Quantum random number generator integrated on basis of co-fired ceramic

Abstract

Provided in the present disclosure is a quantum random number generator integrated on the basis of a co-fired ceramic. The quantum random number generator comprises: a co-fired ceramic substrate, and a quantum state preparation unit, a quantum state measurement chip, a first processing unit and a second processing unit, which are jointly integrated on the co-fired ceramic substrate and are connected in sequence, wherein the quantum state preparation unit comprises a laser chip, the quantum state measurement chip comprises an end face coupler, and three-dimensional alignment is achieved between a light outlet of the laser chip and an input end of the end face coupler by means of a preset alignment structure formed on the co-fired ceramic substrate.

Description

Quantum random number generator based on co-fired ceramic integration

[0001] This application claims priority to Chinese Patent Application No. 202411711237.0, filed on November 27, 2024, the contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to the field of quantum random number generation technology, and more specifically, to a quantum random number generator based on co-fired ceramic integration. Background Technology

[0003] Random numbers are a widely used fundamental resource with broad and important applications in numerous fields such as cryptography, numerical computation, neural network computing, traditional information security, and quantum communication. Quantum random number generators, based on the fundamental principles of quantum physics, produce quantum random numbers that are unpredictable and non-repeatable. Compared to traditional pseudo-random number generators and noise-source random number generators, the source of their randomness is clearer, and their randomness can be rigorously proven using minimum entropy theory, thus offering higher security. This makes them particularly suitable for applications requiring high levels of randomness. From a practical perspective, quantum random number generators need to be small in size, have a high random number generation rate, and exhibit strong stability.

[0004] In realizing the concept disclosed herein, the inventors discovered that a quantum random number generator can be implemented using an optical chip scheme based on vacuum state fluctuation measurement. However, the optical chip scheme based on vacuum state fluctuation measurement requires continuous laser as input. Although silicon-based optical chips can achieve monolithic integration of passive devices, silicon is an indirect bandgap semiconductor with very low direct light emission efficiency, making it impossible to directly integrate the light source on a silicon wafer. If traditional grating coupling or lens coupling methods are used to achieve laser input, problems such as low coupling efficiency and difficulty in controlling the overall size arise. Furthermore, the quantum random number generator requires microelectronic circuits to extract randomness from the raw data and perform post-processing. Therefore, there is currently a lack of effective solutions for achieving optoelectronic integration of the light source, passive optical chip, and backend microelectronic circuits. Summary of the Invention

[0005] In view of this, the present disclosure provides a quantum random number generator based on co-fired ceramic integration.

[0006] One aspect of this disclosure provides a quantum random number generator based on co-fired ceramic integration, comprising: a co-fired ceramic substrate, and a quantum state preparation unit, a quantum state measurement chip, a first processing unit, and a second processing unit, all integrated on the co-fired ceramic substrate and connected in sequence. The quantum state preparation unit includes a laser chip, and the quantum state measurement chip includes an end-face coupler. The light output port of the laser chip and the input port of the end-face coupler are three-dimensionally aligned using a preset alignment structure, which is formed on the co-fired ceramic substrate.

[0007] The quantum random number generator based on co-fired ceramic integration provided in this disclosure integrates the quantum state preparation unit, the quantum state measurement chip, the first processing unit, and the second processing unit onto a single co-fired ceramic substrate. This achieves a high degree of optoelectronic integration of the light source, the passive optical chip, and the back-end microelectronic circuitry, improving system stability and output bandwidth. It also effectively reduces the overall size of the quantum random number generator system while lowering costs. Furthermore, by using a pre-designed alignment structure on the co-fired ceramic substrate, the laser chip's output port and the input end of the end-face coupler can be three-dimensionally aligned, minimizing input loss and ensuring high optical coupling efficiency between the laser chip and the end-face coupler. Attached Figure Description

[0008] The above and 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:

[0009] Figure 1 shows a schematic diagram of a quantum random number generator based on co-fired ceramic integration according to an embodiment of the present disclosure;

[0010] Figure 2 shows a top view of a quantum random number generator based on co-fired ceramic integration according to an embodiment of the present disclosure;

[0011] Figure 3 shows a perspective view of a quantum random number generator based on co-fired ceramic integration according to an embodiment of the present disclosure;

[0012] Figure 4 illustrates a quantum state preparation unit and a quantum state measurement chip according to an embodiment of the present disclosure;

[0013] Figure 5 shows a schematic diagram of a quantum random number generator according to an embodiment of the present disclosure.

[0014] Explanation of reference numerals in the attached figures: 100, quantum random number generator; 1, co-fired ceramic substrate; D1, alignment structure; d1, preset groove; 2, quantum state preparation unit; 21, laser chip; 22, vacuum state input; 3, quantum state measurement chip; 31, end-face coupler; 32, passive device; 4, first processing unit; 41, first photodetector chip; 42, transimpedance amplifier; 43, second photodetector chip; 5, second processing unit; 51, operational amplifier; 52, analog-to-digital converter; 53, randomness extraction circuit; 54, microcontroller unit; 55, memory unit. Detailed Implementation

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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 a person 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.).

