Offset-adjustable entanglement source generating device

Abstract

The invention relates to the technical field of optics, and provides a bias-adjustable entangled source generation device, which is characterized in that a first compressed light generation module generates first compressed light, the loss a of the first compressed light is adjusted through a first adjustable optical loss device, a second compressed light generation module generates second compressed light, the loss b of the second compressed light is adjusted through a second adjustable optical loss device, and a bias-adjustable entangled source is generated. The first compressed light after the loss a is adjusted and the second compressed light after the loss b is adjusted are coupled on the adjustable beam splitter to generate an entanglement source; the entanglement source respectively enters the third adjustable optical loss device to adjust loss c and enters the fourth adjustable optical loss device to adjust loss d, and the entanglement source after the loss c and the loss d are adjusted enters the combined measurement module to carry out combined measurement. The device can flexibly adjust the offset of the entanglement source, namely, the difference value between the orthogonal amplitude and the phase relevance, so that the diversified requirements of different quantum application scenes on the entanglement source characteristics are met, and a solid foundation is laid for promoting further development and wide application of quantum science and technology.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical technology, and particularly relates to a bias-adjustable entangled source generation device. BACKGROUND

[0002] An entangled source is a typical non-classical light field which breaks the independent and separable properties of light in classical physics. In the magical world of quantum mechanics, when multiple particles or light fields are in an entangled state, a special correlation is formed between them, which is not limited by spatial distance. Even if the particles are far apart, the measurement of one particle will instantly affect the state of the other particle, which is the famous "quantum entanglement" phenomenon. Entangled sources are based on this property to generate light fields with entanglement characteristics. In the light field generated by the entangled source, there is a unique correlation between the orthogonal amplitude and the phase, which is the key to realizing many quantum applications. For example, in quantum communication, the characteristics of the entangled source can be used to achieve secure key distribution that cannot be eavesdropped; in quantum computing, it can provide special quantum correlation resources for quantum bit operations, greatly improving computing speed; in quantum measurement and sensing, entangled sources can break the classical limit of measurement precision and achieve ultra-high precision measurement. Therefore, entangled sources play an extremely important role in the development process of modern quantum technology.

[0003] In the field of quantum communication, security and efficiency are eternal pursuit goals, and the characteristics of the entangled source play a key role in this process. Taking continuous variable quantum key distribution technology as an example, it is an important way to use the continuous variable characteristics of light field to achieve secure key distribution. In this process, the correlation degree of the orthogonal amplitude and the phase becomes the core element of optimizing the key generation rate and communication distance. When the communication demand focuses on achieving extremely high key generation rate in a short distance, increasing the orthogonal amplitude correlation and reducing the orthogonal phase correlation is an effective strategy. This is because in short distance transmission, the signal attenuation is relatively small, and by enhancing the orthogonal amplitude correlation, information can be more efficiently encoded and transmitted, thereby significantly improving the speed and quantity of key generation. Conversely, when facing the challenge of long communication distance, due to the inevitable signal loss and interference in the transmission process, it is particularly important to appropriately reduce the orthogonal amplitude correlation and increase the orthogonal phase correlation. Increased orthogonal phase correlation can enhance the anti-interference ability of the signal, reduce the information loss and bit error rate caused by the increase of transmission distance, and thus ensure the stability and reliability of communication, and realize secure communication over a longer distance.

[0004] In the field of quantum measurement, multi-parameter quantum measurement technology aims to obtain accurate information of multiple physical quantities simultaneously to break through the limitations of traditional measurement methods. The unique properties of entangled sources make this possible, and by finely adjusting the correlation of orthogonal amplitude and phase, simultaneous measurement of multiple orthogonal components can be achieved. When measuring multiple parameters of a microscopic quantum system, traditional measurement methods are often limited by measurement accuracy and sequence, and cannot accurately obtain the values of multiple parameters simultaneously. With the help of entangled sources and their strong correlation between orthogonal components, measurement schemes can be designed to make the information of multiple orthogonal components interrelated and complementary, thus obtaining accurate measurement results of multiple parameters simultaneously in one measurement process, greatly improving measurement efficiency and accuracy, and providing a more powerful measurement method for quantum physics research and related technology applications.

[0005] Given the key role of entangled sources in the above quantum technology field, it is necessary to design a bias-adjustable entangled source generation device. SUMMARY

[0006] To solve the above problems, the purpose of the present application is to provide a bias-adjustable entangled source generation device that can flexibly adjust the bias of the entangled source, i.e., the difference in the correlation of orthogonal amplitude and phase, to meet the diverse needs of different quantum application scenarios for entangled source characteristics, and lay a solid foundation for further development and widespread application of quantum technology.

[0007] The above invention purpose of the present application is realized by the following technical scheme:

[0008] A bias-adjustable entangled source generation device, comprising: a first compressed light generation module, a second compressed light generation module, a first adjustable optical loss device, a second adjustable optical loss device, an adjustable beam splitter, a third adjustable optical loss device, a fourth adjustable optical loss device, and a joint measurement module.

[0009] The first compressed light generation module is used to generate first compressed light, the second compressed light generation module is used to generate second compressed light, the first adjustable optical loss device is used to adjust the loss a introduced at the first compressed state output end, the second adjustable optical loss device is used to adjust the loss b introduced at the second compressed state output end, the adjustable beam splitter is used to adjust the splitting ratio, the third adjustable optical loss device is used to adjust the loss c introduced at the first coupling output end, and the fourth adjustable optical loss device is used to adjust the loss d introduced at the second coupling output end.

[0010] The first compression light generating module generates the first compression light, and the first adjustable optical loss device adjusts the loss a; the second compression light generating module generates the second compression light, and the second adjustable optical loss device adjusts the loss b; the first compression light after the loss a is adjusted and the second compression light after the loss b is adjusted are coupled on the adjustable beam splitter to generate an entanglement source.

[0011] The entanglement source enters the third adjustable optical loss device to adjust the loss c, and enters the fourth adjustable optical loss device to adjust the loss d; the entanglement source after the loss c and the loss d are adjusted enters the joint measurement module for joint measurement.

