Quantum correlation measurement-based ranging imaging method and system with high anti-noise capability

Abstract

The invention discloses a high-noise-immunity ranging imaging method and system based on quantum correlation measurement, belongs to the technical field of quantum radar and single photon detection, and particularly relates to a high-noise-immunity ranging imaging system and method based on quantum correlation measurement. Comprising a narrowband energy-time entangled two-photon source, a free space optical transceiving unit and a physical information acquisition unit, two photons with entanglement characteristics output by the narrowband energy-time entanglement two-photon source are respectively input into the free space optical transceiver unit and the physical information acquisition unit. The physical information acquisition unit jointly receives the photons directly output by the narrowband energy-time entanglement two-photon source and the photons output by the free space optical transceiving unit, so that the physical information of the measured object is obtained; according to the invention, the problems of small signal-to-background ratio and input saturation of the single-photon detector in the quantum correlation measurement field are solved, so that the system can carry out clear imaging under the condition of larger background noise.

Description

Technical Field

[0001] The present invention relates to the field of quantum radar and single photon detection technology, and in particular to a high noise-resistant ranging imaging method and system based on quantum correlation measurement. Background Art

[0002] Precision ranging has always been a hot area of ​​human research. It plays an irreplaceable role in positioning and imaging, and is widely used in satellite positioning, radar imaging, and micro-surface detection. Traditional optical imaging obtains and interprets multi-dimensional light field information by regulating physical quantities such as light intensity, polarization, spectrum, and phase, thereby obtaining physical information of detected objects. Traditional optical imaging is applied to biological microscopy, high-speed photography, light field imaging, non-line-of-sight imaging, single-pixel imaging, and scattering imaging.

[0003] Since the establishment of quantum theory, quantum mechanics has penetrated into experiments and science, especially distance measurement schemes based on quantum entanglement are constantly emerging. One of them, quantum correlation distance measurement, is still a new research field. Carrying out research on quantum distance measurement and counting is not only a forward-looking measure, but also has great strategic significance. Distance measurement using the correlation between entangled photon pairs has higher signal-to-noise ratio and signal-to-background ratio than classical methods. However, quantum imaging is easily affected by ambient light.

[0004] Therefore, it is necessary to develop a high noise-resistant ranging imaging method and system based on quantum correlation measurement to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to design a high noise-resistant ranging imaging method and system based on quantum correlation measurement in order to solve the above problems.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] A high noise-resistant ranging imaging method based on quantum correlation measurement includes using signal photons in a quantum light source with narrowband energy-time entanglement characteristics to illuminate the detection target, performing coincidence counting through the energy-time entanglement characteristics between the signal photons reflected by the target and the idler photons, filtering out background light that does not have quantum entanglement characteristics, and suppressing crosstalk during the propagation of entangled photons, thereby improving the coincidence counting rate and signal-to-background ratio at the detection end, and achieving high-quality imaging under large background noise and long-distance conditions.

[0008] The high noise-resistant ranging imaging system based on quantum correlation measurement includes:

[0009] A narrowband energy-time entangled light source; the narrowband energy-time entangled light source comprises a laser pump source, a pump filter, a nonlinear optical medium, a first spectroscopic filter, and a second spectroscopic filter connected in sequence;

[0010] A free-space optical transceiver unit; the free-space optical transceiver unit comprises a three-port optical circulator and a fiber-coupled telescope module; the signal light outlet of the second optical splitter filter is connected to the first port of the three-port optical circulator, and the second port of the three-port optical circulator is connected to the fiber-coupled telescope module; the extended line of the axis of the fiber-coupled telescope module coincides with the point to be measured;

[0011] Physical information acquisition unit; the physical information acquisition unit includes a single-photon detector group, a time digital converter and a host computer; the single-photon detector group includes two single-photon detectors, the input end of one single-photon detector is connected to the idle light outlet of the second spectroscopic filter, the input end of the other single-photon detector is connected to the third port of the three-port optical circulator, the output ends of the two single-photon detectors are connected to the time digital converter, and the time digital converter is connected to the host computer.

[0012] The beneficial effects of the present invention are:

[0013] 1. An energy-time entangled two-photon source that can distinguish the basic states of entangled photons only by detecting time without the need for any optical elements and can effectively prevent crosstalk during the propagation of entangled photons.

[0014] 2. Using spatial and spectral filtering methods, the background noise can be further reduced by embedding a spectroscopic filter in the fiber-coupled telescope module and using a narrow-bandwidth energy-time entangled light source.

[0015] 3. Compared with the traditional laser ranging solution, the present invention has higher distance resolution and stronger noise resistance when measuring the same distance, and can correctly obtain measurement results under higher background noise.

