Sunlight-pumped quantum entanglement light source system

Abstract

The invention belongs to the technical field of light quantum information, and particularly relates to a sunlight-pumped quantum entanglement light source system which comprises a sunlight collecting and filtering module, a sun tracking module, an optical fiber and an entanglement generating module. Wherein the sunlight collecting and filtering module comprises a secondary condensation system and a secondary filtering system; the sunlight tracking module is used for aligning the sunlight collecting and filtering module to the sun; the entanglement generation module comprises a pump light regulation and control system, a nonlinear crystal group and a polarization entanglement generation system. Sunlight is coupled to the optical fiber through the sunlight collecting and filtering module, and the filtered sunlight is transmitted to the entanglement generating module through the optical fiber. The filtered sunlight is used as pump light to generate entangled photon pairs through the entanglement generation module. Sunlight is used as a pump light source in the quantum entanglement light source, so that the preparation cost and the operation cost of the quantum light source can be effectively reduced, the environmental protection characteristic of the quantum light source is improved, and the application of the quantum technology is expanded to a wider scene.

Description

Technical Field

[0001] The invention belongs to the field of optical quantum information technology, and in particular relates to a solar light-pumped quantum entangled light source system. Background Art

[0002] As the global population increases, the environment warms, and the economy is in a downturn, energy issues are becoming increasingly tense. More and more people are beginning to pay attention to the development and utilization of clean energy. Among them, sunlight has gradually stood out because of its large reserves and high safety. As a clean and renewable energy source, solar energy has been widely used in various fields, including solar panels, solar water heaters, and solar power plants. It has not yet been applied in the field of quantum information. The development and utilization of new energy represented by solar energy has become a basic decision in my country's sustainable development strategy.

[0003] Quantum information technology is the core driving force for the revolutionary changes in information technology and the information industry in the future, and will have a significant impact on the entire information industry. Breakthroughs in quantum information science are the key to the development and application of quantum information technology. As one of the physical carriers of quantum information, photons have unique advantages such as long coherence time, multiple encoding methods, simple single-bit manipulation, and fast transmission speed. They have been widely used in research fields such as quantum communication, quantum computing, quantum precision measurement, and quantum cryptography. Among them, entangled photon pairs generated by entangled light sources will affect the results of related quantum technologies. An entangled photon pair is a pair of photons with entangled quantum states, characterized by the existence of quantum entanglement between their states, that is, the state of one photon will be affected by the state of another photon, even if they are far apart. Common methods for generating entangled light sources include spontaneous parametric down-conversion (SPDC) and spontaneous four-wave mixing (SFWM).

[0004] The problems with existing entangled light source generation technology include: In these technologies, lasers are generally used as pump light sources to directly excite nonlinear media to generate entangled photon pairs, but the energy directly obtained comes from chemical energy or other non-clean energy, and there is no quantum entangled light source that uses sunlight to directly pump entangled photon pairs. This leads to the current entangled light sources having problems such as high energy consumption and environmental pollution, and lacking the characteristics of green environmental protection and energy conservation and emission reduction. At the same time, the common lasers currently have the problems of high equipment cost and heavy weight.

[0005] In addition, the development of quantum technology in space has great potential. The quantum entangled light sources currently used in space still rely on lasers driven by electrical energy. This reliance on electrical energy supply faces problems such as unstable electrical energy supply, limited energy reserves, and additional load on the power system in space. At the same time, the heavy weight of the laser will also bring additional load to the spacecraft, which will increase the launch cost.

[0006] Therefore, there is an urgent need to research and develop green and energy-saving entangled light sources pumped by sunlight to promote the development of optical quantum technology in a more sustainable, environmentally friendly and practical direction. Summary of the invention

[0007] The sunlight is coupled into the optical fiber through the sunlight collection and filtering module, and the filtered sunlight is transmitted to the entanglement generation module through the optical fiber; The sunlight tracking module is used to align the sunlight collection and filtering module with the sun; The filtered sunlight is the pump light, which directly pumps the nonlinear crystal in the entanglement generation module to generate entangled photon pairs, which are used to form a quantum entangled light source.

[0008] The sunlight collection and filtering module is installed on the top of the sunlight tracking module; The solar tracking module includes a GPS locator, a control system and an actuator.