[0019] In the embodiments disclosed herein, the collection, updating, analysis, processing, use, transmission, provision, disclosure, and storage of data (e.g., including but not limited to user personal information) comply with relevant laws and regulations, are used for legitimate purposes, and do not violate public order and good morals. In particular, necessary measures have been taken to prevent unauthorized access to user personal information data and to safeguard user personal information security and network security.

[0020] In the embodiments disclosed herein, user authorization or consent is obtained before acquiring or collecting user personal information.

[0021] Random numbers are a widely used fundamental resource with broad and important applications in many fields, including cryptography, numerical computation, neural network computing, traditional information security, and quantum communication. Quantum random number generators, based on the fundamental principles of quantum physics, produce quantum random numbers that are unpredictable and non-repeatable. Compared to traditional pseudo-random number generators and noise-source random number generators, the source of their randomness is clearer, and their randomness can be rigorously proven using minimum entropy theory, thus offering higher security and making them particularly suitable for applications requiring high levels of randomness.

[0022] Quantum random number generators have been implemented in various ways, such as photon path selection, photon arrival time, laser phase fluctuation, and vacuum state fluctuation measurement. From a practical perspective, quantum random number generators need to be small in size, have a high random number generation rate, and be highly stable. The optical chip solution based on vacuum state fluctuation measurement does not require an optical interferometer, has a simple optical structure, and can be integrated on a single silicon chip. Quantum state measurement can be directly realized on the chip, and the final random number generation rate can reach over 10 Gbps. This meets the standards of small size, high stability, and high speed for next-generation quantum communication systems, and therefore has the best application prospects.

[0023] The aforementioned optical chip solution based on vacuum fluctuation measurement requires continuous laser as input. While silicon-based optical chips can achieve monolithic integration of passive devices, silicon, being an indirect bandgap semiconductor, has very low direct light emission efficiency, making it impossible to directly integrate the light source on a silicon wafer. Using traditional grating coupling or lens coupling for laser input presents problems of low coupling efficiency and difficulty in controlling the overall size. Furthermore, the quantum random number generator requires microelectronic circuits to extract randomness from the raw data and perform post-processing. Therefore, a highly effective solution for achieving optoelectronic integration of the light source, passive optical chip, and backend microelectronic circuitry is currently lacking.

[0024] To at least partially address the technical problems existing in related technologies, this disclosure provides a quantum random number generator based on co-fired ceramic integration. The quantum random number generator based on co-fired ceramic integration includes: a co-fired ceramic substrate, and a quantum state preparation unit, a quantum state measurement chip, a first processing unit, and a second processing unit, all integrated on the co-fired ceramic substrate and connected sequentially. The quantum state preparation unit includes a laser chip, and the quantum state measurement chip includes an end-face coupler. The light output port of the laser chip and the input port of the end-face coupler are three-dimensionally aligned using a preset alignment structure, which is formed on the co-fired ceramic substrate.

[0025] Figure 1 shows a schematic diagram of a quantum random number generator based on co-fired ceramic integration according to an embodiment of the present disclosure.

[0026] Figure 2 shows a top view of a quantum random number generator based on co-fired ceramic integration according to an embodiment of the present disclosure.

[0027] According to embodiments of this disclosure, as shown in Figures 1 and 2, the quantum random number generator 100 includes: a co-fired ceramic substrate 1, and a quantum state preparation unit 2, a quantum state measurement chip 3, a first processing unit 4, and a second processing unit 5, all integrated on the co-fired ceramic substrate 1 and connected sequentially. The quantum state preparation unit 2 includes a laser chip 21, and the quantum state measurement chip 3 includes an end-face coupler 31. The light output port of the laser chip 21 and the input port of the end-face coupler 31 are three-dimensionally aligned using a preset alignment structure D1, which is formed on the co-fired ceramic substrate 1.

[0028] According to embodiments of this disclosure, a co-fired ceramic substrate can be manufactured from many monolithic ceramic substrates through processes such as lamination, hot pressing, debinding, and sintering. Due to the multilayer structure of the co-fired ceramic substrate, its wiring density is high, and the interconnect length can be minimized, thereby improving assembly density and signal transmission speed. Thus, the co-fired ceramic substrate can meet the requirements of quantum random number generators for system miniaturization, high density, multifunctionality, high reliability, high speed, and high power.

[0029] According to embodiments of this disclosure, a quantum random number generator can generate truly random numbers based on quantum physics principles. These numbers possess characteristics such as unpredictability, non-repeatability, and unbiasedness, making them a key core component in quantum communication systems.

