Optical quantum chip and teaching machine system

Abstract

The application discloses a kind of optical quantum chip and teaching machine system, optical quantum chip includes six mode interference network, with 6 photon input end, 11 MZ interferometers and 6 photon output end, 11 MZ interferometers cascade form network structure, optical path is simple and has the characteristics of full connectivity, programmable, phase stability;The state of different MZ interferometers is programmed and controlled by the software operating system installed on host computer, different experimental parameters are input when different experiments are carried out, the rapid switching of different experimental light paths is realized, it is easy to operate, simultaneously realizes the multiplexing of peripheral high-priced devices such as light source, detector etc., greatly reduces experimental cost, is suitable for quantum teaching and demonstration;Adopt unified fixed input and output interface, eliminate the switching of interface under different experimental scenarios, avoid the problem that optical path and optical fiber interface are damaged due to student misoperation in teaching scene, improve the stability of teaching machine system and reduce the failure rate of teaching machine system.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of quantum information and quantum teaching, and particularly relates to an optical quantum chip and a teaching machine system. BACKGROUND

[0002] Quantum information technology is a frontier direction of science and technology competition among countries, including quantum computing, quantum key distribution, quantum precision measurement and other subfields. Due to the superposition, uncertainty and entanglement of quantum mechanics, quantum information technology can achieve advantages such as storage and computing power beyond classical computers, unconditionally secure communication in the sense of information theory, and measurement precision beyond the classical resolution limit. Quantum optics is an important way and research basis for the realization of quantum information technology. Integrated optical chip technology has the advantages of high stability, low cost and mass production compared with spatial optical path. In recent years, using integrated optical chip technology to realize quantum information experiments has become a research hotspot and development trend.

[0003] Single-photon interference and two-photon interference (also known as HOM interference) are the most basic experiments and technologies in quantum optics. Single-photon interference is widely used in various quantum key distribution protocols (such as BB84 protocol), quantum sensing, path encoding of quantum computing, and two-photon interference is applied to boson sampling, measurement device-independent quantum key distribution protocol, etc.

[0004] Boson sampling in a quantum optics system can realize the operation of matrix product, and this operation is difficult for a classical computer, i.e. the computational complexity increases exponentially with the size of the matrix, but for a quantum system with parallel computing ability, the computational complexity is not exponential, so the boson sampling task is a typical experiment to demonstrate the superiority of quantum computing.

[0005] For quantum computing, there are two main computing architectures, namely the quantum gate circuit computing architecture based on unitary evolution and the measurement-based quantum computing model. Both architectures have their own advantages and disadvantages and can achieve universal quantum computing. For the quantum gate circuit model, theoretically, any quantum gate can be composed of two-bit controlled non-gate (CNOT gate) and single-bit quantum gate, i.e. universal quantum computing can be achieved, so the two-bit controlled non-gate is the basic building block of the quantum gate circuit model.

[0006] At present, the development of quantum information technology is still in its infancy, the public has many misunderstandings about quantum information technology, and quantum teaching is still in the theoretical learning stage. In quantum teaching, quantum experiments such as single-photon interference experiments based on a marked single-photon source, single-photon interference experiments based on a single-channel photon, HOM interference experiments, two-photon boson sampling experiments, and two-photon controlled non-gate experiments are particularly important for understanding quantum information technology. The development of quantum information technology urgently needs to cultivate talents, especially for low-grade graduate students, undergraduate and junior college students, high school students, quantum information education and teaching is very important, and a quantum teaching system or equipment that is conducive to large-scale promotion, low cost, easy to operate and high stability needs to be developed. SUMMARY

[0007] Based on the above problems, the present application provides an optical quantum chip and a teaching system, which realizes the switching of different experimental light paths and the multiplexing of optical devices by programming control of the state of the MZ interferometer, reduces the teaching cost, and improves the stability and generalizability of the teaching system. The specific scheme is as follows:

[0008] In a first aspect, the present application discloses an optical quantum chip, which comprises a six-mode interference network, the six-mode interference network comprising six photon input ends, eleven MZ interferometers and six photon output ends; the eleven MZ interferometers are respectively a first MZ interferometer, a second MZ interferometer, a third MZ interferometer, a fourth MZ interferometer, a fifth MZ interferometer, a sixth MZ interferometer, a seventh MZ interferometer, an eighth MZ interferometer, a ninth MZ interferometer, a tenth MZ interferometer and an eleventh MZ interferometer; the six photon input ends are respectively a first photon input end, a second photon input end, a third photon input end, a fourth photon input end, a fifth photon input end and a sixth photon input end, the second photon input end and the third photon input end are used for inputting entangled photons; the six photon output ends are respectively a first photon output end, a second photon output end, a third photon output end, a fourth photon output end, a fifth photon output end and a sixth photon output end, the second photon output end and the third photon output end are used for outputting optical quantum states transmitted through the six-mode interference network;

[0009] The input upper port of the fifth MZ interferometer is connected with the first photon input end, the input lower port of the fifth MZ interferometer is connected with the output upper port of the third MZ interferometer, and the output upper port of the fifth MZ interferometer is connected with the first photon output end;

[0010] The input upper port of the third MZ interferometer is connected with the second photon input end, the input lower port of the third MZ interferometer is connected with the output upper port of the first MZ interferometer through a connecting wire, the input upper port of the eighth MZ interferometer is connected with the output lower port of the fifth MZ interferometer, and the output upper port of the eighth MZ interferometer is connected with the second photon output end; the third MZ interferometer and the eighth MZ interferometer are located in the same row.

[0011] The input upper port of the first MZ interferometer is connected with the third photon input end, the input lower port of the first MZ interferometer is connected with the fourth photon input end, the input upper port of the sixth MZ interferometer is connected with the output lower port of the third MZ interferometer, the input lower port of the sixth MZ interferometer is connected with the input upper port of the fourth MZ interferometer, the input upper port of the eleventh MZ interferometer is connected with the output lower port of the eighth MZ interferometer through a connecting wire, the input lower port of the eleventh MZ interferometer is connected with the output upper port of the tenth MZ interferometer, the output upper port of the eleventh MZ interferometer is connected with the third photon output end, and the output lower port of the eleventh MZ interferometer is connected with the fourth photon output end; the first MZ interferometer, the sixth MZ interferometer and the eleventh MZ interferometer are located in the same row.

