CN216697606U

CN216697606U - Single-photon and double-photon interference device

Info

Publication number: CN216697606U
Application number: CN202123182795.7U
Authority: CN
Inventors: 李健亮
Original assignee: Qingdao Quantum Application Technology Co ltd
Current assignee: Qingdao Quantum Application Technology Co ltd
Priority date: 2021-12-16
Filing date: 2021-12-16
Publication date: 2022-06-07
Anticipated expiration: 2031-12-16

Abstract

The utility model belongs to the technical field of quantum communication, and particularly relates to a single-photon and double-photon interference device which comprises a correlated photon source module, a single-photon and double-photon conversion module, a photon interference module and a photon detection module, wherein the correlated photon source module, the single-photon and double-photon conversion module, the photon interference module and the photon detection module are arranged along the propagation direction of a light path; the correlated photon source module is used for generating a correlated photon source; the single-photon and double-photon conversion module is used for the conversion of single-photon interference and two-photon interference; the photon interference module is used for correlating the interference of photons; the photon detection module is used for receiving the associated photons from the photon interference module and performing coincidence measurement counting. The single-photon and double-photon interference experiment device has the advantages that the single-photon and double-photon conversion modules are arranged, the single-photon and double-photon interference experiment can be respectively carried out by utilizing the same device, the structure is simple, the realization is easy, and the cost is low.

Description

Single-photon and double-photon interference device

Technical Field

The utility model belongs to the technical field of quantum communication, and particularly relates to a single-photon and double-photon interference device.

Background

Quantum interference plays an extremely important role in quantum information science, and is the basis of quantum manipulation technology and an important tool for realizing quantum communication. The progress of quantum interference technology can greatly promote the development of quantum information science.

Single photon interference is an important means to verify the volatility of photons. Therefore, the single-photon interference device is significant for researching and developing the non-classical optical field generated in the parametric process. Two-photon interference also has wide application, for example, Hong-Ou-Mandel interference is used for verifying Bell inequality, performing Bell-based measurement, quantum invisible state transfer and quantum logic gate operation, and the like.

In the implementation process, the two existing optical paths of single photon interference and two-photon interference are in different systems, and the two optical path devices have complex structures and need to be improved.

SUMMERY OF THE UTILITY MODEL

The embodiment of the utility model aims to provide a single-photon and double-photon interference device, and aims to solve the problem that the two optical paths of the existing single-photon interference and double-photon interference are in different systems, and the structures of the two optical path devices are complex.

The embodiment of the utility model is realized in such a way that the single-photon and double-photon interference device comprises a correlated photon source module, a single-photon and double-photon conversion module, a photon interference module and a photon detection module which are arranged along the propagation direction of a light path;

the associated photon source module is used for generating an associated photon source;

the single-photon and double-photon conversion module is used for the conversion of single photon interference and two-photon interference;

the photon interference module is used for correlating the interference of photons;

the photon detection module is used for receiving the associated photons from the photon interference module and performing coincidence measurement counting.

Preferably, the associated photon source module includes a laser, a first modulation unit, a first lens, a nonlinear crystal, a second lens, and a second polarization beam splitter, which are sequentially arranged along the propagation direction of the light path;

the laser is used for pumping a light beam to provide an initial light beam;

the first modulation unit is used for keeping the phase of the pump light stable and adjusting the intensity of the emergent light beam, and comprises a first quarter-wave plate, a first half-wave plate and a first polarization beam splitter which are sequentially arranged along the propagation direction of the light path;

the first lens is used for converging the horizontal polarized light beam to the central position of the nonlinear crystal;

the second lens is used for collimating and outputting the output light of the nonlinear crystal.

Preferably, the first quarter wave plate and the first half wave plate are combined into a wave plate group, and the pump light can be modulated to any phase;

the wave plate group is matched with the first polarization beam splitter to be used for keeping the phase of the pump light stable and adjusting the intensity of the emergent light beam.

Preferably, the focal lengths of the first lens and the second lens are the same, the first lens and the second lens form a 4f system, and the nonlinear crystal is located at the position where the focal points of the two lenses coincide.

Preferably, both end faces of the nonlinear crystal are plated with antireflection films, and the antireflection films are used for enhancing the transmittance of light beams.

