CN111427217A

CN111427217A - Light source module and device for multiple quantum optical experiments

Info

Publication number: CN111427217A
Application number: CN202010299281.0A
Authority: CN
Inventors: 周志远; 李银海; 张万斌; 史保森
Original assignee: Qingdao Quantum Application Technology Co ltd
Current assignee: Hefei Hengyuan Quantum Technology Co ltd; Qingdao Quantum Application Technology Co ltd
Priority date: 2020-04-16
Filing date: 2020-04-16
Publication date: 2020-07-17
Anticipated expiration: 2040-04-16
Also published as: CN111427217B

Abstract

The invention relates to the technical field of laser technology, nonlinear optical physics and atomic physics, in particular to a light source module and a device for various quantum optical experiments. The invention has the advantages that: all optical devices in the light source module are collinear, and optical fiber alignment and coupling operation are facilitated. The wavelength used by the device belongs to a communication waveband and is suitable for long-distance transmission.

Description

Light source module and device for multiple quantum optical experiments

Technical Field

The invention relates to the technical field of laser technology, nonlinear photophysics and atomic physics, in particular to a light source module and a device for various quantum optical experiments.

Background

Quantum photon sources are essential for almost all types of research and applications in quantum information science and technology. The preparation of high-quality quantum photon sources is always the goal of the scientific and technical pursuit of quantum information. A common method of preparing quantum light sources is spontaneous parametric down-conversion or spontaneous four-wave mixing in a nonlinear process. Since the first observed spontaneous parameter down-conversion in d.c. burnham in 1970, spontaneous parameter down-conversion has been widely used to generate various entangled photon sources.

The prior art has two types:

1. the sagnac interferometer is used for generating a polarization entangled photon source, and the structure of the interferometer is adjusted to be complex, so that the light collimation and alignment process is complicated, and a plurality of optical devices are needed, so that the experimental operation process is complex.

2. A BBO crystal with an orthogonal optical axis is used for generating an offset entangled photon source, and because the effective nonlinear coefficient of the BBO crystal is low, the imaging brightness is low, and a pumping beam with higher power needs to be prepared during experiments.

Disclosure of Invention

In order to establish a multipurpose entanglement light source with simple structure and high quality, the invention provides a light source module and a device for various quantum optical experiments. The invention adopts the following technical scheme:

a light source module for multiple quantum optical experiments comprises a pump laser, a first polarization modulation component, a first lens, a first crystal, a second lens, a KTP crystal, a first optical filter, a first single-mode fiber and dense wavelength division multiplexing, wherein the pump laser, the first polarization modulation component, the first lens, the first crystal, the second lens, the KTP crystal, the first optical filter, the first single-mode fiber and the dense wavelength division multiplexing are arranged according to an optical path.

Specifically, the first crystal is any one of a PPKTP crystal, a BBO crystal, a PP L N crystal and an aluminum nitride crystal.

Specifically, the length of the PPKTP crystal is 2mm, the polarization period is 46.2 μm, and the condition of coating along the light transmission direction is as follows: the front end face is S1 AR @775nm and AR @1550nm, and the rear end face is S2 AR @775nm and AR @1550 nm.

Specifically, the length of the KTP crystal is 1mm, and the coating condition along the light transmission direction is as follows: the front end face is S1 AR @775nm and AR @1550nm, and the rear end face is S2 AR @775nm and AR @1550 nm.

The device comprises the light source module for various quantum optical experiments, and further comprises an entanglement generation and projection module arranged behind the light source module, wherein the entanglement generation and projection module comprises one or more of an HOM interference unit, a time energy entanglement unit and a polarization entanglement unit.