[0012] Further, the first compression light generating module is a first optical parametric cavity, and the second compression light generating module is a second optical parametric cavity.

[0013] The first optical parametric cavity receives input first seed light and first pump light to generate first compression light.

[0014] The second optical parametric cavity receives input second seed light and second pump light to generate second compression light.

[0015] Further, the bias-adjustable entanglement source generating device further comprises a laser, a first optical beam splitter, a second optical beam splitter, a third optical beam splitter, and a first fundamental light high-reflection mirror.

[0016] The laser outputs laser light which is split into two beams by the first optical beam splitter; the first beam of the first optical beam splitter passes through the second optical beam splitter, and the first beam of the second optical beam splitter is input into the third optical beam splitter.

[0017] The first beam of the third optical beam splitter is input into the first optical parametric cavity as the first seed light; and the second beam of the third optical beam splitter is input into the second optical parametric cavity as the second seed light after passing through the first fundamental light high-reflection mirror.

[0018] Further, the bias-adjustable entanglement source generating device further comprises an optical filtering cavity.

[0019] The optical filtering cavity is arranged between the laser and the first optical beam splitter, and is used for filtering high-frequency noise of the laser light output by the laser to improve the beam quality and spatial mode distribution of the fundamental light, and to provide a high-quality low-noise light source for preparation and measurement of the bias-adjustable entanglement source.

[0020] Further, the bias-adjustable entanglement source generating device further comprises a first dichroic mirror, a frequency doubling cavity, a fourth optical beam splitter, a second dichroic mirror, a frequency-doubled light high-reflection mirror, and a third dichroic mirror.

[0021] The second beam of the first optical beam splitter enters the frequency doubling cavity through the first dichroic mirror, and the frequency-doubled light generated by the frequency doubling cavity is split by the fourth optical beam splitter;

[0022] The first beam of the fourth optical beam splitter enters the first optical parametric cavity as the first pump light after passing through the second dichroic mirror; the second beam of the fourth optical beam splitter enters the second optical parametric cavity as the second pump light after passing through the frequency-doubled light high-reflection mirror and the third dichroic mirror.

[0023] Further, the bias-adjustable entangled source generation device further comprises:

[0024] The first dichroic mirror is high-reflective to fundamental light and high-transmissive to frequency-doubled light;

[0025] The second dichroic mirror is high-reflective to frequency-doubled light and high-transmissive to fundamental light;

[0026] The third dichroic mirror is high-reflective to frequency-doubled light and high-transmissive to fundamental light.

[0027] Further, it further comprises a second fundamental light high-reflection mirror, a third fundamental light high-reflection mirror, a fourth fundamental light high-reflection mirror, and a fifth fundamental light high-reflection mirror;

[0028] The second fundamental light high-reflection mirror is arranged between the first adjustable optical loss device and the adjustable beam splitter;

[0029] The third fundamental light high-reflection mirror is arranged between the second adjustable optical loss device and the adjustable beam splitter;

[0030] The fourth fundamental light high-reflection mirror is arranged between the adjustable beam splitter and the third adjustable optical loss device;

[0031] The fifth fundamental light high-reflection mirror is arranged between the adjustable beam splitter and the fourth adjustable optical loss device.

[0032] Further, the joint measurement module comprises a first balanced homodyne detector, a second balanced homodyne detector, and a joint measurement device;

[0033] After adjusting the loss c and the loss d, the entangled sources enter the first balanced homodyne detector and the second balanced homodyne detector, respectively, for joint measurement in the joint measurement device.

[0034] Further, the bias-adjustable entangled source generation device further comprises a fifth optical beam splitter, a sixth fundamental light high-reflection mirror, a seventh fundamental light high-reflection mirror, and an eighth fundamental light high-reflection mirror;

[0035] The second beam of the second optical beam splitter provides the first balanced homodyne detector and the second balanced homodyne detector with local light;

[0036] The laser emitted by the second beam of the second optical beam splitter is split into two beams through the fifth optical beam splitter;

[0037] The first beam of the fifth optical beam splitter inputs the first balanced homodyne detector as the local light of the first balanced homodyne detector;

[0038] The second beam of the fifth optical beam splitter inputs the second balanced homodyne detector through the sixth fundamental light high reflection mirror, the seventh fundamental light high reflection mirror and the eighth fundamental light high reflection mirror as the local light of the second balanced homodyne detector.

[0039] Further, the bias-adjustable entangled source generating device further comprises:

[0040] The first adjustable optical loss device is composed of a 15a half-wave plate and a 15b polarization beam splitting prism;

[0041] The second adjustable optical loss device is composed of a 16a half-wave plate and a 16b polarization beam splitting prism;

[0042] The third adjustable optical loss device is composed of a 22a half-wave plate and a 22b polarization beam splitting prism;

[0043] The fourth adjustable optical loss device is composed of a 23a half-wave plate and a 23b polarization beam splitting prism.

[0044] Compared with the prior art, the present application includes at least one of the following beneficial effects:

[0045] (1) Meet the needs of quantum science and technology in multiple scenarios: In the field of quantum computing, different quantum algorithms have different requirements for the characteristics of entangled sources. This device can generate entangled states that adapt to specific algorithms by adjusting the bias, improving the correlation efficiency between quantum bits, and thus accelerating the processing speed of complex computing tasks, promoting the process of quantum computing technology from theory to practicality. In the field of quantum sensing, whether it is small displacement, magnetic field change or biological molecule detection, accurate measurement depends on appropriate entangled sources. By finely adjusting the difference between the orthogonal amplitude and phase correlation, the sensing accuracy and sensitivity can be optimized to meet the high-precision measurement needs of multiple scenarios and expand the application boundaries of quantum sensing. In the field of quantum simulation, the simulation of different quantum systems requires specific entanglement characteristics. This device can simulate a variety of complex quantum environments with the bias-adjustable function, helping researchers to explore the characteristics of quantum materials, the micro-mechanism of chemical reactions, etc., and providing key support for the development of materials science, chemistry and other disciplines.