[0009] The sunlight collection and filtering module is composed of a secondary light collection system and a secondary filtering system; The primary main concentrator of the secondary concentrating system is an optical antenna composed of a Fresnel lens and a plano-convex lens. The right focus of the Fresnel lens coincides with the left focus of the plano-convex lens, which is used to focus the sunlight for the first time. The secondary concentrator is a short-focus microscope objective lens, which is used to direct the focused light spot of the sunlight into the fiber coupler and couple the sunlight into the optical fiber. The first-stage filtering system in the secondary filtering system is a wide-bandwidth bandpass filter placed in front of the Fresnel lens, which is used to preliminarily screen the spectrum of sunlight and transmit it to the secondary filtering system by reducing the intensity of sunlight; The secondary filtering system is a narrow bandwidth bandpass filter placed behind a plano-convex lens to screen the spectrum of sunlight.

[0010] The sunlight collection and filtering module generates pump light after receiving sunlight, and transmits it to the entanglement generation module through optical fiber.

[0011] The sunlight collection and filtering module is connected to the entanglement generation module via an optical fiber; Among them, in the sunlight collection and filtering module, the fiber core at the end face of the optical fiber coincides with the focal position of the microscope objective lens, which is used to couple the sunlight into the optical fiber; In the entanglement generation module, the optical fiber is connected to a fiber collimator, which couples the beam of sunlight into the spatial optical path.

[0012] The invention comprises a pump light control system, a nonlinear crystal group and a polarization entanglement generation system arranged in sequence. The pump light control system can control the output power and polarization state of the pump light; the spontaneous parametric down conversion process in the pump light pumped nonlinear crystal group generates correlated photon pairs; and the polarization entanglement generation system converts the correlated photon pairs into polarization entangled photon pairs.

[0013] The pump light control system consists of a first half-wave plate, a polarization beam splitter, a first reflector, a second reflector, a short-pass filter, a second half-wave plate and a quarter-wave plate. The first half-wave plate and the polarization beam splitter are used to adjust the power of the pump light. The pump light after power adjustment is input into the short-pass filter after passing through the first reflector and the second reflector. The short-pass filter filters out the long-wave part of the pump light. The second half-wave plate and the quarter-wave plate can adjust the polarization angle of the pump light to meet the phase matching condition of the spontaneous parametric down-conversion process.

[0014] The nonlinear crystal group includes two orthogonally arranged periodically poled potassium titanyl phosphate crystals and a pair of lenses placed in front and behind the crystals. The periodically poled potassium titanyl phosphate crystal is of type 0 with a size of 1mm×2mm×10mm. The periodically poled potassium titanyl phosphate crystal is placed in a V-shaped groove. The pump light is incident on the periodically poled potassium titanyl phosphate crystal, and its polarization direction is vertical polarization, and it forms an angle of ° with the side wall of the V-shaped groove. The incident direction is perpendicular to the surface of the periodically poled potassium titanyl phosphate crystal. In the periodically polarized potassium titanyl phosphate crystal, pump light generates a signal photon and an idler photon pair through a pump spontaneous parametric down-conversion process; The wavelength of the pump light satisfies the phase matching condition of the spontaneous parametric down-conversion process; There is a quantum correlation between the signal photon and the idler photon generated by the spontaneous parametric down-conversion process.

[0015] The entanglement generation module includes a dichroic mirror, a long-pass filter, a lens, a beam splitter and a reflector group arranged in sequence.

[0016] The dichroic mirror and long-pass filter in the entanglement generation module are used to filter out the pump light and output correlated photon pairs.

[0017] Due to the indistinguishability of the correlated two-photon state, the correlated photon pair outputted by the long-pass filter and collimated by the lens generates polarization-entangled signal photons and idler photons after passing through the beam splitter. The signal and idler photons are outputted through a reflector group.

[0018] The technical effects achieved by the present invention are: The present invention generates entangled photon pairs through an entanglement generation module, which can achieve efficient output of entangled photon pairs, and the sunlight collection and filtering module and the entanglement generation module used are low in cost. The input pump light source used is sunlight, and the pump light generating device has a simple structure, which can greatly reduce the use of fossil fuels and high-cost equipment.

[0019] The present invention avoids the high cost and energy consumption of lasers by adopting the method of pumping nonlinear media with sunlight, thereby reducing the preparation cost and operation cost of quantum light sources, making them more economical and feasible. In addition, in space missions, the transportation cost and space resources of rocket launches can be reduced through a lighter pump source.