Specifically speaking, HOM interference unit is including the second single mode fiber, second polarization modulation subassembly, the first polarization beam splitter that set gradually, first polarization beam splitter divides into two the tunnel with the light beam, and one way is through third polarization modulation subassembly, third single mode fiber in proper order, and another way is through fourth polarization modulation subassembly, fourth single mode fiber in proper order, photon in third single mode fiber and the fourth single mode fiber is inputed into first optical fiber beam splitter, second single mode fiber obtains the light beam in the intensive wavelength division multiplexing in the light source module output terminal department in setting for the passageway.

Specifically, the time energy entanglement unit comprises a fifth single-mode fiber, a fifth polarization modulation component and a second polarization beam splitter which are sequentially arranged, the second polarization beam splitter divides the light beam into two paths, one path of the light beam is output from the first interferometer after passing through the sixth single-mode fiber, the other path of the light beam is output from the second interferometer after passing through the seventh single-mode fiber, and the fifth single-mode fiber obtains the light beam in the set channel in dense wavelength division multiplexing at the output end of the light source module.

Specifically, the polarization entanglement unit comprises a signal optical path and an idler optical path which are respectively used for transmitting photons of a signal channel and photons of an idler channel in dense wavelength division multiplexing at the output end of the light source module, and the signal optical path comprises a first optical fiber polarization controller, an eighth single-mode optical fiber, an arbitrary phase retarder, a sixth polarization modulation component and a third polarization beam splitter which are sequentially arranged; the idler optical path comprises a second optical fiber polarization controller, a ninth single-mode optical fiber, a seventh polarization modulation component and a fourth polarization beam splitter which are arranged in sequence.

Specifically, the arbitrary phase retarder includes a sixth quarter-wave plate, a sixth half-wave plate, and a seventh quarter-wave plate, which are arranged in this order.

Specifically, the device further comprises a measurement module, wherein the measurement module comprises a first detector and a second detector which are used for detecting photons transmitted by corresponding channels, and a first coincidence counter which is used for receiving signals of the first detector and the second detector.

The invention has the advantages that:

(1) all optical devices in the light source module are collinear, and optical fiber alignment and coupling operation are facilitated. The wavelength used by the device belongs to a communication waveband and is suitable for long-distance transmission.

(2) The PPKTP crystal has high nonlinear coefficient, so that the imaging brightness is high.

(3) The light source module of the invention uses wavelength to distinguish different entangled photon pairs, and the channels in the dense wavelength division multiplexing are divided according to wavelength. Photons from the pump laser are converted under the II-type spontaneous parameters in the PPKTP crystal, namely, the photons are split into a photon pair in the crystal, the original photons are called as 'pump photons', and two photons in the photon pair are respectively and randomly called as 'signal photons' and 'idler photons'. According to the law of conservation of energy and the law of conservation of momentum, the total energy and the total momentum of the photon pair are equal to the energy and the momentum of the pump photon. However, the photons have frequency difference, the photon source uses dense wavelength division multiplexing to separate the photons according to the wavelength to form different output channels, each output channel has H photons and V photons, and different experiments are carried out according to different channels.

(4) The device can be used for any one or any several of an HOM interference unit, a time energy entanglement unit and a polarization entanglement unit to work simultaneously.

Drawings

FIG. 1 is an experimental setup of a high quality generic photon source device of the present invention for use in various quantum optical experiments;

FIG. 2 is a block diagram of a light source module according to the present invention;

fig. 3 is a block diagram of a first variant of the entanglement generation and projection module according to the invention, namely the HOM interference module.

FIG. 4 is a block diagram of a second version of the entanglement generation and projection module of the present invention, a two-photon Franson interference module;

FIG. 5 is a block diagram of an experimental block for a third version of the entanglement generation and projection module of the present invention, namely polarization entanglement generation and characterization;

FIG. 6 is a block diagram of a test module provided in accordance with an embodiment of the present invention;

FIG. 7 is an experimental result of different types of photon sources provided by an embodiment of the present invention, wherein FIG. 7(a) is a result measured by the apparatus when the entanglement generation and projection module adopts a first scheme, FIG. 7(b) is a result measured by the apparatus when the entanglement generation and projection module adopts a second scheme, FIG. 7(c) is a visibility parameter of an associated channel when the entanglement generation and projection module adopts a third scheme, and FIG. 7(d) is a curved interference visibility value corresponding to two channels when the entanglement generation and projection module adopts a third scheme;

FIG. 8 is a reconstructed density matrix of polarization-entangled photon pairs for the front facet S1 and the back facet I1 provided by an embodiment of the present invention.

