A high-stability common optical path quantum interference radar

Abstract

The application discloses a high-stability common optical path quantum interference radar, comprising a quadrilateral common optical path interferometer, which comprises a beam splitter, first, second, third and fourth plane mirrors; an incident entangled light source is incident to the quadrilateral common optical path interferometer, and the entangled photons are divided into first transmitted photons and first reflected photons through the beam splitter; the first transmitted photons are reflected back to the beam splitter through the third, second, first plane mirrors and a target object, and second reflected photons are generated; the first reflected photons are reflected back to the beam splitter through the first, second, third and fourth plane mirrors, and third transmitted photons are generated; the second reflected photons and the third transmitted photons generate interference, that is, target detection light and local reference light generate interference, and thus distance information of the target object is acquired; a delay optical path between the third and fourth plane mirrors is used for adjusting an optical path difference of the two beams of light, so that the two beams of light synchronously interfere. The common optical path interference light splitting technology is adopted to overcome the instability problem of independent two arms.

Description

Technical Field

[0001] This invention belongs to the field of quantum technology, specifically relating to a highly stable common-path quantum interference radar. Background Technology

[0002] Classical radar technology has gradually encountered technical bottlenecks in practical applications, such as sensitivity, anti-interference, and anti-stealth. Applying the basic principles of quantum mechanics to traditional lidar technology can utilize the many characteristics of quantum entangled states to surpass traditional lidar technology. This technology is called quantum radar technology.

[0003] Quantum measurement systems enhance detection performance through non-classical signals. Entangled states are the most mature non-classical signal, and photon entanglement is the optimal choice for propagation in free space for quantum radar. Classical radar uses conventional electromagnetic waves to detect targets, and its signal consists of a large number of photons. Quantum radar, based on quantum effects, uses a small number of photons to detect and image distant targets. Based on different photon emission mechanisms, quantum radar can be broadly classified into three categories: quantum radar emits entangled quantum electromagnetic waves, quantum radar emits unentangled quantum electromagnetic waves, and quantum radar emits classical electromagnetic waves and uses quantum-enhanced detection technology at the receiver. Among these, entangled quantum radar technology generates a pair of entangled photons at the transmitter. One photon is emitted as a signal photon towards the target area, while the other is retained in the receiver as an idle photon. The signal photon is reflected back into the system by the target and received by the receiver. The target is detected by extracting the quantum correlation characteristics between the signal photon and the idle photon. Currently, various entangled quantum radar schemes have emerged, such as quantum interference radar and quantum illumination radar. Among them, interferometric quantum radar technology has the ability to break through the standard quantum limit. Current measurement methods for quantum interference radar include quantum interference measurement, attenuated quantum interference measurement, and separable state measurement. Since the operation of a quantum interference radar system is similar to that of a long-arm interferometer, its performance can be analyzed using a Mach-Zehnder interferometer. It has been confirmed that using highly entangled states for interferometric phase measurement can achieve the Heisenberg limit in sensitivity, breaking the standard quantum limit of classical radar measurement.

[0004] Quantum radar currently faces many challenges. Because the detection environment contains various noises and interferences, the quantum signal inevitably interacts with the environment and target during detection, leading to decoherence and affecting the radar's performance. Simultaneously, the interference process occurs in an attenuating medium, and entangled states are attenuated to some extent during transmission. Quantum interferometric radars are mostly based on Mach-Zehnder interferometer systems for optical design. They use a quantum transmitter to emit highly entangled signals to detect the target and environment. The returned signal and the confinement signal re-converge through the system, interfering and being received by a quantum receiver. High-precision phase measurements are then performed using the nonlocality of the quantum entangled states.

[0005] Current quantum interference radars all face a common problem: the decoherence of entangled states is highly susceptible to environmental attenuation. This is due, on the one hand, to atmospheric attenuation limitations during long-distance detection by the transmitting arm; and on the other hand, to the use of non-common-path interferometric beam splitting in the two arms. In non-common-path interferometric beam splitting, the beam travels independently within each arm, such as... Figure 3 As shown, in reality, the two independent arms are highly susceptible to environmental disturbances such as temperature and vibration, leading to instability in the coherent state. However, the common-path interferometry technique, by aligning the beam paths of the two arms, cancels out the thermodynamic deformations caused by external environmental disturbances, resulting in a more stable coherent state. Summary of the Invention

[0006] The purpose of this invention is to provide a high-stability common-path quantum interference radar. It uses common-path interference splitting technology to overcome the instability of the independent two arms in non-common-path interference splitting types, changes the basic configuration of traditional quantum interference radar, and gives it the advantages of high stability and strong anti-interference capability, while retaining its original advantages such as high sensitivity and high resolution.

