Quantum information analog-digital conversion device and optical wave spatial information coherent time domain transmission system

Abstract

This invention provides a quantum information analog-to-digital converter and a coherent time-domain transmission system for spatial optical information, relating to the field of quantum information analog-to-digital conversion. The quantum information analog-to-digital converter includes: N cascaded first conversion modules, the nth first conversion module comprising: a first momentum translation component, used to apply momentum translation to the left-hand and right-hand circularly polarized components of a photon in the target spatial dimension; a first position translation component, used to apply spatial position translation to the first and second linearly polarized components of the photon, coupling at least a portion of the quantum information on the spatial wavefunction to the polarization state of the photon; and a first delay component, used to introduce a time delay between the second linearly polarized component and the first linearly polarized component of the photon, outputting a single photon with a 2-1... n The (n+1)th coherent beam of a time pattern. The device of this embodiment of the invention is capable of encoding continuous quantum information into multi-order discrete time patterns.

Description

Technical Field

[0001] This invention relates to the field of analog-to-digital conversion of quantum information, and particularly to a quantum information analog-to-digital conversion device and a coherent time-domain transmission system for optical spatial information. Background Technology

[0002] The core task of analog-to-digital conversion (ADC) technology is to map continuous physical quantities into discrete, digitally representable information. In optical quantum information processing, this task is specifically manifested in the discretization and encoding of the continuous variable information carried by the photon space wavefunction. Traditional cameras discretize the photon space intensity distribution into multiple pixel units for sampling and output classical electrical signals, which cannot retain the coherent characteristics of quantum information in photon quantum states. To extract the quantum information contained in the light field space, classical optics has developed Shack-Hartmann wavefront sensors and wavefront sensing techniques based on weak measurements to measure the wavefront phase distribution of classical light fields.

[0003] However, these methods are essentially classical photoelectric detection processes, outputting directly readable classical signals, which have inherent limitations in quantum information processing: on the one hand, the photoelectric detection process destroys the quantum state of photons, causing quantum information to lose coherence; on the other hand, these methods cannot map the quantum state information carried by photons to discrete photon degrees of freedom (such as time patterns, path patterns, etc.), making it difficult to support subsequent quantum information processing. Therefore, the above methods belong to quantum information measurement schemes and cannot realize the conversion mechanism of quantum information from continuous to discrete dimensions. To address the practical need for direct conversion of quantum information from continuous to discrete dimensions, existing research has built discrete variable quantum information processing systems around various discrete degrees of freedom of photons: in recent years, the path, orbital angular momentum, time, and frequency degrees of freedom of photons have been widely used in discrete variable quantum information processing tasks. Among them, time patterns and orbital angular momentum patterns have realized the pattern reuse and encoding of quantum information in high-dimensional quantum key distribution, while path encoding constructs high-dimensional discrete quantum states carrying quantum information through linear optical networks. However, the above achievements are limited to the conversion and processing of quantum information between different discrete dimensions, and there is still a lack of physical mechanisms that can realize the direct conversion of quantum information between continuous and discrete dimensions. Summary of the Invention

[0004] In view of this, a first aspect of the present invention provides a quantum information analog-to-digital converter, comprising:

[0005] N cascaded first conversion modules, wherein the nth first conversion module includes:

[0006] The first momentum translation component is suitable for applying equal and opposite momentum translations, first and second momentum translations, to the left-hand and right-hand circularly polarized components of a photon in the target spatial dimension; wherein the spatial wave function of the photon in the coherent beam carries quantum information, and a single photon of the nth coherent beam has There are several time patterns; 1 ≤ n ≤ N;

[0007] The first position translation component, for a photon from the first momentum translation component, is adapted to apply a first spatial position translation and a second spatial position translation of equal magnitude and opposite direction to the first linear polarization component and the second linear polarization component of the photon in the target spatial dimension, so as to generate quantum entanglement between the spatial wave function and the polarization state of the photon, and couple at least a portion of the quantum information on the spatial wave function to the polarization state of the photon.

[0008] The first delay component, for photons from the first position translation component, is used to delay the second linear polarization component of the photon relative to the first linear polarization component, and to convert the polarization direction of the second linear polarization component to the same polarization direction as the first linear polarization component, thereby exchanging the polarization state and time state of the photon, and outputting a single photon with... The (n+1)th coherent beam of the time pattern realizes the analog-to-digital conversion of quantum information.

[0009] According to an embodiment of the present invention, the polarization directions of the first linear polarization component and the second linear polarization component are the horizontal polarization direction and the vertical polarization direction, respectively;

[0010] The first delay component includes:

[0011] The first polarization beam splitter, for photons from the first position translation component, is adapted to transmit the first linearly polarized component of the photon and reflect the second linearly polarized component of the photon, so that the first linearly polarized component of the photon is transmitted along the first optical path.

[0012] The first transmission unit, in conjunction with the first polarization beam splitter, enables the second linearly polarized component to be transmitted along the second optical path;

[0013] The second polarization beam splitter is adapted to reflect the second linearly polarized component that propagates along the second optical path and transmit the first linearly polarized component that propagates along the first optical path, so as to combine the first linearly polarized component and the second linearly polarized component to obtain photons that have been combined by the second polarization beam splitter.

[0014] The first transmission unit is configured such that the length of the second optical path is greater than the length of the first optical path, thereby causing a time delay between the second linear polarization component and the first linear polarization component.

[0015] According to an embodiment of the present invention, the first coherent beam is a beam having a horizontal polarization direction;

[0016] The first delay component also includes:

[0017] The first polarization conversion device is adapted to convert the polarization direction of the second linear polarization component of photons combined by the second polarization beam splitter into a horizontal polarization direction.

[0018] According to an embodiment of the present invention, when 2≤n<N, the difference between the length of the second optical path and the length of the first optical path in the (n+1)th first conversion module is twice the difference between the length of the second optical path and the length of the first optical path in the nth first conversion module.

[0019] According to an embodiment of the present invention, photons from the first momentum translation component have a first linear polarization component and a second linear polarization component;

[0020] The first position translation component includes:

[0021] The first quarter-wave plate, for photons from the first momentum translation component, is suitable for converting the first linear polarization component and the second linear polarization component of the photon into the left-hand circular polarization component and the right-hand circular polarization component of the photon, respectively.

[0022] The first lens, for photons from the first quarter-wave plate, is suitable for performing Fourier transform on the photons, converting the spatial position distribution of the photons in the target plane into the momentum distribution in the Fourier plane;

[0023] The first offset element, located on the Fourier surface, is used to apply equal and opposite momentum shifts to the left-hand circularly polarized component and the right-hand circularly polarized component of the photon from the first lens, so that the left-hand circularly polarized component is converted into the right-hand circularly polarized component and the right-hand circularly polarized component is converted into the left-hand circularly polarized component.

[0024] The second lens has the same focal length as the first lens, and the front focal plane of the second lens coincides with the rear focal plane of the first lens. For photons from the first offset device, the second lens is used to perform Fourier transforms on the left-hand circularly polarized component and the right-hand circularly polarized component of the photon, so that the left-hand circularly polarized component and the right-hand circularly polarized component of the photon produce spatial position translations of equal magnitude and opposite direction in the target space dimension.

[0025] The second quarter-wave plate, for photons from the second lens, is suitable for converting the left-hand circularly polarized component and the right-hand circularly polarized component of the photon into the second linearly polarized component and the first linearly polarized component of the photon, respectively; wherein, the target plane is parallel to the Fourier surface, which is the back focal plane of the first lens or the front focal plane of the second lens.

[0026] According to an embodiment of the present invention, the first momentum translation component is a first polarization grating, and the grating period of the first polarization grating of the (n+1)th first conversion module is twice the grating period of the first polarization grating of the nth first conversion module, where 1 ≤ n < N.

[0027] According to an embodiment of the present invention, the first offset element is a second polarization grating, and the grating period of the second polarization grating of the (n+1)th first conversion module is half of the grating period of the second polarization grating of the nth first conversion module, where 1 ≤ n < N.