[0046] (2) Promoting quantum science frontier research: It provides a powerful tool for quantum mechanics basic research. With its ability to precisely control the bias of entangled sources, researchers can deeply explore the essential characteristics of quantum entanglement, verify some frontier theories in quantum mechanics, such as quantum non-locality and quantum correlation, and deepen human understanding of the microscopic world. In exploring new quantum states, the device can create a variety of different biased entangled states, providing the possibility of discovering new quantum phenomena and quantum states, and helping to expand the theoretical boundaries of quantum technology and lay the theoretical foundation for subsequent technological breakthroughs.

[0047] (3) Improve the compatibility and expandability of quantum technology: Its design has high flexibility and scalability, and can be compatible with a variety of existing quantum technologies and devices. In building large-scale quantum networks, the bias of entangled sources can be adjusted flexibly according to the functional requirements of different nodes to achieve efficient quantum information transmission and processing. When integrated with other quantum optical elements or quantum computing chips, it can also optimize the performance of the entire system by virtue of its adjustable characteristics, promoting the integration and large-scale development of quantum technology. This compatibility and expandability make the device a key link in the quantum technology ecosystem, pushing quantum technology from isolated experiments to systematic and engineering applications. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 The bias-adjustable entangled source diagram of the present application;

[0049] Figure 2 The bias-adjustable entangled source device diagram of the present application;

[0050] Figure 3 The relationship between the four variables and the quantum correlation degree when the beam splitting ratio is 0.5.

[0051] Figure 4 The relationship between the four variables and the quantum correlation degree when the beam splitting ratio is 0.45.

[0052] Figure 5 The relationship between the four variables and the quantum correlation degree when the beam splitting ratio is 0.55.

[0053] REFERENCE NUMERALS

[0054] 1: laser; 2: optical filter cavity; 3: first optical beam splitter; 4: second optical beam splitter; 5: third optical beam splitter; 6: first fundamental light high reflection mirror; 7: first optical parametric cavity; 8: second optical parametric cavity; 9: frequency doubling cavity; 10: first dichroic mirror; 11: fourth optical beam splitter; 12: second dichroic mirror; 13: frequency doubling light high reflection mirror; 14: third dichroic mirror; 15: first adjustable optical loss device; 16: second adjustable optical loss device; 17: second fundamental light high reflection mirror; 18: third fundamental light high reflection mirror; 19: adjustable beam splitter; 20: fourth fundamental light high reflection mirror; 21: fifth fundamental light high reflection mirror; 22: third adjustable optical loss device; 23: fourth adjustable optical loss device; 24: first balanced homodyne detector; 25: second balanced homodyne detector; 26: fifth optical beam splitter; 27: sixth fundamental light high reflection mirror; 28: seventh fundamental light high reflection mirror; 29: eighth fundamental light high reflection mirror; 30: joint measurement device. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0056] Those skilled in the art can understand that, unless specifically stated, the singular forms "one", "a", "said" and "the" used herein also include the plural forms. It should be further understood that the phrase "comprising" used in the specification of the present application means that the features, integers, steps, operations, elements and / or components exist, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0057] The entangled source is generated by coupling of two squeezed light fields, including the quadrature amplitude correlation V(X a +X b ) and the quadrature phase correlation V(Y a -Y b ), and the difference between the correlations of the two quadratures is defined as the bias, i.e.

[0058] ΔV=V(X a +X b )-V(Y a -Y b )

[0059] wherein X a and X bY a and Y b are the quadrature amplitude components of the two modes a and b of the entangled source, V represents the variance, ΔV represents the bias, which is used to describe the difference degree of the correlation between the two quadrature components of the entangled source.

[0060] The quadrature amplitude correlation is represented as

[0061] V(X a +X b ) = α1[(1-ε a )V1(X) + ε a ] + β1[(1-ε b )V2(Y) + ε b ] + ε c + ε d

[0062] The quadrature phase correlation is represented as

[0063] V(Y a -Y b ) = α2[(1-ε a )V1(Y) + ε a ] + β2[(1-ε b )V2(X) + ε b ] + ε c + ε d

[0064] where V1(X) and V1(Y) are the quadrature amplitude variance and quadrature phase variance of the first squeezed state light field respectively, V2(X) and V2(Y) are the quadrature amplitude variance and quadrature phase variance of the second squeezed state light field respectively, ε a is the loss introduced at the output end of the first squeezed state, ε b is the loss introduced at the output end of the second squeezed state, ε c is the loss introduced at the first coupling output end, ε d is the loss introduced at the second coupling output end, α1, β1, α2, β2 are coefficients related to the loss (ε c and ε d ) of the detection end and the splitting ratio T, and are represented as

[0065]

[0066]

[0067] First embodiment

[0068] As Figure 1As shown, the embodiment provides a bias-adjustable entanglement source generation device, comprising: a first compressed light generation module, a second compressed light generation module, a first adjustable optical loss device 15, a second adjustable optical loss device 16, an adjustable beam splitter 19, a third adjustable optical loss device 22, a fourth adjustable optical loss device 23, and a joint measurement module.

[0069] The first compressed light generation module is used to generate first compressed light, the second compressed light generation module is used to generate second compressed light, the first adjustable optical loss device 15 is used to adjust the loss a introduced at the first compressed state output end, the second adjustable optical loss device 16 is used to adjust the loss b introduced at the second compressed state output end, the adjustable beam splitter 19 is used to adjust the splitting ratio, the third adjustable optical loss device 22 is used to adjust the loss c introduced at the first coupling output end, and the fourth adjustable optical loss device 23 is used to adjust the loss d introduced at the second coupling output end.

[0070] After the first compressed light generation module generates the first compressed light, the loss a is adjusted through the first adjustable optical loss device 15, and after the second compressed light generation module generates the second compressed light, the loss b is adjusted through the second adjustable optical loss device 16. The first compressed light after adjusting the loss a and the second compressed light after adjusting the loss b are coupled on the adjustable beam splitter 19 to generate an entanglement source.

[0071] The entanglement source enters the third adjustable optical loss device 22 to adjust the loss c and enters the fourth adjustable optical loss device 23 to adjust the loss d. After adjusting the loss c and the loss d, the entanglement source enters the joint measurement module for joint measurement.