Fig. 9 shows an analog spectrum of photon pairs emitted from the light source module of the present invention and a transmission spectrum of 100GHz dense optical wave multiplexing.

The notations in the figures have the following meanings:

1-light source module 11-pump laser

12-the first polarization modulation component 121-the first one-half wave plate 122-the first one-quarter wave plate

13-first lens 14-PPKTP crystal 15-second lens 16-KTP crystal

17-first optical filter 18-first single mode fiber

19-DWDM 191-center channel C34192-Signal channel 193-Idle channel

2-entanglement Generation and projection Module

211-second single mode fiber 212-second polarization modulation assembly

2121-second quarter-wave plate 2122-second half-wave plate

213-first polarization beam splitter 214-third polarization modulation assembly

2141-third quarter waveplate 2142-third half waveplate

215-third single mode fiber 216-fourth polarization modulation assembly

2161-fourth quarter wave plate 2162-fourth half wave plate

217-fourth single mode fiber 218-first fiber splitter

221-fifth single mode fiber 222-fifth polarization modulation assembly

2221-fifth quarter wave plate 2222-fifth half wave plate

223-second polarization beam splitter

224-sixth single-mode fiber 225-first unbalanced michelson interferometer

226-seventh single-mode fiber 227-second unbalanced michelson interferometer

231-first fiber polarization controller 232-second fiber polarization controller

233-eighth single mode fiber 234-ninth single mode fiber

235-arbitrary phase retarder 2351-sixth quarter wave plate

2352-sixth half wave plate 2353-seventh quarter wave plate

236-sixth polarization modulation assembly

2361-eighth quarter wave plate 2362-seventh half wave plate

237-seventh polarization modulating component

2371 ninth quarter wave plate 2372 eighth half wave plate

238-third polarization beam splitter 239-fourth polarization beam splitter

31-first detector 32-second detector 33-first coincidence counter

Detailed Description

Example 1

As shown in fig. 2, a light source module for multiple quantum optical experiments includes a pump laser 11, a first polarization modulation component 12, a first lens 13, a PPKTP crystal 1614, a second lens 15, a KTP crystal 16, a first optical filter 17, a first single-mode fiber 18, and dense wavelength division multiplexing 19, which are sequentially disposed.

The pump laser 11 is used for exciting pump laser, the wavelength is 775.06nm, and the line width is less than 1 MHz.

The first polarization modulation component 12 comprises a first half-wave plate 121 and a first quarter-wave plate 122, the center wavelengths of which are 775nm, and the polarization state of the pump light is controlled by adjusting the fast axis directions of the first half-wave plate 121 and the first quarter-wave plate 122, so that conditions are provided for the conversion under the type II spontaneous parameter in the PPKTP crystal 1614.

The first lens 13 is used for focusing pump light, the pump light can be focused in the PPKTP crystal 1614, the beam waist size is proper, and the coating parameter of the first lens 13 is AR @775 nm.

The length of the PPKTP crystal 1614 is 2mm, the polarization period is 46.2 mu m, and the film coating condition along the light transmission direction is as follows: the front end face S1 AR @775nm, the AR @1550nm, the rear end face S2 AR @775nm and the AR @1550nm, the pumping light can generate a II-type spontaneous parameter down-conversion process inside the PPKTP crystal 1614, the polarization of the generated H photons and the polarization of the generated V photons are orthogonal, and the generated photon pair is approximately degenerate in frequency.