Preferably, a first optical filter is arranged on one side of the second polarization beam splitter, which is far away from the second lens, a second optical filter is arranged on one side of the second polarization beam splitter, which is adjacent to the first optical filter, the direction of the optical path where the second optical filter is located is perpendicular to the direction of the optical path where the first optical filter is located, and the first optical filter and the second optical filter are used for filtering non-single photon signals in the spatial light beam to complete the optical filtering function on the optical frequency, so that the signal-to-noise ratio is improved.

Preferably, the single-photon and double-photon conversion module comprises a second modulation unit, a third polarization beam splitter and a fourth half-wave plate;

the second modulation unit is used for modulating the single photon polarization state into horizontal polarization light and comprises a second quarter-wave plate and a second half-wave plate which are sequentially arranged along the propagation direction of the light path;

the third modulation unit is used for modulating the single photon polarization state into vertical polarization light and comprises a third quarter-wave plate and a third half-wave plate which are sequentially arranged along the propagation direction of the light path;

emergent light of the second modulation unit and the third modulation unit enters a third polarization beam splitter;

the fourth half-wave plate is arranged at the emergent end of the third polarization beam splitter and used for the conversion of single photon interference and two-photon interference.

Preferably, the photonic interference module comprises a fourth polarization beam splitter, a fourth quarter wave plate, a first mirror, a fifth quarter wave plate, a second mirror, a fifth half wave plate, a fifth polarization beam splitter;

the fourth polarization beam splitter is used for splitting an incident light beam into a horizontally polarized transmitted light beam and a vertically polarized reflected light beam;

the fourth quarter-wave plate and the first reflector are used for converting the vertical polarization reflected beam into a horizontal polarization transmitted beam and returning the horizontal polarization transmitted beam back to the fourth polarization beam splitter;

the fifth quarter wave plate and the second reflector are used for converting the horizontally polarized transmitted beam into a vertically polarized reflected beam and returning the vertically polarized reflected beam back to the fourth polarization beam splitter;

the fifth half-wave plate is arranged at one output end of the fourth polarization beam splitter and is used for adjusting the polarization states of the horizontally polarized transmitted beam and the vertically polarized reflected beam;

and the fifth polarization beam splitter receives emergent light of the fifth half-wave plate and is used for splitting a single-photon beam in a 45-degree polarization state into two beams to be emitted into the photon detection module.

Preferably, a third optical filter and a fourth optical filter are respectively arranged at two emergent ends of the fifth polarization beam splitter, and the third optical filter and the fourth optical filter are band-pass optical filters and are used for filtering non-single photon signals in the spatial light beam to complete the optical frequency filtering function, so as to improve the signal-to-noise ratio of the test system.

Preferably, the photon detection module comprises a first optical fiber collimator, a first optical fiber, a first single-photon detector, a second optical fiber collimator, a second optical fiber, a second single-photon detector and a coincidence counter;

the first optical fiber collimator, the first optical fiber and the first single-photon detector are sequentially connected and used for receiving single photons, detecting photon information by utilizing a photoelectric conversion principle and transmitting the photon information to the coincidence counter;

the second optical fiber collimator, the second optical fiber and the second single-photon detector are sequentially connected and used for receiving the single photons, detecting photon information by utilizing a photoelectric conversion principle and transmitting the photon information to the coincidence counter;

the coincidence counter is used for coincidence counting.

The single-photon interference and double-photon interference device provided by the embodiment of the utility model enables single-photon interference and double-photon interference experiments to be in the same system. The utility model has the advantages of simple and convenient light path, high preparation efficiency of the associated photon pair, small volume, light weight and easy movement, is easier to apply to actual life compared with other photon interference devices, and has important significance for the field of quantum interference.

Drawings

FIG. 1 is a block diagram of a single-photon or dual-photon interference apparatus according to the present invention;

FIG. 2 is a block diagram of an associated photon source module of the present invention;

FIG. 3 is a block diagram of a single-double photon conversion module of the present invention;

FIG. 4 is a block diagram of a photonic interference module of the present invention;

FIG. 5 is a block diagram of a photon detection module of the present invention;

FIG. 6 is a graph of experimental data results of the present invention.