[0028] As a second aspect of the present invention, a coherent time-domain transmission system for optical spatial information is also provided, comprising:

[0029] A quantum information analog-to-digital converter suitable for converting a first coherent beam into a quantum information analog-to-digital converter with 2... N The (N+1)th coherent beam of the time pattern;

[0030] N cascaded second conversion modules are suitable for converting the N+1th coherent beam into the first coherent beam, so as to realize the transmission of the first coherent beam.

[0031] According to an embodiment of the present invention, the Nth second conversion module and the Nth first conversion module are connected via a single-mode optical fiber;

[0032] The nth second conversion module includes:

[0033] The second delay component is suitable for:

[0034] For the photon of the (n+1)th coherent beam, the photon is in the first position in the time domain The polarization direction of the photon component of each time mode is converted to obtain the converted (n+1)th coherent beam; wherein the polarization direction of the converted photon component is orthogonal to the polarization direction of the photon component before conversion.

[0035] For the photons of the converted (n+1)th coherent beam, the second delay component is also adapted to delay the second linear polarization component of the photon relative to the first linear polarization component, so that the output single photon has The nth coherent beam of the time pattern couples the quantum information of the time state of the photon to the polarization state of the photon;

[0036] The second position translation component is adapted to apply a second spatial position translation and a first spatial position translation to the second linear polarization component and the first linear polarization component of the photon, respectively, so that the second linear polarization component is converted into the first linear polarization component and the first linear polarization component is converted into the second linear polarization component.

[0037] The second momentum translation component, for photons from the second position translation component, is suitable for applying a second momentum translation and a first momentum translation to the left-hand circular polarization component and the right-hand circular polarization component of the photon, respectively, to couple the quantum information in the polarization state of the photon to the spatial wave function of the photon.

[0038] According to an embodiment of the present invention, the optical spatial information coherent time-domain transmission system further includes:

[0039] At least one polarization beam splitter is disposed between the Nth first conversion module and the Nth second conversion module, and is adapted to allow the portion of the (N+1)th coherent beam output by the Nth first conversion module that has the same polarization direction as the first coherent beam to pass through.

[0040] According to an embodiment of the present invention, the quantum information of the continuous spatial wave function of photons is converted into a quantum modulus of discrete time dimension through the coordinated cooperation of momentum translation component, position translation component and delay component.

[0041] The embodiments of the present invention have the following effects: the first momentum translation component of the embodiments of the present invention applies equal and opposite momentum translation operations to the left-hand circularly polarized components and the right-hand circularly polarized components of the photon, pre-couples the quantum information such as amplitude and phase information contained in the spatial wave function to the polarization degree of freedom of the photon; the first position translation component realizes the quantum entanglement relationship between the spatial wave function and the polarization state of the photon, and transfers the quantum information to the polarization state of the photon; the first delay component completes the information exchange between the polarization state and the time state of the photon by relying on a pure optical path that does not involve photoelectric conversion, and the entire information conversion process does not have the loss caused by photoelectric conversion, and the coherence characteristics of the spatial wave function of the photon can be completely maintained.

[0042] The quantum information analog-to-digital converter that transfers the spatial wave function of a photon to the time dimension provided in this embodiment of the invention can support subsequent quantum information processing tasks because it can preserve the coherence of the spatial wave function of the photon and reversibly map it to the time dimension of discrete photons. Attached Figure Description

[0043] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings.

[0044] Figure 1 A schematic diagram of a quantum information analog-to-digital converter provided according to an embodiment of the present invention is shown.

[0045] Figure 2 A schematic diagram of a quantum circuit for quantum analog-to-digital conversion provided according to an embodiment of the present invention is shown.

[0046] Figure 3A schematic diagram of a coherent time-domain transmission system for optical spatial information provided according to an embodiment of the present invention is shown.

[0047] Figure 4A A conversion effect diagram of a quantum information analog-to-digital converter provided according to an embodiment of the present invention is shown.

[0048] Figure 4B A conversion effect diagram of a quantum information analog-to-digital converter provided according to another embodiment of the present invention is shown.

[0049] Figure 5A A conversion effect diagram of a quantum information analog-to-digital converter provided according to another embodiment of the present invention is shown.

[0050] Figure 5B A conversion effect diagram of a quantum information analog-to-digital converter provided according to yet another embodiment of the present invention is shown.

[0051] Explanation of reference numerals in the attached figures

[0052] 10. First conversion module; 11. First momentum translation component; 12. First position translation component; 13. First delay component; 121. First quarter-wave plate; 122. First lens; 123. First offset component; 124. Second lens; 125. Second quarter-wave plate; 131. First polarization beam splitter; 132. First transmission unit; 1321. Third lens; 1322. Fourth lens; 1323. First reflector; 133. Second polarization beam splitter; 134. First polarization conversion component; 20. Second conversion module; 21. Second delay component; 211. Second polarization converter; 212. Third polarization beam splitter; 213. Second transmission unit; 2131. Fifth lens; 2132. Sixth lens; 2133. Second reflector; 214. Fourth polarization beam splitter; 22. Second position translation assembly; 221. Third quarter-wave plate; 222. Seventh lens; 223. Second offsetting element; 224. Eighth lens; 225. Fourth quarter-wave plate; 23. Second momentum translation assembly; 30. Single-mode fiber; 40. Polarization beam splitter assembly; 50. First fiber coupler; 60. Second fiber coupler. Detailed Implementation

[0053] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0054] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0055] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0056] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0057] Figure 1 A schematic diagram of a quantum information analog-to-digital converter provided according to an embodiment of the present invention is shown.

[0058] like Figure 1 As shown, the quantum information analog-to-digital converter includes N cascaded first conversion modules 10. The nth first conversion module 10 includes: a first momentum translation component 11, a first position translation component 12, and a first delay component 13.

[0059] The first momentum translation component 11 is adapted to apply equal and opposite first and second momentum translations to the left-hand and right-hand circularly polarized components of the photon of the nth coherent beam in the target spatial dimension; wherein, the spatial wave function of the photon of the nth coherent beam carries quantum information (e.g., phase or amplitude), and a single photon of the coherent beam has A time pattern; 1 ≤ n ≤ N. A first position translation component 12, for photons from a first momentum translation component 11, is adapted to apply equal and opposite spatial position translations to the first and second linearly polarized components of the photon in the target spatial dimension, causing quantum entanglement between the spatial wavefunction and the photon's polarization state, coupling at least a portion of the quantum information on the spatial wavefunction to the photon's polarization state. A first delay component 13, for photons from the first position translation component 12, is used to delay the second linearly polarized component of the photon relative to the first linearly polarized component, converting the polarization direction of the second linearly polarized component to the same polarization direction as the first linearly polarized component, exchanging the photon's polarization state and time state, and outputting a single photon with... The (n+1)th coherent beam of the time pattern realizes the analog-to-digital conversion of quantum information.

[0060] According to an embodiment of the present invention, the quantum information carried by the continuous spatial wave function of photons is converted into quantum modulus in the discrete time dimension through the coordinated cooperation of the momentum translation component, the position translation component and the delay component.

[0061] In this embodiment of the invention, the first momentum translation component 11 applies equal and opposite momentum translation operations to the left-hand and right-hand circularly polarized components of the photon, pre-coupling quantum information such as amplitude and phase information contained in the spatial wave function to the polarization degree of freedom of the photon; the first position translation component 12 realizes the quantum entanglement between the spatial wave function and the polarization state of the photon, transferring quantum information to the polarization state of the photon; the first delay component 13 completes the information exchange between the polarization state and the time state of the photon by relying on a pure optical path that does not involve photoelectric conversion. The entire information conversion process does not have the loss caused by photoelectric conversion, and the coherence characteristics of the spatial wave function of the photon can be completely maintained.

[0062] The quantum information analog-to-digital converter that transfers the spatial wave function of a photon to the time dimension provided in this embodiment of the invention can support subsequent quantum information processing tasks because it can preserve the coherence of the spatial wave function of the photon and reversibly map it to the time dimension of discrete photons.