[0007] The technical solution of the present invention is as follows:

[0008] A highly stable co-optical-path quantum interference radar includes a quadrilateral co-optical-path interferometer; the quadrilateral co-optical-path interferometer includes a beam splitter, a first plane mirror, a second plane mirror, a third plane mirror, and a fourth plane mirror;

[0009] An incident entangled light source is incident on a quadrilateral common-path interferometer. The entangled photons are split into a first transmitted photon and a first reflected photon by a beam splitter. The first transmitted photon is reflected by a third plane mirror, a second plane mirror, and a first plane mirror, and then directed toward the target space until it encounters the target object and is reflected back. It is then reflected back to the beam splitter by the first, second, and third plane mirrors, where it generates a second reflected photon and a second transmitted photon. The first reflected photon is reflected by a first, second, and third plane mirror and then directed toward a fourth plane mirror. It is reflected back by the fourth plane mirror and then reflected back to the beam splitter by the third, second, and first plane mirrors, where it generates a third reflected photon and a third transmitted photon.

[0010] The second reflected photon and the third transmitted photon interfere with each other, that is, the target detection light and the local reference light interfere with each other, thereby obtaining the distance information of the target object; the delayed optical path between the third plane mirror and the fourth plane mirror is used to adjust the optical path difference between the target detection light and the local reference light, so that the two beams interfere synchronously.

[0011] Furthermore, the radar also includes a detection and acquisition module, which is used to acquire interference signals.

[0012] Furthermore, the detection and acquisition module employs photon counting measurement.

[0013] Furthermore, the radar also includes a converging mirror or a group of converging mirrors for projecting interferometric converging images onto the detector pixels of the detection and acquisition module.

[0014] Furthermore, converging lenses or converging lens assemblies include refractive and reflective types.

[0015] Furthermore, the radar also includes a host computer processing system for processing and analyzing interference signals to obtain distance information of the target object.

[0016] Furthermore, the radar also includes a front optical system located in front of the quadrilateral common-path interferometer, which is used to convert the light passing through the front optical system into parallel light.

[0017] Furthermore, the front optical system includes a converging lens, an aperture stop, and a collimating lens arranged in sequence.

[0018] Furthermore, the incident entangled light source includes entangled state light source, coherent entangled state light source, compressed state light source, and coherent state light source.

[0019] Furthermore, beam splitters include cubic beam splitters, planar beam splitters, and prisms coated with semi-transparent and semi-reflective beam splitting films.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] (1) High stability. This quantum interference radar is based on common-path technology, and the common-path interferometric system has high stability. Traditional quantum interference radar detection technology uses non-common-path interferometric systems, which are easily affected by external thermodynamic changes, causing changes in optical path difference, which in turn causes interference shift and phase instability, resulting in large instrument errors and inaccurate high-precision measurements. After using common-path beam splitting technology, external thermodynamic changes act on both arms of the interferometer simultaneously, so the resulting optical path difference can cancel each other out, and the formed coherent state is more stable, resulting in higher interferometer stability.

[0022] (2) Strong structural robustness. The quantum interference radar has a flexible structural design, and the input light source can be either an entangled state light source or a coherent state light source.

[0023] (3) Wide range of applications. Due to the adoption of the common optical path splitting method, the stability of the quantum interference radar detection system is greatly improved and the anti-interference capability is enhanced. Therefore, there are more application scenarios and the application fields will be wider.

[0024] (4) Simple structure and easy to miniaturize. The common-path quantum interference radar detection scheme proposed in this invention can be composed of only a planar beam splitter and four plane mirrors. Removing some plane mirrors in the non-common-path interference system makes the whole structure more compact. It is easy to miniaturize without losing light flux. Moreover, due to the extremely high sensitivity of quantum measurement, the quantum radar requires lower transmission power while ensuring detection capability, which is more conducive to equipment miniaturization.

[0025] (5) High sensitivity, which can break through the classical limit of interferometry. The accuracy of traditional radar imaging is limited by the diffraction limit, while quantum radar uses the higher-order correlation characteristics of electromagnetic fields for imaging, and the resolution can break through the diffraction limit, further improving the imaging and detection accuracy.