[0016] 4. Compared with other quantum imaging solutions, the present invention has a higher signal-to-background ratio and can clearly image under the condition of large background noise. The use of narrow-bandwidth quantum entangled two-photon source solves the problem that quantum imaging is sensitive to broadband noise photons. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative work, among which:

[0018] Figure 1 It is a schematic diagram of the framework of the present invention.

[0019] Marked in the figure: 1-laser pump source, 2-pump filter, 3-nonlinear optical medium, 4-broadband spectroscopic filter, 5-narrowband spectroscopic filter, 6-three-port optical circulator, 7-fiber-coupled telescope module, 8-single-photon detector group, 9-time digital converter, 10-host computer. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0023] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use, or are directions or positional relationships commonly understood by those skilled in the art. These directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0024] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and are not to be understood as indicating or implying relative importance.

[0025] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms such as "setting" and "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings.

[0027] A high noise-resistant ranging imaging method based on quantum correlation measurement includes using signal photons in a quantum light source with narrowband energy-time entanglement characteristics to illuminate a detection target, performing coincidence counting through the energy-time entanglement characteristics between the signal photons reflected by the target and the idler photons, filtering out background light that does not have quantum entanglement characteristics, and suppressing crosstalk during the propagation of entangled photons, thereby increasing the coincidence counting rate and signal-to-background ratio at the detection end, and achieving high-quality imaging under large background noise and long-distance conditions. The specific implementation method includes the following steps:

[0028] S1, narrowband energy-time entangled light source continuously outputs narrow-bandwidth signal light and idler light;

[0029] S2, the signal light passing through the second spectroscopic filter 5 is injected into the fiber-coupled telescope module 7 through the three-port optical circulator 6 and emitted to the surface of the object to be measured; the reflected light from the surface of the object to be measured is collected by the fiber-coupled telescope 7 and transmitted to the second port of the three-port optical circulator 6; the three-port optical circulator 6 receives the light input from the second port and outputs it to another single-photon detector 8 through the third port;

[0030] S3, the signal light and idler light input to the single photon detector are recorded via the time-to-digital converter 9 to match the number and time of arrival of photons;

[0031] S4. By observing the peak value and the corresponding time in the number-time coordinate of the arrival of photons in the host computer 10, physical information such as the distance between the object to be measured and the detection device and the surface reflectivity of the object to be measured are obtained.

[0032] The coincidence counting rate in step S3 is:

[0033]

[0034] in and are the transmission efficiencies of signal light and idler light, respectively. and are the number of detected photons of signal light and idler light, The width of the time window for matching counts.

[0035] Specifically, when the signal light and the idler light are incident on the single-photon detector, their light fields are:

[0036]

[0037]

[0038] in is the signal light frequency, is the idler frequency, is a quantum operator, is the signal light propagation time, is the idler propagation time; the propagation wave function is:

[0039]

[0040] Then the second-order correlation function is:

[0041]

[0042] set up ,Right now is the difference in propagation time between the signal light and the idler light; the calculated wave function is:

[0043]

[0044] in Represents the spectral function The Fourier transform of In the coordinate system of There is a peak at . Substituting into the second-order correlation function, we get:

[0045]

[0046] The ideal coincidence count rate is thus:

[0047]

[0048] in It represents whether the accidental coincidence count is within the measurement time interval, if yes, it takes 1, otherwise it takes 0; by checking the peak of the coincidence rate, the optical path difference between the signal light and the idler light can be determined, thereby determining the distance information of the target object.

[0049] In order to evaluate the system performance, it is necessary to calculate the signal-to-background ratio and signal-to-noise ratio. The system signal-to-background ratio and signal-to-noise ratio are:

[0050]

[0051] in, , , , They represent wide bandwidth signal-to-background ratio, narrow bandwidth signal-to-background ratio, wide bandwidth signal-to-noise ratio and narrow bandwidth signal-to-noise ratio respectively; C represents the coincidence count generated by the signal and idler light, represents the coincidence count generated by the background light, C' is the coincidence count generated by the narrow bandwidth signal and the idler light; N and Represent the number of detected photons in wide bandwidth and narrow bandwidth cases respectively; is the efficiency factor; T is the data acquisition time.

[0052] Furthermore, when the laser emits light of equal intensity at each wavelength, we have , k is a constant, and w is the selected bandwidth length.

[0053] Furthermore, when the laser cross-sectional intensity is Gaussian and the Gaussian full width is , then:

[0054]

[0055] Among them, Erf() is the error function; efficiency factor for:

[0056]

[0057] Furthermore, the high noise-resistant ranging imaging system and method based on quantum correlation measurement is characterized in that the signal-to-background ratio and signal-to-noise ratio are improved to:

[0058]

[0059] This improves the imaging quality of the system under large background noise and long-distance conditions.