[0063] It should be noted that in the quantum realm, photons can be decomposed into components according to different polarization dimensions. They can be decomposed into left-handed and right-handed circularly polarized components, or into two linearly polarized components with orthogonal polarization directions. In this embodiment of the invention, the polarization direction of the first linearly polarized component is, for example, horizontal, and the polarization direction of the second linearly polarized component is, for example, vertical. Therefore, the first linearly polarized component can be called, for example, the horizontal linearly polarized component, and the second linearly polarized component can be called, for example, the vertical linearly polarized component. Both the left-handed and right-handed circularly polarized components can be decomposed into horizontal and vertical linearly polarized components; each of these two linearly polarized components can also be further decomposed into left-handed and right-handed circularly polarized components.

[0064] Furthermore, the first linear polarization components obtained after photons are processed by different devices in a quantum information analog-to-digital converter are different, but the polarization direction of the first linear polarization components output by each device remains consistent. Similarly, the polarization direction of the second linear polarization components output by each device also remains consistent. This rule also applies to left-handed and right-handed circular polarization components; that is, the left-handed circular polarization components output by each device are all left-handed, and the right-handed circular polarization components output by each device are all right-handed. The following combines... Figure 1 The quantum information analog-to-digital converter provided in the embodiments of the present invention will be described in detail.

[0065] According to an embodiment of the present invention, the first coherent beam received by the first momentum translation component 11 of the first first conversion module 10 is the incident beam input to the quantum information analog-to-digital converter. The first coherent beam can be, for example, horizontally linearly polarized light (i.e., a beam in the horizontally linear polarization direction) or vertically linearly polarized light (i.e., a beam in the vertically linear polarization direction). To better illustrate this scheme, Figure 1 The first coherent beam used in this embodiment of the invention is a beam with a horizontal polarization direction, that is, the first coherent beam is horizontally linearly polarized light.

[0066] According to an embodiment of the present invention, the first momentum translation component 11 may be, for example, a first polarization grating. The first polarization grating is composed of liquid crystal molecules or other equivalent materials, and its optical fast axis direction continuously varies along a fixed direction in space. The polarization direction of photons in horizontally linearly polarized light is the horizontal polarization direction, and photons with the horizontal polarization direction can be decomposed into left-hand circularly polarized components and right-hand circularly polarized components. Therefore, the first momentum translation component can apply momentum translation operations to the photons of the first coherent beam in opposite directions according to the left-hand and right-hand circularly polarized components, with the magnitude of the translation momentum being... , among them The grating period is the period of the first polarization grating.

[0067] According to an embodiment of the present invention, the grating period of the first polarization grating of the (n+1)th first conversion module 10 is twice the grating period of the first polarization grating of the nth first conversion module 10, where 1 ≤ n < N.

[0068] According to an embodiment of the present invention, the momentum translation applied by the first polarization grating is along the lateral direction. The amount of momentum translation applied by the first polarization grating along the lateral direction is inversely proportional to the grating period. When the grating period of the first polarization grating is doubled, the amplitude of a single momentum translation operation is halved. The grating period of the first polarization grating in each stage of the first conversion module 10 increases progressively by a factor of two. Each stage can perform layered binary sampling of the lateral position degree of freedom of photons. By progressively subdividing the lateral distribution interval of the continuous spatial wave function, the amplitude and phase information of the spatial wave function in the entire spatial domain can be completely collected, avoiding sampling loss of spatial quantum information. The lateral direction is along the arrangement direction of the scribe lines of the first polarization grating, which is orthogonal to the extension direction of the scribe lines.

[0069] According to an embodiment of the present invention, the first position translation component 12 includes: a first quarter-wave plate 121, a first lens 122, a first offset member 123, a second lens 124, and a second quarter-wave plate 125.

[0070] For photons from the first momentum translation component 11, the first quarter-wave plate 121 is adapted to convert the first and second linearly polarized components of the photon into left-handed and right-handed circularly polarized components, respectively. For photons from the first quarter-wave plate 121, the first lens 122 is adapted to perform a Fourier transform on the photon, converting the spatial position distribution of the photon in the target plane into a momentum distribution on the Fourier surface. The first offsetting element 123, located on the Fourier surface, is adapted to apply equal and opposite momentum translations to the left-handed and right-handed circularly polarized components of the photon from the first lens 122, converting the left-handed circularly polarized component into a right-handed circularly polarized component and vice versa.

[0071] The second lens 124 has the same focal length as the first lens 122, and the front focal plane of the second lens 124 coincides with the rear focal plane of the first lens 122. The second lens 124 and the first lens 122 form a 4f system, namely the first 4f system. For photons from the first offset element 123, the second lens 124 performs Fourier transforms on the left-hand and right-hand circularly polarized components of the photons, causing the left-hand and right-hand circularly polarized components of the photons to undergo spatial position translations of equal magnitude and opposite directions in the target space dimension. The second quarter-wave plate 125, for photons from the second lens 124, converts the left-hand and right-hand circularly polarized components of the photons into the second linearly polarized component and the first linearly polarized component of the photons, respectively. The target plane is parallel to the Fourier surface, which is either the rear focal plane of the first lens 122 or the front focal plane of the second lens 124. The fast axis angle of the first quarter-wave plate 121 and the second quarter-wave plate 125 is 45 degrees to enable the conversion between the circularly polarized state and the linearly polarized state of photons.

[0072] According to an embodiment of the present invention, the first offset element 123 is a second polarization grating. The grating period of the second polarization grating of the (n+1)th first conversion module 10 is half the grating period of the second polarization grating of the nth first conversion module 10, where 1 ≤ n < N. The lateral position translation of the second polarization grating is inversely proportional to the grating period; when the grating period is reduced to half, the lateral position translation is doubled. The grating period of the second polarization grating of the first conversion module 10 is gradually reduced by half, which enables further subdivision of each lateral spatial interval based on the coarse division of the previous first polarization grating, thereby progressively improving the sampling precision of the spatial wave function and completely capturing the amplitude and phase information of the lateral global spatial wave function.

[0073] Schematic, the polarization directions of the first and second linearly polarized components of the photons from the first position translation component 12 are the horizontal polarization direction and the vertical polarization direction, respectively.

[0074] The first delay component 13 includes: a first polarization beam splitter 131, a first transmission unit 132, and a second polarization beam splitter 133. Figure 1The system may have multiple first transmission units 132 and second polarization beamsplitters 133. The first polarization beamsplitter 131, for photons from the first position translation component 12, is adapted to transmit the first linearly polarized component of the photon and reflect the second linearly polarized component, causing the first linearly polarized component to propagate along a first optical path, where the first optical path is direct transmission from the first polarization beamsplitter 131 to the second polarization beamsplitter 133. The first transmission unit 132, in conjunction with the first polarization beamsplitter 131, causes the second linearly polarized component to propagate along a second optical path, where the second optical path originates from the first polarization beamsplitter 131, passes through the first transmission unit 132, and then to the second polarization beamsplitter 133. The second polarization beamsplitter 133 is adapted to reflect the second linearly polarized component propagating along the second optical path and transmit the first linearly polarized component propagating along the first optical path, thereby combining the first and second linearly polarized components to obtain a combined photon. The first transmission unit 132 is configured such that the length of the second optical path is greater than the length of the first optical path, causing a time delay between the second linearly polarized component and the first linearly polarized component. The first transmission unit 132 includes two 4f systems; the first 4f system can be referred to as the second 4f system, and the second 4f system as the third 4f system. The image plane of the second 4f system is connected to the object plane of the third 4f system. The first transmission unit 132 also includes multiple first reflecting mirrors 1323 for changing the optical path. The second 4f system includes two third lenses 1321, and the third 4f system includes two fourth lenses 1322. The vertical linearly polarized component travels through the longer optical path, while the horizontal linearly polarized component travels through the shorter optical path. The two 4f systems placed along the longer optical path ensure that the phase distribution of the photon's spatial wave function maintains spatial coherence during free-space propagation, preventing changes as the photon propagates in free space.