[0012] The input upper port of the second MZ interferometer is connected with the output lower port of the first MZ interferometer, the input lower port of the second MZ interferometer is connected with the fifth photon input end, the two input ports of the fourth MZ interferometer are respectively connected with the two output ports of the second MZ interferometer, the input upper port of the ninth MZ interferometer is connected with the output lower port of the sixth MZ interferometer, the input lower port of the ninth MZ interferometer is connected with the output upper port of the seventh MZ interferometer, the two input ports of the tenth MZ interferometer are respectively connected with the two output ports of the ninth MZ interferometer, and the output lower port of the tenth MZ interferometer is connected with the fifth photon output end; the second MZ interferometer, the fourth MZ interferometer, the ninth MZ interferometer and the tenth MZ interferometer are located in the same row.

[0013] The input upper port of the seventh MZ interferometer is connected with the output lower port of the fourth MZ interferometer, the input lower port of the seventh MZ interferometer is connected with the sixth photon input end, and the output lower port of the seventh MZ interferometer is connected with the sixth photon output end.

[0014] Furthermore, the optical quantum chip further comprises four edge couplers, the second photon input end, the third photon input end, the second photon output end and the third photon output end are respectively connected with one of the edge couplers.

[0015] Further, the optical quantum chip further comprises four edge couplers, the second photon input end, the third photon input end, the second photon output end and the third photon output end are respectively connected with one of the edge couplers.

[0016] Further, the MZ interferometer comprises a first 50:50 beam splitter, an upper interference arm, a lower interference arm, a second 50:50 beam splitter, an in-loop thermo-optic phase modulator and an out-loop thermo-optic phase modulator, two ends of the upper interference arm are connected with an output upper port of the first 50:50 beam splitter and an input upper port of the second 50:50 beam splitter respectively, two ends of the lower interference arm are connected with an output lower port of the first 50:50 beam splitter and an input lower port of the second 50:50 beam splitter respectively, the in-loop thermo-optic phase modulator is arranged on the upper interference arm, and the out-loop thermo-optic phase modulator is arranged on the input upper port of the first 50:50 beam splitter.

[0017] In a second aspect, the present application discloses a photonic quantum teaching machine system, comprising a host computer, a light source, a control module, two detectors and the photonic quantum chip.

[0018] The host computer is installed with a software operating system, and a user initializes and configures the control module, sets experimental parameters, and demonstrates, reads and counts experimental results through the software operating system.

[0019] The light source is used for generating entangled photon pairs, the frequency and / or energy sum of the entangled photon pairs is fixed, and the entangled photon pairs are input into the second photon input end and the third photon input end of the photonic quantum chip respectively.

[0020] One of the detectors is used for detecting the photonic quantum state output from the second photon output end and outputting a response electrical signal, and the other detector is used for detecting the photonic quantum state output from the third photon output end and outputting a response electrical signal.

[0021] The control module is used for receiving instructions of the software operating system, and driving and controlling the light source, the photonic quantum chip and the detectors based on the instructions.

[0022] Further, the photonic quantum teaching machine system further comprises an adjustable delay module used for delaying the entangled photons input into the third photon input end, the adjustable delay module is arranged on a transmission path of the entangled photons transmitted to the third photon input end, and the control module is connected with the adjustable delay module.

[0023] Further, the control module comprises a light source switch control unit, a detector switch control unit, a thermal-optical phase modulator current driving and control unit and a photon counting unit. The light source switch control unit controls the on or off of the light source based on the instruction input by the software operating system. The detector switch control unit controls the on or off of the two detectors based on the instruction input by the software operating system. The thermal-optical phase modulator current driving and control unit adjusts the phase of the entangled photons and the beam splitting ratio of the MZ interferometer based on the current value input by the software operating system. The photon counting unit receives the electrical signal output by the detector and performs coincidence counting.

[0024] Preferably, the light source is a silicon waveguide-based four-wave mixing entangled light source, a silicon nitride microcavity structure-based four-wave mixing entangled light source, a BBO crystal spontaneous parametric down-conversion-based entangled light source, a periodically poled KTP crystal spontaneous parametric down-conversion-based entangled light source or a periodically poled lithium niobate crystal spontaneous parametric down-conversion-based entangled light source.

[0025] Preferably, the detector is a single-photon detector.

[0026] Preferably, the adjustable delay module is a free-space type optical delay line or a delay chip.

[0027] Further, the control module further comprises an adjustable delay control unit, which controls the adjustable delay module to adjust the delay time of the input of the entangled photons to the third photon input end based on the instruction input by the software operating system.

[0028] Overall, compared with the prior art, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0029] This invention provides a quantum optical chip and a teaching system. The quantum optical chip includes a six-mode interference network with six photon inputs, eleven MZ interferometers, and six photon outputs. The eleven MZ interferometers are cascaded to form a network structure, resulting in a simple optical path that is fully connected, programmable, and phase-stable. The switching and control of the quantum optical path are achieved by controlling the beam splitting ratio of different MZ interferometers in the six-mode interference network using a software operating system installed on a host computer. Based on the quantum optical chip and teaching system disclosed in this invention, five fundamental quantum information experiments can be performed: single-photon interference experiments based on labeled single-photon sources, single-photon interference experiments based on single-channel photons, two-photon interference experiments, two-photon boson sampling experiments, and two-photon controlled NOT gate experiments. This achieves the reuse of optical paths and optical devices without requiring changes to external light sources, detectors, or other connection structures. The MZ interferometer's state is controlled by a software operating system installed on a host computer. Different experimental parameters are input into the software operating system during different experiments, enabling rapid switching between different experimental optical paths. This convenient operation also allows for the reuse of expensive peripheral components such as light sources and detectors, significantly reducing experimental costs. It is suitable for quantum teaching and demonstration and has broad applicability. Furthermore, this invention uses the second and third photon input terminals as fixed input terminals and the second and third photon output terminals as fixed output terminals, eliminating the need for interface switching in different experimental scenarios. This avoids damage to the optical path and fiber optic interfaces caused by student misoperation in teaching scenarios, further improving the stability of the teaching system and reducing its failure rate. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in this embodiment or the prior art, the drawings used in the description of the embodiment 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.