In the drawings: 100. an associated photon source module; 101. a laser; 102. a first quarter wave plate; 103. A first half wave plate; 104. a first polarizing beam splitter; 105. a first lens; 106. a nonlinear crystal; 107. a second lens; 108. a second polarizing beam splitter; 109. a first optical filter; 110. a second optical filter; 200. A single-double photon conversion module; 201. a second quarter wave plate; 202. a second half-wave plate; 203. a third polarization beam splitter; 204. a third quarter wave plate; 205. a third half-wave plate; 206. a fourth half-wave plate; 300. a photon interference module; 301. a fourth polarizing beam splitter; 302. a fourth quarter wave plate; 303. a first reflector; 304. a fifth quarter wave plate; 305. a second reflector; 306. a fifth half-wave plate; 307. A fifth polarizing beam splitter; 308. a third optical filter; 309. a fourth optical filter; a 400 photon detection module; 401. a first fiber collimator; 402. a second fiber collimator; 403. a first optical fiber; 404. a second optical fiber; 405. a first single photon detector; 406. a second single-photon detector; 407. a coincidence counter.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and are not intended to limit the utility model.

Specific implementations of the present invention are described in detail below with reference to specific embodiments.

As shown in fig. 1, a single-photon and dual-photon interference apparatus provided for an embodiment of the present invention includes a correlated photon source module 100, a single-photon and dual-photon conversion module 200, a photon interference module 300, and a photon detection module 400 arranged along a propagation direction of an optical path;

the associated photon source module 100 is for generating an associated photon source;

the single-photon and double-photon conversion module 200 is used for the conversion of single photon interference and two-photon interference;

the photon interference module 300 is used for correlating the interference of photons;

the photon detection module 400 is configured to receive the associated photons from the photon interference module 300 and perform coincidence measurement counting.

In this embodiment, the correlated photon source module 100 is controlled to generate a single photon light source, and the embodiment is described by taking a two-photon interference debugging experiment as an example, where the central wavelength of a light beam of the light source is 405nm, and a mixed light beam with wavelengths of 405nm and 810nm is obtained after further processing by the correlated photon source module 100. The single and double photon conversion module 200 processes the beams generated by the associated photon source. The photon interference module 300 changes two photons into photons having the same time and polarization, i.e., identical photons, before the two photons enter the photon detection module 400. The photon detection module 400 includes two receiving ends that receive light from the photon interference module 300. The reflection mirror in the photon interference module 300 is moved, and the image of two-photon interference can be calculated through correlation calculation. It should be noted that, the process of the association calculation may be performed on other computer devices, and the apparatus provided in the embodiment of the present invention is mainly used for acquiring data, and of course, combining an operation function with the apparatus provided in the embodiment of the present invention belongs to an optional specific implementation manner of the present invention.

The single-photon and double-photon interference device provided by the embodiment of the utility model enables single-photon interference and double-photon interference experiments to be in the same system, and is easy to operate. The utility model has the advantages of simple and convenient optical path, high preparation efficiency of the associated photon pair, small volume, light weight and easy movement, is easier to apply to practical life compared with other photon interference devices, and has important significance for the field of quantum interference.

As shown in fig. 2, in an embodiment of the present invention, the associated photon source module 100 includes a laser 101, a first modulation unit, a first lens 105, a nonlinear crystal 106, a second lens 107, and a second polarization beam splitter 108, which are sequentially arranged along a propagation direction of an optical path;

the laser 101 is used for pumping a light beam to provide an initial light beam;

the first modulation unit is used for adjusting the intensity of an emergent light beam while keeping the phase of pump light stable, and comprises a first quarter wave plate 102, a first half wave plate 103 and a first polarization beam splitter 104 which are sequentially arranged along the propagation direction of an optical path;

the first lens 105 is used for converging the horizontal polarized light beam to the central position of the nonlinear crystal 106;

the second lens 107 is used for collimating and outputting the output light of the nonlinear crystal 106.

In this embodiment, the laser 101 is a semiconductor continuous laser emitting device, and provides an initial beam as a pump beam for the whole device. The central wavelength of the light beam is 405nm, the spectral line width is less than 0.06nm, and the output power can reach 66 mW.

In this embodiment, the nonlinear crystal 106 is a PPKTP crystal (potassium titanyl phosphate crystal) for generating orthogonal polarized correlated photon pairs. The nonlinear crystal 106 converts the 405nm pump light incident to the crystal into 810nm light by using a spontaneous parametric down-conversion process, and the light emitted by the nonlinear crystal 106 is a mixed light beam of 405nm and 810 nm. The length of the nonlinear crystal 106 is 20mm, two end faces of the nonlinear crystal 106 in the light propagation direction are coated with antireflection films with wavelengths of 405nm and 810nm, when the pump light intensity is 1mw, the generation rate of the associated photon pairs is 50000/mw/s, and the brightness is high.