[0020] The present invention utilizes sunlight as an energy source and directly applies it to the excitation process of nonlinear crystals, thereby realizing the generation of entangled light sources. This method eliminates the dependence on traditional lasers and makes the energy source of the light source more environmentally friendly and sustainable.

[0021] The present invention, a device for generating entangled light sources by using sunlight to pump nonlinear crystals, pushes light source technology in a more portable and scalable direction. By providing a stable and high-performance entangled light source, it is conducive to promoting the development of fields such as quantum communication, quantum computing and quantum imaging, and promoting the promotion and application of quantum technology in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of a solar light-pumped quantum entangled light source proposed by the present invention; Figure 2 It is a schematic diagram of the structure of the quantum entangled light source and entangled detection system pumped by 405nm-band sunlight of the present invention; Figure 3 is a parameter table of the bandpass filter in the present invention; Figure 4 It is a structural schematic diagram of the method for placing periodically polarized potassium titanyl phosphate crystals in the present invention.

[0023] In the accompanying drawings, the components represented by the reference numerals are listed as follows: In the figure: 1. 405nm broadband wideband pass filter; 2. Fresnel lens; 3. Plano-convex lens; 4. 405nm narrow bandwidth bandpass filter; 5. Microscope objective; 6. Fiber coupling bracket; 7. Optical fiber; 8. Fiber collimator; 9. First 405nm half-wave plate; 10. Polarization beam splitter; 11. Short-pass filter; 12. Second 405nm half-wave plate; 13. 405nm quarter-wave plate; 14. Dichroic mirror; 15. Long-pass filter; 16. 810nm beam splitter; 17. First reflector; 18. Second reflector; 19. First fused silica lens; 20. Two periodically polarized potassium titanyl phosphate crystals; 21. Second fused silica lens; 22. Third reflector; 23. Fourth reflector; 24. Fifth reflector; 25. Sixth reflector; 26. V-groove.

[0024] HWP: Half-wave plate; PBS: polarization beam splitter; QWP: Quarter Wave Plate; PPKTP (Periodically Poled KTiOPO4): Periodically poled potassium titanyl phosphate crystal; DM: dichroic mirror; LP: long pass filter; BS: beam splitter; SPF: Short pass filter; SMFC (Single Mode Fiber Coupler): single mode fiber coupler or fiber coupler; M is a reflector; SPDC: spontaneous parametric down-conversion; SFWM: spontaneous four-wave mixing. DETAILED DESCRIPTION

[0025] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific embodiments of the present invention, and does not strictly limit the scope of protection of the specific claims of the present invention.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0027] According to an embodiment of the present invention, a quantum entangled light source device pumped by sunlight in the 405 nm band is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system comprising at least one set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in an order different from that shown here.

[0028] The method embodiments associated therewith may also be executed in an electronic device comprising a memory and a processor, a similar control device or a cloud. Taking an electronic device as an example, the electronic device may include one or more processors and a memory for storing data. Optionally, the electronic device may also include a communication device and a display device for communication functions. A person of ordinary skill in the art may understand and know that the above structural description is only illustrative and does not limit the structure of the above electronic device. For example, the electronic device may also include more or fewer components than the above structural description, or have a configuration different from the above structural description.

[0029] The processor may include one or more processing units. For example, the processor may include a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processing (DSP) chip, a microcontroller unit (MCU), a field-programmable gate array (FPGA), a neural-network processing unit (NPU), a tensor processing unit (TPU), an artificial intelligence (AI) type processor, and other processing devices. Among them, different processing units may be independent components or integrated into one or more processors. In some instances, the electronic device may also include one or more processors.

[0030] The memory can be used to store computer programs, such as storing the computer program corresponding to the entanglement detection module in the embodiment of the present invention. The processor realizes the above-mentioned detection result of the two-photon entangled state by running the computer program stored in the memory. The memory may include a high-speed random access memory, and may also include a non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory may further include a memory remotely arranged relative to the processor, and these remote memories can be connected to the electronic device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0031] The communication device is used to receive or send data via a network. The specific example of the above network may include a wireless network provided by a communication provider of the mobile terminal. In one example, the communication device includes a network adapter (network interface controller, NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the communication device can be a radio frequency (radio frequency, RF) module, which is used to communicate with the Internet wirelessly. In some embodiments of the present solution, the communication device is used to connect to mobile devices such as mobile phones and tablets, and instructions can be sent to electronic devices through the mobile device.