[0031] Figure 1 This is a schematic diagram of the structure of a photonic quantum chip provided in an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the structure of a photonic quantum chip according to another embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the structure of the MZ interferometer provided in an embodiment of the present invention;

[0034] Figure 4 This is a schematic diagram of the structure of a quantum optical teaching machine system provided in an embodiment of the present invention;

[0035] Figure 5A structure schematic diagram of a light quantum teaching machine system provided for another embodiment of the present application;

[0036] Figure 6 A quantum state labeling schematic diagram at different positions of the MZ interferometer in the embodiment of the present application;

[0037] Figure 7 A single photon interference experiment optical path diagram based on a marked single photon source in the present application;

[0038] Figure 8 A single photon interference experiment optical path diagram based on a single channel photon in the present application;

[0039] Figure 9 A two-photon interference experiment optical path diagram in the present application;

[0040] Figure 10 A two-photon Bose sampling experiment optical path diagram in the present application;

[0041] Figure 11 A two-photon controlled non-gate experiment optical path diagram in the present application.

[0042] Wherein, 11-first MZ interferometer, 12-second MZ interferometer, 13-third MZ interferometer, 14-fourth MZ interferometer, 15-fifth MZ interferometer, 16-sixth MZ interferometer, 17-seventh MZ interferometer, 18-eighth MZ interferometer, 19-ninth MZ interferometer, 110-tenth MZ interferometer, 111-eleventh MZ interferometer; 21-first photon input end, 22-second photon input end, 23-third photon input end, 24-fourth photon input end, 25-fifth photon input end, 26-sixth photon input end; 31-first photon output end, 32-second photon output end, 33-third photon output end, 34-fourth photon output end, 35-fifth photon output end, 36-sixth photon output end; 4-edge coupler;

[0043] TOPM1-in-loop thermo-optic phase modulator, TOPM2-out-of-loop thermo-optic phase modulator; BS1-first 50:50 beam splitter, BS2-second 50:50 beam splitter. DETAILED DESCRIPTION

[0044] In order to make the above objectives, characteristics and advantages of the present application more apparent, comprehensible and easy to understand, the embodiments of the present application will be further described in detail below with reference to the drawings and specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0045] In the following description, a lot of specific details are set forth in order to provide a thorough understanding of the present application, however, the present application can be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the present application, therefore, the present application is not limited to the specific embodiments disclosed below.

[0046] In order to facilitate understanding and explaining the technical solutions provided by the embodiments of the present application, the background art of the present application will be described first.

[0047] At present, the development of quantum information technology is still in the initial stage, which is the front direction of the competition of science and technology of various countries, including quantum computing, quantum key distribution, quantum precision measurement and other subfields. Due to the superposition, uncertainty and entanglement of quantum mechanics, quantum information technology can realize the advantages of exceeding the storage and computing capacity of classical computers, unconditional secure communication in the sense of information theory, and measurement precision exceeding the classical resolution limit.

[0048] At present, the public has many misunderstandings about quantum information technology, and quantum teaching is still in the theoretical learning stage. In quantum teaching, quantum experiments such as single photon interference experiment based on marked single photon source, single photon interference experiment based on single channel photon, HOM interference experiment, two photon boson sampling experiment and two photon controlled non gate experiment are particularly important for understanding quantum information technology. The development of quantum information technology urgently needs to cultivate talents, especially for low-grade graduate students, undergraduate and junior college students, high school students, quantum information education and teaching is very important, therefore, it is necessary to develop optical quantum chip and quantum teaching system or equipment which is beneficial to large-scale promotion, low cost, convenient operation and high stability.

[0049] Based on this, the present application discloses an optical quantum chip, as shown in the figure, Figure 1 As shown in the figure, the optical quantum chip includes a six-mode interference network, the six-mode interference network includes 6 photon input ends, 11 MZ interferometers and 6 photon output ends, and the 11 MZ interferometers are cascaded to form a network structure.

[0050] For the convenience of describing the position and connection relationship, the 11 MZ interferometers are named as first MZ interferometer 11, second MZ interferometer 12, third MZ interferometer 13, fourth MZ interferometer 14, fifth MZ interferometer 15, sixth MZ interferometer 16, seventh MZ interferometer 17, eighth MZ interferometer 18, ninth MZ interferometer 19, tenth MZ interferometer 110 and eleventh MZ interferometer 111; the six photon input ends are first photon input end 21, second photon input end 22, third photon input end 23, fourth photon input end 24, fifth photon input end 25 and sixth photon input end 26, wherein the second photon input end 22 and the third photon input end 23 are used for inputting entangled photons; the six photon output ends are first photon output end 31, second photon output end 32, third photon output end 33, fourth photon output end 34, fifth photon output end 35 and sixth photon output end 36, wherein the second photon output end 32 and the third photon output end 33 are used for outputting the optical quantum state transmitted through the six-mode interference network.

[0051] The interference network formed by cascading the 11 MZ interferometers, and the specific connection structure is referred to Figure 1 The input upper port of the fifth MZ interferometer 15 is connected with the first photon input end 21, the input lower port of the fifth MZ interferometer 15 is connected with the output upper port of the third MZ interferometer 13, and the output upper port of the fifth MZ interferometer 15 is connected with the first photon output end 31.

[0052] The input upper port of the third MZ interferometer 13 is connected with the second photon input end 22, the input lower port of the third MZ interferometer 13 is connected with the output upper port of the first MZ interferometer 11 through a connecting wire, the input upper port of the eighth MZ interferometer 18 is connected with the output lower port of the fifth MZ interferometer 15, and the output upper port of the eighth MZ interferometer 18 is connected with the second photon output end 32; the third MZ interferometer 13 and the eighth MZ interferometer 18 are located in the same row.