[0026] (6) Strong target detection capability. Compared with classical radar, quantum radar uses the properties of photons for detection. Since the emitted photons have quantum characteristics, it is only necessary to identify the state of the returned photons to detect the interference behavior of special coatings of stealth aircraft, which significantly improves the radar detection capability.

[0027] (7) Strong concealment. Compared with traditional radar that emits electromagnetic radiation to detect objects, quantum radar emits very little energy (photons), making it difficult to detect. This gives quantum radar strong concealment, allowing it to detect objects without easily exposing itself, which has great practical significance in real-world applications.

[0028] (8) Longer detection range. When quantum particles are in an entangled state, their correlation and interaction are independent of distance, while the detection range of traditional radar depends on the transmission power of electromagnetic waves. Furthermore, quantum technology can improve the sensitivity of the detection system, enabling it to detect weaker signals. Therefore, the detection range of quantum radar can be several times or even tens of times that of traditional radar. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the optical principle of the high-stability common-path quantum interference radar technology of the present invention;

[0030] Figure 2 This is a schematic diagram of the high-stability common-path quantum interference radar structure of the present invention;

[0031] Figure 3 This is a model diagram of a two-mode quantum interference radar based on a coherent state light source.

[0032] In the figure: 1—Incident entangled light source, 2—Beam splitter, 3—First plane mirror, 4—Second plane mirror, 5—Third plane mirror, 6—Fourth plane mirror, 7—Target object, 8—Interference photon, 9—Front optical system, 10—Converging mirror (group), 11—Detection and acquisition module, 12—Host computer processing module. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] This invention proposes a novel high-stability quantum interferometric radar detection technology and its application system. This high-stability quantum interferometric radar detection technology and its application system combine the principle of a common-path interferometer and use common-path interferometric beam splitting technology to overcome the instability problem of independent two arms. It changes the basic configuration of traditional quantum interferometric radar, giving it the advantages of high stability and strong anti-interference capability, while retaining its original advantages such as high sensitivity and high resolution.

[0035] See Figure 1This is a preferred implementation method. The quantum interference radar technology is based on a quadrilateral common-path interferometer. This interferometer consists of a semi-transparent, semi-reflective beam splitter and four plane mirrors. Entangled photons from the target enter the interferometer in parallel, and are then separated by the beam splitter, referred to as the first transmitted photon and the first reflected photon. The first transmitted photon is reflected by three mirrors and then propagates towards the target space for detection until it encounters the target object, is reflected back, and then reflected back to the beam splitter by the three mirrors, generating the target detection light. The first reflected photon is reflected sequentially by the four mirrors and returns to the beam splitter, forming the local reference light. The two beams returning to the beam splitter are then transmitted and reflected again, forming four optical signals. Each pair of beams generates an interference photon pair, one of which returns to the incident direction of the light source, while the other propagates in another direction (perpendicular to the incident direction of the light source in the diagram), i.e., the target detection light interferes with the local reference light. By collecting and analyzing the quantum information perpendicular to the incident direction of the light source, the location of the target object and other necessary information can be obtained.

[0036] The characteristics of each part of the device are described in detail below:

[0037] The interferometer is positioned on the incident light path of the entangled light source 1, and the incident position must be within the effective range of the beam splitter 2. After being split by the beam splitter 2, the light is reflected by the first plane mirror 3, the second plane mirror 4, the third plane mirror 5, the fourth plane mirror 6 within the interferometer, and the target object 7, ultimately obtaining the target interference photon 8. Due to the design of the four mirrors, the photons, after being split by the interferometer beam splitter 2, pass through the same interference devices within the interferometer, forming a common-path interferometer.

[0038] The incident entangled light source 1 can be a non-classical light source such as entangled state, coherent entangled state, or squeezed state, or a coherent state light source can be used.

[0039] The beam splitter 2 can be a cube-shaped beam splitter or a flat beam splitter. If the interferometer is a solid structure, it can be achieved by coating the prisms that make up the interferometer with a semi-transparent and semi-reflective beam splitting film.