[0032] The display device may be a touch screen type liquid crystal display (LCD) and a touch display (also referred to as a "touch screen" or "touch display screen"). The liquid crystal display may enable a user to interact with a user interface of the electronic device. In some embodiments, the electronic device has a graphical user interface (GUI), and a user may interact with the GUI by touching a finger release and / or gestures on a touch-sensitive surface, and executable instructions for executing the above-mentioned human-computer interaction functions are configured / stored in a computer program product or a readable storage medium executable by one or more processors. like Figure 1-2 As shown, a solar light-pumped quantum entangled light source system includes a solar light collection and filtering module that receives solar light and inputs it into an optical fiber to generate pump light, which is then input into an entanglement generation module through an optical fiber 7. An optical fiber collimator 9 in the entanglement generation module couples the pump light to free space transmission. The pump light is incident on a nonlinear crystal group, and correlated photon pairs are generated through a spontaneous parametric down-conversion process. The correlated photon pairs are converted into entangled photon pairs through a polarization entanglement generation system to form a quantum entangled light source.

[0033] Preferably, the entanglement generation module generates entangled photon pairs through a spontaneous parametric down-conversion process, and the entangled photons include signal photons and idler photons.

[0034] Furthermore, in order to detect the entanglement characteristics of the entangled photon pairs generated by the quantum entangled light source, the quantum entangled photon pairs output by the quantum entangled light source are detected by the entanglement detection module, and the corresponding detection results are output.

[0035] Embodiment 1: See here for details Figure 1 and Figure 2 The above-mentioned sunlight collection and filtering module is composed of a secondary focusing system and a secondary filtering system.

[0036] Among them, the primary main concentrator of the secondary concentrating system is an optical antenna composed of a Fresnel lens 2 with a diameter of 300mm and a focal length of 600mm, and a plano-convex lens 3 with a diameter of 25.4mm and a focal length of 30mm, which is used to focus the sunlight for the first time; the secondary concentrator is a microscope objective lens 5 with a magnification of 20X and a focal length of 9mm, which can effectively reduce the spot size and enter the fiber coupler 6, which helps to couple the sunlight into the optical fiber 7. The primary filter in the secondary filtering system is a wide-bandwidth interference bandpass filter 1, which is placed in front of the Fresnel lens 2, with a central wavelength of 405nm and a FWHM of 50nm. Its main function is to preliminarily screen the spectrum of sunlight, reduce the intensity of sunlight, and relieve the pressure of the secondary filtering system; the secondary filter is a narrow-band hard film bandpass filter 4, with a central wavelength of 405nm and a FWHM of 3nm, which is placed behind the plano-convex lens 3 to further screen the spectrum of sunlight. Since this two-stage focusing system has no central obstruction, it has good focusing effect and low loss, and is suitable for receiving sunlight with a large aperture. In addition, the structure is more compact and generally there is no need to adjust the optical axis.

[0037] Among them, the specific parameters of interference bandpass filter and hard film bandpass filter can be referred to Figure 3 .

[0038] For further information, please refer to the attached Figure 1 The sunlight collection and filtering module is installed on the top of the sunlight tracking module to achieve stable, continuous and accurate tracking of sunlight; the sunlight tracking module includes a GPS locator, a control system and an actuator, and its function is to accurately align with the sun and improve the efficiency and stability of collecting sunlight.

[0039] According to the above structure, sunlight passes through the atmosphere to the surface of the earth. Under the action of the sunlight collection and filtering module, the secondary concentrator system can collect the sunlight into the optical fiber, and the secondary filtering system can perform specific filtering processing on the sunlight to be collected so that it meets the subsequent pumping conditions.

[0040] Furthermore, the sunlight tracking module is used to track the position of the sun and adjust the positioning technology of the solar energy equipment, the GPS locator is used to detect the position of the sun, and the control system calculates the position that the sunlight collection and filtering module should be adjusted according to the GPS locator, and realizes the adjustment through the actuator.