[0072] The above technical solution can precisely control the key parameters affecting the bias of the entanglement source by independently setting the first to fourth adjustable optical loss devices and the adjustable beam splitter. This means that the difference between the orthogonal amplitude and phase correlation of the entanglement source can be quickly and flexibly adjusted according to the needs of different quantum application scenarios, greatly expanding the applicability of the entanglement source in various quantum technologies. Whether it is to pursue the ultimate quantum state preparation accuracy or to meet the specific requirements of complex quantum algorithms for entanglement characteristics, this device can provide an adaptive entanglement source through parameter adjustment, effectively improving the performance and efficiency of the quantum system.

[0073] In the embodiment, the first compressed light generation module is a first optical parametric cavity 7, and the second compressed light generation module is a second optical parametric cavity 8. The first optical parametric cavity 7 receives input first seed light and first pump light to generate first compressed light. The second optical parametric cavity 8 receives input second seed light and second pump light to generate second compressed light.

[0074] In this embodiment, the seed light, pump light and compressed light are further described:

[0075] Seed light: The seed light is essentially a low-intensity input light signal that plays the role of a "starting template" throughout the optical process. In this device, the first seed light and the second seed light received by the first optical parametric cavity 7 and the second optical parametric cavity 8 respectively provide the initial light field basis for the subsequent generation of compressed light. By analogy with the process of laser amplification, the seed light is like a spark, although its energy is not high, but it can trigger a series of subsequent optical changes. It interacts with the pump light in the optical parametric cavity, and the characteristics of its light field, such as frequency, phase and polarization state, will be preserved and amplified in the subsequent process. In the process of optical parametric amplification, the frequency of the seed light determines the frequency range of the final generated compressed light, and its phase information will affect the quantum properties of the compressed light.

[0076] Pump light: Compared with the seed light, the pump light has higher intensity and energy. In this device, it provides the necessary energy for the amplification of the seed light and the generation of compressed light. From the perspective of energy conversion, the pump light is like the fuel of the engine, constantly injecting power into the optical process. In the first optical parametric cavity 7 and the second optical parametric cavity 8, the pump light and the seed light are coupled in the nonlinear optical medium. The energy of the pump light is transferred to the seed light, so that the intensity of the seed light is enhanced, and its quantum fluctuation characteristics are changed, thereby generating compressed light. In the optical parametric process based on the second-order nonlinear optical effect, the photons of the pump light are converted into pairs of signal light (seed light) and idler light photons in the nonlinear medium, thereby realizing the amplification of the seed light and the generation of compressed light.

[0077] Compressed light: Compressed light belongs to non-classical light field, which has unique quantum properties compared with ordinary light. The fluctuations of the electric field and the magnetic field of ordinary light are uniformly distributed in all directions, but the quantum fluctuations of the light field in the orthogonal components (such as orthogonal amplitude and orthogonal phase) are changed through specific optical processes, such as the interaction of seed light and pump light in the optical parametric cavity in this device. The quantum fluctuations of one of the orthogonal components are compressed, while the fluctuations of the other orthogonal component are increased accordingly. This property has important application value in quantum communication, quantum measurement, etc. In quantum communication, the low fluctuation characteristics of the orthogonal components of compressed light can be used to improve the transmission quality of the signal, reduce the interference of noise on the signal, and realize more secure and efficient quantum key distribution; in quantum measurement, compressed light can break through the precision limit of classical measurement and achieve ultra-high precision measurement of small physical quantities.

[0078] In the embodiment, the bias-adjustable entanglement source generation device further comprises: a laser 1, a first optical beam splitter 3, a second optical beam splitter 4, a third optical beam splitter 5, a first fundamental light high-reflection mirror 6;

[0079] The laser 1 outputs laser light which is split into two beams by the first optical beam splitter 3, the first beam of the first optical beam splitter 3 passes through the second optical beam splitter 4, and the first beam of the second optical beam splitter 4 is input into the third optical beam splitter 5;

[0080] The first beam of the third optical beam splitter 5 is input into the first optical parametric cavity 7 as the first seed light, and the second beam of the third optical beam splitter 5 passes through the first fundamental light high-reflection mirror 6 and is input into the second optical parametric cavity 8 as the second seed light.

[0081] In the embodiment, the bias-adjustable entanglement source generation device further comprises: an optical filtering cavity 2;

[0082] The optical filtering cavity 2 is arranged between the laser 1 and the first optical beam splitter 3, and is used for filtering high-frequency noise of the laser light output by the laser 1, so as to improve the beam quality and spatial mode distribution of the fundamental light, and to provide a high-quality low-noise light source for preparation and measurement of the bias-adjustable entanglement source.

[0083] In the embodiment, the bias-adjustable entanglement source generation device further comprises: a first dichroic mirror 10, a frequency doubling cavity 9, a fourth optical beam splitter 11, a second dichroic mirror 12, a frequency-doubled light high-reflection mirror 13, and a third dichroic mirror 14; the second beam of the first optical beam splitter 3 enters the frequency doubling cavity 9 through the first dichroic mirror 10, the frequency doubling cavity 9 generates frequency-doubled light which is split by the fourth optical beam splitter 11; the first beam of the fourth optical beam splitter 11 passes through the second dichroic mirror 12 and is input into the first optical parametric cavity 7 as the first pump light; the second beam of the fourth optical beam splitter 11 passes through the frequency-doubled light high-reflection mirror 13 and the third dichroic mirror 14 and is input into the second optical parametric cavity 8 as the second pump light.

[0084] In addition, the first dichroic mirror 10 has high reflectivity to fundamental light and high transmissivity to frequency-doubled light; the second dichroic mirror 12 has high reflectivity to frequency-doubled light and high transmissivity to fundamental light; and the third dichroic mirror 14 has high reflectivity to frequency-doubled light and high transmissivity to fundamental light. The first dichroic mirror 10 has high reflectivity to fundamental light, so that the fundamental light split from the first optical beam splitter 3 is reflected and changes the direction of propagation into the frequency-doubling cavity 9; meanwhile, the first dichroic mirror 10 has high transmissivity to frequency-doubled light, so that the frequency-doubled light generated by the frequency-doubling cavity 9 can pass through smoothly and continue the subsequent optical path. The second dichroic mirror 12 and the third dichroic mirror 14 have high reflectivity to frequency-doubled light, respectively reflecting the frequency-doubled light in specific optical paths to the first optical parametric cavity 7 and the second optical parametric cavity 8 to provide pump light for generating compressed light; and the second dichroic mirror 12 and the third dichroic mirror 14 have high transmissivity to fundamental light, so as not to interfere with the propagation of fundamental light in other optical paths, ensuring that the fundamental light and the frequency-doubled light propagate according to the predetermined path and realize the orderly distribution of the optical field.