[0040] The four reflectors are used to alter the spatial path of photons. The first plane reflector 3, the second plane reflector 4, and the third plane reflector 5 can be designed with an asymmetrical structure; that is, they are not strictly symmetrical about the beam-splitting axis, but rather have a certain degree of translation. For example, the second plane reflector 4 and the third plane reflector 5 could be translated to the right. The amount of translation depends on the required spatial dimensions of the structure. Furthermore, when adjusting the translation, the goal should be to ensure that the first reflected photon, after passing through the reflection surfaces of the first plane reflector 3, the second plane reflector 4, and the third plane reflector 5, can be smoothly reflected by the reflection surface of the fourth plane reflector 6. The first transmitted photon, after passing through the reflection surfaces of the third plane reflector 5, the second plane reflector 4, and the first plane reflector 3, can directly exit and search for the target object 7 without passing through the beam splitter 2.

[0041] Besides its reflective function, the fourth plane mirror 6 is also an important component of the delay line. The delay line is the optical path between the third plane mirror 5 and the fourth plane mirror 6. Quantum interferometry radar systems generally detect remote targets by the round-trip time of pulse signals and obtain more accurate target distances through phase estimation. However, when the optical path difference between the local reference light and the target detection light is too large, the two beams of light will arrive at the detector at different times. To solve this problem, a delay line needs to be added to the local reference light to solve the time delay problem.

[0042] The device is followed by a signal detection system. When using parity detection, the signal to be measured is the parity operator, which is directly represented by the parity of the number of received photons.

[0043] It should be noted that although the common optical path of this invention is also based on a quadrilateral common optical path, it differs from traditional common optical paths mainly in the following aspects: First, traditional common optical paths involve self-interference after the target light is split, such as CN114739509B, while this invention is based on the principle of quantum interference radar, where the interference is the quantum interference between the distant target light and the local reference light; Second, this invention modifies the optical path by adding a sixth reflecting mirror below the beam splitter, so that the optical path is no longer a complete quadrilateral. This is to adapt to the principle of quantum interference radar, retaining the local reference light while leaving room for the detection optical path. Furthermore, this invention differs significantly from other current common optical path lidars in terms of optical path shape and purpose. Other common optical path lidars are mostly designed to solve the problem of blind spots in short-range detection, while the common optical path of this invention aims to improve the stability of local radar measurements.

[0044] Furthermore, current quantum interference radar employs a long-arm interference optical path based on a Mach-Zehnder interferometer, such as... Figure 3As shown, the internal optical path of the interferometer is susceptible to instability due to environmental interference such as temperature and vibration. This invention employs a common-path interference method, based on the classical quantum interference radar optical path principle, to improve the measurement stability of quantum interference radar.

[0045] Using this technology, a quantum interference radar device can be designed, such as... Figure 2 As shown.

[0046] In practical systems, coherent state laser sources can currently be used. Coherent state sources are easier to implement than entangled state sources, and under high attenuation conditions, coherent states can achieve the best shot noise sensitivity in the returned power, avoiding the influence of insufficient entanglement strength. Moreover, using only coherent states can break the Rayleigh diffraction limit and achieve high sensitivity requirements.

[0047] The coherent laser source enters the quantum interference radar device after passing through the pre-optical system 9, where it is split into a first transmitted photon and a first reflected photon by the beam splitter 2. The first transmitted photon passes through the third plane mirror 5, the second plane mirror 4, and the first plane mirror 3 respectively before being emitted toward the target object 7. After detecting the target object 7, it is reflected and then returns to the beam splitter 2 through the first plane mirror 3, the second plane mirror 4, and the third plane mirror 5, generating a second reflected photon and a second transmitted photon. The second reflected photon is emitted to generate the target detection light. The first reflected photon passes through the first plane mirror 3, the second plane mirror 4, and the third plane mirror 5 to reach the time-delay fiber (between the third plane mirror 5 and the fourth plane mirror 6). After passing through the fourth plane mirror 6, it returns to the beam splitter 2 along the original path, generating a third reflected photon and a third transmitted photon. The third transmitted photon is emitted to form a local reference light and interferes with the second reflected photon to form an emitted interference signal. After passing through the converging mirror (group) 10, it reaches the detector image plane of the detection and acquisition module 11. After preprocessing such as acquisition, amplification, and noise reduction, it enters the host computer processing module 12 for further processing and inversion, thereby accurately measuring the distance information of the target.

[0048] The coherent laser source first enters the front optical system 9. The front optical system 9 includes a converging lens f, an aperture e, and a collimating lens d arranged sequentially. The target light is converged by the converging lens f, the aperture e filters and restricts the shape of the image plane of the converging lens f and prevents stray light, and then collimated by the collimating lens d, making the light passing through the front optical system 9 parallel. The front optical system 9 can employ various forms such as refraction, catadioptric reflection, and total internal reflection, with the aim of converting the target radiation into parallel rays. Depending on design requirements, the collimating lens d can be removed from the front optical system 9 to become a converging optical path, or the front optical system 9 can be omitted entirely.