[0053] The input upper port of the first MZ interferometer 11 is connected with the third photon input end 23, the input lower port of the first MZ interferometer 11 is connected with the fourth photon input end 24, the input upper port of the sixth MZ interferometer 16 is connected with the output lower port of the third MZ interferometer 13, the input lower port of the sixth MZ interferometer 16 is connected with the input upper port of the fourth MZ interferometer 14, the input upper port of the eleventh MZ interferometer 111 is connected with the output lower port of the eighth MZ interferometer 18 through a connecting wire, the input lower port of the eleventh MZ interferometer 111 is connected with the output upper port of the tenth MZ interferometer 110, the output upper port of the eleventh MZ interferometer 111 is connected with the third photon output end 33, and the output lower port of the eleventh MZ interferometer 111 is connected with the fourth photon output end 34; the first MZ interferometer 11, the sixth MZ interferometer 16 and the eleventh MZ interferometer 111 are located in the same row.

[0054] The input upper port of the second MZ interferometer 12 is connected with the output lower port of the first MZ interferometer 11, the input lower port of the second MZ interferometer 12 is connected with the fifth photon input end 25, the two input ports of the fourth MZ interferometer 14 are respectively connected with the two output ports of the second MZ interferometer 12, the input upper port of the ninth MZ interferometer 19 is connected with the output lower port of the sixth MZ interferometer 16, the input lower port of the ninth MZ interferometer 19 is connected with the output upper port of the seventh MZ interferometer 17, the two input ports of the tenth MZ interferometer 110 are respectively connected with the two output ports of the ninth MZ interferometer 19, and the output lower port of the tenth MZ interferometer 110 is connected with the fifth photon output end 35; the second MZ interferometer 12, the fourth MZ interferometer 14, the ninth MZ interferometer 19 and the tenth MZ interferometer 110 are located in the same row.

[0055] The input upper port of the seventh MZ interferometer 17 is connected with the output lower port of the fourth MZ interferometer 14, the input lower port of the seventh MZ interferometer 17 is connected with the sixth photon input end 26, and the output lower port of the seventh MZ interferometer 17 is connected with the sixth photon output end 36.

[0056] In addition, the third MZ interferometer 13 and the fourth MZ interferometer 14 are located in the same column, the fifth MZ interferometer 15, the sixth MZ interferometer 16 and the seventh MZ interferometer 17 are located in the same column, and the eighth MZ interferometer 18 and the ninth MZ interferometer 19 are located in the same column.

[0057] In another embodiment of the present application, the optical quantum chip further comprises four edge couplers 4, as shown in FIG. 2. Figure 2As shown, the second photon input end 22, the third photon input end 23, the second photon output end 32 and the third photon output end 33 correspond to connecting one of the edge couplers 4 respectively. The two edge couplers 4 connected with the second photon input end 22 and the third photon input end 23 are used for coupling the entangled photons generated by the light source to the six-mode interference network, and the two edge couplers 4 connected with the second photon output end 32 and the third photon output end 33 are used for coupling the optical quantum state transmitted through the six-mode interference network to be output.

[0058] Specifically, in the present application, the MZ interferometer includes a first 50:50 beam splitter BS1, an upper interference arm, a lower interference arm, a second 50:50 beam splitter BS2, an in-loop thermo-optic phase modulator TOPM1 and an out-of-loop thermo-optic phase modulator TOPM2, and the specific structure is as shown in Figure 3 As shown, the two ends of the upper interference arm are connected with the output upper port of the first 50:50 beam splitter BS1 and the input upper port of the second 50:50 beam splitter BS2 respectively, the two ends of the lower interference arm are connected with the output lower port of the first 50:50 beam splitter BS1 and the input lower port of the second 50:50 beam splitter BS2 respectively, the in-loop thermo-optic phase modulator TOPM1 is arranged on the upper interference arm, and the out-of-loop thermo-optic phase modulator TOPM2 is arranged on the input upper port of the first 50:50 beam splitter BS1. The in-loop thermo-optic phase modulator TOPM1 and the out-of-loop thermo-optic phase modulator TOPM2 are used for adjusting the phase of the entangled photons according to different experiments, and by adjusting the phase values of the in-loop thermo-optic phase modulator TOPM1 and the out-of-loop thermo-optic phase modulator TOPM2, the path selection of the entangled photons and the switching of the light intensity of the photon output end from 0% to 100% can be realized.

[0059] The optical quantum chip of the present application is formed by cascading 11 MZ interferometers to form a network structure, and the optical path is simple and has the characteristics of full connectivity, programmability and phase stability. The switching and control of the optical quantum optical path are realized by controlling the beam splitting ratio of different MZ interferometers in the six-mode interference network. In the present application, the second photon input end 22 and the third photon input end 23 are used as fixed input ends, and the second photon output end 32 and the third photon output end 33 are used as fixed output ends, so that the switching of the interface in different experimental scenarios is avoided, and the problem of damage to the optical path and the optical fiber interface caused by the misoperation of students in the teaching scenario is avoided.

[0060] Based on the above embodiment, another embodiment of the present application further provides an optical quantum teaching machine system, as shown in Figure 4 , which comprises a host computer, a light source, a control module, two detectors and the above-mentioned optical quantum chip.

[0061] The upper computer is installed with a software operating system, and a user initializes and configures the control module, sets experimental parameters, and realizes demonstration, reading and statistics of experimental results through the software operating system.

[0062] The light source is used for generating entangled photon pairs, and the frequency and / or energy sum of the entangled photon pairs is fixed, and the entangled photon pairs are input into the second photon input end 22 and the third photon input end 23 of the optical quantum chip respectively.

[0063] In the optical quantum chip disclosed in the application, the second photon input end 22 and the third photon input end 23 are fixed photon input ends, and other photon input ends are not connected with light sources, that is, the entangled photon pairs generated by the light source are input into the six-mode interference network from the second photon input end 22 and the third photon input end 23, external interface switching is avoided, and the stability of the system can be further improved and the failure rate of the system can be reduced.

[0064] The light source can be integrated on the optical quantum chip or can be a discrete device. In the application, the light source for generating entangled photon pairs can be a four-wave mixing entangled light source based on a silicon waveguide, a four-wave mixing entangled light source based on a silicon nitride microcavity structure, an entangled light source based on BBO crystal spontaneous parametric down-conversion, a periodically poled KTP crystal spontaneous parametric down-conversion entangled light source or a periodically poled lithium niobate crystal spontaneous parametric down-conversion entangled light source.