[0075] According to an embodiment of the present invention, when 2≤n<N, the difference between the length of the second optical path and the length of the first optical path in the (n+1)th first conversion module 10 is twice the difference between the length of the second optical path and the length of the first optical path in the nth first conversion module 10, that is, the optical path difference between the first linearly polarized component and the second linearly polarized component in the (n+1)th first conversion module 10 is twice the optical path difference between the first linearly polarized component and the second linearly polarized component in the nth first conversion module 10.

[0076] According to an embodiment of the present invention, the first optical path and the second optical path respectively transmit the two types of linearly polarized components of the photon after beam splitting. The optical path difference between the two optical paths directly determines the time delay value of the output of the two types of photon components. Doubling the optical path difference results in a corresponding doubling of the time delay. A time pattern is an orthogonal quantum basis vector that is distinguishable by the propagation delay of photons, independent on the time axis, and mutually recognizable. It is used to encode the discrete-time degrees of freedom of photons carrying quantum information, and can also be called the time-dimensional quantum basis vector. The same photon will produce a fixed arrival time difference after passing through optical paths of different lengths. Each non-overlapping independent arrival time interval corresponds to an independent time pattern. The optical path difference increases progressively in a doubling ratio, enabling the decomposition of new independent discrete time patterns based on the previous level of time delay. A single-stage module can increase the number of discrete time patterns carried by a single photon from... Expand to By progressively building an exponentially large set of discrete-time patterns, we can realize the allocation of horizontally continuous spatial quantum information to more dimensional time qubits.

[0077] According to an embodiment of the present invention, for a photon from the first position translation component 12, the first delay component 13 is used to separate the horizontal linear polarization component and the vertical linear polarization component of the photon. The first delay component 13 further includes a first polarization conversion element 134, which converts the polarization direction of the second linear polarization component of the photon, which has been combined by the second polarization beam splitter, to a horizontal polarization direction. The first polarization conversion element 134 can be, for example, a high-speed Pockels cell, and its function is to apply different polarization rotation operations to polarization components that pass through at different times. Specifically, it rotates the vertical linear polarization component with a longer path (longer optical path) by 90 degrees, converting it to a horizontal linear polarization state, i.e., having a horizontal polarization direction. For the horizontal linear polarization component with a shorter optical path, no operation is performed, maintaining the horizontal linear polarization state, i.e., maintaining the horizontal polarization direction. The overall effect is to reset the polarization state of the photon to a horizontal linear polarization state.

[0078] Figure 2 A schematic diagram of a quantum circuit for quantum analog-to-digital conversion provided according to an embodiment of the present invention is shown.

[0079] like Figure 2 As shown, the circuit includes one continuous-state path and N discrete-state quantum bit paths, where , , ... Represents multiple initial states in the ground state Discrete qubits. These are polarized qubits, i.e., the polarization state of a photon. It is a spatial wave function. , ... These are time qubits, i.e., the time state of a photon. Operators that represent spatial translation operations. This represents the momentum translation operator, where n is 1, 2, ..., N-1, N. This represents the spatial position translation operation and momentum translation operation applied in the nth first transformation module. For the nth first transformation module, the input continuous spatial wavefunction is first processed... , making the space wave function and Quantum entanglement occurs, coupling quantum information to polarized qubits. Subsequently, the delay component inside the first conversion module performs a quantum state swapping operation, converting the polarization qubits... Quantum information transfer to .

[0080] According to embodiments of the present invention, the working principles of the first momentum translation component, the first position translation component, and the first delay component are explained below in conjunction with formulas.

[0081] In the nth first conversion module, the first momentum translation component can be a first polarization grating, whose momentum translation operator... It is represented by equation (1).

[0082] (1);

[0083] in, and The Pauli operator for the polarization state of a photon is expressed as equation (2).

[0084] , (2);

[0085] in, and These represent right-handed and left-handed circularly polarized states, respectively. yes Hermitian conjugate, yes Hermitian conjugate; and These represent the horizontal linear polarization state and the vertical linear polarization state, respectively. yes Hermitian conjugate, yes Hermitian conjugate; This is the horizontal position operator, where horizontal refers to the arrangement direction of the grating lines of the first polarization grating. The grating period of the first polarization grating. Let be the spatial distribution characteristic size of the photon's spatial wave function, where the spatial wave function is located... The proportion of the modulus integral value within the defined spatial region to the total modulus integral value of the spatial wavefunction is greater than or equal to 99%. The grating period used to determine the first polarization grating. The grating period of the first polarization grating in the nth first conversion module. It can be determined using equation (3).

[0086] (3).

[0087] Furthermore, the first position translation component consists of a second polarization grating, a first 4f system, and two quarter-wave plates. The second polarization grating is placed on the Fourier surface of the first 4f system to convert the momentum translation operation into a position translation operation, the translation distance being... It is represented by equation (4).

[0088] (4).

[0089] in, Let λ be the wavelength of the photon in the nth coherent beam. Let be the focal length of the two lenses in the first 4f system. The first quarter-wave plate and the second quarter-wave plate are placed in front of and behind the first 4f system, respectively, with their fast axis directions aligned to _____. Spend; The period of the second polarization grating is [value], and its size is [value]. The specific mathematical expression for spatial translation when n has different values. It can be written as equation (5) and equation (6).

[0090] (5);

[0091] (6).

[0092] in, It is a transverse momentum operator. Indicates the order of application of the first The first position translation component This represents the total number of the first transformation modules, which is also the total number of the first position translation components, where i is the imaginary unit. The operator for tensor product. Represents the polarization Pauli z-operator .

[0093] Furthermore, the first conversion modules, connected in N cascades, sequentially apply momentum translation corresponding to the first momentum translation component. After the optical operation represented by the position translation operator corresponding to the first position translation component and the first delay component, the global unitary evolution applied to the photon carrying quantum information can be expressed as Equation (7).

[0094] (7);

[0095] The subscript s ranges from 0 to 1. Discrete qubits, such as Figure 2 In , , ... Discrete qubits belong to two-level discrete quantum systems, which differs from the continuous state corresponding to the photon's spatial wavefunction. Representing discrete bits and The exchange operator is used to exchange the quantum states between discrete qubits. As the basis vectors of discrete qubits, it is possible to... and The expansion is determined by the binary number of the index s, and the basis vector form is determined by the binary code corresponding to the index s. For example, index s=6 represents... basis vectors ; For the basis vector The spatial shift of the lower spatial wave function, the magnitude of which is ;in, Let s be the value of the nth bit of the binary number with index s, where n = 1, 2, ..., N; The additional phase applied to each basis vector during the transformation process, with a magnitude of The above formula utilizes mathematical approximation relationships: .

[0096] Furthermore, the above formula can be applied to... A further approximation is obtained under the condition that the space wave function is at a scale of The rate of change of space over length is very small. Within the range of length, it can be approximated as a constant, thus yielding formula (8).

[0097] (8).

[0098] After the coordinated action of the first momentum translation component 11, the first position translation component 12, and the first delay component 13, the discrete qubits and the spatial wave function carrying the original quantum information are separated; the spatial wave function samples the position in the target space dimension. The corresponding discrete-time patterns formed by photons passing through different time delay combinations in each of the first delay components, all 2 NThe basis vectors correspond to 2 N These mutually orthogonal and independently distinguishable discrete-time modes enable the mapping of continuous spatial quantum information carried by photons in a coherent beam to the photon temporal state, thus completing the analog-to-digital conversion of quantum information. The evolutionary laws at each stage are related to the output of the nth first conversion module, where a single photon possesses a 2... n The optical path evolution patterns of each time mode are consistent.

[0099] Furthermore, the photons obtained after analog-to-digital conversion can be coupled into the single-mode fiber 30 for transmission. Since the quantum information carried by the photons is encoded in the time dimension, the photons obtained after analog-to-digital conversion can be connected to a photonic chip, or connected to the single-mode fiber 30 through a polarization beam splitter 40 and a first fiber coupler 50 for long-distance transmission and subsequent operations.