[0030] According to one embodiment of this disclosure, the structure of a quantum random number generator may include three parts: an entropy source, a measurement, and post-processing. The entropy source outputs a quantum state, which is the source of quantum randomness. The measurement is a measurement of the entropy source, generating initial random numbers. The initial data is affected by factors such as environmental noise, non-ideal entropy source, and measurement noise, thus having certain biases and correlations. First, entropy estimation needs to be performed on the original data, and then randomness is extracted through a post-processing algorithm to finally obtain completely random quantum numbers.

[0031] According to embodiments of this disclosure, as shown in Figures 1 and 2, the quantum state preparation unit 2 can be used to output a quantum state, and the quantum state measurement chip 3 can be used to measure random signals generated by quantum fluctuations. The first processing unit 4 and the second processing unit 5 can be used to process the data to obtain real-time generated quantum random numbers. The co-fired ceramic substrate 1 can be used as a substrate to support the aforementioned quantum state preparation unit 2, quantum state measurement chip 3, first processing unit 4, and second processing unit 5, and provide electronic connections for each unit.

[0032] According to embodiments of this disclosure, the co-fired ceramic substrate 1 can provide physical support and electronic connections for the quantum state preparation unit 2, the quantum state measurement chip 3, the first processing unit 4, and the second processing unit 5, achieving a high degree of optoelectronic integration of the light source, passive optical chip, and back-end microelectronic circuitry. This improves system stability and output bandwidth, and effectively reduces the overall system size of the quantum random number generator 100 while lowering costs. As just one example, compared to a solution using lens optical coupling with a heat sink substrate, the overall system size of the quantum random number generator 100 provided in this disclosure embodiment is reduced by 50%.

[0033] According to embodiments of this disclosure, quantum random number generators can be classified into discrete and continuous types depending on the random source.

[0034] According to one embodiment of this disclosure, a continuous quantum random number generator uses continuous laser pulses as an entropy source, enabling the generation of multiple random bits in a single measurement. It is not limited by single-photon detectors, resulting in a higher quantum random number generation rate. A representative example is the quantum random number generator based on vacuum shot noise. Vacuum shot noise is essentially the statistical fluctuation of observational data caused by vacuum fluctuations. The measured value of the canonical component X or P of the vacuum state is a Gaussian random variable, which can typically be measured using a zero-difference detection device. For example, it can be implemented using an optical chip scheme based on vacuum state fluctuation measurement. The advantages of this scheme are that the vacuum state is easy to prepare, the system is simple and easy to integrate, and shot noise is theoretically white noise with infinite bandwidth, thus allowing for the generation of a large number of raw random numbers in a single sampling.

[0035] According to embodiments of this disclosure, a coherent state is a pure state in quantum mechanics, which is closest to the quantum state of a classical light field. The photon number distribution in a coherent state follows a Poisson distribution, and the quantum noise of its two orthogonal components is equal, conforming to the minimum uncertainty relation. In practical applications, coherent states are often used to describe the light field output by a laser. The vacuum state is a special case of the photon number state where n=0, representing a quantum state without any photons. Although there are no photons in the vacuum state, quantum fluctuations still exist in the electromagnetic field; these fluctuations are called vacuum fluctuations. The vacuum state represents the lowest limit of quantum noise, also known as the quantum noise limit. In a quantum random number generator, the fluctuations of the vacuum state can serve as a source for generating truly random numbers.

[0036] According to embodiments of this disclosure, as shown in Figures 1 and 2, the quantum state preparation unit 2 includes a laser chip 21, and the quantum state measurement chip 3 includes an end-face coupler 31. The laser chip 21 is used to provide continuous laser light, i.e., coherent light. One input terminal of the end-face coupler 31 receives the coherent light output from the laser chip 21, while the other input terminal is left unused, serving as a vacuum state input 22. The output port of the laser chip 21 and the input terminal of the end-face coupler 31 are three-dimensionally aligned using a preset alignment structure D1, which is formed on a co-fired ceramic substrate 1. Exemplarily, the alignment structure D1 can be selected as a groove structure or a boss structure, etc.

[0037] According to embodiments of this disclosure, the end-face coupler 31 can be understood as a coupler located at the edge of the optical chip. The end-face coupler can achieve efficient transmission of optical signals by precisely aligning the optical chip and the light source, and has advantages such as high coupling efficiency and large operating bandwidth.

[0038] Understandably, the three-dimensional alignment of the end-face coupler 31 with the light source is crucial for achieving high optical coupling efficiency of the end-face coupler 31. This is because only when the light emitted from the light source (such as the laser chip 21) precisely matches the optical mode field (mode spot) of the end-face coupler 31 can light reflection and scattering be minimized, thereby improving light transmission efficiency. For example, three-dimensional alignment may include vertical alignment (ensuring the beam is height-aligned with the waveguide end face), horizontal alignment (ensuring the beam is centered on the waveguide end face for maximum optical coupling efficiency), and angular alignment (ensuring the beam is at the correct angle to the waveguide axis).

