourth-level intensity modulator 7 is suitable for modulating the working photon to modulate an optical pulse signal containing a signal state and an optical pulse signal containing a vacuum state.

[0132] According to some embodiments of this disclosure, the intensity of the initial pulse light signal and the first pulse light signal is controlled by the controller through the first-level intensity modulator 4 and the second-level intensity modulator 5, thereby realizing the decoy state; the signal state is the photon state containing key information, and the vacuum state is the state that does not contain any photons.

[0133] According to some embodiments of this disclosure, the intensity of an initial continuous optical signal is modulated by four intensity modulators connected in series to optimize the initial continuous optical signal and improve the extinction ratio. The vacuum state refers to a photon state with zero photons, generated by the intensity modulators through destructive interference using an unequal-arm interferometer structure. Various defects in actual optical quantum chip transmitter systems make it impossible to achieve a true photon count of zero; a small portion of light always passes through the intensity modulators. Increasing the number of intensity modulators, so that they are all in an extinction state, can significantly reduce the average photon count in the actual vacuum state. The extinction ratio is the ratio of the maximum optical power to the minimum optical power output of an optical device. Multiple series-connected intensity modulators in extinction states significantly reduce the vacuum state optical power, thereby greatly improving the extinction ratio.

[0134] According to some embodiments of this disclosure, the first-level intensity modulator 4 and the second-level intensity modulator 5 sequentially modulate the initial continuous optical signal to achieve a decoy state; the third-level intensity modulator 6 is suitable for modulating reference photons and working photons, and these two types of photons can be distinguished by a specific modulation mode; the fourth-level intensity modulator 7 is suitable for modulating signal state and vacuum state, with the vacuum state generally used to increase the extinction ratio or as part of a dual-field protocol. When the first-level intensity modulator 4 and the second-level intensity modulator 5 are modulated into a vacuum state, both the third-level intensity modulator 6 and the fourth-level intensity modulator 7 can be in a low photon intensity state to increase the extinction ratio.

[0135] According to some embodiments of this disclosure, the intensity modulator can achieve signal and vacuum states by changing the intensity or duration of photons. For example, signal states of different intensities can be created by increasing or decreasing the number of photons or adjusting the width of the light pulse; while a vacuum state can be achieved by completely blocking the light pulse. By precisely adjusting the parameters of the intensity modulator, fine control of photon intensity can be achieved, thereby obtaining the desired signal and vacuum states.

[0136] According to some embodiments of this disclosure, the working photon is suitable for carrying key information; the reference photon is suitable for adjusting the phase of the signal photon based on the interference information of the reference photon in the quantum communication process, so as to ensure the identity of the two optical pulse signals generated by the transmitting end and the measuring end respectively arriving at the measuring end.

[0137] According to some embodiments of this disclosure, optical pulses can be specifically encoded or marked by changing their intensity, frequency, phase, or other characteristics to modulate reference photons and working photons.

[0138] According to some embodiments of this disclosure, reference photons are primarily used to calibrate and stabilize optical pulses in quantum communication systems. When two independent systems, Alice and Bob, emit optical pulses through their respective lasers, the characteristics of these pulses may differ due to various factors such as initial phase differences in the lasers and variations in ambient temperature. To ensure that these optical pulses can form stable and effective interference at Charlie, a reference photon is required.

[0139] According to some embodiments of this disclosure, reference photons are transmitted together with signal photons, passing through the same path and multiple cascaded intensity modulators. These multiple cascaded intensity modulators are also equivalent to multiple interferometers. During transmission, temperature changes cause variations in the interferometer arm lengths, affecting the reference photons and resulting in corresponding phase changes. By observing and measuring the interference patterns of the reference photons, information about these phase changes can be obtained; based on the interference information of the reference photons, the phase of the signal photons can be calibrated and adjusted. Adjusting the phase of the signal photons based on the interference information of the reference photons during quantum communication ensures that the light pulses emitted by Alice and Bob have high uniformity at Charlie, forming a stable and clear interference pattern. The working photons are the carriers of the actual transmitted information in quantum communication; after passing through the intensity modulators, the working photons are divided into different states, including a signal state, a vacuum state, and a decoy state. The signal state working photons carry actual quantum information, while the vacuum state does not contain any photons.

