An apparatus for implementing photonic multi-degree-of-freedom quantum logic gate manipulation

Abstract

The application discloses a device for realizing photon multi-degree-of-freedom quantum logic gate operation, which comprises a state preparation part, a state operation part and a state measurement part arranged in sequence according to the propagation order of optical signals; the state preparation part comprises a first modulator and a first half-wave plate, and an optical signal is prepared into an optical signal of an arbitrary three-bit state through the first modulator and the first half-wave plate and is radiated to the state operation part; the state operation part comprises a second modulator, a second half-wave plate and a third mirror; the optical signal is executed through the second modulator, the second half-wave plate and the third mirror, and is radiated to the state measurement part through a first radiation end or a second radiation end; the state measurement part comprises a plurality of CCD cameras, which are used for collecting optical signals and decoding three-bit states of the optical signals. The device can arbitrarily control multiple degrees of freedom of a single photon to realize different quantum logic operations by simply changing the configuration of the device, so that various quantum logic gates can be flexibly realized.

Description

Technical Field

[0001] This invention relates to the field of quantum logic gate control technology, and in particular to a device for realizing the manipulation of photons using multi-degree-of-freedom quantum logic gates. Background Technology

[0002] The multiple degrees of freedom of a single photon, such as polarization [1] Time-frequency [2] and spatial patterns [3] Quantum circuits are widely used to construct logic gates for quantum computing. However, as the number of encoded qubits increases, the resources required for quantum circuits rise exponentially. For example, a single-photon quantum circuit encoding 10 qubits often requires an interference network consisting of 10 paths. [4] .

[0003] To overcome this limitation of single-photon quantum computing, researchers have begun to utilize nonlinear effects to entangle multiple degrees of freedom of a single photon, and to couple and control these degrees of freedom using linear optical elements. Recent research has achieved entanglement of single-photon polarization and orbital angular momentum (angular mode). [5] And apply it to optical quantum computing. [6] To further explore the potential of single-photon quantum computing, researchers have begun to entangle the polarization and spatial mode degrees of freedom of single photons in quantum computing. Abouraddy et al. [7] Modified Mach-Zehnder interferometers were used to manipulate the polarization, X-axis, and Y-axis spatial modes of single photons, realizing quantum logic gates such as controlled NOT gates, controlled phase rotation gates, and Fredkin gates. However, this approach lacked flexibility in implementing different logic gates. Hor-Meyll et al. [8] Using spatial light modulators to control the polarization, X-axis, and Y-axis spatial modes of photons, normalization of unitary matrix traces and demonstration of the Deutsch-Jozsa algorithm were achieved, but these methods cannot be applied to integrated optical quantum computing. Kagalwala et al. [9] By utilizing the polarization selectivity of spatial light modulators, the polarization, X-axis, and Y-axis spatial modes of single photons can be controlled, enabling various three-qubit single-photon quantum logic operations, but this is quite difficult to achieve.

[0004] Slussarenko

[10] and Zeng

[11] Researchers used the Sagnac interferometer to realize a controlled NOT gate based on single-photon polarization and angular spatial degrees of freedom, but their scheme could not flexibly realize multiple quantum logic gates and could not fully utilize the angular and radial spatial modes of single photons.

[12] Researchers have applied multi-plane light convention to spatial light modulators, realizing various quantum logic gates based on single-photon angular and radial spatial modes. However, their schemes cannot utilize the polarization degree of freedom of photons. Looking back at existing technologies, there is a lack of research on applying the polarization, radial, and angular spatial modes of single photons together to quantum information processing.

[0005] References

[0006] [1]JLO'Brien,GJPryde,AGWhite,TCRalph,D.Branning.Demonstration of an all-optical quantum controlled-NOT gate[J].Nature,2003,426(6964):264–267), path (M.Fiorentino,FNWong.Deterministic controlled-NOT gate for single-photon two-qubit quantum logic[J].Physical Review Letters,2004,93(7):070502

[0007] [2]SLBraunstein,P.Van Loock.Quantum information with continuous variables[J].Review of Modern Physics,2005,77(2):513

[0008] [3] NCMenicucci,

[0009] [4]M.Reck,A.Zeilinger,HJBernstein,P.Bertani.Experimentalrealization of any discrete unitary operator[J].Physical Review Letters,1994,73(1):58

[0010] [5]E.Karimi,J.Leach,S.Slussarenko,B.Piccirillo,L.Marrucci,L.Chen,W.She,S.Franke-Arnold,M.J.Padgett,E.Santamato.Spin-orbit hybrid entanglementofphotons and quantum contextuality[J].Physical Review A,2010,82(2):022115

[0011] [6]The polarizing Sagnac interferometer:a tool for light orbitalangular momentumsorting and spin-orbit photon processing[J].Optics Express,2010,18(26):27205–27216

[0012] [7]A.F.Abouraddy,G.Di Giuseppe,T.Yarnall,M.Teich,B.E.Saleh.