In this embodiment, the second polarizing beam splitter 108 operates at a center wavelength of 810nm and functions to split the mixed beam, which is normally incident on its end face, into a horizontally polarized transmitted beam and a vertically polarized reflected beam.

In one embodiment of the present invention, the first quarter waveplate 102 and the first half waveplate 103 are combined into a waveplate set, which can modulate the pump light to any phase;

the wave plate and the first polarization beam splitter 104 cooperate to adjust the intensity of the outgoing beam while maintaining the phase stability of the pump light.

In this embodiment, the working wavelengths of the first quarter wave plate 102, the first half wave plate 103, and the first polarization beam splitter 104 are all 405nm, the wave plates are mainly used for adjusting the polarization state of the light beam, and the first quarter wave plate 102 and the first half wave plate 103 are combined into a wave plate set, which can modulate the pump light to any phase. The wave plate group and the first polarization beam splitter 104 cooperate to adjust the intensity of the emergent beam while maintaining the phase stability of the pump light. After the 405nm pump light passes through the first quarter wave plate 102, the first half wave plate 103 and the first polarization beam splitter 104, the horizontal polarized light with the phase-stable light intensity of 1mw is output.

In one embodiment of the present invention, the focal lengths of the first lens 105 and the second lens 107 are the same, and both constitute a 4f system, and the nonlinear crystal 106 is located at the position where the focal points of the two lenses coincide.

In this embodiment, the first lens 105 has an operating wavelength of 405nm and a focal length of 50mm, and the second lens 107 has an operating wavelength of 810nm and a focal length of 50 mm. The first lens 105 is used for converging the horizontally polarized light beam to the central position of the nonlinear crystal 106, and the second lens 107 is used for collimating and outputting the output light of the nonlinear crystal 106.

In an embodiment of the present invention, both end faces of the nonlinear crystal 106 are plated with antireflection films, and the antireflection films are used to enhance the transmittance of light beams.

In this embodiment, the manufacturing process of the antireflection film according to the embodiment of the present invention is not specifically limited, and may be implemented by referring to the prior art; the antireflection film is arranged to enhance the transmittance, and belongs to an optional optimization scheme.

In an embodiment of the present invention, a first optical filter 109 is disposed on a side of the second polarization beam splitter 108 away from the second lens 107, a second optical filter 110 is disposed on a side of the second polarization beam splitter 108 adjacent to the first optical filter 109, a light path direction of the second optical filter 110 is perpendicular to a light path direction of the first optical filter 109, and the first optical filter 109 and the second optical filter 110 are configured to filter non-single photon signals in the spatial light beam to complete a filtering function on optical frequencies, so as to improve a signal-to-noise ratio.

In this embodiment, the first filter 109 is located at the end of the transmission optical path of the second polarization beam splitter 108, and is used for receiving and filtering the horizontally polarized transmission beam; the second filter 110 is located at the end of the reflected light path of the second polarization beam splitter 108 for receiving the vertically polarized reflected light beam. The first filter 109 emits a first spin single photon beam, and the second filter 110 emits a second spin single photon beam. The first filter 109 and the second filter 110 both allow only light with a wavelength of 810nm to pass through, and can prevent light with a wavelength of 405nm from passing through, so that the device can be protected. The first optical filter 109 and the second optical filter 110 are bandpass filters of the same type, the wavelength of the working center of the bandpass filters is 800nm, the full width at half maximum is 40nm, non-single photon signals in the spatial light beams are filtered, the optical frequency filtering function is completed, and the signal-to-noise ratio of the test system is improved. The correlated photon source module 100 of the utility model prepares the correlated photon pair through the nonlinear crystal 106, the light path is simple and convenient, and the preparation efficiency of the correlated photon pair is high.