[0100] Furthermore, the quantum analog-to-digital conversion process is reversible, and multiple temporal modes of quantum information photons can be converted into continuously distributed spatial wave functions. Based on this concept, embodiments of the present invention also provide a coherent temporal domain transmission system for optical spatial information.

[0101] Figure 3 A schematic diagram of a coherent time-domain transmission system for optical spatial information provided according to an embodiment of the present invention is shown.

[0102] like Figure 3 As shown, taking N=2 as an example, the optical spatial information coherent time-domain transmission system and its implementation are illustrated. The optical spatial information coherent time-domain transmission system includes: a quantum information analog-to-digital converter and N cascaded second conversion modules 20. The quantum information analog-to-digital converter is suitable for converting the first coherent beam into a quantum information ... The N+1th coherent beam of a time pattern. N cascaded second conversion modules 20 are adapted to convert the N+1th coherent beam to obtain the first coherent beam, so as to realize the transmission of the first coherent beam.

[0103] According to an embodiment of the present invention, the Nth second conversion module 20 and the Nth first conversion module 10 are connected by a single-mode optical fiber 30.

[0104] The nth second conversion module 20 includes: a second delay component 21, a second position translation component 22, and a second momentum translation component 23.

[0105] The second delay component 21 includes a second polarization conversion element 211, which is adapted to convert the polarization direction of the (n+1)th coherent beam to obtain the (n+1)th coherent beam converted by the second polarization conversion element 211; wherein the polarization direction of the (n+1)th coherent beam and the polarization direction of the polarization-converted (n+1)th coherent beam are orthogonal to each other. For the photons of the polarization-converted (n+1)th coherent beam, the second delay component 21 is also adapted to cause a time delay in the second linear polarization component of the photon relative to the first linear polarization component, outputting a single photon with... The nth coherent beam of a time pattern couples the quantum information of the photon's temporal state to the photon's polarization state. The polarization direction of the second linearly polarized component is vertical, and the polarization direction of the first linearly polarized component is horizontal. Specifically, the second delay component 21 also includes a third polarization beam splitter 212, a second transmission unit 213, and a fourth polarization beam splitter 214. For photons from the second polarization converter 211, the third polarization beam splitter 212 is adapted to transmit the first linearly polarized component of the photon and reflect the second linearly polarized component of the photon, causing the first linearly polarized component of the photon to propagate along a third optical path. The second transmission unit 213 cooperates with the third polarization beam splitter 212 to cause the second linearly polarized component to propagate along a fourth optical path. The fourth polarization beam splitter 214 is adapted to reflect the second linearly polarized component propagating along the fourth optical path and transmit the first linearly polarized component propagating along the third optical path, so as to combine the first linearly polarized component and the second linearly polarized component, resulting in photons combined by the fourth polarization beam splitter 214.

[0106] The second transmission unit 213 is configured such that the length of the fourth optical path is greater than the length of the third optical path, causing a time delay between the second linearly polarized component of the photon and the first linearly polarized component of the photon, outputting the nth coherent beam, and coupling the quantum information of the photon's time state to the photon's polarization state. The first linearly polarized component is a horizontal linearly polarized component, and the second linearly polarized component is a vertical linearly polarized component. The second transmission unit 213 includes two 4f systems; the first 4f system can be referred to as the fourth 4f system, and the second 4f system as the fifth 4f system. The image plane of the fourth 4f system is connected to the object plane of the fifth 4f system. The second transmission unit 213 also includes multiple second reflecting mirrors 2133 for changing the optical path; the fourth 4f system includes two fifth lenses 2131, and the fifth 4f system includes two sixth lenses 2132. The vertical linearly polarized component output by the third polarization beam splitter 212 passes through the longer optical path, while the horizontal linearly polarized component passes through the shorter optical path. Two 4f systems arranged along a relatively long optical path are used to ensure that the phase distribution of the spatial wave function of photons maintains spatial coherence during free space propagation, and does not change as photons propagate in free space. This ensures that the spatial distribution of photons after the delay is complete and distortion-free, providing a stable optical field basis for subsequent polarization beam combining and quantum information coupling.

[0107] The second position translation component 22, for photons from the second delay component 21, is adapted to apply a second spatial position translation and a first spatial position translation to the second linear polarization component and the first linear polarization component of the photon, respectively. The second position translation component 22 includes a third quarter-wave plate 221, a seventh lens 222, a second offset element 223, an eighth lens 224, and a fourth quarter-wave plate 225 arranged sequentially along the optical path. The second offset element 223 can be, for example, a third polarization grating. The second position translation component 22 is the reverse optical path structure corresponding to the aforementioned first position translation component 12. Its overall working principle is the reverse of that of the first position translation component 12, enabling the reverse restoration of the photon's spatial translation; details will not be elaborated here. The second momentum translation component 23, for photons from the second position translation component, is adapted to apply a second momentum translation and a first momentum translation to the left-hand circular polarization component and the right-hand circular polarization component of the photon, respectively, coupling the quantum information in the photon's polarization state to the photon's spatial wave function. The second momentum translation component 23 can be, for example, a fourth polarization grating.

[0108] According to an embodiment of the present invention, the above-described optical spatial information coherent temporal transmission system further includes a polarization beam splitter 40, disposed between the Nth first conversion module 10 and the Nth second conversion module 20, adapted to allow the portion of the beam output by the Nth first conversion module 10 with the same polarization direction as the first coherent beam to pass through. When the polarization direction of the first coherent beam is horizontal, the polarization beam splitter 40 is adapted to allow the portion of the beam output by the Nth first conversion module 10 with a horizontal polarization direction to pass through.

[0109] Figure 3 The first conversion module 10 on the left is the first conversion module 10, and the first conversion module 10 on the right is the second conversion module 10; the second conversion module 20 on the right is the first conversion module 20, and the second conversion module 20 on the left is the second conversion module 20.

[0110] It should be noted that, in this embodiment, the first momentum translation component 11 of the first conversion module 10 and the second momentum translation component 23 of the first conversion module 20 employ polarization gratings with a grating period of 1600 micrometers, while the first momentum translation component 11 of the second conversion module 10 and the second momentum translation component 23 of the second conversion module 20 employ polarization gratings with a grating period of 3200 micrometers. The first offset component 123 of the first conversion module 10 and the second offset component 223 of the first conversion module 20 employ polarization gratings with a grating period of 400 micrometers, while the first offset component 123 of the second conversion module 10 and the second offset component 223 of the second conversion module 20 employ polarization gratings with a grating period of 200 micrometers. The focal length of the first lens 122 and the second lens 124 of the two first conversion modules 10, and the seventh lens 222 and the eighth lens 224 of the two second conversion modules 20, is 10 cm. The focal lengths of the third lens 1321 and fourth lens 1322 of the first conversion module 10, and the fifth lens 2131 and sixth lens 2132 of the first conversion module 20, are 25 cm. The focal lengths of the third lens 1321 and fourth lens 1322 of the second conversion module 10, and the fifth lens 2131 and sixth lens 2132 of the second conversion module 20, are 50 cm. Furthermore, in this embodiment, all quarter-wave plates, except for the third quarter-wave plate 221 whose fast axis direction is -45 degrees, have a fast axis direction of 45 degrees. Both the first polarization converter and the second polarization converter involved in this embodiment can be high-speed Pockels cells.

[0111] The coherent beam to be processed, namely the first coherent beam, enters from the left side of the system. The wavelength of this coherent beam is 800 nm, the polarization direction is set to horizontal polarization, and the coherent beam is pulsed light with a pulse length of 200 ps.