[0065] One of the detectors is used for detecting the optical quantum state output from the second photon output end 32 and outputting a response electrical signal, and the other detector is used for detecting the optical quantum state output from the third photon output end 33 and outputting a response electrical signal.

[0066] The second photon output end 32 and the third photon output end 33 are fixed output ends, and the entangled photon pairs are transmitted to the detectors through the edge coupler 4 from the second photon output end 32 and the third photon output end 33 after quantum state modulation and path selection under different experimental conditions. The detectors receive the optical quantum state and detect the information of the photons by using the photoelectric conversion principle. In the application, the detector is preferably a single-photon detector. The single-photon detector can be integrated on the optical quantum chip or can be a discrete device together with the light source, the optical quantum chip and the control module to form a system.

[0067] The control module is configured to receive instructions of the software operating system and to drive and control the light source, the light quantum chip and the detector based on the instructions.

[0068] Specifically, the control module comprises a light source switch control unit, a detector switch control unit, a thermal light phase modulator current drive and control unit and a photon counting unit. The light source switch control unit controls the on or off of the light source based on the instructions input by the software operating system. The detector switch control unit controls the on or off of the two detectors based on the instructions input by the software operating system. The thermal light phase modulator current drive and control unit adjusts the phase of the entangled photons and the beam splitting ratio of the MZ interferometer based on the current value input by the software operating system. The photon counting unit is configured to receive the electrical signals output by the detectors and perform coincidence counting.

[0069] When different experiments are performed, the transmission paths of the entangled photon pairs in the six-mode interference network are different. The path selection of the photons, the preparation and modulation of the quantum states and other functions are achieved by adjusting the control current of the thermal light phase modulator in different MZ interferometers.

[0070] In another embodiment, the optical quantum teaching machine system further comprises an adjustable delay module, as shown in Figure 5 The adjustable delay module is configured to delay the entangled photons input to the third photon input end 23. The adjustable delay module is arranged on the transmission path of the entangled photons transmitted to the third photon input end 23, and the control module is connected to the adjustable delay module. Accordingly, an adjustable delay control unit is arranged in the control module. The adjustable delay control unit controls the adjustable delay module to adjust the delay time of the entangled photons input to the third photon input end 23 based on the instructions input by the software operating system. The two detectors detect the quantum states of the photons and output response electrical signals. The photon counting unit in the control unit receives the electrical signals output by the detectors and performs coincidence counting, and transmits the coincidence counting result to the host computer. The host computer forms a curve of the coincidence counting of the two detectors with the change of the delay time of the two photons based on the delay time input by the software operating system and the received coincidence counting result. The technical solution in this embodiment can be applied in a two-photon interference experiment.

[0071] In the present application, the adjustable delay module is a free-space type optical delay line or a delay chip. When the adjustable delay module is a delay chip, it can be integrated on the optical quantum chip. The free-space type optical delay line uses a mechanical delay method, has a simple structure and is easy to implement, and is currently the main commercial type. It is usually composed of two self-focusing lenses, a right-angle prism, a moving bracket and a high-precision lead screw. Its delay mechanism is as follows: the distance between the right-angle prism and the self-focusing lens is changed, so that the round-trip optical path of the light beam in space changes continuously, thereby obtaining the corresponding delay.

[0072] The optical quantum chip and teaching machine system disclosed by the application can operate five quantum information basic experiments: single photon interference experiment based on a marked single photon source, single photon interference experiment based on a single channel photon, two-photon interference experiment, two-photon boson sampling experiment and two-photon controlled non-gate experiment, realize multiplexing of optical paths and optical devices and do not need to change the connection structure of external light sources, detectors and the like. The state of different MZ interferometers is controlled through software operation programming installed on the host computer. When different experiments are performed, different experimental parameters are input in the software operation system, so that the rapid switching of different experimental optical paths is realized, the operation is convenient, the multiplexing of peripheral high-priced devices such as light sources and detectors is realized, the experimental cost is greatly reduced, it is suitable for quantum teaching and demonstration and has generalizability.

[0073] The switching process of the optical quantum chip in the five experiments is as follows: first, the user selects an experiment in the software operation system on the host computer, the software operation system calculates the control current values of the in-loop thermal optical phase modulator TOPM1 and the out-of-loop thermal optical phase modulator TOPM2 in the 11 MZ interferometers according to the corresponding optical paths under different experiments, and the control module controls the corresponding current to be loaded onto the optical quantum chip. The light source and the detector start to work, the experiment starts, and finally the corresponding experimental results are obtained, and the corresponding experiment is completed.

[0074] The following will be described one by one for the above five experiments. In order to facilitate explanation and convenient description of path selection under different experiments, first, the quantum states at different positions of the MZ interferometer are marked, as shown in Figure 6 The quantum states at different positions of the MZ interferometer are marked as |0>, |1>, |2>, |3>, |4>, |5> respectively. The entangled photon pairs generated by the light source are marked as photon 1 and photon 2. Photon 1 is input to the second photon input end 22 through the edge coupler 4, and photon 2 is input to the third photon input end 23 through the edge coupler 4. The second photon output end 32 is connected with a single photon detector through the edge coupler 4, and the third photon output end 33 is connected with another single photon detector through the edge coupler 4. The first photon output end 21, the fourth photon output end 34, the fifth photon output end 35 and the sixth photon output end 36 are not connected with single photon detectors at the rear end, so the quantum states transmitted to the four photon output ends are invalid transmission and do not play a role in the experiment.