[0039] According to embodiments of this disclosure, by using the pre-designed alignment structure D1 on the co-fired ceramic substrate 1, the output port of the laser chip 21 and the input end of the end coupler 31 can be three-dimensionally aligned to minimize input loss, thereby ensuring high optical coupling efficiency between the laser chip 21 and the end coupler 31.

[0040] Therefore, the quantum random number generator 100 based on co-fired ceramic integration provided in this embodiment achieves a high degree of optoelectronic integration of the light source, passive optical chip, and back-end microelectronic circuit by integrating the quantum state preparation unit 2, quantum state measurement chip 3, first processing unit 4, and second processing unit 5 onto a single co-fired ceramic substrate 1. This improves system stability and output bandwidth, and effectively reduces the overall size of the quantum random number generator 100 system while lowering costs. Furthermore, by using the pre-designed alignment structure D1 on the co-fired ceramic substrate 1, the output port of the laser chip 21 and the input end of the end-face coupler 31 can be three-dimensionally aligned to minimize input loss, thereby ensuring high optical coupling efficiency between the laser chip 21 and the end-face coupler 31.

[0041] According to an embodiment of this disclosure, a preset groove d1 is formed on the co-fired ceramic substrate 1, and the laser chip 21 is fixed in the preset groove. The light output port of the laser chip 21 and the end face coupler 31 are aligned in three dimensions using the preset groove d1.

[0042] Figure 3 shows a perspective view of a quantum random number generator based on co-fired ceramic integration according to an embodiment of the present disclosure. Figure 4 shows a quantum state preparation unit and a quantum state measurement chip according to an embodiment of the present disclosure.

[0043] According to one embodiment of this disclosure, as shown in Figures 3 and 4, a preset groove d1 is formed on the co-fired ceramic substrate 1. The laser chip 21 is fixed in the preset groove d1, and the light output port of the laser chip 21 and the end face coupler 31 are three-dimensionally aligned using the preset groove d1.

[0044] As an example only, based on the multilayer structure and fabrication process of the co-fired ceramic substrate 1, a preset groove d1 can be made on at least one monolithic ceramic substrate by means of mechanical punching / laser punching, so that the light output port of the laser chip 21 and the input end of the end coupler 31 can be aligned in three dimensions using the preset groove d1.

[0045] Compared to boss structures, the method of forming groove structures on co-fired ceramic substrates has advantages such as simple process, less material usage, low cost, and high integration.

[0046] According to an embodiment of this disclosure, the depth of the preset groove d1 is determined based on the height difference between the laser chip 21 and the end face coupler 31. The depth of the preset groove d1 enables the light output port of the laser chip 21 and the input end of the end face coupler 31 to be aligned in the vertical direction. The fixed position of the laser chip 21 in the preset groove d1 is determined based on the maximum optical coupling efficiency between the laser chip 21 and the end face coupler 31.

[0047] According to the embodiments of this disclosure, as shown in Figures 3 and 4, the height difference between the laser chip 21 and the end face coupler 31 can be accurately measured first, and then the height difference can be determined as the depth of the preset groove d1. This allows the light output port of the laser chip 21 and the input end of the end face coupler 31 to be aligned in the vertical direction based on the preset groove d1, thereby ensuring that the light emitted by the laser chip 21 is height-aligned with the waveguide end face.

[0048] According to the embodiments of this disclosure, as shown in Figures 3 and 4, the maximum optical coupling efficiency between the laser chip 21 and the end-face coupler 31 within the preset groove d1 can be determined first, and then the position corresponding to the maximum optical coupling efficiency can be determined as the fixed position of the laser chip 21. This allows the light output port of the laser chip 21 and the input end of the end-face coupler 31 to be aligned horizontally and angularly based on the preset groove d1.

[0049] Therefore, based on the preset groove d1 formed on the co-fired ceramic substrate 1, three-dimensional alignment between the light output port of the laser chip 21 and the input end of the end coupler 31 can be achieved, thereby effectively reducing light loss and ensuring high optical coupling efficiency between the laser chip 21 and the end coupler 31.

[0050] According to an embodiment of this disclosure, the method for fixing the laser chip 21 includes: placing the laser chip 21 in a preset groove d1 to align the light output port of the laser chip 21 with the input end of the end face coupler 31 in the vertical direction; moving the laser chip 21 in the preset groove d1 in the horizontal direction according to a preset step size to determine the maximum optical coupling efficiency between the laser chip 21 and the end face coupler 31; determining the position corresponding to the maximum optical coupling efficiency as the fixed position of the laser chip 21; and fixing the laser chip 21 in the fixed position to achieve three-dimensional alignment between the light output port of the laser chip 21 and the input end of the end face coupler 31.