[0013] Implementing one-photon three-qubit quantum gates using spatiallightmodulators[J].Physical Review A,2012,86(5):050303

[0014] [8]M.Hor-Meyll,D.Tasca,S.Walborn,P.S.Ribeiro,M.Santos,E.Duzzioni.Deterministic quantum computation with one photonic qubit[J].Phys.Rev.A,2015,92(1):012337

[0015] [9]KHKagalwala,G.Di Giuseppe,AFAbouraddy,BESaleh.Single-photonthree-qubit quantum logic using spatial light modulators[J].NatureCommunication,2017,8(1):739

[0016]

[10] Slussarenko S, D'Ambrosio V, Piccirillo B, et al. The polarizingSagnacinterferometer: a tool for light orbital angular momentum sorting and spin-orbitphoton processing[J]. Optics Express, 2010, 18(26):27205-27216.

[0017]

[11] Zeng Q, Li T, Song X, et al. Realization of optimized quantum controlled-logic gate based on the orbital angular momentum of light[J]. Optics Express, 2016, 24(8):8186-8193.

[0018]

[12] Brandt F, M, Bouchard F, et al. High-dimensional quantumgates using full-field spatial modes of photons[J]. Optica, 2020, 7(2):98-107. Summary of the Invention

[0019] In view of this, the purpose of this invention is to provide a device for realizing the manipulation of photon multi-degree-of-freedom quantum logic gates, which can realize a variety of different deterministic multi-bit single-photon quantum logic gates.

[0020] According to one aspect of the present invention, an apparatus for realizing photon multi-degree-of-freedom quantum logic gate manipulation is provided, comprising a state preparation section, a state operation section, and a state measurement section arranged sequentially in the order of optical signal propagation;

[0021] The state preparation section includes a first modulator and a first half-wave plate. The optical signal is prepared into an arbitrary three-bit optical signal through the first modulator and the first half-wave plate and then radiated to the state operation section.

[0022] The state operation section includes a second modulator, a second half-wave plate, and a third reflector; the optical signal is executed by arbitrary quantum logic gates through the second modulator, the second half-wave plate, and the third reflector, and is radiated to the state measurement section through the first radiating end or the second radiating end;

[0023] The state measurement section includes several CCD cameras used to collect optical signals and decode the three-bit state of the optical signals.

[0024] In the above technical solution, the device consists of three parts: a state preparation section, a state manipulation section, and a state measurement section. The state preparation section mainly consists of a laser source, a spatial light modulator, and a half-wave plate. The state manipulation section is a modified Sagnac interferometer containing a spatial light modulator. The state measurement section mainly consists of a polarization beam splitter cube and a CCD camera. The device utilizes a modified Sagnac interferometer containing a spatial light modulator to manipulate multiple degrees of freedom of a single photon to achieve specific quantum logic operations. Furthermore, the device possesses strong reconfigurability; by simply changing the device's configuration, multiple degrees of freedom of a single photon can be arbitrarily manipulated to achieve different quantum logic operations, thereby flexibly realizing various quantum logic gates. The utilization of multiple degrees of freedom of a single photon can exponentially increase the information storage capacity of a single photon. The flexibility of the device in realizing various quantum logic gates can greatly reduce the hardware resources required for optical quantum computing. Moreover, the optical waveplate and spatial light modulator can be integrated on a silicon-based chip. Therefore, this device is suitable for participating in the construction of integrated optical quantum computing platforms.

[0025] In some embodiments, the state preparation part includes, in sequence, a light source, a first lens, a second lens, a first modulator, a third lens, an aperture, a fourth lens, and a first half-wave plate arranged in the order of optical path propagation;

[0026] The third lens and the fourth lens together form a 4f system.

[0027] In the above technical solution, the polarization, angular, and radial spatial modes of a single photon are used as qubits. The spatial mode of the single photon is modulated using a first modulator, and the polarization state of the single photon is modulated using a first half-wave plate. By electronically controlling the fast axis angle of the spatial light modulator and the rotating wave plate, all three-qubit states of a single photon can be prepared.

[0028] In some embodiments, the state operation section includes a first polarizing beam splitter, a Dove prism, a second mirror, a second modulator, a first mirror, a second half-wave plate, and a third mirror;

[0029] The optical signal is divided into a horizontal polarization part and a vertical polarization part by the first polarizing beam splitter. The propagation sequence of the optical path in the vertical polarization part is: Dove prism, second mirror, second modulator, first mirror, second half-wave plate. The propagation sequence of the optical path in the horizontal polarization part is: second half-wave plate, first mirror, second modulator, second mirror, Dove prism.

[0030] The third reflector is disposed on one side of the first polarizing beam splitter, and the reflecting surface of the third reflector is parallel to the dielectric polarizing beam splitter film of the first polarizing beam splitter.

[0031] In the above technical solution, in the state operation part, based on the Sagnac interferometer, one of the reflectors is replaced with a second modulator with polarization selectivity, and some optical elements, such as Dove prisms and waveplates, are added to meet the requirements for realizing quantum logic gates. The second modulator has the function of selecting the response polarization state and controlling the spatial mode, the reflector and Dove prism have the function of reversing the angular spatial mode, rotating the Dove prism can introduce coupling between the single-photon angular spatial mode and its phase, and the waveplate has the function of controlling the polarization state.

[0032] In some embodiments, the state operation section includes a first polarizing beam splitter, a Dove prism, a second mirror, a second modulator, a first mirror, a second half-wave plate, and a third mirror;

[0033] The optical signal is divided into a horizontal polarization part and a vertical polarization part by the first polarizing beam splitter. The propagation sequence of the optical path in the vertical polarization part is: Dove prism, second mirror, second modulator, first mirror, second half-wave plate. The propagation sequence of the optical path in the horizontal polarization part is: second half-wave plate, first mirror, second modulator, second mirror, Dove prism.