As shown in fig. 3, in one embodiment of the present invention, the single-double photon conversion module 200 includes a second modulation unit, a third polarization beam splitter 203 and a fourth half-wave plate 206;

the second modulation unit is used for modulating the single photon polarization state into horizontal polarization light and comprises a second quarter-wave plate 201 and a second half-wave plate 202 which are sequentially arranged along the propagation direction of the light path;

the third modulation unit is used for modulating the single photon polarization state into vertical polarization light, and comprises a third quarter-wave plate 204 and a third half-wave plate 205 which are sequentially arranged along the propagation direction of the light path;

the emergent light of the second modulation unit and the third modulation unit enters a third polarization beam splitter 203;

the fourth half-wave plate 206 is disposed at the horizontal polarized light exit end of the third polarization beam splitter 203, and is used for conversion between single photon interference and two-photon interference.

In this embodiment, the operating wavelengths of the second quarter-wave plate 201, the second half-wave plate 202, the third quarter-wave plate 204, and the third half-wave plate 205 in the second modulation unit and the third modulation unit are 810nm, and the wave plates are mainly used for adjusting the polarization states of the light beams. The second modulation unit modulates all the single-photon polarization state into horizontal polarization light, the third modulation unit modulates all the single-photon polarization state into vertical polarization light, and the two beams of light enter the third polarization beam splitter 203 to be mixed at the same time.

In this embodiment, the operating wavelengths of the third polarization beam splitter 203 and the fourth half-wave plate 206 are both 810nm, and the original polarization state of the single photons in the two polarization states from the third polarization beam splitter 203 is not changed by rotating the fourth half-wave plate 206 to be at the position of the long axis; the single photons of both polarization states then enter the photonic interference module 300.

As shown in FIG. 4, in one embodiment of the present invention, the photonic interference module 300 includes a fourth polarization beam splitter 301, a fourth quarter wave plate 302, a first mirror 303, a fifth quarter wave plate 304, a second mirror 305, a fifth half wave plate 306, a fifth polarization beam splitter 307;

the fourth polarization beam splitter 301 is used for splitting the incident light beam into a horizontally polarized transmitted light beam and a vertically polarized reflected light beam;

the fourth quarter waveplate 302 and the first mirror 303 are used to convert the vertically polarized reflected beam into a horizontally polarized transmitted beam and back into the fourth polarization beam splitter 301;

the fifth quarter waveplate 304 and the second mirror 305 are used to convert the horizontally polarized transmitted beam into a vertically polarized reflected beam and back into the fourth polarization beam splitter 301;

the fifth half-wave plate 306 is disposed at an output end of the fourth polarization beam splitter, and is used for adjusting the polarization states of the horizontally polarized transmitted beam and the vertically polarized reflected beam;

the fifth polarization beam splitter 307 receives the emergent light of the fifth half-wave plate 306, and is used for splitting the single photon beam with the polarization state of 45 degrees into two beams to be emitted into the photon detection module 400.

In the present embodiment, the fourth polarization beam splitter 301 is configured to split the incident light beam into a horizontally polarized transmitted beam and a vertically polarized reflected beam, and the operating wavelength is 810 nm; the fourth quarter waveplate 302 and the first mirror 303 convert the vertically polarized reflected beam into a horizontally polarized transmitted beam and return to the fourth polarization beam splitter 301, and similarly, the fifth quarter waveplate 304 and the second mirror 305 convert the horizontally polarized transmitted beam into a vertically polarized reflected beam and return to the fourth polarization beam splitter 301; the distance between the two mirrors is adjusted so that the two beams reach the fifth half-wave plate 306 simultaneously.

In this embodiment, the operating wavelengths of the fourth quarter wave plate 302, the first mirror 303, the fifth quarter wave plate 304 and the second mirror 305 are all 810nm, and the distance between the first mirror 303 and the fourth polarization beam splitter 301 and the distance between the second mirror 305 and the fourth polarization beam splitter 301 are adjusted to be the same.

In this embodiment, the fifth half-wave plate 306 is adjusted so that the horizontally polarized transmitted beam is in the same polarization state as the vertically polarized reflected beam; the fifth polarization beam splitter 307 splits the single photon beam with the same polarization state into two beams, which are incident on the photon detection module 400.

In an embodiment of the present invention, a third optical filter 308 and a fourth optical filter 309 are respectively disposed at two exit ends of the fifth polarization beam splitter 307, and the third optical filter 308 and the fourth optical filter 309 are bandpass optical filters, and are configured to filter non-single photon signals in a spatial light beam, so as to complete a filtering function on optical frequencies, so as to improve a signal-to-noise ratio of the test system.