[0075] Experiment one: single photon interference experiment based on a marked single photon source

[0076] The single photon interference experiment light path of the marked single photon source is as shown in Figure 7 The single photon interference experiment light path of the marked single photon source is as shown in Figure 7The dashed path indicates that photons 1 and 2 do not pass through this area. This representation method is also applied to the optical path diagrams of Experiments 2, 3, 4, and 5 described below. Photon 1 undergoes MZ interference at the fifth MZ interferometer 15 and enters the external single-photon detector via the second photon output terminal 32 and the edge coupler 4. Photon 2 passes through a series of MZ interferometers with a phase of 0 / π in the in-ring thermo-optical phase modulator TOPM1, and then enters the external single-photon detector via the third photon output terminal 33 and the edge coupler 4. Since the generation of the two-photon entangled source is a spontaneous parametric down-conversion process, photons 1 and 2 are generated strictly simultaneously in the time dimension. Therefore, a time coincidence measurement can be performed on photons 1 and 2; that is, only when both single-photon detectors respond simultaneously is it counted as a valid count. Thus, the role of photon 2 is to mark the appearance of photon 1, thereby reducing experimental noise and improving the experimental effect of single-photon interference.

[0077] The quantum state evolution process of photon 1 is described in detail below. After photon 1 is input into the six-mode interferometer network via edge coupler 4, it first enters the third MZ interferometer 13. The phase of the thermo-optical phase modulator TOPM1 within the interferometer ring is set to 0. At this time, the third MZ interferometer 13 is equivalent to a mirror, as shown below. Figure 7 As shown, photon 1 is input from the second photon input terminal 22 to the input port of the third MZ interferometer 13, and then output entirely from the output port of the third MZ interferometer 13, without any other change to the quantum state of the photon. Afterwards, photon 1 enters the fifth MZ interferometer 15, according to... Figure 6 As indicated by the annotation, assuming that before photon 1 enters the fifth MZ interferometer 15, the quantum state of photon 1 is |1>, and after passing through the first 50:50 beam splitter BS1 in the fifth MZ interferometer 15, the quantum state becomes:

[0078]

[0079] After passing through the intra-ring thermo-optical phase modulator TOPM1 in the fifth MZ interferometer 15, the phase of the quantum state |2> will be modulated, increasing the phase modulation term e. iφ Where i refers to the imaginary number i, and φ is the phase of the thermo-optical phase modulator TOPM1 in the ring of the fifth MZ interferometer 15, the quantum state becomes:

[0080]

[0081] After passing through the second 50:50 beam splitter BS2 in the fifth MZ interferometer 15, the quantum state becomes

[0082]

[0083] After that, the photon 1 outputted from the fifth MZ interferometer 15 lower port enters the eighth MZ interferometer 18, and the in-loop thermo-optic phase modulator TOPM1 in the eighth MZ interferometer 18 is set to 0, that is, the photon 1 enters the external single-photon detector through the second photon output end 32.

[0084] From the above formula, it can be seen that the probability of the fifth MZ interferometer 15 outputting the quantum state |5> can be expressed as That is, when the in-loop thermo-optic phase modulator TOPM1 in the fifth MZ interferometer 15 changes the phase, the intensity of the photon 1 outputted from the second photon output end 32 will change accordingly, and the interference will change from constructive to destructive, which is single-photon interference.

[0085] Experiment two: single-photon interference experiment based on single-channel photons

[0086] Unlike the single-photon interference experiment based on the marked single-photon source described above, the single-photon interference experiment based on single-channel photons only uses photon 1 for single-photon interference. The experimental optical path design is as shown in Figure 8

[0087] After passing through the third MZ interferometer 13 and the fifth MZ interferometer 15, the photon 1 enters the eighth MZ interferometer 18 and undergoes single-photon interference. Unlike the above experiment one, this time the photon 1 enters the eighth MZ interferometer 18 in the quantum state |0>, so the final output quantum state is:

[0088]

[0089] Among them, the quantum states |4>, |5> in the eighth MZ interferometer 18 are inputted into the second photon output end 32 and the third photon output end 33 respectively, and φ is the phase adjusted by the in-loop thermo-optic phase modulator TOPM1 in the eighth MZ interferometer 18.

[0090] The single-photon counts outputted from the second photon output end 32 and the third photon output end 33 will change from constructive to destructive interference as φ changes, and the sum of the two is a constant. By measuring the interference curve, the user can complete the single-channel single-photon interference experiment.

[0091] It should be noted here that the photon 2 is discarded after passing through the path selection after entering the six-mode interference network and does not play a role in this experiment.

[0092] Experiment three: two-photon interference experiment

[0093] The two-photon interference experiment is also known as the HOM interference experiment, which refers to the phenomenon that two photons undergo two-photon interference at a beam splitter and take the same path. The optical path design of the two-photon interference experiment is as shown in Figure 9 Figure 9 ​​The thick solid line path in the middle is the combined path of photon 1 and photon 2 after interference. This representation method is also applied to the optical path diagrams of the following described experiment four and experiment five. Photon 1 and photon 2 interfere with each other in the sixth MZ interferometer 16. The specific interference process is as follows. Before photon 1 and photon 2 enter the first 50:50 beam splitter BS1 in the sixth MZ interferometer 16, the quantum state can be written as:

[0094]

[0095] The subscript represents photon 1 and photon 2. After passing through the first 50:50 beam splitter BS1 in the sixth MZ interferometer 16, the quantum state is transformed into:

[0096]

[0097] The phase of the photon passing through the in-loop thermal optical phase modulator TOPM1 in the sixth MZ interferometer 16 is modulated to π / 2, and the quantum state changes to:

[0098]

[0099] After passing through the second 50:50 beam splitter BS2, the quantum state changes to:

[0100]

[0101] Since the wavelengths and polarizations of photon 1 and photon 2 are completely consistent, if the delay of photon 1 and photon 2 reaching the second 50:50 beam splitter BS2 in the sixth MZ interferometer 16 is adjusted so that the two photons also arrive at the same time in time, at this time photon 1 and photon 2 cannot be distinguished in all dimensions such as polarization, wavelength and arrival time, so that |5>1|4>2 = |4>1|5>2, the above quantum state can be written as:

[0102]

[0103] Where |4>1|5>2, |5>1|4>2 represent that the two photons take two paths respectively, and |4>1|4>2, |5>1|5>2 represent that the two photons take the same path. From the above derivation, it can be seen that after two-photon interference, both photons take the same path, and the quantum states taking different paths cancel each other out.