[0034] The third reflector is disposed on one side of the first polarizing beam splitter, and the reflecting surface of the third reflector is parallel to the dielectric polarizing beam splitter film of the first polarizing beam splitter.

[0035] The second modulator is located at the image plane position of the 4f system.

[0036] In the above technical solution, in the state operation part, based on the Sagnac interferometer, one of the reflectors is replaced with a second modulator with polarization selectivity, and some optical elements, such as Dove prisms and waveplates, are added to meet the requirements for realizing quantum logic gates. The second modulator has the function of selecting the response polarization state and controlling the spatial mode. The reflector and Dove prism have the function of reversing the angular spatial mode. Rotating the Dove prism can introduce coupling between the single-photon angular spatial mode and its phase. The waveplate has the function of controlling the polarization state. Setting the second modulator at the image plane position of the 4f system can obtain the best modulation effect.

[0037] In some embodiments, the state measurement section includes a first receiving end and a second receiving end; wherein, the first receiving end includes a fifth lens, a second polarizing beam splitter, a first CCD camera disposed at the reflecting end of the second polarizing beam splitter, and a second CCD camera disposed at the transmitting end of the second polarizing beam splitter, arranged sequentially in the optical path propagation order; the second receiving end includes a sixth lens, a third polarizing beam splitter, a third CCD camera disposed at the transmitting end of the third polarizing beam splitter, and a fourth CCD camera disposed at the reflecting end of the third polarizing beam splitter, arranged sequentially in the optical path propagation order.

[0038] In the above technical solution, in the state measurement section, a polarization beam splitter is used to separate the horizontal and vertical polarization states, and a CCD camera is used to capture the optical signal. The CCD camera can display the intensity distribution of the light field, thereby decoding the two spatial modes of light. In the state measurement section, the polarization of light and the two spatial modes can be obtained, thus decoding the three-bit state carried by the light.

[0039] In some embodiments, the light source is linearly polarized light.

[0040] In the above technical solution, for circularly polarized light sources, the first half-wave plate can be replaced with a quarter-wave plate to convert the circularly polarized light into linearly polarized light in the encoding scheme of this invention; for partially polarized light sources, a polarizer can be added in front of the first half-wave plate, and the placement angle of the first half-wave plate can be adjusted according to the placement angle of the polarizer to obtain the linearly polarized light in the encoding scheme of this invention. This invention can realize the encoding of light sources with arbitrary polarization states.

[0041] According to another aspect of the present invention, a method for realizing photonic multi-degree-of-freedom quantum logic gate manipulation is provided, based on the above-described apparatus for realizing photonic multi-degree-of-freedom quantum logic gate manipulation, the method comprising the following steps:

[0042] State preparation section: Linearly polarized light output from the light source passes through a first modulator and a first half-wave plate. The first modulator loads a hologram to modulate the spatial mode of the linearly polarized light, and the first half-wave plate polarizes the polarization state of the linearly polarized light to obtain linearly polarized light carrying an arbitrary three-bit state, which is then radiated to the state operation section.

[0043] The state operation section carries linearly polarized light carrying any three-bit state. By adding or removing the second half-wave plate or the third mirror, or changing the hologram loaded by the second modulator, the linearly polarized light is radiated to the first receiving end or the second receiving end of the state operation section to execute different quantum logic gates.

[0044] The state measurement section: linearly polarized light is radiated to the first or second receiver, and after passing through the fifth or sixth lens, it is radiated to the second or third polarization beam splitter to be separated into a horizontally polarized part and a vertically polarized part, which are then captured and decoded by the CCD camera.

[0045] In the above technical solution, the device consists of three parts: a state preparation section, a state manipulation section, and a state measurement section. The state preparation section mainly consists of a laser source, a spatial light modulator, and a half-wave plate. The state manipulation section is a modified Sagnac interferometer containing a spatial light modulator. The state measurement section mainly consists of a polarization beam splitter cube and a CCD camera. The device utilizes a modified Sagnac interferometer containing a spatial light modulator to manipulate multiple degrees of freedom of a single photon to achieve specific quantum logic operations. Furthermore, the device possesses strong reconfigurability; by simply changing the device's configuration, multiple degrees of freedom of a single photon can be arbitrarily manipulated to achieve different quantum logic operations, thereby flexibly realizing various quantum logic gates. The utilization of multiple degrees of freedom of a single photon can exponentially increase the information storage capacity of a single photon. The flexibility of the device in realizing various quantum logic gates can greatly reduce the hardware resources required for optical quantum computing. Moreover, the optical waveplate and spatial light modulator can be integrated on a silicon-based chip. Therefore, this device is suitable for participating in the construction of integrated optical quantum computing platforms.

[0046] In some embodiments, the hologram modulated by the first modulator and the second modulator includes:

[0047] First hologram: Modulate the angular spatial mode number and radial spatial mode number of linearly polarized light to preset values;

[0048] Second hologram: Modulate the spatial mode number of the linearly polarized light angle to a preset value plus one, and modulate the radial spatial mode number of the linearly polarized light angle to a preset value;

[0049] The third hologram modulates the spatial mode number of the linearly polarized light angle to a preset value, and modulates the radial spatial mode number of the linearly polarized light angle to a preset value plus one.