[0049] The function of the converging lens (group) 10 is to converge the interference formed by the interferometer onto the detector pixels of the detection and acquisition module 11. The converging lens (group) 10 can be individual lenses or a combination of lenses, with the latter facilitating the elimination of aberrations. The converging lens (group) 10 can be either refracting or reflecting, and its main purpose is to converge the interfering photons onto the detector image plane.

[0050] The detection and acquisition module 11 employs photon counting measurement. Based on current quantum technology, compared to the N00N and M&M' schemes, the parity detection scheme using a coherent laser source is easier to implement and more stable. The signal to be measured is the parity operator, which is directly represented by the parity of the number of received photons. Therefore, the receiver should use a detector with single-photon resolution capability, such as a single-photon counter or an EMCCD.

[0051] The present invention can also add a host computer processing system 12. The computer processing system 12 performs data processing and analysis on the interference signal acquired by the detection and acquisition module 11, including processes such as filtering, amplification, noise reduction, integration, and counting of the raw data, so as to obtain more accurate photon number information and thus accurately measure the distance information of the target.

[0052] Based on this principle, other forms of quantum interference radar technology and devices can be derived. By adding or removing certain components, such as eliminating the front optical system, the size and weight of the instrument can be reduced; by adding polarization devices to the optical path, a polarization-type quantum interference radar can be formed.

[0053] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0054] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-stability common optical path quantum interference radar, characterized in that, The radar includes a quadrilateral common-path interferometer; the quadrilateral common-path interferometer includes a beam splitter, a first plane mirror, a second plane mirror, a third plane mirror, and a fourth plane mirror; An incident entangled light source is incident on a quadrilateral common-path interferometer, and the entangled photons are split into a first transmitted photon and a first reflected photon by a beam splitter. The first transmitted photon is reflected by the third, second, and first plane mirrors and then propagates towards the target space until it encounters the target object and is reflected back. It is then reflected back by the first, second, and third plane mirrors and returns to the beam splitter, where it generates the second reflected photon and the second transmitted photon. The first reflected photon is reflected by the first, second, and third plane mirrors and then propagates towards the fourth plane mirror. It is reflected back by the fourth plane mirror and then reflected back by the third, second, and first plane mirrors and returns to the beam splitter, where it generates the third reflected photon and the third transmitted photon. The second reflected photon and the third transmitted photon interfere with each other, that is, the target detection light and the local reference light interfere with each other, thereby obtaining the distance information of the target object; the delayed optical path between the third plane mirror and the fourth plane mirror is used to adjust the optical path difference between the target detection light and the local reference light, so that the two beams interfere synchronously to obtain the distance information of the target object.

2. The high-stability common-path quantum interference radar according to claim 1, characterized in that, The radar also includes a detection and acquisition module, which is used to acquire interference signals.

3. The high-stability common-path quantum interference radar according to claim 2, characterized in that, The detection and acquisition module uses photon counting measurement.

4. The high-stability common-path quantum interference radar according to claim 2, characterized in that, The radar also includes a converging mirror or a group of converging mirrors for projecting interferometric converging images onto the detector pixels of the detection and acquisition module.

5. The high-stability common-path quantum interference radar according to claim 4, characterized in that, Converging lenses or assemblies of converging lenses include refractive and reflective types.

6. The high-stability common-path quantum interference radar according to claim 4, characterized in that, The radar also includes a host computer processing system for processing and analyzing interference signals to obtain distance information of the target object.

7. The high-stability common-path quantum interference radar according to claim 1, characterized in that, The radar also includes a front optical system, which is located in front of the quadrilateral common-path interferometer and is used to make the light passing through the front optical system parallel.

8. The high-stability common-path quantum interference radar according to claim 7, characterized in that, The front optical system includes a converging lens, an aperture stop, and a collimating lens arranged in sequence.

9. The high-stability common-path quantum interference radar according to claim 1, characterized in that, Incident entangled light sources include entangled state light sources, coherent entangled state light sources, compressed state light sources, and coherent state light sources.

10. The high-stability common-path quantum interference radar according to claim 1, characterized in that, Beam splitters include cubic beam splitters, planar beam splitters, and prisms coated with semi-transparent and semi-reflective beam splitting films.

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