[0140] According to some embodiments of this disclosure, in quantum communication, Alice transmits encrypted information to Bob by sending working photons in different states; Bob receives these working photons and decodes the information by measuring their states. Due to the properties of quantum mechanics, any unauthorized third party attempting to eavesdrop on or tamper with this information will be detected immediately, thus ensuring the security of the communication.

[0141] According to some embodiments of this disclosure, such as Figure 4 As shown, multiple phase modulators include Phase modulator 81 Phase modulator 82 Phase modulator 83 and Phase modulator 84.

[0142] According to some embodiments of this disclosure, phase randomization is achieved by configuring multiple phase modulators connected in series. Phase modulator 81 can modulate 0 and Two phases; Phase modulator 82 can modulate 0 and Two phases; Phase modulator 83 can modulate 0 and Two phases; Phase modulator 84 can modulate 0 and Two phases. Phase modulator 81 Phase modulator 82 Phase modulator 83 and The phase modulator 84, with its four phase modulators, generates a combination of phases corresponding to a four-bit binary code from 0000, 0001, ..., 1111. For example: The phase of the phase modulator 84 is modulated from 0 to... This corresponds to changing the fourth bit of the code from 0 to 1.

[0143] According to some embodiments of this disclosure, the phase randomization module includes four phase modulators, each of which has two states: a non-zero modulation voltage and a zero modulation voltage, so that the phase randomization module has 16 different phase states, thereby realizing 16 phase random modulations.

[0144] According to some embodiments of this disclosure, since all devices of the quantum key chip transmitter are integrated on the lithium niobate optical chip, the voltage corresponding to the phase change generated by each phase modulator during the modulation of the phase of the optical pulse signal can be less than 3V. This results in lower power consumption of the quantum key chip transmitter, and the low-voltage phase modulator is easier to integrate with other optoelectronic components. This makes the electro-optic crystal length required for the later phase modulators shorter, reducing the size of the fabricated lithium niobate optical chip and improving the integration of the device.

[0145] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0146] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A modulation method suitable for optical signals, comprising: The level states of two electrical signals containing single-bit information are represented using binary numbers; The electrical signal is output as a modulation electrical signal according to the stated level state; The modulation component in the quantum key chip transmitter device is controlled according to the modulation electrical signal, thereby modulating the degrees of freedom of the optical signal applied to the modulation component to realize the encoding of single-bit information. The modulation component includes: A first intensity modulator is adapted to chop an initial pulsed optical signal based on the modulated electrical signal to form a first pulsed optical signal containing different photon states; and The second intensity modulator is adapted to modulate the first pulse optical signal based on the modulating electrical signal to form a plurality of second pulse optical signals with different intensities; The controller applies two modulation signals to the first intensity modulator and the second intensity modulator, respectively, including the first modulation signal and the second modulation signal. The controller regulates the first intensity modulator and the second intensity modulator to change the intensity of the first pulse light signal and the second pulse light signal, thereby achieving a decoy state.

2. A quantum key chip transmitter device, wherein, include: The light source module is suitable for outputting initial pulse light signals; The controller is configured to use binary numbers to represent the level states of two electrical signals containing single-bit information, and output the electrical signals as modulated electrical signals according to the level states; as well as A modulation component is configured to modulate the degrees of freedom of the initial pulse optical signal under the control of the controller in order to encode single-bit information; The modulation component includes: A first intensity modulator is adapted to chop the initial pulsed optical signal based on the modulated electrical signal to form a first pulsed optical signal containing different photon states; and The second intensity modulator is adapted to modulate the first pulse optical signal based on the modulating electrical signal to form a plurality of second pulse optical signals with different intensities; The controller applies two modulation signals to the first intensity modulator and the second intensity modulator, respectively, including the first modulation signal and the second modulation signal. The controller regulates the first intensity modulator and the second intensity modulator to change the intensity of the first pulse light signal and the second pulse light signal, thereby achieving a decoy state.