[0050] Fourth hologram: The number of spatial modes of the linearly polarized light angle is modulated to a preset value plus one, and the number of radial spatial modes of the linearly polarized light angle is modulated to a preset value plus one.

[0051] In the above technical solution, the modulator can prepare light in different spatial modes by using different hologram settings.

[0052] In some embodiments, the state preparation section: linearly polarized light output from the light source passes through a first modulator and a first half-wave plate. The first modulator modulates the spatial mode of the linearly polarized light by loading a hologram, and the first half-wave plate polarizes the polarization state of the linearly polarized light to obtain linearly polarized light carrying an arbitrary three-bit state, which is then radiated to the state operation section. Specifically:

[0053] The linearly polarized light output from the light source is collimated and expanded by the first lens and the second lens and then radiated to the first modulator. The first modulator modulates the spatial mode of the linearly polarized light through a hologram. After modulation, the light is radiated to the third lens and the fourth lens to form a 4f system and an aperture to shape and filter the light field. After shaping and filtering, the light is radiated to the first half-wave plate to polarize the light and obtain linearly polarized light carrying arbitrary three-bit states.

[0054] The light field described above is:

[0055] E l，r (ρ, φ, z) = Φ l，r (ρ,φ)E0(z)

[0056] Where E0(z) is the plane wave light field, Φ l，r (ρ, φ) represents the phase modulation introduced in the state preparation process, which can be expressed as:

[0057]

[0058] Where l and r are the angular and radial spatial modes of linearly polarized light, respectively, and their values ​​are 0 or 1, corresponding to the binary count of the qubit. ρ B is the polar radius of the linearly polarized light.

[0059] In the above technical solution, l and r are the angular and radial spatial modes of linearly polarized light, respectively. The values ​​of these two modes are either 0 or 1; that is, in the angular spatial mode, l = 0 represents logic "0", and l = 1 represents logic "1"; in the radial spatial mode, r = 0 represents logic "0", and r = 1 represents logic "1". By modulating the spatial modes of linearly polarized light with a hologram, different spatial modes of light can be continuously generated: (i) l = 0, r = 0; (ii) l = 1, r = 0; (iii) l = 0, r = 1; (iv) l = 1, r = 1. The polarization state of the light can be controlled by rotating the first half-wave plate to a suitable angle. Horizontal polarization is logic "0", and vertical polarization is logic "1". In the state preparation section, the polarization of the light and both spatial modes are modulated, allowing the preparation of arbitrary three-bit states with polarization, angular, and radial spatial modes as qubits.

[0060] In some embodiments, quantum logic gates include:

[0061] Pauli X-gate with inverted polarization and angular spatial mode: The second half-wave plate is placed at an angle of 45° with the horizontal direction on its fast axis, the second modulator loads the second hologram, and linearly polarized light is emitted through the first radiating end, while the third reflecting mirror is retained.

[0062] Pauli X-gate with inverted polarization and radial spatial mode: The second half-wave plate is placed at an angle of 45° with the horizontal direction on its fast axis, the second modulator loads the third hologram, and linearly polarized light is emitted through the first radiating end, while the third mirror is retained.

[0063] Pauli X-gate with reverse polarization and two spatial modes: The second half-wave plate is placed at an angle of 45° with the horizontal direction on its fast axis, the second modulator loads the fourth hologram, and the linearly polarized light is emitted through the first radiating end, while the third reflecting mirror is retained.

[0064] P-lCNOT, a controlled NOT gate with polarization as the control position and angular spatial mode as the target position: remove the second half-wave plate, load the second hologram into the second modulator, and emit linearly polarized light through the second radiating end;

[0065] The controlled NOT gate P-rCNOT with polarization as the control position and radial spatial mode as the target position: remove the second half-wave plate, load the third hologram into the second modulator, and emit linearly polarized light through the second radiating end.

[0066] In the above technical solution, this device can realize a variety of different deterministic multi-qubit single-photon quantum logic gates simply by electronically controlling the modulator or changing the optical components within the device. The utilization of the multiple degrees of freedom of single photons can exponentially increase the information storage capacity of single photons, and the flexibility of realizing various quantum logic gates can significantly reduce the hardware resources required for optical quantum computing. Furthermore, the optical waveplate and spatial light modulator can be integrated onto a silicon-based chip. Therefore, this device is suitable for participating in the construction of integrated optical quantum computing platforms. Attached Figure Description

[0067] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0068] Figure 1 This is a schematic diagram of an embodiment of the device for realizing photon multi-degree-of-freedom quantum logic gate manipulation according to the present invention;

[0069] Figure 2This is a hologram of an embodiment of the device for realizing photonic multi-degree-of-freedom quantum logic gate manipulation according to the present invention;

[0070] Figure 3 This is a quantum circuit diagram of a quantum logic gate in an embodiment of the device for realizing photon multi-degree-of-freedom quantum logic gate manipulation according to the present invention;

[0071] Figure 4 This is an experimental result of implementing three Pauli X gates in one embodiment of the device for realizing photonic multi-degree-of-freedom quantum logic gate manipulation according to the present invention;

[0072] Figure 5 This is an experimental result of implementing two controlled NOT gates in one embodiment of the device for controlling photon multi-degree-of-freedom quantum logic gates according to the present invention. Detailed Implementation

[0073] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the invention. Similarly, the following embodiments are only some, not all, embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0074] This invention provides a device for realizing the manipulation of photon multi-degree-of-freedom quantum logic gates, which can realize a variety of different deterministic multi-bit single-photon quantum logic gates.