[0051] As an example, since the depth of the preset groove d1 is determined based on the height difference between the laser chip 21 and the end-face coupler 31, placing the laser chip 21 within the preset groove d1 allows for vertical alignment of the laser chip 21's output port with the end-face coupler 31's input port. In the horizontal direction, the laser chip 21 can be held in place by an electrically powered clamp and moved within the preset groove d1 in preset steps. Simultaneously, an electric coupling stage can be connected to the laser chip 21. Because the electrically powered clamp is conductive and holds the laser chip 21, an electrical connection can be established between the electric coupling stage and the laser chip 21, enabling the measurement of the optical coupling efficiency between the laser chip 21 and the end-face coupler 31. By measuring the optical coupling efficiency at various positions within the preset groove d1, the position corresponding to the maximum optical coupling efficiency can be found, and this position can be designated as the fixed position of the laser chip 21. The laser chip 21 can then be fixed at this fixed position using adhesive dispensing, thus achieving the fixation of the laser chip 21.

[0052] Preferably, the alignment error between the output port of the laser chip 21 and the input port of the end coupler 31 in all directions (front-back, left-right, up-down) needs to be controlled within 50μm, so as to ensure high-efficiency coupling of optical signals.

[0053] According to an embodiment of the present disclosure, the quantum state measurement chip 3 further includes a passive device 32, which is integrated on the quantum state measurement chip 3; the output end of the quantum state measurement chip 3 is constructed as a beveled structure so that the optical signal can undergo total internal reflection at the output end of the quantum state measurement chip 3, thereby changing the output direction of the optical signal from the horizontal direction to the vertical direction.

[0054] According to embodiments of this disclosure, as shown in Figures 1-4, the quantum state measurement chip 3 further includes a passive device 32 integrated on-chip. The quantum state measurement chip 3 is used to receive the optical signal output from the end-face coupler 31 and to perform quantum state measurement. The quantum state measurement chip 3 can, for example, be a silicon-based optical chip. Exemplarily, the end-face receiver can couple the continuous laser input from the laser chip 21 into the quantum state measurement chip 3, thereby outputting the optical signal to the passive device 32 integrated on the quantum state measurement chip 3.

[0055] According to embodiments of this disclosure, based on the refractive index characteristics of the silicon dioxide waveguide, the output end of the quantum state measurement chip 3 is constructed as a beveled structure. More preferably, the angle of this beveled structure can be set to 45°. The optical signal can undergo total internal reflection at the output end of the quantum state measurement chip 3, changing the output direction of the optical signal from horizontal to vertical.

[0056] According to embodiments of this disclosure, the optical signal includes a coherent state sub-signal and a vacuum state sub-signal. The first processing unit 4 includes a first photodetector chip 41, a transimpedance amplifier 42, and a second photodetector chip 43 connected in sequence. The first photodetector chip 41 and the second photodetector chip 43 are used to receive the coherent state sub-signal and the vacuum state sub-signal output by the quantum state measurement chip 3. The first photodetector chip 41 is used to output a first electrical signal, and the second photodetector chip 43 is used to output a second electrical signal. The transimpedance amplifier 42 is used to receive the differential mode signal between the first electrical signal and the second electrical signal. The photosensitive surface of the first photodetector chip 41 is perpendicular to the light emission direction of the coherent state sub-signal, and the electrode of the first photodetector chip 41 is horizontally bonded to the electrode of the co-fired ceramic substrate 1. The photosensitive surface of the second photodetector chip 43 is perpendicular to the light emission direction of the vacuum state sub-signal, and the electrode of the second photodetector chip 43 is horizontally bonded to the electrode of the co-fired ceramic substrate 1.

[0057] According to embodiments of this disclosure, the first processing unit 4 is used to perform photoelectric conversion and amplification of the optical signal. As shown in Figures 1-4, the first processing unit 4 includes a first photodetector chip 41, a transimpedance amplifier 42, and a second photodetector chip 43 connected in sequence. The first photodetector chip 41 and the second photodetector chip 43 are used for photoelectric conversion, and the transimpedance amplifier 42 is used for signal amplification.

[0058] According to one embodiment of this disclosure, the first photodetector chip 41 and the second photodetector chip 43 have the same structure, and are preferably low-noise, high-response photodetector chips. The first photodetector chip 41 and the second photodetector chip 43 are used to receive the coherent state sub-signal and the vacuum state sub-signal output by the quantum state measurement chip 3. The first photodetector chip 41 is used to output a first electrical signal, and the second photodetector chip 43 is used to output a second electrical signal. The transimpedance amplifier 42 is used to receive the differential-mode signal between the first and second electrical signals. The first electrical signal characterizes the detection result of the first photodetector chip 41 on the coherent state sub-signal and the vacuum state sub-signal, and the second electrical signal characterizes the detection result of the second photodetector chip 43 on the coherent state sub-signal and the vacuum state sub-signal. The difference between the first and second electrical signals can be determined as the differential-mode signal, which can be used to characterize the vacuum state sub-signal.