[0104] REFERENCE Figure 9, the path of photon 1 and photon 2 after two-photon interference in the sixth MZ interferometer 16 is coincided, forming a composite path of photon 1 and photon 2, which enters the external single-photon detector through the second photon output end 32 and the third photon output end 33 respectively. Two single-photon detectors detect the optical quantum state and output a response electrical signal, and the photon counting unit in the control unit receives the electrical signal output by the single-photon detector and performs coincidence counting while transmitting the coincidence counting result to the upper computer. The upper computer forms a curve of coincidence counting of two single-photon detectors varying with two-photon delay based on the delay time input by the software operating system and the coincidence counting result.

[0105] When the arrival time of photon 1 and photon 2 at the sixth MZ interferometer 16 is different, the terms |4>1|5>2, |5>1|4>2 in the quantum state cannot cancel each other out, and at this time, the coincidence counting is larger. When the arrival time of photon 1 and photon 2 at the sixth MZ interferometer 16 is exactly the same, at this time, both photons take the same path and cannot produce coincidence counting, and at this time, the coincidence counting is the smallest. Thus, the two-photon interference phenomenon can be observed.

[0106] Experiment four: two-photon bosonic sampling experiment Figure 10 The two-photon bosonic sampling experiment uses the statistical distribution of the output photons after the interference of photons in the beam splitter network to equivalently solve the mathematical problem of the product sum formula of the matrix. The light path of the two-photon bosonic sampling experiment is shown in

[0107] Assuming that the unitary matrix composed of the three interferometers is:

[0108]

[0109] Photon 1 enters the six-mode interference network from the second photon input end 22, and photon 2 enters the six-mode interference network from the third photon input end 23. The quantum state entering the unitary matrix can be represented as |I> = |0, 1, 1>, and the input photon matrix U I is:

[0110]

[0111] The photon output from the upper port of the eighth MZ interferometer 18 enters a single photon detector through the second photon output end 32, and the photon output from the lower port of the eighth MZ interferometer 18 enters another single photon detector through the eleventh MZ interferometer 111 and the third photon output end 33. Since the photon output from the upper port of the fifth MZ interferometer 15 is not received by a single photon detector, the output quantum state is |I> = |0, 1, 1>. The output photon matrix U I,O may be expressed as:

[0112]

[0113] Therefore, the probability that one photon is simultaneously detected on the two paths of the photon output from the upper port of the eighth MZ interferometer 18 transmitted to the second photon output end 32 and the photon output from the lower port of the eighth MZ interferometer 18 transmitted to the third photon output end 33 through the eleventh MZ interferometer 111 is:

[0114]

[0115] where Per(U) represents the permanent of the matrix.

[0116] Therefore, by measuring the coincidence count rate of the above two paths, the calculation result of the product-sum of the sub-matrix of any unitary matrix formed by the interference network can be obtained. That is, the two-photon, three-dimensional matrix bosonic sampling experiment can be realized by using this scheme.

[0117] Experiment five: two-photon controlled non-gate experiment

[0118] A two-qubit controlled non-gate can be probabilistically realized by using linear optical devices. The specific experimental scheme is as shown in Figure 11 Photon 1 is input to the third MZ interferometer 13, and photon 2 is input to the second MZ interferometer 12, which are modulated into two qubits of path encoding. The modulated quantum state is The in-loop thermal optical phase modulator TOPM1 of the fifth MZ interferometer 15, the sixth MZ interferometer 16, and the seventh MZ interferometer 17 takes a suitable phase value to make the three MZ interferometers equivalent to a beam splitter with a splitting ratio of 1:2. The fourth MZ interferometer 14 and the ninth MZ interferometer 19 are equivalent to a beam splitter with a splitting ratio of 50:50. Therefore, the quantum state in all dimensions before reaching the eighth MZ interferometer 18 and the tenth MZ interferometer 10 is:

[0119]

[0120] Wherein |ψ> is the photon quantum state output by the first photon output end 31, the fourth photon output end 34, the fifth photon output end 35 and the sixth photon output end 36, and the first photon output end 31, the fourth photon output end 34, the fifth photon output end 35 and the sixth photon output end 36 are not connected with single photon detectors at the rear end, and the quantum state will be discarded by the post-selection process after path selection. Except for the quantum state |ψ>, the quantum state

[0121] is a controlled NOT gate.

[0122] Therefore, the experiment finally realizes the function of the controlled NOT gate with a probability of 1 / 9. The eighth MZ interferometer 18 and the tenth MZ interferometer 110 respectively constitute the arbitrary quantum state projection measurement bases of the path dimension, and can complete the arbitrary projection measurement of two quantum bits.

[0123] In the specification, each embodiment is described in a progressive manner, or in a parallel manner, or in a combination of the progressive and parallel manners, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0124] It should be noted that, in this document, the relationship terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the article or device including the above element.