[0075] Please see Figure 1 The device comprises the following components:

[0076] (1) State Preparation: Linearly polarized light output from light source 1 is collimated and expanded by first lens 2 and second lens 3 before striking the liquid crystal region of first modulator 4. First modulator 4 modulates the spatial mode of the light, and then the light field is shaped and filtered by a 4f system composed of third lens 5 and fourth lens 7 and aperture 6 to obtain the light field. First modulator 4 is a spatial light modulator. In the state preparation section, the polarization, angular, and radial spatial modes of a single photon are used as qubits. The spatial mode of the single photon is controlled by the spatial light modulator, and the polarization state of the single photon is controlled by a waveplate. By electronically controlling the fast axis angle of the spatial light modulator and the rotating waveplate, all single-photon three-qubit states can be prepared.

[0077] (2) The State Operation section includes a first polarizing beam splitter 9, a Dove prism 14, a second mirror 13, a second modulator 12, a first mirror 11, a second half-wave plate 10, and a third mirror 15. In the State Operation section, based on the Sagnac interferometer, one of the mirrors is replaced with a spatial light modulator with polarization selectivity, and some optical elements, such as Dove prisms and wave plates, are added to meet the requirements for realizing quantum logic gates. The spatial light modulator has the function of selecting the response polarization state and controlling the spatial mode. The mirrors and Dove prisms have the function of reversing the angular spatial mode. Rotating the Dove prism can introduce coupling between the single-photon angular spatial mode and its phase. The wave plate has the function of controlling the polarization state.

[0078] In this process, the optical signal passes through the first polarizing beam splitter to form a horizontally polarized part and a vertically polarized part. The propagation sequence of the optical path in the vertically polarized part is: Dove prism 14, second reflector 13, second modulator 12, first reflector 11, and second half-wave plate 10. The propagation sequence of the optical path in the horizontally polarized part is: second half-wave plate 10, first reflector 11, second modulator 12, second reflector 13, and Dove prism 14. The third reflector 15 is disposed on one side of the first polarizing beam splitter 9, and the reflecting surface of the third reflector 15 is parallel to the dielectric polarizing beam splitter film of the first polarizing beam splitter 9.

[0079] The second modulator 12 is a spatial light modulator with polarization selectivity.

[0080] (3) State Detection: Based on the implemented quantum logic gates, the light from either the first radiating end A or the second radiating end B is measured. The state detection section includes a first receiving end and a second receiving end; wherein, the first receiving end corresponding to the first radiating end A includes a fifth lens 16, a second polarizing beam splitter 18, a first CCD camera 20 disposed at the reflecting end of the second polarizing beam splitter 18, and a second CCD camera 21 disposed at the transmitting end of the second polarizing beam splitter; the second receiving end corresponding to the second radiating end B includes a sixth lens 17, a third polarizing beam splitter 19, a third CCD camera 22 disposed at the transmitting end of the third polarizing beam splitter 19, and a fourth CCD camera 23 disposed at the reflecting end of the third polarizing beam splitter 19, arranged in the order of light propagation. In the state detection section, the polarizing beam splitter cube is used to separate the horizontal and vertical polarization states, and the CCD camera is used to capture the light signal.

[0081] Light passes through a polarizing beam splitter, separating its polarization state. Horizontally polarized light is transmitted, while vertically polarized light is reflected. The polarization state of the light can be determined by checking the signal reception of the CCD camera. The lens images the light onto the CCD camera, and based on the light intensity distribution, the spatial pattern of the light can be obtained, thus decoding the three-bit state of the light.

[0082] Based on the above-described device, its usage method is as follows:

[0083] State preparation section: Linearly polarized light output from the light source passes through a first modulator and a first half-wave plate. The first modulator loads a hologram to modulate the spatial mode of the linearly polarized light, and the first half-wave plate polarizes the polarization state of the linearly polarized light to obtain linearly polarized light carrying an arbitrary three-bit state, which is then radiated to the state operation section.

[0084] The state operation section carries linearly polarized light carrying any three-bit state. By adding or removing the second half-wave plate or the third mirror, or changing the hologram loaded by the second modulator, the linearly polarized light is radiated to the first receiving end or the second receiving end of the state operation section to execute different quantum logic gates.

[0085] The state measurement section: linearly polarized light is radiated to the first or second receiver, and after passing through the fifth or sixth lens, it is radiated to the second or third polarization beam splitter to be separated into a horizontally polarized part and a vertically polarized part, which are then captured and decoded by the CCD camera.

[0086] Please refer to Figure 2 The hologram modulated by the first and second modulators includes:

[0087] First hologram i: Modulate the angular spatial mode number and radial spatial mode number of the linearly polarized light to preset values;

[0088] Second hologram ii: Modulate the spatial mode number of the linearly polarized light angle to a preset value plus one, and modulate the radial spatial mode number of the linearly polarized light angle to a preset value;

[0089] Third hologram iii: Modulate the spatial mode number of the linearly polarized light angle to a preset value, and modulate the radial spatial mode number of the linearly polarized light angle to a preset value plus one;

[0090] Fourth hologram iv: Modulate the spatial mode number of the linearly polarized light angle to a preset value plus one, and modulate the radial spatial mode number of the linearly polarized light angle to a preset value plus one.