[0060] like Figure 1 As shown, the high noise-resistant ranging imaging system based on quantum correlation measurement includes:

[0061] A narrowband energy-time entangled light source; the narrowband energy-time entangled light source comprises a laser pump source 1, a pump filter 2, a nonlinear optical medium 3, a first spectroscopic filter 4, and a second spectroscopic filter 5 which are connected in sequence;

[0062] A free-space optical transceiver unit; the free-space optical transceiver unit is used to focus the light in the optical fiber and hit the detection object, and receive the light reflected from the detection object and input it into the three-port optical circulator; the free-space optical transceiver unit includes a three-port optical circulator 6 and a fiber-coupled telescope module 7; the signal light outlet of the second spectroscopic filter 5 is connected to the first port of the three-port optical circulator 6, and the second port of the three-port optical circulator 6 is connected to the fiber-coupled telescope module 7; the extended axis of the fiber-coupled telescope module 7 coincides with the point to be measured;

[0063] Physical information acquisition unit; the physical information acquisition unit is used to realize time-related single-photon detector and compliance technology measurement, and calculate and analyze the position of the measured object and surface reflection information based on the measurement results; the physical information acquisition unit includes a single-photon detector group 8, a time digital converter 9 and a host computer 10; the single-photon detector group 8 includes two single-photon detectors, the input end of one single-photon detector is connected to the idle light outlet of the second spectroscopic filter 5, the input end of the other single-photon detector is connected to the third port of the three-port optical circulator 6, the output ends of the two single-photon detectors are connected to the time digital converter 9, and the time digital converter 9 is connected to the host computer 10.

[0064] In some embodiments, the laser pump source 1 includes any pulse or direct current laser light source of semiconductor laser, gas laser, dye laser and solid laser.

[0065] In some embodiments, the pump filter 2 is a filter device consisting of a circulator plus a fiber grating, a multi-layer coated optical filter, a micro-electromechanical system optical filter, a Fabry-Perot optical filter, an arrayed waveguide grating filter, and an optical wavelength division multiplexing device, or a combination of any of the above; the transmission wavelength of the pump filter 2 is consistent with the central wavelength of the laser pump source 1.

[0066] In some embodiments, the nonlinear optical medium 3 is any one of a second-order nonlinear optical crystal, a second-order nonlinear optical crystal waveguide, a third-order nonlinear quartz fiber-based waveguide, a third-order nonlinear silicon-based waveguide, or a third-order nonlinear chalcogenide-based waveguide.

[0067] In some embodiments, the first spectroscopic filter 4 and the second spectroscopic filter 5 are both filter devices consisting of a circulator plus a fiber grating, a multi-layer coated optical filter, a micro-electromechanical system optical filter, a Fabry-Perot optical filter, an arrayed waveguide grating filter, and an optical wavelength division multiplexing device, or a combination of any of them.

[0068] In some embodiments, the single photon detector is an avalanche photodiode or a superconducting waveguide device.

[0069] In some embodiments, the time-to-digital converter is at least one of a single-chip microcomputer, a programmable logic device, a digital signal processing chip, an embedded chip, and a delayed AND device.

[0070] The technical solution of the present invention can be summarized as follows: a ranging imaging device based on quantum correlation detection technology, comprising a narrowband energy-time entangled two-photon source, a free-space optical transceiver unit, and a physical information acquisition unit; two photons with entanglement characteristics output by the narrowband energy-time entangled two-photon source are respectively input into the free-space optical transceiver unit and the physical information acquisition unit, and the physical information acquisition unit jointly receives photons directly output from the narrowband energy-time entangled two-photon source and photons output from the free-space optical transceiver unit, thereby obtaining physical information of the measured object.

[0071] A narrowband energy-time entangled two-photon source is used, and signal photons in a quantum light source with narrowband energy-time entangled characteristics are used to illuminate the detection target. Coincidence counting is performed through the energy-time entangled characteristics between the signal photons reflected by the target and the idler photons to filter out background light that does not have quantum entanglement characteristics, thereby improving the coincidence counting rate and signal-to-background ratio, enabling the system to achieve high-quality imaging under greater background noise and long-distance conditions; and the use of an energy-time entangled two-photon source can distinguish the basic states of entangled photons only by detecting time without the need for any optical elements, and can effectively prevent crosstalk during the propagation of entangled photons.