[0041] This embodiment aims to use sunlight as an energy source and directly apply it to the excitation process of nonlinear crystals, thereby achieving the generation of entangled light sources. This method eliminates the dependence on traditional lasers, making the energy source of the light source more environmentally friendly and sustainable.

[0042] In addition, the invention of using sunlight to pump nonlinear crystals to generate entangled light sources has pushed light source technology in a more portable and scalable direction. By providing a stable, high-performance entangled light source, this invention is expected to promote the development of fields such as quantum communication, quantum computing, and quantum imaging, and promote the promotion and application of quantum technology in practical applications, such as passive quantum communication between the earth and satellites, and quantum communication in uninhabited areas (areas without power supply).

[0043] The sunlight collection and filtering module generates pump light after receiving sunlight, and transmits it to the entanglement generation module through a multimode optical fiber. The multimode optical fiber is a type of optical fiber in this embodiment.

[0044] The sunlight collection and filtering module is connected to the entanglement generation module through optical fiber 7. In the sunlight collection and filtering module, the core of the optical fiber 7 end face coincides with the focal position of the microscope objective 5, which is used to couple the sunlight into the optical fiber 7 to improve the coupling efficiency. In the entanglement generation module, the optical fiber 7 is connected to a fiber collimator 8, which couples the sunlight beam into the spatial light path.

[0045] The first half-wave plate HWP9 and the polarization beam splitter PBS10 are used to change the pump power of the pump light; the short-pass filter 11 is used to filter out the long-wave component in the pump light; the second half-wave plate HWP12 and the quarter-wave plate QWP13 are placed at the front end of the nonlinear crystal group to change the polarization angle of the pump light so that it meets the phase matching condition of spontaneous parametric down-conversion.

[0046] According to the above, when the spontaneous parametric down-conversion process is used to generate entangled photon pairs, the method for the entanglement generation module to generate entangled photons includes the following steps: S1: The entanglement generation module controls the input pump light power through the first half-wave plate HWP9 and the polarization beam splitter PBS10; S2: The pump light processed by S1 passes through the collimated optical path formed by the first reflector 17 and the second reflector 18, and then passes through the short-pass filter SPF11; S3: The pump light then passes through a polarization controller composed of a second half-wave plate HWP12 and a quarter-wave plate QWP13, and is transmitted and sequentially passes through a F=100mm fused silica lens 19, two orthogonally placed PPKTP crystals 20 that meet the type 0 phase matching condition, a dichroic mirror DM14, a long-pass filter LPF15, a F=100mm fused silica lens 21, and a beam splitter BS16; when the pump light passes through the second half-wave plate HWP12 and the quarter-wave plate QWP13, and is focused onto the nonlinear crystal with a specific polarization, the two PPKTP crystals 20 will respectively generate correlated photon pairs with polarization states of diagonal state D and anti-diagonal state A. At this time, the photon polarization state changes as shown in the following formula: when , the polarization state of the correlated photon pair is: ; when , the polarization state of the correlated photon pair is: When the correlated photon pair is incident on the beam splitter BS16, the following quantum state transformation occurs: S4: The entangled photon pair is coupled into the single-mode optical fiber through the third reflector 22, the fourth reflector 23, the fifth reflector 24, the sixth reflector 25 and the single-mode optical fiber coupler 6 respectively; Figure 1 and Figure 2 The single-mode fiber coupler 6 is a device for coupling spatial light into an optical fiber, and then the single-mode optical fiber is connected to the entanglement detection module.

[0047] S5: The entangled photon pairs generated by the spontaneous parametric down-conversion process in the process of S1-S4 are detected by the entanglement detection module. Through the means of coincidence counting, they are post-selected and the obtained The detection results of the entanglement detection module are connected to the display device through wired or wireless means. In addition to outputting the results, the display device can also realize touch or audio and video interaction.

[0048] According to the above steps, entangled photon pairs are generated through the spontaneous parametric down-conversion process, which can achieve efficient output of entangled photon pairs. The sunlight collection and filtering module and the entanglement generation module used are low in cost, and the input pump light source used is sunlight. The pump light generating device has a simple structure, which can greatly reduce the use of fossil fuels and high-cost equipment.

[0049] By adopting the sunlight pumping method, the high cost and energy consumption problems of lasers are avoided, thereby reducing the preparation cost and operation cost of quantum light sources, making them more economical and feasible.