[0091] The state preparation section involves the following: linearly polarized light output from the light source passes through a first modulator and a first half-wave plate. The first modulator modulates the spatial mode of the linearly polarized light using a hologram, and the first half-wave plate polarizes the polarization state of the linearly polarized light to obtain linearly polarized light carrying an arbitrary three-bit state, which is then radiated to the state operation section. Specifically:

[0092] The linearly polarized light output from the light source is collimated and expanded by the first lens and the second lens and then radiated to the first modulator. The first modulator modulates the spatial mode of the linearly polarized light through a hologram. After modulation, the light is radiated to the third lens and the fourth lens to form a 4f system and an aperture to shape and filter the light field. After shaping and filtering, the light is radiated to the first half-wave plate to polarize the light and obtain linearly polarized light carrying arbitrary three-bit states.

[0093] The light field described above is:

[0094] E l，r (ρ, φ, z) = Φ l，r (ρ,φ)E0(z)

[0095] Where E0(z) is the plane wave light field, Φ l，r (ρ, φ) represents the phase modulation introduced in the state preparation process, which can be expressed as:

[0096]

[0097] Where l and r are the angular and radial spatial modes of linearly polarized light, respectively, and their values ​​are 0 or 1, corresponding to the binary count of the qubit. ρ B Let l be the polarimeter of the linearly polarized light. l and r are the angular and radial spatial modes of the linearly polarized light, respectively. The values ​​of these modes are either 0 or 1: for the angular spatial mode, l = 0 represents logic "0", and l = 1 represents logic "1"; for the radial spatial mode, r = 0 represents logic "0", and r = 1 represents logic "1". By modulating the spatial modes of the linearly polarized light using a hologram, different spatial modes can be continuously generated: (i) l = 0, r = 0; (ii) l = 1, r = 0; (iii) l = 0, r = 1; (iv) l = 1, r = 1. The polarization state of the light can be controlled by rotating the first half-wave plate to a suitable angle. Horizontal polarization is logic "0", and vertical polarization is logic "1". In the state preparation section, the polarization of the light and both spatial modes are modulated, allowing the preparation of arbitrary three-bit states with polarization, angular, and radial spatial modes as qubits.

[0098] In the state operation section, based on the Sagnac interferometer, one of the mirrors is replaced with a second modulator with polarization selectivity, and optical elements such as Dove prisms and waveplates are added to meet the requirements for realizing quantum logic gates. The second modulator selects the response polarization state and modulates the spatial mode. The mirror and Dove prism reverse the angular spatial mode. Rotating the Dove prism introduces coupling between the single-photon angular spatial mode and its phase, and the waveplate modulates the polarization state. Placing the second modulator at the image plane position of the 4f system yields the best modulation effect.

[0099] The state operation section can implement various multi-qubit single-photon quantum logic gates, such as Figure 3 As shown, there are: a Pauli X-gate with inverted polarization and angular spatial modes (P&lX2), a Pauli X-gate with inverted polarization and radial spatial modes (P&rX2), a Pauli X-gate with inverted polarization and both spatial modes (X3), a controlled NOT gate (P-lCNOT) with polarization as the control bit and angular spatial mode as the target bit, and a controlled NOT gate (P-rCNOT) with polarization as the control bit and radial spatial mode as the target bit. The specific implementation methods are as follows:

[0100] Pauli X-gate with inverted polarization and angular spatial mode: The second half-wave plate 10 is placed at an angle of 45° between its fast axis and the horizontal direction, the second modulator 12 loads the second hologram ii, the linearly polarized light is emitted through the first radiating end A, and the third reflecting mirror 15 is retained;

[0101] Pauli X-gate with inverted polarization and radial spatial mode: The second half-wave plate 10 is placed at an angle of 45° with the horizontal direction on its fast axis, the second modulator 12 loads the third hologram, the linearly polarized light is emitted through the first radiating end A, and the third reflecting mirror 15 is retained.

[0102] Pauli X-gate with reverse polarization and two spatial modes: The second half-wave plate 10 is placed at an angle of 45° between its fast axis and the horizontal direction, the second modulator 12 loads the fourth hologram iv, and the linearly polarized light is emitted through the first radiating end A, while the third reflecting mirror is retained.

[0103] A controlled NOT gate with polarization as the control position and angular spatial mode as the target position: remove the second half-wave plate 10, load the second hologram ii onto the second modulator 12, and linearly polarized light is emitted through the second radiating end B;

[0104] A controlled NOT gate with polarization as the control position and radial spatial mode as the target position: the second half-wave plate 10 is removed, the second modulator 12 loads the third hologram, and the linearly polarized light is emitted through the second radiating end B.