[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A high noise-resistant ranging imaging method and system based on quantum correlation measurement, characterized in that: include: The detection target is illuminated by signal photons from a quantum light source with narrowband energy-time entanglement characteristics, and coincidence counting is performed through the energy-time entanglement characteristics between the signal photons reflected by the target and the idler photons. The background light without quantum entanglement characteristics is filtered out, and the crosstalk during the propagation of entangled photons is suppressed, thereby improving the coincidence counting rate and signal-to-background ratio at the detection end, and achieving high-quality imaging under large background noise and long-distance conditions.

2. The method and system for ranging imaging with high noise immunity based on quantum correlation measurement according to claim 1, characterized in that: The coincidence count rate is: , in and are the transmission efficiencies of signal light and idler light, and are the number of detected photons of signal light and idler light, The width of the time window for matching counts.

3. The high noise immunity ranging imaging method and system based on quantum correlation measurement according to claim 1 is characterized in that: When the signal light and idler light are incident on the single-photon detector, their light fields are: , , in is the signal light frequency, is the idler frequency, is a quantum operator, is the signal light propagation time, is the idler propagation time; the propagation wave function is: , Then the second-order correlation function is: , set up ,Right now is the difference in propagation time between the signal light and the idler light; the calculated wave function is: , in Represents the spectral function The Fourier transform of In the coordinate system of There is a peak at , and substituting it into the second-order correlation function gives: , The ideal coincidence count rate is thus: , in It represents whether the accidental coincidence count is within the measurement time interval, if yes, it takes 1, otherwise it takes 0; by checking the peak of the coincidence rate, the optical path difference between the signal light and the idler light can be determined, thereby determining the distance information of the target object.

4. A high noise-resistant ranging imaging system based on quantum correlation measurement, characterized in that: include: Narrowband energy-time entangled light source; The narrowband energy-time entangled light source comprises a laser pump source (1), a pump filter (2), a nonlinear optical medium (3), a first spectroscopic filter (4), and a second spectroscopic filter (5) which are connected in sequence; A free-space optical transceiver unit; the free-space optical transceiver unit comprises a three-port optical circulator (6) and a fiber-coupled telescope module (7); the signal light outlet of the second optical splitter filter (5) is connected to the first port of the three-port optical circulator (6), and the second port of the three-port optical circulator (6) is connected to the fiber-coupled telescope module (7); the extended axis of the fiber-coupled telescope module (7) coincides with the point to be measured; A physical information acquisition unit; the physical information acquisition unit comprises a single-photon detector group (8), a time digital converter (9) and a host computer (10); the single-photon detector group (8) comprises two single-photon detectors, the input end of one single-photon detector is connected to the idle light outlet of the second spectroscopic filter (5), the input end of the other single-photon detector is connected to the third port of the three-port optical circulator (6), the output ends of the two single-photon detectors are both connected to the time digital converter (9), and the time digital converter (9) is connected to the host computer (10).

5. The high noise immunity ranging imaging system based on quantum correlation measurement according to claim 4 is characterized in that: The laser pump source (1) comprises any pulse or direct current laser light source of semiconductor laser, gas laser, dye laser and solid laser.

6. The high noise immunity ranging imaging system based on quantum correlation measurement according to claim 4 is characterized in that: The pump filter (2) is a filter device composed of a circulator and a fiber grating, a multilayer coated optical filter, a micro-electromechanical system optical filter, a Fabry-Perot optical filter, an arrayed waveguide grating filter, and an optical wavelength division multiplexing device, or a combination of any of the above. The transmission wavelength of the pump filter (2) is consistent with the central wavelength of the laser pump source (1).

7. The high noise immunity ranging imaging system based on quantum correlation measurement according to claim 4 is characterized in that: The nonlinear optical medium (3) is any one of a second-order nonlinear optical crystal, a second-order nonlinear optical crystal waveguide, a third-order nonlinear quartz fiber-based waveguide, a third-order nonlinear silicon-based waveguide or a third-order nonlinear chalcogenide-based waveguide.

8. The high noise immunity ranging imaging system based on quantum correlation measurement according to claim 4 is characterized in that: The first splitter filter (4) and the second splitter filter (5) are both filter devices composed of a circulator and a fiber grating, a multilayer coated optical filter, a micro-electromechanical system optical filter, a Fabry-Perot optical filter, an arrayed waveguide grating filter, and an optical wavelength division multiplexing device, or a combination of any of the above.

9. The high noise immunity ranging imaging system based on quantum correlation measurement according to claim 4, characterized in that: The single photon detector is an avalanche photodiode or a superconducting waveguide device.

10. The high noise immunity ranging imaging system based on quantum correlation measurement according to claim 4, characterized in that: The time-to-digital converter is at least one of a single-chip microcomputer, a programmable logic device, a digital signal processing chip, an embedded chip and a delayed AND device.

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