[0112] The first coherent beam undergoes a polarization-controlled momentum translation operation after passing through the first momentum translation component 11 (a polarization grating with a grating period of 1600 micrometers) of the first conversion module 10. The grating lines of the polarization grating are perpendicular to the direction outward from the paper (or the target direction). The momentum translation operation includes… The phase bias is achieved by adjusting the position of the polarization grating at which the beam is incident. Specifically, the polarization is measured at the center of the beam after it passes through the grating, and the polarization state of the transmitted beam is ensured by moving the grating along the grating lines. Linear polarization. Further, the photon enters the first position translation component 12 of the first conversion module 10. This first position translation component 12 is sequentially arranged along the optical path as a first quarter-wave plate 121, a first lens 122, a first offset element 123, a second lens 124, and a second quarter-wave plate 125. The first lens 122 and the second lens 124 have equal focal lengths and form a first 4f system. The first offset element 123 is arranged on the Fourier surface of the first 4f system. The first offset element 123 is a polarization grating with a grating period of 400 micrometers, and the grating lines are distributed along the target direction. Photons from the first momentum translation component 11 first pass through the first quarter-wave plate 121, where the horizontal and vertical linear polarization components of the photons are converted into left-hand and right-hand circular polarization components, respectively. The first lens 122 performs a Fourier transform on the received photons, converting the spatial distribution of the photons on the target plane into a momentum distribution at the Fourier surface. The first offset component 123, located at the Fourier surface, applies equal and opposite momentum translations to the left-hand and right-hand circular polarization components of the photons from the first lens. At this time, the left-hand circularly polarized component of the photon is converted to a right-hand circularly polarized component, and the right-hand circularly polarized component is converted to a left-hand circularly polarized component. The second lens 124 is used to perform a Fourier transform, so that the left-hand circularly polarized component and the right-hand circularly polarized component of the received photon are translated in the target space dimension by equal magnitude and opposite direction, and the two types of polarization components are offset from each other by 0.4 mm in the target direction. Then, the photon passes through the second quarter-wave plate 125, and its left-hand circularly polarized component and right-hand circularly polarized component are converted back into a vertical linear polarization component and a horizontal linear polarization component. Among them, the fast axis direction of the first quarter-wave plate 121 and the second quarter-wave plate 125 are both 45 degrees, which is used to realize the mutual conversion between circular polarization state and linear polarization state. After the photon passes through the first 4f system composed of the first lens 122 and the second lens 124, the spatial wave function is distributed on the image plane of the first 4f system as an inverted image, that is, it undergoes a central symmetry operation.

[0113] Furthermore, the photon enters the first delay component 13 of the first conversion module 10. The horizontal linearly polarized component exits sequentially through the transmission ends of the first polarization beamsplitter 131 and the second polarization beamsplitter 133, while the vertical linearly polarized component passes through the reflection end of the first polarization beamsplitter 131, and after passing through two sets of 4f systems composed of the third lens 1321 and the fourth lens 1322 of the first conversion module 10, it is reflected by the second polarization beamsplitter 133 and combined with the horizontal linearly polarized component.

[0114] Furthermore, the object plane of the 4f system composed of the two third lenses 1321 is located at the exact center of the first polarization beamsplitter 131 of the first conversion module 10, while the image plane coincides with the 4f system composed of the two fourth lenses 1322. The image plane of the 4f system composed of the two fourth lenses 1322 is located at the exact center of the second polarization beamsplitter 133 of the first conversion module 10. After passing through these two 4f systems, the spatial distribution of the vertical linear polarization component of the photon is completely transmitted to the second polarization beamsplitter 133 of the first conversion module 10, avoiding changes in spatial distribution caused by the propagation of photons in free space. Since the vertical linear polarization component takes a longer path through the first delay component 13 of the first conversion module 10, it has a time delay relative to the horizontal linear polarization component. The optical path difference between the two components is 2m, resulting in a total delay of 6.67ns.

[0115] Furthermore, the photon enters the first polarization converter, which can be, for example, a high-speed Pockel cell. The high-speed Pockel cell does not operate on the undelayed component of the photon, but applies a polarization rotation to the delayed component, so that the polarization state of the photon is reset to a single horizontal linear polarization state, eliminating the entanglement between polarization and time modes.

[0116] Furthermore, the photon enters the first position translation component 12 of the second first conversion module 10. The first position translation component 12 of the second first conversion module 10 is sequentially arranged along the optical path as a first quarter-wave plate 121, a first lens 122, a first offset component 123, a second lens 124, and a second quarter-wave plate 125. The first lens 122 and the second lens 124 have equal focal lengths and constitute a first 4f system within the second first conversion module 10. The first offset component 123 of the second first conversion module 10 is arranged on the Fourier surface of the first 4f system. The first offset component 123 of the second first conversion module 10 is a second polarization grating with a grating period of 200 micrometers, and the grating lines are distributed along the target direction. Photons from the first momentum translation component 11 of the second first conversion module 10 first pass through the first quarter-wave plate 121, where the horizontal and vertical linear polarization components of the photons are converted into left-hand circular polarization components and right-hand circular polarization components, respectively. The first lens 122 performs a Fourier transform on the received photons, converting the spatial position distribution of the photons in the target plane into a momentum distribution at the Fourier surface. The first offset component 123 of the second first conversion module 10 at the Fourier surface applies equal and opposite momentum translations to the left-hand and right-hand circular polarization components of the photons, converting the left-hand circular polarization component into a right-hand circular polarization component and vice versa. The second lens 124 performs Fourier transforms on the left-hand and right-hand circular polarization components of the received photons, applying equal and opposite spatial position translations to the left-hand and right-hand circular polarization components of the photons in the target space dimension. This causes the two types of polarization components to be offset by 0.8 mm in a direction perpendicular to the plane of the image. Then, the photon passes through the second quarter-wave plate 125, and the left-hand circularly polarized component and the right-hand circularly polarized component are reconverted into the second linearly polarized component and the first linearly polarized component. The fast axis directions of both the first quarter-wave plate 121 and the second quarter-wave plate 125 are 45 degrees, enabling the mutual conversion between circularly polarized and linearly polarized states.

[0117] Furthermore, after the photon passes through the polarization beam splitter 40 after the second first conversion module 10, its polarization state is projected onto the horizontal linear polarization state again, and then enters the interior of the first fiber coupler 50, and is finally coupled into the single-mode fiber 30 to complete the beam transmission.

[0118] Furthermore, after the photon is transmitted through the single-mode fiber 30, it is emitted from the second fiber coupler 60. After passing through the polarization beam splitter 40, the polarization state of the photon is projected onto the horizontal linear polarization state.

[0119] Furthermore, the photon enters the second conversion module 20 ( Figure 3The second delay component 21 (left side) modulates the polarization direction of the incident photons using a second polarization converter within it. Specifically, the second polarization converter 211 within the second delay component 21 modulates the polarization direction of the incident photons in the time domain. The photon components of each time mode undergo a polarization reversal operation, i.e., a half-wave voltage is applied using the second polarization converter 211, and the applied voltage is removed after 13.333 ns, so that the photon components are in a later time domain. The polarization direction of the photon components in each time mode does not flip. The photons continue to propagate within the second delay component 21 of the second conversion module 20, and the vertical linear polarization component is delayed by 13.333 ns relative to the horizontal linear polarization component, so that the photon components of different time modes with a time interval of 13.333 ns are combined.

[0120] Furthermore, the photon sequentially passes through the second position translation component 22 within the second conversion module 20. The grating line direction of the polarization grating in the second position translation component 22 is opposite to that in the first position translation component 12 of the second conversion module 10. The quarter-wave plate 221 needs to be placed at -45 degrees to cancel the polarization modulation effect opposite to that of the second delay component 21 and the first delay component 13. The photon continues to be incident on the second momentum translation component 23 within the second conversion module 20. The grating line direction in the second momentum translation component 23 is opposite to that in the first momentum translation component 11 of the second conversion module 10, thereby completing the second position translation operation and the second momentum translation operation. Reverse operation.

[0121] Furthermore, the photon enters the first second conversion module 20 ( Figure 3 The second delay component 21 (located on the right side of the middle section) further modulates the polarization of the incident photons using a second polarization conversion element within it. A polarization reversal operation is performed on the photon component with the shortest delay. At this time, a half-wave voltage is applied to the second polarization conversion element, and the applied voltage is removed after 6.67 ns, ensuring that the polarization of photon components arriving at subsequent times does not reverse.