[0085] In the embodiment, the bias-adjustable entanglement source generating device further comprises a second fundamental light high-reflection mirror 17, a third fundamental light high-reflection mirror 18, a fourth fundamental light high-reflection mirror 20, and a fifth fundamental light high-reflection mirror 21; the second fundamental light high-reflection mirror 17 is arranged between the first adjustable optical loss device 15 and the adjustable beam splitter 19; the third fundamental light high-reflection mirror 18 is arranged between the second adjustable optical loss device 16 and the adjustable beam splitter 19; the fourth fundamental light high-reflection mirror 20 is arranged between the adjustable beam splitter 19 and the third adjustable optical loss device 22; and the fifth fundamental light high-reflection mirror 21 is arranged between the adjustable beam splitter 19 and the fourth adjustable optical loss device 23.

[0086] The primary role of these high-reflection mirrors for fundamental light is to change the direction of propagation of the fundamental light. In a complex optical system of the device, they act as "traffic controllers", ensuring that the fundamental light adjusted by the first and second adjustable optical loss devices can accurately and reliably propagate to the adjustable beam splitter 19 for coupling to generate entangled sources. The generated entangled sources can also be guided by them to smoothly enter the third and fourth adjustable optical loss devices to achieve precise control of the optical path and ensure the orderly progress of the entire optical process. Multiple reflections can increase the propagation path length and time of light in the device. For the key process of generating entangled sources, i.e. the interaction of light between various optical elements, longer propagation path means more interactions of light with nonlinear optical media, adjustable optical loss devices, etc. In the adjustable optical loss device, after multiple reflections, light can interact more fully with related elements, thereby more finely adjusting the loss of light and improving the control accuracy of the characteristics of the entangled source. Through reflection, these high-reflection mirrors can improve the spatial distribution and mode of the optical field. In the optical system, the uniformity and mode stability of the optical field have an important influence on the generation and performance of the entangled source. They can make the optical field more uniform during propagation, reduce the divergence or distortion of the optical field, thereby optimizing the quality of the optical field entering the adjustable beam splitter and subsequent optical elements, and help to generate more stable and better performing entangled sources. During the entire operation of the device, small changes in the external environment may interfere with the optical path. The fixed reflection characteristics of these high-reflection mirrors can offset the influence of external interference on the optical path to some extent, maintaining the stability of the optical path. Even if the performance of the light source or other optical elements appears to fluctuate slightly, they can ensure that the light propagates according to the predetermined path, ensuring the reliability of the entangled source generation process and reducing experimental errors and device operation failures.

[0087] In the present embodiment, the joint measurement module comprises a first balanced homodyne detector 24, a second balanced homodyne detector 25, and a joint measurement device 30; the entangled sources after adjusting the loss c and the loss d enter the first balanced homodyne detector 24 and the second balanced homodyne detector 25 respectively in the joint measurement device 30 for joint measurement.

[0088] The balanced homodyne detector has extremely high measurement accuracy, can effectively suppress classical noise, and accurately measure the quantum fluctuations of the quadrature components (such as quadrature amplitude and quadrature phase) of the optical field. In the device, the first and second balanced homodyne detectors measure the entangled source after loss c and loss d adjustment, respectively, and can obtain accurate information of the quadrature components of the entangled source. In quantum optics experiments, small quantum fluctuation changes are crucial, and the balanced homodyne detector can capture these subtle changes to provide accurate data support for studying the characteristics of the entangled source. The joint measurement device can comprehensively analyze the measurement results of the two balanced homodyne detectors, and can obtain more comprehensive quantum characteristics of the entangled source. The correlation of the quadrature amplitude and quadrature phase of the entangled source is an important quantum characteristic, and by measuring the entangled source from different angles through the two detectors and integrating the data by the joint measurement device, the entanglement degree and correlation characteristics of the entangled source can be accurately judged. This has important significance for evaluating whether the entangled source meets the requirements of specific quantum applications and for in-depth study of quantum entanglement phenomena. Through the measurement results of the joint measurement module on the entangled source, it can be verified whether the device successfully produces an entangled source with the expected characteristics. If the measurement results do not match the theoretical expectations, researchers can analyze the working state of each component in the device to find out the problem, such as whether the loss adjustment is accurate, whether the beam splitting ratio is appropriate, etc., and then optimize and improve the device to improve the quality and stability of the entangled source produced by the device.

[0089] In the present embodiment, the bias-adjustable entangled source generation device further comprises a fifth optical beam splitter 26, a sixth fundamental light high reflector 27, a seventh fundamental light high reflector 28, and an eighth fundamental light high reflector 29.

[0090] The second beam of the second optical beam splitter 4 provides the first balanced homodyne detector 24 and the second balanced homodyne detector 25 with background light; the laser emitted by the second beam of the second optical beam splitter 4 is split into two beams by the fifth optical beam splitter 26; the first beam of the fifth optical beam splitter 26 is input into the first balanced homodyne detector 24 as the background light of the first balanced homodyne detector 24; the second beam of the fifth optical beam splitter 26 is input into the second balanced homodyne detector 25 through the sixth fundamental light high reflector 27, the seventh fundamental light high reflector 28, and the eighth fundamental light high reflector 29 as the background light of the second balanced homodyne detector 25.