The second lens 15 is used for collimating the H photons and the V photons, so that the H photons and the V photons can be efficiently coupled into the first single-mode fiber 18; and the coating parameter of the second lens 1515 is AR @1550 nm.

The length of the KTP crystal 16 is 1mm, and the film coating condition along the light transmission direction is as follows: the optical axis of the front end faces S1 AR @775nm and AR @1550nm and the optical axis of the rear end faces S2 AR @775nm and AR @1550nm are in a perpendicular state with respect to the optical axis of the PPKTP crystal 1614, and the function of the front end faces is to compensate time delay between H photons and V photons.

The first filter 17 filters the original pump beam, so that H photons and V photons can pass through smoothly.

The first single mode fiber 18 transmits the coupled-in H and V photons to the dense wavelength division multiplexing 19.

The dwdm 19 has 32 channels with a frequency spacing of 100GHz, a transmission width of 66GHz per channel, and a channel isolation width of 34 GHz. In this embodiment, the selected channel corresponds to a wavelength of 1550.12 nm.

As shown in table 1:

item	Dense wavelength division multiplexing 19 channels	Wavelength (nm)
			Central channel	C34	1550.12
Signal channel 1-Idle channel 1	C33–C35	1550.92-1549.32
			Signal channel 2-idler channel 2	C32–C36	1551.72–1548.52
Signal channel 3-idler channel 3	C31–C37	1552.52–1547.72
			Signal channel 4-idler channel 4	C30–C38	1553.33–1546.92
Signal channel 5-idler channel 5	C29–C39	1554.13–1546.12
			Signal channel 6-idler channel 6	C28–C40	1554.94–1545.32

The corresponding wavelengths of the correlation signal and idler channel 193 photons are defined in table 1. The pump wavelength was 775.06nm, and the center wavelengths of the signal channel 192 photons and idler channel 193 photons were centered in channel C34 (1550.12 nm).

Under the action of the light source module 1, H photons and V photons at the selected channel wavelength are output in an orthogonal state, and the analog spectrum of the emitted photon pair provided by the light source module 1 and the transmission spectrum of the 100GHz dense optical wave multiplexing are shown in fig. 9.

Example 2

As shown in fig. 1, an apparatus including a light source module for various quantum optical experiments according to an embodiment includes an entanglement generating and projecting module 2 disposed behind a light source module 1, and the entanglement generating and projecting module 2 includes one or more of an HOM interference unit, a temporal energy entanglement unit, and a polarization entanglement unit. A measurement module 3 for detecting the entanglement generation and projection module 2 results is also included.

The entanglement generation and projection module 2 and the measurement module 3 are described in detail below, respectively.

Measuring module

As shown in fig. 6, the measurement module includes a first superconductor nanowire single photon detector and a second superconductor nanowire single photon detector 32 for detecting photons transmitted by corresponding channels, where the first detector 31 and the second detector 32 are both superconductor nanowire single photon detectors, and further includes a first coincidence counter 33 for receiving signals of the first and second superconductor nanowire single photon detectors 32. The first coincidence counter 33 is of the type Timeharp 260Pico and has a coincidence window of 0.8 ns, which measures the coincidence of the electrical signals transmitted by the first detector 31 and the second detector 32.

HOM interference unit

As shown in fig. 3, the HOM interference unit includes a second single-mode fiber 211, a second polarization modulation component 212, and a first polarization beam splitter 213 that are sequentially arranged, where the first polarization beam splitter 213 splits a light beam into two paths, one path of the light beam sequentially passes through a third polarization modulation component 214 and a third single-mode fiber 215, and the other path of the light beam sequentially passes through a fourth polarization modulation component 216 and a fourth single-mode fiber 217, photons in the third single-mode fiber 215 and the fourth single-mode fiber 217 are input into the first fiber beam splitter 218, and the second single-mode fiber 211 obtains the light beam in a set channel in the dense wavelength division multiplexing 19 at the output end of the light source module 1.