[0122] Furthermore, the photons continue to propagate within the second delay component 21 of the first second conversion module 20, where the vertical linear polarization component is delayed by 6.67 ns relative to the horizontal linear polarization component, causing the photons of different time modes with a time interval of 6.67 ns to be combined.

[0123] Furthermore, the photon sequentially passes through the second position translation component 22 within the first second conversion module 20. The grating line direction within the second position translation component 22 is opposite to the grating line direction within the first position translation component 12 of the first first conversion module 10. The quarter-wave plate 221 needs to be placed at -45 degrees to cancel the polarization modulation effect opposite to that of the second delay component 21 and the first delay component 13. The photon continues to be incident on the second momentum translation component 23 within the first second conversion module 20. The grating line direction within the second momentum translation component 23 is opposite to that within the first momentum translation component 11 of the first first conversion module 10, thereby completing the first position translation operation and the first momentum translation operation. The corresponding inverse operation.

[0124] Furthermore, the spatial wave function of the photon before entering the N second conversion modules is partially restored after transmission through single-mode fiber and after the final-stage second momentum translation component in the first second conversion module of the device.

[0125] Figure 4A A conversion effect diagram of a quantum information analog-to-digital converter provided according to an embodiment of the present invention is shown.

[0126] Figure 4A Part (a) is a schematic diagram of the spatial distribution of the input Gaussian mode beam with half truncated; the horizontal and vertical axes are used together to determine the spatial position of the photon, and the color represents the real part of the amplitude of the spatial wave function. Figure 4A Part (a) can intuitively present the single-spot Gaussian distribution of the input beam as a single-sided truncated beam.

[0127] like Figure 4A Part (b) is a schematic diagram of the density matrix of a two-qubit state in the time dimension; it is a... Figure 4A The result of encoding the photons in part (a) with two qubits is that... Figure 4A The result of converting the quantum information on the spatial wave function of the photon in part (a) to two time qubits is shown. The horizontal and vertical axes are the four sets of binary time mode basis vectors corresponding to the two qubits, and the vertical axis represents the real part of the density matrix. It can be seen that the continuous spatial quantum information carried by the spatial wave function of the photon is mapped to each set of discrete time modes. The height of the vertical axis is used to intuitively characterize the quantum state coherence weights corresponding to different time modes.

[0128] like Figure 4A Part (c) shows a schematic diagram of the spatial distribution of photons obtained after the inverse transformation; the horizontal and vertical axes are used together to determine the spatial position of the photons, and the color represents the real part of the amplitude of the spatial wave function. Figure 4A By comparing the two images (a), it can be verified that the reverse optical path can effectively restore the spatial wave function of the initial photon.

[0129] Figure 4B A conversion effect diagram of a quantum information analog-to-digital converter provided according to another embodiment of the present invention is shown.

[0130] like Figure 4B Part (a) shows the spatial distribution of the input Gaussian mode beam truncated in half; the horizontal and vertical axes are used together to determine the spatial position of the photons, and the color represents the real part of the amplitude of the spatial wave function. Figure 4B Part (a) can intuitively present the single-spot Gaussian distribution of the input beam as a single-sided truncated beam.

[0131] like Figure 4B Part (b) is a schematic diagram of the density matrix of the three-qubit states in the time dimension; it is a... Figure 4B The result of encoding the photon in part (a) with three qubits is that... Figure 4B The result of converting the quantum information on the spatial wave function of the photon in part (a) to three time qubits is shown. The horizontal and vertical axes are the basis vectors of the eight sets of binary time modes corresponding to the three qubits, and the vertical axis represents the real part of the density matrix. It can be seen that the continuous spatial quantum information carried by the spatial wave function of the photon is mapped to each set of discrete time modes. The height of the vertical axis is used to intuitively characterize the coherence weight of the quantum state corresponding to different time modes.

[0132] like Figure 4B Part (c) shows a schematic diagram of the spatial distribution of photons obtained after the inverse transformation; the horizontal and vertical axes are used together to determine the spatial position of the photons, and the color represents the real part of the amplitude of the spatial wave function. Figure 4B By comparing the two images (a), it can be verified that the reverse optical path can effectively restore the spatial wave function of the initial photon.

[0133] Figure 5A A conversion effect diagram of a quantum information analog-to-digital converter provided according to another embodiment of the present invention is shown.

[0134] Figure 5A Part (a) is a schematic diagram of the spatial distribution of the input Hermetic Gaussian mode beam; the horizontal and vertical axes are used together to determine the spatial position of the photon, and the color represents the real part of the amplitude of the spatial wave function, which can intuitively show that the input beam has the characteristics of a dual-spot Hermetic Gaussian distribution.

[0135] like Figure 5A Part (b) is a schematic diagram of the density matrix of a two-qubit state in the time dimension, which is a representation of... Figure 5A The result of encoding the photons in part (a) of the equation with two qubits, i.e., the result of encoding the photons in part (a) of the equation with two qubits. Figure 5AThe result of converting the quantum information on the spatial wave function of the photon in part (a) to two time qubits is shown. The horizontal and vertical axes are the four sets of binary time mode basis vectors corresponding to the two qubits, and the vertical axis represents the real part of the density matrix. It can be seen that the continuous spatial quantum information carried by the spatial wave function of the photon is mapped to each set of discrete time modes. The height of the vertical axis is used to intuitively characterize the quantum state coherence weights corresponding to different time modes.

[0136] like Figure 5A Part (c) shows a schematic diagram of the spatial distribution of photons obtained after the inverse transformation; the horizontal and vertical axes are used together to determine the spatial position of the photons, and the color represents the real part of the amplitude of the spatial wave function. Figure 5A By comparing the two images (a), it can be verified that the reverse optical path can effectively restore the spatial wave function of the initial photon.

[0137] Figure 5B A conversion effect diagram of a quantum information analog-to-digital converter provided according to yet another embodiment of the present invention is shown.

[0138] like Figure 5B Part (a) is a schematic diagram of the spatial distribution of the input Hermetic Gaussian mode beam; the horizontal and vertical axes are used together to determine the spatial position of the photon, and the color represents the real part of the amplitude of the spatial wave function, which can intuitively show that the input beam has the characteristics of a dual-spot Hermetic Gaussian distribution.

[0139] like Figure 5B Part (b) is a schematic diagram of the density matrix of the three-qubit states in the time dimension, which is a representation of... Figure 5B The result of encoding the photons in part (a) of the equation with three qubits is that... Figure 5B The result of converting the quantum information on the spatial wave function of the photon in part (a) to three time qubits is shown. The horizontal and vertical axes are the basis vectors of the eight sets of binary time modes corresponding to the three qubits, and the vertical axis represents the real part of the density matrix. It can be seen that the continuous spatial quantum information carried by the spatial wave function of the photon is mapped to each set of discrete time modes. The height of the vertical axis is used to intuitively characterize the coherence weight of the quantum state corresponding to different time modes.

[0140] like Figure 5B Part (c) shows a schematic diagram of the spatial distribution of photons obtained after the inverse transformation; the horizontal and vertical axes are used together to determine the spatial position of the photons, and the color represents the real part of the amplitude of the spatial wave function. Figure 5B By comparing the two images (a), it can be verified that the reverse optical path can effectively restore the spatial wave function of the initial photon.

[0141] This invention provides a coherent time-domain transmission system for optical spatial information based on the principle of quantum analog-to-digital conversion. It enables the transfer of quantum information from the spatial wavefunction of photons to a discrete time dimension. This technology offers a method for transmitting continuous photon spatial wavefunctions via single-mode fiber, quantum storage, and direct on-chip integrated photonic chip processing, filling a gap in this technological field and supporting the fundamental requirements of coherence and programmability for optical quantum computing, quantum state preparation, and high-speed quantum communication. Furthermore, this technology employs all-optical processing methods, avoiding photoelectric conversion, thus enabling real-time transmission and processing of quantum information.