[0091] In the embodiment, the bias-adjustable entanglement source generation device further comprises: the first adjustable optical loss device 15 is composed of a 15a half-wave plate and a 15b polarization beam splitter prism; the second adjustable optical loss device 16 is composed of a 16a half-wave plate and a 16b polarization beam splitter prism; the third adjustable optical loss device 22 is composed of a 22a half-wave plate and a 22b polarization beam splitter prism; and the fourth adjustable optical loss device 23 is composed of a 23a half-wave plate and a 23b polarization beam splitter prism.

[0092] In the embodiment, the working process of the bias-adjustable entanglement source generation device is as follows: the laser output by the laser 1 passes through the optical filtering cavity 2 to filter high-frequency noise, improve the beam quality and spatial mode distribution of the fundamental frequency light, and provide a high-quality low-noise light source for the preparation and measurement of the bias-adjustable entanglement source. The laser passes through the first optical beam splitter 3 to be divided into two beams, one of which passes through the second optical beam splitter 4, the third optical beam splitter 5 and the first fundamental frequency light high-reflection mirror 6 to enter the first optical parametric cavity 7 and the second optical parametric cavity 8 respectively as the seed light of the two optical parametric cavities, and the other passes through the first dichroic mirror 10 to enter the frequency doubling cavity 9 to generate frequency-doubled light which passes through the fourth optical beam splitter 11, the second dichroic mirror 12, the frequency-doubled light high-reflection mirror 13, the third dichroic mirror 14 to enter the two optical parametric cavities respectively as the pump light of the two optical parametric cavities. The compressed light generated by the two optical parametric cavities passes through the first adjustable optical loss device 15 and the second adjustable optical loss device 16, and the second fundamental frequency light high-reflection mirror 17 and the third fundamental frequency light high-reflection mirror 18 respectively, and is coupled on the adjustable beam splitter 19 to generate an entanglement source. The entanglement source passes through the fourth fundamental frequency light high-reflection mirror 20 and the fifth fundamental frequency light high-reflection mirror 21 to enter the third adjustable optical loss device 22 and the fourth adjustable optical loss device 23 respectively, and finally enters the first balanced homodyne detector 24 and the second balanced homodyne detector 25 for joint measurement 30. The background light of the balanced homodyne detector is provided by the other beam of the second optical beam splitter 4, which passes through the fifth optical beam splitter 26, the sixth fundamental frequency light high-reflection mirror 27, the seventh fundamental frequency light high-reflection mirror 28 and the eighth fundamental frequency light high-reflection mirror 29 to enter the two balanced homodyne detectors respectively as the background light of the balanced homodyne detector.

[0093] Second embodiment

[0094] As shown in Figure 2 , an example of a specific experimental device of a bias-adjustable entanglement source generation device is provided. In the embodiment, the optical filtering cavity 2 adopts a mode cleaner 2, the first optical beam splitter 3 adopts a first polarization beam splitter prism 3, the second optical beam splitter 4 adopts a second polarization beam splitter prism 4, the third optical beam splitter 5 adopts a third polarization beam splitter prism 5, the fourth optical beam splitter 11 adopts a fourth polarization beam splitter prism 11, and the fifth optical beam splitter 26 adopts a fifth polarization beam splitter prism 26.

[0095] The laser output from laser 1 is filtered by mode cleaner 2 to remove high-frequency noise, improve the fundamental frequency beam quality and spatial mode distribution, and provide a high-quality, low-noise light source for the preparation and measurement of bias-tunable entangled sources. The beam is split into two beams by the first polarizing beam splitter 3. One beam passes through the second polarizing beam splitter 4, the third polarizing beam splitter 5, and the first fundamental frequency high-reflection mirror 6, and enters the first optical parametric cavity 7 and the second optical parametric cavity 8, respectively, serving as the seed light for the two optical parametric cavities. The other beam passes through the first dichroic mirror 10 and enters the frequency doubling cavity 9. The generated frequency-doubled light passes through the fourth polarizing beam splitter 11, the second dichroic mirror 12, the frequency doubling high-reflection mirror 13, and the third dichroic mirror 14, and enters the two optical parametric cavities, respectively, serving as the pump light for the two optical parametric cavities. The compressed light generated by the two optical parametric cavities passes through the first adjustable optical loss device 15 (composed of a 15a half-wave plate and a 15b polarizing beam splitter prism) and the second adjustable optical loss device 16 (composed of a 16a half-wave plate and a 16b polarizing beam splitter prism), as well as the second fundamental frequency high-reflection mirror 17 and the third fundamental frequency high-reflection mirror 18, and is coupled on the adjustable beam splitter 19 to generate an entangled source. The entangled source enters the third adjustable optical loss device 22 (composed of a half-wave plate 22a and a polarizing beam splitter 22b) and the fourth adjustable optical loss device 23 (composed of a half-wave plate 23a and a polarizing beam splitter 23b) respectively through the fourth fundamental frequency high-reflection mirror 20 and the fifth fundamental frequency high-reflection mirror 21. Finally, it enters the first balanced null detector 24 and the second balanced null detector 25 for joint measurement 30. The background light of the balanced null detector is provided by another beam from the second polarizing beam splitter 4. After passing through the fifth polarizing beam splitter 26, the sixth fundamental frequency high-reflection mirror 27, the seventh fundamental frequency high-reflection mirror 28, and the eighth fundamental frequency high-reflection mirror 29, it enters the two balanced null detectors respectively as the background light of the balanced null detectors.

[0096] Third Embodiment

[0097] like Figure 3 As shown in Figures 4 and 5, the four variables ε are displayed when the beam splitting ratio T = 0.5, 0.45, and 0.55, respectively. a ε b ε c ε d Regarding the relationship with quantum correlation, the black straight line in the diagram represents orthogonal phase correlation, the black dashed line represents orthogonal amplitude correlation, and the black dotted line represents bias. We can see that by changing ε... a ε b ε c ε d The values ​​ε and T can alter the orthogonal amplitude and phase correlations of the entangled sources, thereby changing the bias ΔV. Therefore, an adjustable ε can be set in the optical path. a ε b ε c ε dWith T, the bias can be adjusted.