The second single mode fiber 211 receives signals in the C34191 central channel of the dwdm 19, which are H and V photons with a wavelength of 1550.12nm, and the second single mode fiber 211 transmits the polarization orthogonal H and V photons to the second polarization modulation component 212.

The second polarization modulation assembly 212 includes a second quarter wave plate 2121 (with a center wavelength of @1550nm) and a second half wave plate 2122 (with a center wavelength of @1550nm) in order to compensate for the polarization of the photons, the second quarter wave plate 2121 and the second half wave plate 2122 are sequentially replaceable. To align the polarization state of the photons with the polarization state at the time of generation, the polarization states of the H and V photons are controlled by adjusting the fast axis directions of the second quarter-wave plate 2121 and the second half-wave plate 2122.

The first polarization beam splitter 213 is used for separating H photons and V photons with orthogonal polarization, the H photons are transmitted from the horizontal direction, the V photons are refracted at 90 degrees and then emitted out of the surface of the first polarization beam splitter 213, the coating wave parameter of the first polarization beam splitter 213 is AR @1550nm, and the incident angle is 0 degree.

The third polarization modulation element 214 includes a third quarter waveplate 2141 (centered at @1550nm) and a third half waveplate 2142 (centered at @1550 nm). By adjusting the fast axis direction of the third quarter waveplate 2141 and the third half waveplate 2142, the polarization state of the H photons can be controlled.

The third single-mode fiber 215 is configured on a one-dimensional translation stage, and the direction of the one-dimensional translation stage is a light path direction, and the one-dimensional translation stage is used for transmitting the H photons with the polarization direction being a horizontal direction and changing a light path difference between the H photons and the V photons.

The fourth polarization modulation component 216 includes a fourth quarter wave plate 2161 (centered at @1550nm) and a fourth half wave plate 2162 (centered at @1550 nm). By adjusting the fast axis direction of the fourth quarter wave plate 2161 and the fourth half wave plate 2162, the polarization state of the V photons can be adjusted.

The fourth single-mode fiber 217 is configured to transmit the V photons with a polarization direction in a vertical direction.

The first fiber splitter 218 is a 2 × 2 device with a working wavelength of 1550nm, which generates HOM interference of H and V photons with orthogonal polarization in the first fiber splitter 218 and outputs the photons to the test module, and two output ends of the first fiber splitter 218 are respectively connected to the first superconductor nanowire single photon detector and the second detector 32.

Based on the general photon source device formed by the light source module 1, the HOM interference unit, and the measurement module, the experimental result is shown in fig. 7(a), the delay time is taken as an independent variable, the coincidence count is a function image of a vertical axis, when the time delay of the H photon and the V photon is zero, the coincidence count number is close to zero, and when the time delay of the H photon and the V photon is increased, the coincidence count number is increased. Visibility of interference (V ═ C)_max-C_min)/C_max) Is (99.50 +/-0.12)%, wherein C_maxIs the maximum coincidence count, C_minThe half-width of the region is 9.46ps, and is consistent with the transmission bandwidth (66GHz) of the dense optical wave multiplexing, in this embodiment, the power of the pump laser 11 is 256mW, the wavelength is 775.08nm, and the single-pass counts of the two detectors are 2.1 × 10⁴cps and 1.7 × 10⁴And cps. After interfering with zero delay in the first fiber splitter 218, the photons are in a photon count and path entangled state

Time energy entanglement unit

As shown in fig. 4, the time energy entanglement unit includes a fifth single-mode fiber 221, a fifth polarization modulation assembly 222, and a second polarization beam splitter 223, which are sequentially arranged, where the second polarization beam splitter 223 splits a light beam into two paths, one path of the sixth single-mode fiber 224 is output from the first unbalanced michelson interferometer 225, and the other path of the sixth single-mode fiber passes through a seventh single-mode fiber 226 and is output from the second unbalanced michelson interferometer 227.