[0142] It should be noted that, compared to existing schemes that transfer continuous spatial wavefunctions to the path dimension, this invention transfers the spatial wavefunction of photons to the discrete time dimension (i.e., converting quantum information into time qubits). The processed quantum information can be directly coupled into a single-mode optical fiber and further connected to a photonic chip to complete quantum information processing. The path dimension is not a transmission degree of freedom supported by single-mode optical fibers, and quantum information encoded on multiple paths cannot be directly imported into the fiber; while the time dimension can be stably transmitted in the optical fiber. Therefore, compared to path encoding schemes, the conversion method of this application has a wider range of applicable scenarios and unique applications that path encoding cannot achieve, including but not limited to: serving as an interface for photonic chips to process spatial wavefunction information, adapting to existing solid-state quantum memory devices, and transmitting optical field spatial wavefunction information using commercial optical fibers; at the classical level, it can realize holographic image transmission without the need for photoelectric conversion devices throughout the process, with extremely low signal transmission delay.

[0143] The embodiments of the present invention have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

Claims

1. A quantum information analog-to-digital converter, characterized in that, include: N cascaded first conversion modules, wherein the nth first conversion module includes: The first momentum translation component is suitable for applying equal and opposite momentum translations, first and second, to the left-hand and right-hand circularly polarized components of a photon in the target spatial dimension; wherein the spatial wave function of the photon in the nth coherent beam carries quantum information, and a single photon of the nth coherent beam has… There are several time patterns; 1 ≤ n ≤ N; The first position translation component, for a photon from the first momentum translation component, is adapted to apply a first spatial position translation and a second spatial position translation of equal magnitude and opposite direction to the first linear polarization component and the second linear polarization component of the photon in the target spatial dimension, so as to generate quantum entanglement between the spatial wave function and the polarization state of the photon, and couple at least a portion of the quantum information on the spatial wave function to the polarization state of the photon. The first delay component, for photons from the first position translation component, is used to delay the second linear polarization component of the photon relative to the first linear polarization component, and to convert the polarization direction of the second linear polarization component to the same polarization direction as the first linear polarization component, thereby exchanging the polarization state and time state of the photon, and outputting a single photon with... The (n+1)th coherent beam of the time pattern realizes the analog-to-digital conversion of quantum information.

2. The quantum information analog-to-digital converter according to claim 1, characterized in that, The polarization directions of the first linear polarization component and the second linear polarization component are the horizontal polarization direction and the vertical polarization direction, respectively; The first delay component includes: The first polarization beam splitter, for photons from the first position translation component, is adapted to transmit the first linearly polarized component of the photon and reflect the second linearly polarized component of the photon, so that the first linearly polarized component of the photon is transmitted along the first optical path. The first transmission unit, in conjunction with the first polarization beam splitter, enables the second linearly polarized component to be transmitted along the second optical path; The second polarization beam splitter is adapted to reflect the second linearly polarized component that propagates along the second optical path and transmit the first linearly polarized component that propagates along the first optical path, so as to combine the first linearly polarized component and the second linearly polarized component to obtain photons that have been combined by the second polarization beam splitter. The first transmission unit is configured such that the length of the second optical path is greater than the length of the first optical path, thereby causing a time delay between the second linear polarization component and the first linear polarization component.

3. The quantum information analog-to-digital converter according to claim 2, characterized in that, The first coherent beam is a beam with a horizontal polarization direction; The first delay component also includes: The first polarization conversion device is adapted to convert the polarization direction of the second linear polarization component of photons combined by the second polarization beam splitter into a horizontal polarization direction.

4. The quantum information analog-to-digital converter according to claim 2, characterized in that, When 2 ≤ n < N, the difference between the length of the second optical path and the length of the first optical path in the (n+1)th first conversion module is twice the difference between the length of the second optical path and the length of the first optical path in the nth first conversion module.

5. The quantum information analog-to-digital converter according to claim 2, characterized in that, Photons from the first momentum translation component have a first linear polarization component and a second linear polarization component; The first position translation component includes: The first quarter-wave plate, for photons from the first momentum translation component, is suitable for converting the first linear polarization component and the second linear polarization component of the photon into the left-hand circular polarization component and the right-hand circular polarization component of the photon, respectively. The first lens, for photons from the first quarter-wave plate, is suitable for performing Fourier transform on the photons, converting the spatial position distribution of the photons in the target plane into the momentum distribution in the Fourier plane; The first offset element, located on the Fourier surface, is used to apply equal and opposite momentum shifts to the left-hand circularly polarized component and the right-hand circularly polarized component of the photon from the first lens, so that the left-hand circularly polarized component is converted into the right-hand circularly polarized component and the right-hand circularly polarized component is converted into the left-hand circularly polarized component. The second lens has the same focal length as the first lens, and the front focal plane of the second lens coincides with the rear focal plane of the first lens. For photons from the first offset device, the second lens is used to perform Fourier transforms on the left-hand circularly polarized component and the right-hand circularly polarized component of the photon, so that the left-hand circularly polarized component and the right-hand circularly polarized component of the photon produce spatial position translations of equal magnitude and opposite direction in the target space dimension. The second quarter-wave plate, for photons from the second lens, is suitable for converting the left-hand circularly polarized component and the right-hand circularly polarized component of the photon into the second linearly polarized component and the first linearly polarized component of the photon, respectively. The target plane is parallel to the Fourier surface, which is either the back focal plane of the first lens or the front focal plane of the second lens.

6. The quantum information analog-to-digital converter according to claim 5, characterized in that, The first momentum translation component is the first polarization grating. The grating period of the first polarization grating of the (n+1)th first conversion module is twice the grating period of the first polarization grating of the nth first conversion module, where 1 ≤ n < N.

7. The quantum information analog-to-digital converter according to claim 5, characterized in that, The first offset element is the second polarization grating. The grating period of the second polarization grating of the (n+1)th first conversion module is half of the grating period of the second polarization grating of the nth first conversion module, where 1 ≤ n < N.

8. A coherent time-domain transmission system for optical spatial information, characterized in that, include: The quantum information analog-to-digital converter as described in any one of claims 1 to 7 is suitable for converting a first coherent beam into a quantum information analog-to-digital converter with... The (N+1)th coherent beam of the time pattern; N cascaded second conversion modules are suitable for converting the N+1th coherent beam into the first coherent beam, so as to realize the transmission of the first coherent beam.

9. The optical spatial information coherent time-domain transmission system according to claim 8, characterized in that, The Nth second conversion module and the Nth first conversion module are connected via single-mode fiber; The nth second conversion module includes: The second delay component is suitable for: For the photon of the (n+1)th coherent beam, the photon is in the first position in the time domain The polarization direction of the photon component of each time mode is converted to obtain the converted (n+1)th coherent beam; wherein the polarization direction of the converted photon component is orthogonal to the polarization direction of the photon component before conversion. For the photons of the converted (n+1)th coherent beam, the second delay component is also adapted to delay the second linear polarization component of the photon relative to the first linear polarization component, so that the output single photon has The nth coherent beam of the time pattern couples the quantum information of the time state of the photon to the polarization state of the photon; The second position translation component is adapted to apply a second spatial position translation and a first spatial position translation to the second linear polarization component and the first linear polarization component of the photon, respectively, so that the second linear polarization component is converted into the first linear polarization component and the first linear polarization component is converted into the second linear polarization component. The second momentum translation component, for photons from the second position translation component, is suitable for applying a second momentum translation and a first momentum translation to the left-hand circular polarization component and the right-hand circular polarization component of the photon, respectively, to couple the quantum information in the polarization state of the photon to the spatial wave function of the photon.

10. The optical spatial information coherent time-domain transmission system according to claim 8, characterized in that, The optical spatial information coherent time-domain transmission system also includes: At least one polarization beam splitter is disposed between the Nth first conversion module and the Nth second conversion module, and is adapted to allow the portion of the (N+1)th coherent beam output by the Nth first conversion module that has the same polarization direction as the first coherent beam to pass through.

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