3. The quantum key chip transmitter device according to claim 2, wherein, The modulation component quantum key chip transmitter device includes: A polarization encoding module is suitable for modulating the second pulsed optical signal into different polarization states based on the modulated electrical signal, so as to encode the transmitted key information into the second pulsed optical signal with different polarization states; The controller adjusts the first intensity modulator and the second intensity modulator to change the intensity of the first pulse light signal and the second pulse light signal, thereby achieving a decoy state. The polarization encoding module is controlled by the controller to control different polarization states of the second pulse light signal, thereby realizing decoy state polarization encoding.

4. The quantum key chip transmitter device according to claim 3, wherein, The polarization encoding module includes: A beam splitter is suitable for dividing the second pulse optical signal into two equal branches of optical signals. Two parallel polarization coding branches, each polarization coding branch includes: A phase modulator, suitable for modulating the phase of the branch optical signal; and An attenuator, suitable for attenuating the branch optical signal to adjust the intensity of the branch optical signal and outputting a modulated optical signal; and A polarization beam splitter is suitable for combining two modulated optical signals into a single beam signal and splitting the combined beam signal into horizontally polarized light and vertically polarized light according to the polarization direction.

5. The quantum key chip transmitter device according to claim 4, wherein, The phase modulated by the first phase modulator of the two phase modulators includes 0 and The two phase modulators, the second phase modulator of which modulates the phase includes 0 and 1. two.

6. The quantum key chip transmitter device according to claim 5, wherein, If the modulation phase of the first phase modulator is 0 and the modulation phase of the second phase modulator is 0, the output polarization state is 0. The first encoded information is 00; and / or If the first phase modulator modulates the phase The second phase modulator modulates the phase to 0 and outputs the second polarization state. The second encoded information is 01; and / or If the modulation phase of the first phase modulator is 0, the modulation phase of the second phase modulator is... Output the third polarization state The third encoded information is 10; and / or If the first phase modulator modulates the phase The second phase modulator modulates the phase as follows: Output the fourth polarization state The fourth encoding information is 11; in, The horizontally polarized light, For the vertically polarized light, The number is complex; there are two pairs of perpendicular basis vectors with an included angle of 45° between the first polarization state and the second polarization state, and between the second polarization state and the fourth polarization state.

7. A quantum key chip transmitter device, comprising: A continuous laser source, suitable for outputting an initial continuous optical signal; The controller is configured to use binary numbers to represent the level states of two electrical signals containing single-bit information, and output the electrical signals as modulated electrical signals according to the level states; Multiple intensity modulators connected in series are suitable for modulating the initial continuous optical signal based on the modulation electrical signal to generate optical pulse signals with different intensities; as well as A phase randomization module is adapted to modulate the phase of the optical pulse signal based on the modulating electrical signal, so that the optical pulse signal has a variety of different phase states; the phase randomization module includes a plurality of phase modulators connected in series, each of the phase modulators being adapted to modulate the phase of the initial continuous optical signal; Specifically, the controller regulates the intensity modulator to control the intensity of the initial pulsed light signal, thereby achieving a decoy state; the controller also regulates the phase randomization module to modulate the phase of the light pulse signal, thereby achieving phase randomization; the initial pulsed light signal is obtained by chopping an initial continuous light signal. The controller applies multiple modulation signals to a series of intensity modulators and phase randomization modules, and modulates each modulation signal accordingly.

8. The quantum key chip transmitter device according to claim 7, wherein, The plurality of intensity modulators include: A first-level intensity modulator is suitable for chopping the initial continuous optical signal to convert the continuous initial optical signal into an initial pulsed optical signal. A secondary intensity modulator is used to modulate the initial pulse optical signal to form a first pulse optical signal with a changed intensity. A three-stage intensity modulator, suitable for modulating the intensity of the first pulsed optical signal to generate a reference photon and a working photon; and A four-level intensity modulator is suitable for modulating the working photons to produce optical pulse signals containing signal states and optical pulse signals containing vacuum states; The controller regulates the first-level intensity modulator and the second-level intensity modulator to control the intensity of the initial pulse light signal and the first pulse light signal, thereby achieving a decoy state; the signal state is a photon state containing key information, and the vacuum state is a state that does not contain any photons.

9. The quantum key chip transmitter device according to claim 7, wherein, The phase randomization module includes four phase modulators, each of which has two states: a non-zero modulation voltage and a zero modulation voltage. This allows the phase randomization module to have 16 different phase states, thereby achieving 16 types of phase random modulation.

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