[0125] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A photonic quantum teaching machine system, characterized by, The device comprises a host computer, a light source, a control module, two detectors and a quantum chip. The host computer is installed with a software operating system, and a user initializes and configures the control module, sets experimental parameters, and demonstrates, reads and counts experimental results through the software operating system. The light source is used to generate entangled photon pairs, the frequency and / or energy sum of the entangled photon pairs is fixed, and the entangled photon pairs are input into the second photon input end and the third photon input end of the quantum chip, respectively. One of the detectors is used to detect the quantum state of light output from the second photon output end and output a response electrical signal, and the other detector is used to detect the quantum state of light output from the third photon output end and output a response electrical signal. The control module is used to receive instructions from the software operating system, drive and control the light source, the quantum chip and the detectors based on the instructions, and operate five quantum information basic experiments, i.e., a single-photon interference experiment based on a labeled single-photon source, a single-photon interference experiment based on a single-channel photon, a two-photon interference experiment, a two-photon boson sampling experiment and a two-photon controlled non-gate experiment. The quantum chip comprises a six-mode interference network, the six-mode interference network comprises six photon input ends, 11 MZ interferometers and six photon output ends, the 11 MZ interferometers are respectively a first MZ interferometer, a second MZ interferometer, a third MZ interferometer, a fourth MZ interferometer, a fifth MZ interferometer, a sixth MZ interferometer, a seventh MZ interferometer, an eighth MZ interferometer, a ninth MZ interferometer, a tenth MZ interferometer and an eleventh MZ interferometer, the six photon input ends are respectively a first photon input end, a second photon input end, a third photon input end, a fourth photon input end, a fifth photon input end and a sixth photon input end, the second photon input end and the third photon input end are used to input entangled photons, and the six photon output ends are respectively a first photon output end, a second photon output end, a third photon output end, a fourth photon output end, a fifth photon output end and a sixth photon output end, the second photon output end and the third photon output end are used to output the quantum state of light transmitted through the six-mode interference network. The input upper port of the fifth MZ interferometer is connected with the first photon input end, the input lower port of the fifth MZ interferometer is connected with the output upper port of the third MZ interferometer, and the output upper port of the fifth MZ interferometer is connected with the first photon output end. The input upper port of the third MZ interferometer is connected with the second photon input end, the input lower port of the third MZ interferometer is connected with the output upper port of the first MZ interferometer through a connecting wire, the input upper port of the eighth MZ interferometer is connected with the output lower port of the fifth MZ interferometer, the output upper port of the eighth MZ interferometer is connected with the second photon output end, and the third MZ interferometer and the eighth MZ interferometer are located in the same row. The input upper port of the first MZ interferometer is connected with the third photon input end, the input lower port of the first MZ interferometer is connected with the fourth photon input end, the input upper port of the sixth MZ interferometer is connected with the output lower port of the third MZ interferometer, the input lower port of the sixth MZ interferometer is connected with the input upper port of the fourth MZ interferometer, the input upper port of the eleventh MZ interferometer is connected with the output lower port of the eighth MZ interferometer through a connecting wire, the input lower port of the eleventh MZ interferometer is connected with the output upper port of the tenth MZ interferometer, the output upper port of the eleventh MZ interferometer is connected with the third photon output end, and the output lower port of the eleventh MZ interferometer is connected with the fourth photon output end; the first MZ interferometer, the sixth MZ interferometer and the eleventh MZ interferometer are located in the same row. The input upper port of the second MZ interferometer is connected with the output lower port of the first MZ interferometer, the input lower port of the second MZ interferometer is connected with the fifth photon input end, the two input ports of the fourth MZ interferometer are respectively connected with the two output ports of the second MZ interferometer, the input upper port of the ninth MZ interferometer is connected with the output lower port of the sixth MZ interferometer, the input lower port of the ninth MZ interferometer is connected with the output upper port of the seventh MZ interferometer, the two input ports of the tenth MZ interferometer are respectively connected with the two output ports of the ninth MZ interferometer, and the output lower port of the tenth MZ interferometer is connected with the fifth photon output end; the second MZ interferometer, the fourth MZ interferometer, the ninth MZ interferometer and the tenth MZ interferometer are located in the same row. The input upper port of the seventh MZ interferometer is connected with the output lower port of the fourth MZ interferometer, the input lower port of the seventh MZ interferometer is connected with the sixth photon input end, and the output lower port of the seventh MZ interferometer is connected with the sixth photon output end. The third MZ interferometer and the fourth MZ interferometer are located in the same column, the fifth MZ interferometer, the sixth MZ interferometer and the seventh MZ interferometer are located in the same column, and the eighth MZ interferometer and the ninth MZ interferometer are located in the same column.

2. A photonic quantum teaching machine system according to claim 1, wherein, The optical quantum chip further comprises four edge couplers, and the second photon input end, the third photon input end, the second photon output end and the third photon output end are respectively connected with one of the edge couplers.

3. A photonic quantum teaching machine system according to claim 1, wherein, The MZ interferometer comprises a first 50:50 beam splitter, an upper interference arm, a lower interference arm, a second 50:50 beam splitter, an in-loop thermo-optic phase modulator and an out-of-loop thermo-optic phase modulator, two ends of the upper interference arm are respectively connected with an output upper port of the first 50:50 beam splitter and an input upper port of the second 50:50 beam splitter, two ends of the lower interference arm are respectively connected with an output lower port of the first 50:50 beam splitter and an input lower port of the second 50:50 beam splitter, the in-loop thermo-optic phase modulator is arranged on the upper interference arm, and the out-of-loop thermo-optic phase modulator is arranged on the input upper port of the first 50:50 beam splitter.

4. A photonic quantum teaching machine system according to claim 1, wherein, The optical quantum teaching machine system further comprises an adjustable delay module for delaying the entangled photons input into the third photon input end, the adjustable delay module is arranged on a transmission path of the entangled photons transmitted to the third photon input end, and the control module is connected with the adjustable delay module.

5. A photonic quantum teaching machine system according to claim 1, wherein, The control module comprises a light source switch control unit, a detector switch control unit, a thermal light phase modulator current drive and control unit, and a photon counting unit. The light source switch control unit controls the opening or closing of the light source based on the instructions input by the software operating system. The detector switch control unit controls the opening or closing of the two detectors based on the instructions input by the software operating system. The thermal light phase modulator current drive and control unit adjusts the phase of the entangled photons and the beam splitting ratio of the MZ interferometer based on the current value input by the software operating system. The photon counting unit receives the electrical signals output by the detectors and performs coincidence counting.

6. A photonic quantum teaching machine system according to claim 1, wherein, The light source is a four-wave mixing entangled light source based on a silicon waveguide, a four-wave mixing entangled light source based on a silicon nitride microcavity structure, an entangled light source based on a BBO crystal spontaneous parametric down-conversion, an entangled light source based on a periodically poled KTP crystal spontaneous parametric down-conversion, or an entangled light source based on a periodically poled lithium niobate crystal spontaneous parametric down-conversion.

7. A photonic quantum teaching machine system according to claim 1, wherein, The detector is a single-photon detector.

8. A photonic quantum teaching machine system according to claim 4, wherein, The adjustable delay module is a free-space optical delay line or a delay chip.

9. A photonic quantum teaching machine system according to claim 5, wherein, The control module further comprises an adjustable delay control unit, which controls the adjustable delay module to adjust the delay time of the entangled photons input to the third photon input end based on the instructions input by the software operating system.

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