The fifth single mode fiber 221 receives signals in the C34191 central channel of the dwdm 19, which are H and V photons with a wavelength of 1550.12nm, and the second single mode fiber 211 transmits the polarization orthogonal H and V photons to the fifth polarization modulation component 222.

The fifth single mode fiber 221 transmits H and V photons with orthogonal polarizations into a fifth polarization modulation component 222.

The fifth polarization modulation element 222 includes a fifth quarter-wave plate 2221 (with a center wavelength of @1550nm) and a fifth half-wave plate 2222 (with a center wavelength of @1550 nm). By adjusting the fast axis directions of the fifth quarter wave plate 2221 and the fifth half wave plate 2222, the polarization states of H photons and V photons can be controlled.

The sixth single-mode fiber 224 is used for transmitting the H photons with the polarization direction being the horizontal direction.

The seventh single-mode fiber 226 is used for transmitting the V photons with the polarization direction being the vertical direction.

The second polarization beam splitter 223 is used for separating H photons and V photons with orthogonal polarization, the H photons are transmitted out from the horizontal direction, and the V photons are refracted and emitted at 90 degrees. The surface coating of the second polarization beam splitter 223 is AR @1550nm, and the incident angle is 0 degree.

The first unbalanced michelson interferometer 225 is comprised of a 50: 50 and two faraday rotators, the phase shift phi being varied by varying the temperature of the first unbalanced michelson interferometer 225_sThe optical fiber beam splitter equally divides the H photons into two paths which are transmitted along a short path S and a long path L, and the Faraday rotation mirror returns the photons of the corresponding path to be output to the corresponding superconductor nanowire single photon detector in the test module through the optical fiber beam splitter.

The second unbalanced michelson interferometer 227 consists of a 50: 50 optical fiber beam splitter and two faraday rotators, the temperature of the second unbalanced michelson interferometer 227 is kept unchanged, the optical fiber beam splitter equally divides the V photons into two paths which are transmitted along a short path S and a long path L, and the faraday rotators return the photons of the corresponding paths and output the photons to corresponding superconductor nanowire single photon detectors in the test module through the optical fiber beam splitter.

Based on the general photon source device formed by the light source module 1, the time energy entanglement unit and the measurement module, the experimental result is shown in fig. 7(b), and the phase shift phi of the second non-equilibrium michelson interferometer 227 is used_sThe time difference between the two arms of the first unbalanced michelson interferometer 225 and the second unbalanced michelson interferometer 227, which are independent variables and correspond to the image of the function with the count as the vertical axis, is 1.6ns, and the function is to perform two-photon Franson interference, wherein the photons cannot be distinguished when passing through a long path and a short path. Can be expressed by the expression:

l denotes long path and S denotes short path we are given the formula V ═ C_Max-C_Min)/(C_Max+C_Min) To calculate the visibility of the interference, where C_MaxAnd C_MinRepresenting the maximum and minimum coincidence count numbers, respectively. When phi is₁When equal to 0, the visibility of interference is (99.17. + -. 0.35)%, when φ₁Is equal to

The visibility of the interference was (99.59. + -. 0.24)%, indicating that the two photons had high entanglement quality and the single counts of the two detectors were 7.3 × 10, respectively³cps and 6.7 × 10³cps。

Polarization entanglement unit

As shown in fig. 5, the polarization entanglement unit includes a signal optical path and an idler optical path for transmitting photons of a signal channel 192 and photons of an idler channel 193 in the dense wavelength division multiplexing 19 at the output end of the light source module 1, respectively, where the signal optical path includes a first fiber polarization controller 231, an eighth single-mode fiber 233, an arbitrary phase retarder 235, a sixth polarization modulation component 236, and a third polarization beam splitter 238, which are sequentially arranged; the idler optical path includes a second fiber polarization controller 232, a ninth single-mode fiber 234, a seventh polarization modulation component 237, and a fourth polarization beam splitter 239, which are sequentially arranged. The components are described in detail as follows:

the signal channel 192 may transmit photons of the signal channel 192 in the dense wavelength division multiplex 19 of the corresponding wavelength; the idler channel 193 can transmit photons of the idler channel 193 in the dense wavelength division multiplexing 19 at a corresponding wavelength. The corresponding wavelengths of the correlation signal and idler channel 193 photons can be found in Table 1.