[0098] (a) such as Figure 3 As shown, the case where the beam splitting ratio is 0.5 is as follows:

[0099] Figure 3 (a) demonstrates ε b =0, ε c =0, ε d =0, T=0.5, the effect of loss a on quantum correlation Figure 3 (b) demonstrates ε a =0, ε c =0, ε d =0, T=0.5, the effect of loss b on quantum correlation Figure 3 (c) demonstrates ε a =0, ε b =0, ε d =0, T=0.5, the effect of loss c on quantum correlation Figure 3 (d) demonstrates ε a =0, ε b =0, ε c =0, T=0.5, the effect of loss d on quantum correlation

[0100] from Figure 3 As can be seen, when the beam splitting ratio is 0.5: loss a only affects amplitude correlation; increasing loss a decreases amplitude correlation, while phase correlation remains unchanged and bias increases; loss b only affects phase correlation; increasing loss b decreases phase correlation, while amplitude correlation remains unchanged and bias decreases; loss c has the same effect on amplitude correlation and phase correlation; increasing loss c decreases both amplitude correlation and phase correlation, while bias remains unchanged; loss d has the same effect on amplitude correlation and phase correlation; increasing loss d decreases both amplitude correlation and phase correlation, while bias remains unchanged.

[0101] (ii) Figure 4 As shown, the case with a beam splitting ratio of 0.45 is as follows:

[0102] Figure 4 (a) demonstrates ε b =0, ε c =0, ε d =0, T=0.45, the effect of loss a on quantum correlation Figure 4 (b) demonstrates ε a =0, ε c =0, ε d =0, T=0.45, the effect of loss b on quantum correlation Figure 4 (c) demonstrates ε a =0, ε b =0, ε d= 0, T = 0.45, the influence of loss a on quantum correlation Figure 4 (d) shows ε a = 0, ε b = 0, ε c = 0, T = 0.45, the influence of loss b on quantum correlation

[0103] From Figure 4 , it can be seen that when the beam splitting ratio is less than 0.5 (taking T = 0.45 as an example): loss a has an influence on both amplitude correlation and phase correlation, and has a greater influence on amplitude correlation, when loss a is increased, amplitude correlation decreases sharply, phase correlation increases slowly, and bias increases; loss b has an influence on both amplitude correlation and phase correlation, and has a greater influence on phase correlation, when loss b is increased, phase correlation decreases sharply, amplitude correlation increases slowly, and bias decreases; loss c has an influence on both amplitude correlation and phase correlation, and has a greater influence on amplitude correlation, when loss c is increased, amplitude correlation decreases sharply, phase correlation increases slowly, and bias increases; loss d has an influence on both amplitude correlation and phase correlation, and has a greater influence on phase correlation, when loss d is increased, phase correlation decreases sharply, amplitude correlation increases slowly, and bias decreases. By comparing Figure 4 (a) to Figure 4 (d), it is found that the influence trend of loss a and loss c on bias is similar, but the influence of loss c on bias is obviously greater than that of loss a on bias. Similarly, the influence trend of loss b and loss d on bias is similar, but the influence of loss d on bias is obviously greater than that of loss b on bias. Figure 4

[0104] (Three) as Figure 5 shown, when the beam splitting ratio is 0.55, the following conditions exist:

[0105] Figure 5 (a) shows ε b = 0, ε c = 0, ε d = 0, T = 0.55, the influence of loss a on quantum correlation Figure 5 (b) shows ε a = 0, ε c = 0, ε d = 0, T = 0.55, the influence of loss b on quantum correlation Figure 5 (c) shows ε a = 0, ε b = 0, ε d = 0, T = 0.55, the influence of loss c on quantum correlation Figure 5 (d) shows ε a = 0, ε b = 0, ε c = 0, T = 0.55, the influence of loss d on quantum correlation​

[0106] From Figure 5 it can be seen that when the splitting ratio is greater than 0.5 (taking T=0.55 as an example): the loss a has an influence on both the amplitude correlation and the phase correlation, and has a greater influence on the amplitude correlation, when the loss a is increased, the amplitude correlation is sharply reduced, the phase correlation is slowly increased, and the bias is increased; the loss b has an influence on both the amplitude correlation and the phase correlation, and has a greater influence on the phase correlation, when the loss b is increased, the phase correlation is sharply reduced, the amplitude correlation is slowly increased, and the bias is reduced; the loss c has an influence on both the amplitude correlation and the phase correlation, and has a greater influence on the phase correlation, when the loss c is increased, the phase correlation is sharply reduced, the amplitude correlation is slowly increased, and the bias is reduced. The loss d has an influence on both the amplitude correlation and the phase correlation, and has a greater influence on the amplitude correlation, when the loss d is increased, the amplitude correlation is sharply reduced, the phase correlation is slowly increased, and the bias is increased; by comparing Figure 5 , it can be seen that Figure 5 (a) to Figure 5 (d), it is found that the influence of the loss a and the loss d on the bias has a similar trend, but the influence of the loss d on the bias is obviously greater than the influence of the loss a on the bias. Similarly, the influence of the loss b and the loss c on the bias has a similar trend, but the influence of the loss c on the bias is obviously greater than the influence of the loss b on the bias.

[0107] By comparing Figures 3-5 , it is found that when the splitting ratio is 0.5, the loss c and the loss d have no influence on the bias, and when the splitting ratio is not 0.5, the influence of the loss c and the loss d on the bias is shown. By comparing Figure 4 and Figure 5 , when the splitting ratio is greater than 0.5 and less than 0.5, the influence of the loss c and the loss d on the bias is reversed.

[0108] The above only describes the preferred embodiments of the present application, and the protection scope of the present application is not limited to the above-described embodiments, and any technical solutions falling within the concept of the present application shall fall within the protection scope of the present application. It should be noted that for ordinary skilled persons in the art, some improvements and refinements without departing from the principles of the present application shall also be considered as the protection scope of the present application.

[0109] The technical features of the above-described embodiments can be combined arbitrarily, and in order to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, they shall be considered as the scope of the present application.

[0110] It should be noted that the above embodiments can be freely combined as needed. The above only describes the preferred embodiments of the present application, and it should be pointed out that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be considered as the protection scope of the present application.