[0059] According to one embodiment of this disclosure, the photosensitive surface of the photodetector chip and its electrodes are located on the same plane. If the light emission direction of the quantum state measurement chip 3 is horizontal, the photosensitive surface of the photodetector chip needs to be along a vertical plane, making it difficult to bond its electrodes to the substrate electrodes. However, because the output end of the quantum state measurement chip 3 in this embodiment is constructed with a beveled structure, the light signal can undergo total internal reflection at the output end of the quantum state measurement chip 3, thereby changing the light emission direction of the light signal from horizontal to vertical. Therefore, the photosensitive surface of the photodetector chip can be facing upwards to receive the light signal output by the quantum state measurement chip 3, and the electrodes of the photodetector chip can be directly horizontally bonded to the substrate electrodes.

[0060] Understandably, by using the oblique cut structure designed at the output end of the quantum state measurement chip 3, the direction of light output is changed from horizontal to vertical, allowing the first photodetector chip 41 and the second photodetector chip 43 to be compactly integrated near the quantum state measurement chip 3. At the same time, the electrodes of the first photodetector chip 41 and the second photodetector chip 43 can be directly horizontally bonded to the substrate electrodes, thereby improving the output bandwidth and reducing the system size and noise crosstalk.

[0061] According to an embodiment of this disclosure, the second processing unit 5 includes: an operational amplifier 51, an analog-to-digital converter 52, a randomness extraction circuit 53, a microcontroller unit 54, and a memory unit 55, wherein the operational amplifier 51, the analog-to-digital converter 52, and the randomness extraction circuit 53 are connected in sequence, and the output terminal of the transimpedance amplifier 42 is connected to the input terminal of the operational amplifier 51.

[0062] According to embodiments of this disclosure, the second processing unit 5 is used to acquire electrical signals characterizing quantum fluctuations and to perform post-processing on the electrical signals. As shown in Figures 1-4, the second processing unit 5 includes an operational amplifier 51, an analog-to-digital converter 52, a randomness extraction circuit 53, a microcontroller unit (MCU) 54, and a memory unit 55.

[0063] According to an embodiment of this disclosure, as shown in Figures 1-4, an operational amplifier 51, an analog-to-digital converter 52, and a randomness extraction circuit 53 are connected in sequence, and the output terminal of the transimpedance amplifier 42 is connected to the input terminal of the operational amplifier 51.

[0064] According to embodiments of this disclosure, the transimpedance amplifier 42, operational amplifier 51, analog-to-digital converter 52, randomness extraction circuit 53, microcontroller unit 54, and memory unit 55 are all connected to the electrodes of the co-fired ceramic substrate 1 via surface mount technology.

[0065] According to embodiments of this disclosure, the use of patch connections facilitates the realization of high-bandwidth, small-size, and low-noise optoelectronic integration of the quantum random number generator 100.

[0066] According to embodiments of this disclosure, the end-face coupler 31 is configured as a silicon-based reverse wedge structure.

[0067] According to embodiments of this disclosure, the end-face coupler 31 of the silicon-based inversed-taper structure can increase the mode field radius of the waveguide, thereby increasing the mode matching degree between the waveguide and the laser, and thus improving the optical coupling efficiency.

[0068] According to an embodiment of this disclosure, the coefficient of thermal expansion of the co-fired ceramic substrate 1 is 3.9 × 10⁻⁶. -6 / ℃~5.5×10 -6 The temperature coefficient of dielectric constant of the co-fired ceramic substrate 1 is 10ppm / K to 20ppm / K.

[0069] According to embodiments of this disclosure, thanks to the small coefficient of thermal expansion and temperature coefficient of dielectric constant of the co-fired ceramic substrate 1, the deformation amplitude of the co-fired ceramic substrate 1 is extremely low under high-temperature conditions. This makes the optical connection between the laser chip 21, the end-face coupler 31, the quantum state measurement chip 3, and the photodetector chip less susceptible to the effects of high-temperature environments, thereby ensuring that the high optical coupling efficiency between the laser chip 21 and the end-face coupler 31 remains stable. Furthermore, without affecting the optical coupling efficiency, the co-fired ceramic substrate 1 can also provide a large operating temperature range for the quantum random number generator 100, meeting the industrial-grade standard of -40℃ to 85℃.

[0070] According to one embodiment of this disclosure, the co-fired ceramic substrate 1 can be selected as a low-temperature co-fired ceramic substrate (LTCC) or a high-temperature co-fired ceramic substrate (HTCC).

[0071] Figure 5 shows a schematic diagram of a quantum random number generator according to an embodiment of the present disclosure.