In this embodiment, the third optical filter 308 and the fourth optical filter 309 are band pass filters, the wavelength of the working center of the band pass filters is 800nm, the full width at half maximum is 40nm, and the non-single photon signals in the spatial light beam are filtered out to complete the filtering function of the optical frequency, so as to improve the signal-to-noise ratio of the test system.

As shown in fig. 5, in one embodiment of the present invention, the photon detection module 400 includes a first fiber collimator 401, a first optical fiber 403, a first single-photon detector 405, a second fiber collimator 402, a second optical fiber 404, a second single-photon detector 406, and an coincidence counter 407;

the first optical fiber collimator 401, the first optical fiber 403 and the first single-photon detector 405 are sequentially connected and used for receiving single photons, detecting photon information by using a photoelectric conversion principle and transmitting the photon information to the coincidence counter 407;

the second optical fiber collimator 402, the second optical fiber 404 and the second single photon detector 406 are sequentially connected and used for receiving the single photon, detecting photon information by using a photoelectric conversion principle and transmitting the photon information to the coincidence counter 407;

the coincidence counter 407 is used for coincidence counting.

In this embodiment, a first spin single photon beam generated by the associated photon source module 100 enters the coincidence counter 407 through the first fiber collimator 401, the first optical fiber 403, and the first single photon detector 405; the second spin single photon beam enters a coincidence counter 407 through a second fiber collimator 402, a second optical fiber 404, and a second single photon detector 406.

In this embodiment, the first fiber collimator 401 and the second fiber collimator 402 are fiber collimators of FC/PC connectors of the same type, and the operating wavelength ranges are as follows: 750nm to 1100nm for coupling a gaussian beam into the fiber. The first optical fiber 403 and the second optical fiber 404 are single mode fibers, the operating wavelength is 810nm, and the single mode fibers can only pass through a zero mode, so that the single mode fibers are used for transmitting and filtering photons. Meanwhile, the first single-photon detector 405 and the second single-photon detector 406 are configured to receive single photons, detect information of the photons by using a photoelectric conversion principle, and transmit the information to the coincidence counter 407.

In the present embodiment, the coincidence counter 407 is used for coincidence counting. The principle is that a dual-channel input signal is adopted to respectively receive output signals from a first single-photon detector 405 and a second single-photon detector 406, each channel counts independently, parameters such as window time and delay time are set through a display screen main interface, detection pulses arrive in a set coincidence time window, and counting is carried out according to coincidence measurement results, namely the number of associated photon pairs.

The embodiment of the utility model also provides a control method of the single-photon and double-photon interference device, which is applied to the single-photon and double-photon interference device according to any one embodiment of the utility model, and the control method of the single-photon and double-photon interference device comprises the following steps:

starting the associated photon source module 100 and adjusting to output horizontal polarized laser light and vertical polarized light with stable phase and light intensity;

the single-double photon conversion module 200 is connected with horizontal polarized light and/or vertical polarized light, and the output light beam enters the photon interference module 300;

the output light of the photon interference module 300 enters the photon detection module 400 for coincidence counting.

In this embodiment, the specific process of the above steps is as follows:

starting and adjusting the associated photon source module 100, and jointly rotating the long axis angles of the first quarter-wave plate 102 and the first half-wave plate 103 to output horizontal polarized laser with stable phase and light intensity; the position of the first lens 105 is adjusted to focus the input light on the nonlinear crystal 106, the position of the second lens 107 is adjusted to collimate the light into the second polarization beam splitter 108, and the second polarization beam splitter 108 splits the mixed light beam into a horizontally polarized transmitted light beam and a vertically polarized reflected light beam when the mixed light beam is vertically incident on the end face thereof.

The horizontal polarized light output by the associated photon source is connected into the second modulation unit, the vertical polarized light is connected into the third modulation unit, the wave plate group is adjusted to enable the light intensity of the two beams of light to be adjusted to be maximum, the time for the horizontal polarized light and the time for the vertical polarized light to reach the fourth half-wave plate 206 are the same, the fourth half-wave plate 206 is adjusted to be in the position of the long axis, and at the moment, the fourth half-wave plate 206 does not deflect the horizontal polarized light or the vertical polarized light; both the horizontally polarized light and the vertically polarized light enter the photonic interference module 300.