[0050] In addition, in space missions, lighter pump sources can also reduce the transportation costs and space resources of rocket launches.

[0051] Please continue to refer to Figure 1 , and further combined with Figure 2 After receiving sunlight, the sunlight collection and filtering module generates pump light, which is transmitted to the entanglement generation module through optical fiber 7. The entanglement generation module outputs a signal with quantum entanglement and idler photons.

[0052] Please refer to Figure 4The nonlinear crystal group includes two orthogonally arranged periodically poled potassium titanyl phosphate crystals 20 , the specifications of the periodically poled potassium titanyl phosphate crystals 20 are 1 mm×2 mm×10 mm, and the periodically poled potassium titanyl phosphate crystals 20 are placed in a V-shaped groove 26 .

[0053] The entangled photon pairs are detected by the entanglement detection module, and data analysis is performed through a computer program, including coincidence counting, two-photon interferometry analysis, and quantum state tomography, which is used to analyze the quality of the quantum light source and subsequently apply the quantum light source to quantum communication, quantum computing, quantum imaging and other technologies.

[0054] Furthermore, the coincidence counting detection method includes setting a single photon detector to obtain an entangled photon pair generated by an entanglement generation module; when a signal photon and an idler photon in the entangled photon pair are detected simultaneously in the entanglement detection module, a coincidence count is formed; Furthermore, in the two-photon interferometry analysis, during the measurement process, the change in the coincidence count can be observed by changing the half-wave plate HWP angle. By analyzing the dependence between the coincidence count and the HWP angle, the coherence and stability of the quantum light source can be understood.

[0055] The specific steps include: S101, inputting the entangled photon pair to be measured into an interferometer, which usually includes a half-wave plate HWP and a polarization beam splitter PBS; S102, changing the angle of the half-wave plate HWP, and observing the change of the coincidence count; S103. Analyze the coherence and stability of the quantum light source based on the dependence between the coincidence count and the HWP angle.

[0056] Furthermore, quantum state tomography analysis reconstructs the density matrix of the entangled state by measuring the projection coefficients of entangled photon pairs under different basis vectors.

[0057] The specific steps include: S201, placing a half-wave plate HWP, a quarter-wave plate QWP and a polarization beam splitter PBS on both optical paths of the signal photon and the idler photon; S202, installing the quarter wave plate QWP and the half wave plate HWP on the two optical paths on the rotary stepping motors respectively; S203. Set the quarter wave plate QWP and the half wave plate HWP on the two optical paths to 16 groups of fixed angles, observe the changes in the coincidence counts, reconstruct the density matrix of the entangled state according to the projection measurement principle, and evaluate the quality of the entangled light source.

[0058] The working principle of the present invention is: entangled photon pairs are generated through the spontaneous parametric down-conversion process in the entanglement generation module, which can achieve efficient output of entangled photon pairs, and the sunlight collection and filtering module and the entanglement generation module used are low in cost, the input pump light source used is sunlight, and the pump light generating device has a simple structure, which can greatly reduce the use of fossil fuels and high-cost equipment.

[0059] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A solar light-pumped quantum entangled light source system, characterized in that: include: The sunlight is coupled into the optical fiber through the sunlight collection and filtering module, and the filtered sunlight is transmitted to the entanglement generation module through the optical fiber; The sunlight tracking module is used to align the sunlight collection and filtering module with the sun; The filtered sunlight is the pump light, which directly pumps the nonlinear crystal in the entanglement generation module to generate entangled photon pairs, which are used to form a quantum entangled light source.

2. A solar light-pumped quantum entangled light source system according to claim 1, characterized in that: The sunlight collection and filtering module is installed on the top of the sunlight tracking module; The solar tracking module includes a GPS locator, a control system and an actuator.

3. The solar-pumped quantum entangled light source system according to claim 1, characterized in that: The sunlight collection and filtering module is composed of a secondary light collecting system and a secondary filtering system; The primary main concentrator of the secondary concentrating system is an optical antenna composed of a Fresnel lens (2) and a plano-convex lens (3), wherein the right focal point of the Fresnel lens (2) and the left focal point of the plano-convex lens (3) coincide with each other, and are used to focus sunlight for the first time; The secondary condenser is a short-focus microscope objective lens (5) for directing the focused light spot of the sunlight into the optical fiber coupler (6) and coupling the sunlight into the optical fiber (7); The first-stage filtering system in the secondary filtering system is a wide-bandwidth bandpass filter (1) placed in front of the Fresnel lens (2) for preliminary screening of the spectrum of sunlight, and then transmitting the sunlight to the secondary filtering system by reducing the intensity of the sunlight; The secondary filtering system is a narrow bandwidth bandpass filter (4) placed after the plano-convex lens (3) to filter the spectrum of sunlight.