[0105] To clearly and intuitively demonstrate the performance of this invention, this embodiment utilizes the invention to realize the aforementioned various quantum logic gates within a classical optical framework. The light source 1 used in the state preparation section is a 532nm semiconductor laser, emitting vertically polarized light. As described above, loading holograms (i), (ii), (iii), and (iv) onto the first modulator 4 allows for different modulation of the light's spatial mode. Placing the first half-wave plate 8 at a 0° angle to the horizontal results in a vertically polarized light state; placing it at a 45° angle to the horizontal results in a horizontally polarized light state. Figure 4 and Figure 5 The input section shown is an adjustment of the configuration of the state preparation section based on the prepared three-bit state, directly connecting the state preparation section and the state measurement section, and the intensity distribution of the prepared light measured by the CCD camera of the state measurement section. The two CCD cameras are responsible for measuring the light signals of two polarization directions respectively. As shown in the figure, "CCD H" represents the CCD camera measuring horizontally polarized light, and "CCD V" represents the CCD camera measuring vertically polarized light. For light emitted from the first radiation port A, CCD camera (21) is "CCD H" and CCD camera (20) is "CCD V"; for light emitted from port B, the third CCD camera 22 is "CCD H" and the fourth CCD camera 23 is "CCD V".

[0106] Based on the usage method described above, the configuration of the state operation section was adjusted, and the light carrying various three-bit states was introduced into the state operation section for control. The controlled light-introduced state measurement section was then measured, and the experimental results are as follows. Figure 4 and Figure 5 The output section is shown below. Among them, Figure 4 (a) shows the experimental results for X3. Figure 4 (b) shows the experimental results for P&X2 and P&rX2. Figure 4 These are experimental results from P-lCNOT and P-rCNOT. Based on the output light intensity distribution, the three-bit state carried by the output light can be decoded. From the relationship between the phase and intensity of light, and the phase distribution corresponding to different spatial modes, it can be seen that there is a dark spot in the center of the spot with angular spatial mode number l≠0, and there is a dark ring in the spot with radial spatial mode number r=1.

[0107] This embodiment strongly demonstrates that the present invention can effectively implement the quantum logic gates described above within a classical optical framework. Furthermore, a single photon is a decay of classical light, and the intensity distribution of classical light directly reflects the quantum state carried by the photon. Therefore, it can be proven that the present invention can efficiently control multiple degrees of freedom of a single photon within a single-photon framework to realize various deterministic multi-qubit single-photon quantum logic gates.

[0108] The above description is only a part of the embodiments of the present invention and does not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made based on the content of the present invention specification and drawings, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A device for realizing multi-degree-of-freedom quantum logic gate manipulation of photons, characterized in that, It includes a state preparation section, a state operation section, and a state measurement section arranged sequentially according to the propagation order of the optical signal; The state preparation section includes a first modulator and a first half-wave plate. The optical signal is prepared into an arbitrary three-bit optical signal through the first modulator and the first half-wave plate and then radiated to the state operation section. The state operation section includes a second modulator, a second half-wave plate, and a third reflector; the optical signal is executed by an arbitrary quantum logic gate through the second modulator, the second half-wave plate, and the third reflector, and is radiated to the state measurement section through the first radiating end or the second radiating end; The state measurement section includes several CCD cameras used to collect the optical signal and decode the three-bit state of the optical signal; Linearly polarized light output from the light source passes through a first modulator and a first half-wave plate. The first modulator modulates the spatial mode of the linearly polarized light by loading a hologram, and the first half-wave plate polarizes the polarization state of the linearly polarized light to obtain linearly polarized light carrying arbitrary three-bit states, which is then radiated to the state operation section. In the state operation section, the optical signal passes through a first polarizing beam splitter to form a horizontal polarization part and a vertical polarization part. The propagation sequence of the optical path in the vertical polarization part is: Dove prism, second mirror, second modulator, first mirror, second half-wave plate; the propagation sequence of the optical path in the horizontal polarization part is: second half-wave plate, first mirror, second modulator, second mirror, Dove prism. The first modulator is a spatial light modulator, and the second modulator is a spatial light modulator. The second modulator has the function of selecting the response polarization state and controlling the spatial mode.

2. The device for realizing photon multi-degree-of-freedom quantum logic gate manipulation as described in claim 1, characterized in that, The state preparation section includes, in sequence, a light source, a first lens, a second lens, a first modulator, a third lens, an aperture, a fourth lens, and a first half-wave plate, arranged in the order of optical path propagation. The third lens and the fourth lens together form a 4f system.

3. The device for realizing photon multi-degree-of-freedom quantum logic gate manipulation as described in claim 1, characterized in that, The state operation section includes a first polarizing beam splitter, a Dove prism, a second mirror, a second modulator, a first mirror, a second half-wave plate, and a third mirror; The third reflector is disposed on one side of the first polarizing beam splitter, and the reflecting surface of the third reflector is parallel to the dielectric polarizing beam splitter film of the first polarizing beam splitter.

4. The device for realizing photon multi-degree-of-freedom quantum logic gate manipulation as described in claim 2, characterized in that, The state operation section includes a first polarizing beam splitter, a Dove prism, a second mirror, a second modulator, a first mirror, a second half-wave plate, and a third mirror; The optical signal is divided into a horizontal polarization part and a vertical polarization part by the first polarizing beam splitter. The propagation sequence of the optical path in the vertical polarization part is: Dove prism, second mirror, second modulator, first mirror, second half-wave plate. The propagation sequence of the optical path in the horizontal polarization part is: second half-wave plate, first mirror, second modulator, second mirror, Dove prism. The third reflector is disposed on one side of the first polarizing beam splitter, and the reflecting surface of the third reflector is parallel to the dielectric polarizing beam splitter film of the first polarizing beam splitter. The second modulator is located at the image plane position of the 4f system.