Adjusting the positions of the first mirror 303 and the second mirror 305 to make the distance between the first mirror 303 and the fourth polarization beam splitter 301 equal to the distance between the second mirror 305 and the fourth polarization beam splitter 301; the long axis angles of the fourth quarter waveplate 302 and the fifth quarter waveplate 304 are adjusted to maximize the single photons reflected by the output mirror.

Adjusting the fifth half-wave plate 306 to make the single photon beam polarization enter the fifth polarization beam splitter 307 at an angle of 45 degrees; the position and angle of the optical fiber are adjusted to collect and couple the signals into the single photon detector, and then the signals generated by the two photons reach the coincidence counter 407 for coincidence measurement counting.

In the embodiment of the present invention, data obtained during a test of a two-photon interference experiment is shown in table 1, and an analysis result is shown in fig. 6, where the experiment shows that when optical paths of two paths are equal, a photon pair will be emitted from the same port of a polarization beam splitter, that is, the probability that photons are emitted from two ends of the polarization beam splitter simultaneously is zero, which indicates that destructive interference occurs. The measurements of fig. 6 show that when the mirror is moved to a certain position, the optical path difference exceeds the coherence length and the two photons become distinguishable in time. In the two-photon state after passing through the polarizing beam splitter, two states of reflection-reflection and transmission-transmission can also be distinguished. These show that we can extract information about the determined path of the photon and also that the disappearance of the interference phenomenon can be explained.

Table 1: test data

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the utility model, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. The single-photon and double-photon interference device is characterized by comprising an associated photon source module, a single-photon and double-photon conversion module, a photon interference module and a photon detection module which are arranged along the propagation direction of an optical path;

the photon detection module is used for receiving the related photons from the photon interference module and performing coincidence measurement counting.

2. The single-photon and double-photon interference device according to claim 1, wherein the associated photon source module comprises a laser, a first modulation unit, a first lens, a nonlinear crystal, a second lens and a second polarization beam splitter, which are arranged in sequence along the propagation direction of the optical path;

the laser is used for pumping a light beam to provide an initial light beam;

3. The single-photon and two-photon interference device according to claim 2, wherein the first quarter-wave plate and the first half-wave plate are combined into a wave plate group, and can modulate the pump light to any phase;

4. The single-photon and two-photon interference device according to claim 2, wherein the focal lengths of the first lens and the second lens are the same, and the first lens and the second lens form a 4f system, and the nonlinear crystal is located at the position where the focal points of the two lenses coincide.

5. The single-photon and double-photon interference device according to claim 2, wherein both end faces of the nonlinear crystal are coated with antireflection films for enhancing the transmittance of light beams.

6. The single-photon and double-photon interference device according to claim 2, wherein a first optical filter is disposed on a side of the second polarization beam splitter away from the second lens, a second optical filter is disposed on a side of the second polarization beam splitter adjacent to the first optical filter, a light path direction of the second optical filter is perpendicular to a light path direction of the first optical filter, and the first optical filter and the second optical filter are configured to filter non-single photon signals in the spatial light beam to complete a filtering function on optical frequencies, so as to improve a signal-to-noise ratio.

7. The single-photon and dual-photon interference device according to claim 1, wherein the single-photon and dual-photon conversion module comprises a second modulation unit, a third polarization beam splitter, and a fourth half-wave plate;

8. The single-photon and two-photon interference device of claim 1, wherein the photonic interference module comprises a fourth polarizing beam splitter, a fourth quarter wave plate, a first mirror, a fifth quarter wave plate, a second mirror, a fifth half wave plate, a fifth polarizing beam splitter;

9. The single-photon and double-photon interference device according to claim 8, wherein a third optical filter and a fourth optical filter are respectively disposed at two exit ends of the fifth polarization beam splitter, and the third optical filter and the fourth optical filter are bandpass optical filters for filtering non-single photon signals in the spatial light beam, so as to complete a filtering function of optical frequency, thereby improving a signal-to-noise ratio of the test system.

10. The single-photon and dual-photon interference device according to claim 1, wherein the photon detection module comprises a first fiber collimator, a first optical fiber, a first single-photon detector, a second fiber collimator, a second optical fiber, a second single-photon detector, and a coincidence counter;

the coincidence counter is used for coincidence counting.