Claims

1. A bias-adjustable entanglement source generation apparatus, comprising: Comprise: The first compression light generating module, the second compression light generating module, the first adjustable optical loss device, the second adjustable optical loss device, the adjustable beam splitter, the third adjustable optical loss device, the fourth adjustable optical loss device, the joint measurement module; The first compression light generating module is used for generating the first compression light, the second compression light generating module is used for generating the second compression light, the first adjustable optical loss device is used for adjusting the loss a introduced at the first compression state output end, the second adjustable optical loss device is used for adjusting the loss b introduced at the second compression state output end, the adjustable beam splitter is used for adjusting the splitting ratio, the third adjustable optical loss device is used for adjusting the loss c introduced at the first coupling output end, and the fourth adjustable optical loss device is used for adjusting the loss d introduced at the second coupling output end; The first compression light generating module generates the first compression light, and the loss a is adjusted through the first adjustable optical loss device after the first compression light is generated; the second compression light generating module generates the second compression light, and the loss b is adjusted through the second adjustable optical loss device after the second compression light is generated; the first compression light after the loss a is adjusted and the second compression light after the loss b is adjusted are coupled on the adjustable beam splitter to generate an entanglement source; The entanglement source enters the third adjustable optical loss device to adjust the loss c and enters the fourth adjustable optical loss device to adjust the loss d, and the entanglement source after the loss c and the loss d are adjusted enters the joint measurement module for joint measurement.

2. The bias tunable entanglement source generation device of claim 1, wherein, The first compression light generating module is a first optical parametric cavity, and the second compression light generating module is a second optical parametric cavity; The first optical parametric cavity receives input first seed light and first pump light to generate first compression light; The second optical parametric cavity receives input second seed light and second pump light to generate second compression light.

3. The bias tunable entanglement source generation apparatus of claim 2, wherein, Further comprise: A laser, a first optical beam splitter, a second optical beam splitter, a third optical beam splitter, and a first fundamental light high reflection mirror; The laser output laser is split into two beams through the first optical beam splitter, the first beam of the first optical beam splitter passes through the second optical beam splitter, the first beam of the second optical beam splitter is input into the third optical beam splitter; The first beam of the third optical beam splitter is input into the first optical parametric cavity as the first seed light; The second beam of the third optical beam splitter is input into the second optical parametric cavity as the second seed light after passing through the first fundamental light high reflection mirror.

4. The bias tunable entanglement source generation apparatus of claim 3, wherein, Further comprise: An optical filtering cavity; The optical filtering cavity is arranged between the laser and the first optical beam splitter, and is used for filtering high-frequency noise of the laser output by the laser to improve the beam quality and spatial mode distribution of the fundamental light, and to provide a high-quality low-noise light source for preparation and measurement of the bias-adjustable entanglement source.

5. The bias tunable entanglement source generation apparatus of claim 3, wherein, Further comprise: A first dichroic mirror, a frequency doubling cavity, a fourth optical beam splitter, a second dichroic mirror, a frequency doubling light high reflection mirror, and a third dichroic mirror; The second beam of the first optical beam splitter enters the frequency doubling cavity through the first dichroic mirror, and the frequency doubling light generated by the frequency doubling cavity is split through the fourth optical beam splitter; The first beam of the fourth optical beam splitter is input into the first optical parametric cavity as the first pump light after passing through the second dichroic mirror; The second beam of the fourth optical beam splitter is input into the second optical parametric cavity as the second pump light after passing through the frequency-doubled light high-reflection mirror and the third dichroic mirror.

6. The bias tunable entanglement source generation device of claim 5, wherein, Further comprising: The first dichroic mirror is high-reflection to fundamental light and high-transmission to frequency-doubled light; The second dichroic mirror is high-reflection to frequency-doubled light and high-transmission to fundamental light; The third dichroic mirror is high-reflection to frequency-doubled light and high-transmission to fundamental light.

7. The bias tunable entanglement source generation device of claim 1, wherein, Further comprising a second fundamental light high-reflection mirror, a third fundamental light high-reflection mirror, a fourth fundamental light high-reflection mirror, and a fifth fundamental light high-reflection mirror; The second fundamental light high-reflection mirror is arranged between the first adjustable optical loss device and the adjustable beam splitter; The third fundamental light high-reflection mirror is arranged between the second adjustable optical loss device and the adjustable beam splitter; The fourth fundamental light high-reflection mirror is arranged between the adjustable beam splitter and the third adjustable optical loss device; The fifth fundamental light high-reflection mirror is arranged between the adjustable beam splitter and the fourth adjustable optical loss device.

8. The bias tunable entanglement source generation device of claim 3, wherein, The joint measurement module comprises a first balanced homodyne detector, a second balanced homodyne detector, and a joint measurement device; After adjusting the loss c and the loss d, the entangled source enters the first balanced homodyne detector and the second balanced homodyne detector, respectively, and performs joint measurement in the joint measurement device.

9. The bias tunable entanglement source generation device of claim 8, wherein, Further comprising: A fifth optical beam splitter, a sixth fundamental light high-reflection mirror, a seventh fundamental light high-reflection mirror, and an eighth fundamental light high-reflection mirror; The second beam of the second optical beam splitter provides the first balanced homodyne detector and the second balanced homodyne detector with local light; The laser emitted by the second beam of the second optical beam splitter is split into two beams by the fifth optical beam splitter; The first beam of the fifth optical beam splitter is input into the first balanced homodyne detector as the local light of the first balanced homodyne detector; The second beam of the fifth optical beam splitter is input into the second balanced homodyne detector as the local light of the second balanced homodyne detector after passing through the sixth fundamental light high-reflection mirror, the seventh fundamental light high-reflection mirror, and the eighth fundamental light high-reflection mirror.

10. The bias tunable entanglement source generation device of claim 1, wherein, Further comprising: The first adjustable optical loss device is composed of a 15a half-wave plate and a 15b polarization beam splitting prism; The second adjustable optical loss device is composed of a 16a half-wave plate and a 16b polarization beam splitting prism; The third adjustable optical loss device is composed of a 22a half-wave plate and a 22b polarization beam splitting prism; The fourth adjustable optical loss device is composed of a 23a half-wave plate and a 23b polarization beam splitting prism.

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