A first optical fiber polarization controller 231, the input end of which inputs photons of a signal channel in the dense wavelength division multiplexing 19;

the input end of the second fiber polarization controller 232 inputs the photons of the idler channel in the dense wavelength division multiplexing 19;

the eighth single-mode fiber 233 is used for transmitting photons of the signal channel 192 with a horizontal polarization direction.

The ninth single-mode fiber 234 is used to transmit the photons of the idler channel 193 with the polarization direction being vertical.

The arbitrary phase retarder 235 includes a sixth quarter wave plate 2351, a sixth half wave plate 2352 and a seventh quarter wave plate 2353, which are sequentially arranged, and the change of the relative phase θ of the stacked state is realized by adjusting the fast axis directions of the sixth quarter wave plate 2351, the sixth half wave plate 2352 and the seventh quarter wave plate 2353.

The sixth polarization modulation element 236 includes an eighth quarter wave plate 2361 and a seventh half wave plate 2362 that are optically disposed. By adjusting the fast axis direction of both, it is possible to adjust the polarization state of the photons of control signal channel 192.

The seventh polarization modulation element 237 includes a ninth quarter waveplate 2371 and an eighth half waveplate 2372 that are optically disposed. By adjusting the fast axis direction of both, it is possible to adjust the polarization state of the photons controlling the idler channel 193.

The eighth polarization modulation component comprises a ninth quarter wave plate and an eighth half wave plate, and the polarization state of the photons of the control signal channel 192 can be adjusted by adjusting the fast axis direction of the ninth quarter wave plate and the eighth half wave plate.

The third polarization beam splitter 238 is combined with the eighth polarization modulation component to perform projection measurement on the photons of the signal channel 192 and output the photons to the detector corresponding to the test module.

The fourth polarization beam splitter 239 is combined with the seventh polarization modulation component 237 to perform projection measurement on the photons of the idler channel 193, and output the photons to the detector corresponding to the test module.

Based on the general photon source device that light source module 1, polarization entanglement unit, measurement module formed, the photon polarization state is:

where H denotes horizontal polarization, V denotes vertical polarization, λ_sDenotes the wavelength, λ, of the H photon_iTaking channels 33 and 35 as an example, we plot an image with the phase of signal channel 192 as the horizontal axis and the coincidence count as the vertical axis, as shown in FIG. 7(C), the visibility of all pairs of correlated channels is higher than 97%. We examined the Bell inequality violation of channel pairs C33 and C35, and measured S parameters are 2.764 + -0.0139 against 55 standard deviations, as shown in FIG. 7(d), the interference visibility values of the two curves are (99.20 + -0.11)% and (98.80 + -0.14)%, respectively, and the single-path counts of the two detectors are 3 × 10%, respectively⁴cps and 1.6 × 10⁴And cps. To test the entanglement quality of different entanglement channel pairs, we measured the interference visibility at 45 degrees basis, we reconstructed the corresponding density matrix using quantum state tomography to determine the quantum state, the imaginary part values of the reconstructed density matrix are all zero, and the real part of the density matrix is shown in fig. 8. HH denotes horizontally polarized photon pairs, HV denotes one of the photon pairs is horizontally polarized and one is vertically polarized. VH is the vertical polarization of the photon pair, one horizontal polarization, and VV is the vertical polarization of both photon pairs. The fidelity of the reconstructed density is 0.9739 + -0.0018, and the experimental deviation is mainly caused by the inaccurate rotation angle of the wave plate.