[0072] According to an embodiment of this disclosure, as shown in FIG5, the laser chip 21 provides continuous laser light, i.e., coherent state sub-signals. coherent state signals The signal enters one input terminal of the quantum state measurement chip 3 through the end-face coupler 31. The other input terminal of the quantum state measurement chip 3 is left unused, serving as a vacuum state sub-signal. enter.

[0073] As shown in Figure 5, coherent state sub-signals and vacuum state sub-signals After processing by the passive device 32 integrated on the quantum state measurement chip 3, two different quantum state lights are output, representing the quantum state... and quantum state

[0074] As shown in Figure 5, the two quantum state lights undergo photoelectric conversion through the first photodetector chip 41 and the second photodetector chip 43, respectively, generating two photocurrents. Photocurrent i1 corresponds to the first electrical signal mentioned above, and photocurrent i2 corresponds to the second electrical signal mentioned above. The two photocurrents are input to the transimpedance amplifier 42, which amplifies the weak high-frequency current signal and converts it into a voltage signal. This voltage signal is the random signal generated by quantum fluctuations.

[0075] As shown in Figure 5, the voltage signal output by the transimpedance amplifier 42 is still relatively weak and needs to be further amplified by the operational amplifier 51 before it can be acquired and quantized by the analog-to-digital converter 52. The amplified voltage signal enters the analog-to-digital converter 52, and after conversion, it generates raw data. After post-processing by the randomness extraction circuit 53, real-time quantum random numbers can be obtained. During this process, the memory unit 55 configures the randomness extraction circuit 53, and the microcontroller unit 54 is responsible for issuing instructions and controlling the overall circuit.

[0076] The working principle of the quantum random number generator according to an embodiment of this disclosure will be explained in detail below with reference to Figures 1-5:

[0077] Quantum fluctuations exist in coherent optical fields, satisfying the principle of minimum uncertainty in amplitude and phase. This random number scheme essentially quantizes and extracts coherent quantum fluctuations. In this embodiment, two photodetector chips are used to perform balanced detection of the two beams output from the quantum state measurement chip 3, thus demonstrating randomness.

[0078] Laser chip 21 has one input source (i.e., continuous laser light) and the other input source (i.e., vacuum state light). Let's assume the quantum states of the two input sources are... remember After processing by the passive device 32 on the quantum state measurement chip 3, the quantum states of the two output lights are denoted as follows: The following relationships exist:

[0079] In equations (1)-(2), That is, a vacuum state;

[0080] After photoelectric conversion, the current passing through the first photodetector chip 41 and the second photodetector chip 43 is:

[0081] In equations (3)-(4), k is the quantum efficiency of the photodetector. The light intensities of the two input photodetectors are respectively corresponding to the light intensities of the two input photodetectors; The superscript "+" has been added to represent Hermitian conjugation of quantum states. The current value should be equal to the product of quantum efficiency and light intensity, and the difference Δi between the two currents is:

[0082] It can be proven that:

[0083] In equation (6), <Δi 2 >Corresponding quantum noise σ q Quantum noise is reflected in the results of equilibrium detection. In this embodiment, the noise σ obtained by the data acquisition and post-processing circuit is... total 2 The distribution is divided into two parts: quantum noise σ q 2 and classical noise σ e 2 , i.e. σ total 2 =σ q 2 +σ e 2 (7)

[0084] Continuous laser light is a coherent source, and its average photon number is denoted as μ. For a coherent source, the photon number n follows a Poisson distribution P(n), which is given by the following equation (8):

[0085] After the two photodetectors perform zero-difference detection of the photodetector results, the photon number p k It follows a Skellam distribution, the distribution of which is given by the following equation (9): p k =P(n1-n2=k)=e -2μ I k (2μ) (9)

[0086] In equation (9), I k (2μ) is the modified Bessel function; n1 and n2 correspond to the average number of photons in the two beams, which are also two parameters of the Skellam distribution, determining the shape of the distribution.

[0087] In this embodiment of the disclosure, the distribution of quantum noise can be obtained through the above calculations.

[0088] Classical noise in the system follows a Gaussian distribution; it is only necessary to measure the noise level when there is no light input.

[0089] Classical noise σ e 2 Then the proportion of quantum noise can be calculated.

[0090] The minimum entropy H is obtained by calculating the quantum noise distribution. ∞ Randomness is quantified by minimum entropy, which is defined as: H ∞ =-log2p max (10)

[0091] In equation (10), p max This represents the probability of the most likely outcome. The random numbers from vacuum fluctuations follow a Skellam distribution, determined by the aforementioned quantum noise variance σ. q 2 Then you can get p max Thus, the minimum entropy can be calculated.

[0092] In the final random number post-processing, the Toeplitz matrix algorithm based on the Fast Fourier Transform is adopted, with a matrix size of n×m. This means that m bits of final random numbers can be extracted from n bits of original quantum random number data, satisfying the following relationship: n / m≤H ∞ The above processing yields the final quantum random number, whose randomness originates from the fundamental principles of quantum physics and is verifiable by information theory.