5. The apparatus for realizing photon multi-degree-of-freedom quantum logic gate manipulation as described in claim 1, characterized in that, The state measurement section includes a first receiving end and a second receiving end; wherein, the first receiving end includes a fifth lens, a second polarizing beam splitter, a first CCD camera disposed at the reflecting end of the second polarizing beam splitter, and a second CCD camera disposed at the transmitting end of the second polarizing beam splitter, arranged in sequence according to the optical path propagation order; the second receiving end includes a sixth lens, a third polarizing beam splitter, a third CCD camera disposed at the transmitting end of the third polarizing beam splitter, and a fourth CCD camera disposed at the reflecting end of the third polarizing beam splitter, arranged in sequence according to the optical path propagation order.

6. A method for realizing photonic multi-degree-of-freedom quantum logic gate manipulation, based on the apparatus for realizing photonic multi-degree-of-freedom quantum logic gate manipulation according to any one of claims 1-5, characterized in that, The method includes the following steps: State preparation section: Linearly polarized light output from the light source passes through a first modulator and a first half-wave plate. The first modulator loads a hologram to modulate the spatial mode of the linearly polarized light, and the first half-wave plate polarizes the polarization state of the linearly polarized light to obtain linearly polarized light carrying an arbitrary three-bit state, which is then radiated to the state operation section. The state operation section: linearly polarized light carrying any three-bit state is input to the state operation section, and by adding or removing the second half-wave plate or the third mirror, or changing the hologram loaded by the second modulator, the linearly polarized light is radiated to the first receiving end or the second receiving end of the state operation section to execute different quantum logic gates; The state measurement section: linearly polarized light is radiated to the first or second receiver, and after passing through the fifth or sixth lens, it is radiated to the second or third polarization beam splitter to be separated into a horizontally polarized part and a vertically polarized part, which are then captured and decoded by the CCD camera.

7. The method for realizing photon multi-degree-of-freedom quantum logic gate manipulation as described in claim 6, characterized in that, The hologram modulated by the first modulator and the second modulator includes: First hologram: Modulate the angular spatial mode number and radial spatial mode number of linearly polarized light to preset values; Second hologram: Modulate the spatial mode number of the linearly polarized light angle to a preset value plus one, and modulate the radial spatial mode number of the linearly polarized light angle to a preset value; The third hologram modulates the spatial mode number of the linearly polarized light angle to a preset value, and modulates the radial spatial mode number of the linearly polarized light angle to a preset value plus one. Fourth hologram: The number of spatial modes of the linearly polarized light angle is modulated to a preset value plus one, and the number of radial spatial modes of the linearly polarized light angle is modulated to a preset value plus one.

8. The method for realizing photon multi-degree-of-freedom quantum logic gate manipulation as described in claim 7, characterized in that, The state preparation section: Linearly polarized light output from the light source passes through a first modulator and a first half-wave plate. The first modulator modulates the spatial mode of the linearly polarized light by loading a hologram, and the first half-wave plate polarizes the polarization state of the linearly polarized light to obtain linearly polarized light carrying arbitrary three-bit states, which is then radiated to the state operation section. Specifically: Linearly polarized light output from the light source is collimated and expanded by the first lens and the second lens and then radiated to the first modulator. The first modulator modulates the spatial mode of the linearly polarized light through the hologram. After modulation, the light is radiated to the third lens and the fourth lens to form a 4f system and an aperture to shape and filter the light field. After shaping and filtering, the light is radiated to the first half-wave plate to polarize the light and obtain linearly polarized light carrying arbitrary three-bit states. The light field is: in, For plane wave light field, The phase modulation introduced in the state preparation section can be expressed as: wherein, and are the angular and radial spatial mode numbers of linearly polarized light, respectively, both mode numbers taking values 0 or 1, corresponding to the binary count of the qubit, is the optical field polar radius of linearly polarized light.

9. A method for realizing photonic multi-degree-of-freedom quantum logic gate manipulation as described in claim 7, characterized in that, The quantum logic gates include: Pauli X-gate with inverted polarization and angular spatial mode: The second half-wave plate is placed at an angle of 45° with the horizontal direction on its fast axis, the second modulator loads the second hologram, and linearly polarized light is emitted through the first radiating end, while the third reflecting mirror is retained. Pauli X-gate with inverted polarization and radial spatial mode: The second half-wave plate is placed at an angle of 45° with the horizontal direction on its fast axis, the second modulator loads the third hologram, and linearly polarized light is emitted through the first radiating end, while the third mirror is retained. Pauli X-gate with reverse polarization and two spatial modes: The second half-wave plate is placed at an angle of 45° with the horizontal direction on its fast axis, the second modulator loads the fourth hologram, and the linearly polarized light is emitted through the first radiating end, while the third reflecting mirror is retained. P-lCNOT, a controlled NOT gate with polarization as the control position and angular spatial mode as the target position: remove the second half-wave plate, load the second hologram into the second modulator, and emit linearly polarized light through the second radiating end; The controlled NOT gate P-rCNOT with polarization as the control position and radial spatial mode as the target position: remove the second half-wave plate, load the third hologram into the second modulator, and emit linearly polarized light through the second radiating end.

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