4. The solar light-pumped quantum entangled light source system according to claim 1, characterized in that: The sunlight collection and filtering module generates pump light after receiving sunlight, and transmits it to the entanglement generation module through optical fiber.

5. The solar light-pumped quantum entangled light source system according to claim 1, characterized in that: The sunlight collection and filtering module is connected to the entanglement generation module via an optical fiber (7); Wherein, in the sunlight collection and filtering module, the end face core of the optical fiber (7) coincides with the focal position of the microscope objective lens (5), so as to couple the sunlight into the optical fiber (7); In the entanglement generation module, the optical fiber (7) is connected to a fiber collimator (8), and the fiber collimator (8) couples the beam of sunlight into the spatial optical path.

6. The solar light-pumped quantum entangled light source system according to claim 1, characterized in that: The invention comprises a pump light control system, a nonlinear crystal group and a polarization entanglement generation system arranged in sequence. The pump light control system can control the output power and polarization state of the pump light; the spontaneous parametric down conversion process in the pump light pumped nonlinear crystal group generates correlated photon pairs; and the polarization entanglement generation system converts the correlated photon pairs into polarization entangled photon pairs.

7. The solar-pumped quantum entangled light source system according to claim 1, characterized in that: The pump light control system is composed of a first half-wave plate (9), a polarization beam splitter (10), a first reflector (17), a second reflector (18), a short-pass filter (11), a second half-wave plate (12) and a quarter-wave plate (13). The first half-wave plate (9) and the polarization beam splitter (10) are used to adjust the power of the pump light. The pump light after the power adjustment is input into the short-pass filter (11) after passing through the first reflector (17) and the second reflector (18). The short-pass filter (11) filters out the long-wave portion of the pump light. The second half-wave plate (12) and the quarter-wave plate (13) can adjust the polarization angle of the pump light so that it meets the phase matching condition of the spontaneous parametric down-conversion process.

8. The solar light-pumped quantum entangled light source system according to claim 1, characterized in that: The nonlinear crystal group includes two orthogonally arranged periodically poled potassium titanyl phosphate crystals (20), and a pair of lenses (19, 21) placed in front and behind the crystals. The periodically poled potassium titanyl phosphate crystal (20) has a size of 1 mm×2 mm×10 mm and is 0-type. The periodically poled potassium titanyl phosphate crystal (20) is placed in a V-shaped groove (26). Pump light is incident on the periodically poled potassium titanyl phosphate crystal (20), and its polarization direction is vertical polarization, and forms an angle of 45° with the side wall of the V-shaped groove (26). The incident direction is perpendicular to the surface of the periodically poled potassium titanyl phosphate crystal (20); In the periodically polarized potassium titanyl phosphate crystal (20), pump light generates a signal photon and an idler photon pair through a pump spontaneous parametric down-conversion process; The wavelength of the pump light satisfies the phase matching condition of the spontaneous parametric down-conversion process; There is a quantum correlation between the signal photon and the idler photon generated by the spontaneous parametric down-conversion process.

9. The solar light-pumped quantum entangled light source system according to claim 1, characterized in that: The entanglement generation module comprises a dichroic mirror (14), a long-pass filter (15), lenses (19, 21), a beam splitter (16), and a reflector group (22, 23, 24, 25) arranged in sequence.

10. The solar light-pumped quantum entangled light source system according to claim 1, characterized in that: The dichroic mirror (14) and the long-pass filter (15) in the entanglement generation module are used to filter out the pump light and output the correlated photon pairs.

11. The solar light-pumped quantum entangled light source system according to claim 1, characterized in that: Due to the indistinguishability of the correlated two-photon state, the correlated photon pair outputted by the long-pass filter (15) and collimated by the lens generates polarization-entangled signal photons and idler photons after passing through the beam splitter (16), and the signal and idler photons are outputted through the reflector group (22, 23, 24, 25).

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