[0093] In the above scheme, the minimum entropy of the original data is calculated based on the measurement results, which can be obtained in real time within the randomness extraction circuit 53, thus achieving accurate estimation of the minimum entropy. After post-processing, the final quantum random numbers of vacuum state fluctuations can be obtained in real time. Through the above scheme, high-speed and stable quantum random numbers can be obtained.

[0094] Those skilled in the art will understand that the features described in the various embodiments of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments of this disclosure can be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0095] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A quantum random number generator based on co-fired ceramic integration, wherein, The quantum random number generator includes: a co-fired ceramic substrate, and a quantum state preparation unit, a quantum state measurement chip, a first processing unit, and a second processing unit, all integrated on the co-fired ceramic substrate and connected in sequence. The quantum state preparation unit includes a laser chip, and the quantum state measurement chip includes an end-face coupler. The light output port of the laser chip and the input port of the end-face coupler are three-dimensionally aligned using a preset alignment structure, which is formed on the co-fired ceramic substrate.

2. The quantum random number generator according to claim 1, wherein, A preset groove is formed on the co-fired ceramic substrate, and the laser chip is fixed in the preset groove. The light output port of the laser chip and the end face coupler are aligned in three dimensions using the preset groove.

3. The quantum random number generator according to claim 2, wherein, The depth of the preset groove is determined based on the height difference between the laser chip and the end face coupler. The depth of the preset groove enables the laser chip's output port and the end face coupler's input port to be aligned in the vertical direction. The fixed position of the laser chip within the preset groove is determined based on the maximum optical coupling efficiency between the laser chip and the end-face coupler.

4. The quantum random number generator according to claim 3, wherein, The method for fixing the laser chip includes: The laser chip is placed in the preset groove to align the light output port of the laser chip with the input end of the end face coupler in the vertical direction. In the horizontal direction, the laser chip is moved within the preset groove according to a preset step size to determine the maximum optical coupling efficiency between the laser chip and the end face coupler; The position corresponding to the maximum optical coupling efficiency is determined as the fixed position of the laser chip, and the laser chip is fixed at the fixed position to achieve three-dimensional alignment between the light output port of the laser chip and the input end of the end face coupler.

5. The quantum random number generator according to any one of claims 1-4, wherein, The quantum state measurement chip also includes passive devices integrated on the quantum state measurement chip; the output end of the quantum state measurement chip is constructed with a beveled structure so that the optical signal can undergo total internal reflection at the output end of the quantum state measurement chip, thereby changing the output direction of the optical signal from the horizontal direction to the vertical direction.

6. The quantum random number generator according to claim 5, wherein, The optical signal includes coherent state sub-signals and vacuum state sub-signals. The first processing unit includes a first photodetector chip, a transimpedance amplifier, and a second photodetector chip connected in sequence. The first photodetector chip and the second photodetector chip are used to receive coherent state sub-signals and vacuum state sub-signals output by the quantum state measurement chip. The first photodetector chip is used to output a first electrical signal, and the second photodetector chip is used to output a second electrical signal. The transimpedance amplifier is used to receive the differential mode signal between the first electrical signal and the second electrical signal. In this configuration, the photosensitive surface of the first photodetector chip is perpendicular to the light emission direction of the coherent state sub-signal, and the electrodes of the first photodetector chip are horizontally bonded to the electrodes of the co-fired ceramic substrate; the photosensitive surface of the second photodetector chip is perpendicular to the light emission direction of the vacuum state sub-signal, and the electrodes of the second photodetector chip are horizontally bonded to the electrodes of the co-fired ceramic substrate.

7. The quantum random number generator according to claim 6, wherein, The second processing unit includes an operational amplifier, an analog-to-digital converter, a randomness extraction circuit, a microcontroller unit, and a memory unit, wherein the operational amplifier, the analog-to-digital converter, and the randomness extraction circuit are connected in sequence, and the output terminal of the transimpedance amplifier is connected to the input terminal of the operational amplifier.

8. The quantum random number generator according to claim 7, wherein, The transimpedance amplifier, the operational amplifier, the analog-to-digital converter, the randomness extraction circuit, the microcontroller unit, and the memory unit are all connected to the electrodes of the co-fired ceramic substrate via surface mount technology.

9. The quantum random number generator according to any one of claims 1-4, wherein, The end-face coupler is configured as a silicon-based reverse wedge structure.

10. The quantum random number generator according to any one of claims 1-4, wherein, The coefficient of thermal expansion of the co-fired ceramic substrate is 3.9 × 10⁻⁶. -6 / ℃~5.5×10 -6 The temperature coefficient of dielectric constant of the co-fired ceramic substrate is 10ppm / K to 20ppm / K.

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