The invention is not to be considered as limited to the specific embodiments shown and described, but is to be understood to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Claims

1. The light source module for various quantum optical experiments is characterized by comprising a pump laser (11), a first polarization modulation component (12), a first lens (13), a first crystal, a second lens (15), a KTP crystal (16), a first optical filter (17), a first single-mode optical fiber (18) and dense wavelength division multiplexing (19) which are arranged according to an optical path.

2. The light source module of claim 1, wherein the first crystal is any one of a PPKTP crystal (1614), a BBO crystal, a PP L N crystal, and an aluminum nitride crystal.

3. The light source module of claim 2, wherein the PPKTP crystal (1614) has a length of 2mm, a polarization period of 46.2 μm, and is coated in the light-transmitting direction: the front end face is S1 AR @775nm and AR @1550nm, and the rear end face is S2 AR @775nm and AR @1550 nm.

4. The light source module for various quantum optical experiments as claimed in claim 1, wherein the KTP crystal (16) has a length of 1mm, and the coating condition along the light passing direction is as follows: the front end face is S1 AR @775nm and AR @1550nm, and the rear end face is S2 AR @775nm and AR @1550 nm.

5. An apparatus comprising a light source module for various quantum optical experiments according to any of claims 1-4, further comprising an entanglement generation and projection module (2) arranged behind the light source module (1), the entanglement generation and projection module (2) comprising one or more of an HOM interference unit, a temporal energy entanglement unit, a polarization entanglement unit.

6. The device according to claim 5, wherein the HOM interference unit comprises a second single mode fiber (211), a second polarization modulation component (212), and a first polarization beam splitter (213) arranged in sequence, the first polarization beam splitter (213) splits the light beam into two paths, one path passes through a third polarization modulation component (213) and a third single mode fiber (215) in sequence, and the other path passes through a fourth polarization modulation component (216) and a fourth single mode fiber (217) in sequence, photons in the third single mode fiber (215) and the fourth single mode fiber (217) are input into the first fiber beam splitter (218), and the second single mode fiber (211) obtains the light beam in a set channel in the dense wavelength division multiplexing (19) at the output end of the light source module (1).

7. The device according to claim 5, characterized in that the time energy entanglement unit comprises a fifth single mode fiber (221), a fifth polarization modulation component (222), and a second polarization beam splitter (223) which are arranged in sequence, the second polarization beam splitter (223) splits the light beam into two paths, one path is output from the first interferometer after the sixth single mode fiber (224), the other path is output from the second interferometer through the seventh single mode fiber, and the fifth single mode fiber (221) obtains the light beam in the set channel in the dense wavelength division multiplexing (19) at the output end of the light source module (1).

8. The apparatus according to claim 5, wherein the polarization entanglement unit comprises a signal optical path and an idler optical path for transmitting photons of a signal channel (192) and photons of an idler channel (193) in dense wavelength division multiplexing (19) at the output of the light source module (1), respectively, the signal optical path comprising a first fiber polarization controller (231), an eighth single mode fiber (233), an arbitrary phase retarder (235), a sixth polarization modulation component (236), a third polarization beam splitter (238) arranged in sequence; the idler optical path comprises a second optical fiber polarization controller (232), a ninth single-mode optical fiber (234), a seventh polarization modulation component (237) and a fourth polarization beam splitter (239) which are arranged in sequence.

9. The apparatus of claim 5, wherein the arbitrary phase retarder (235) comprises a sixth quarter waveplate (2351), a sixth half waveplate (2352), and a seventh quarter waveplate (2353) arranged in sequence.

10. The apparatus according to claim 5, further comprising a measurement module (3), the measurement module (3) comprising a first detector (31) and a second detector (32) for detecting photons delivered by the corresponding channel, further comprising a first coincidence counter (33) for receiving signals of the first detector (31) and the second detector (32).