CN114740669A - Entangled photon source - Google Patents
Entangled photon source Download PDFInfo
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- CN114740669A CN114740669A CN202110022151.7A CN202110022151A CN114740669A CN 114740669 A CN114740669 A CN 114740669A CN 202110022151 A CN202110022151 A CN 202110022151A CN 114740669 A CN114740669 A CN 114740669A
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/3501—Constructional details or arrangements of non-linear optical devices, e.g. shape of non-linear crystals
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
- G02B27/283—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising used for beam splitting or combining
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/355—Non-linear optics characterised by the materials used
- G02F1/3551—Crystals
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- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
The invention discloses an entangled photon source, wherein collinear BBO crystals are used for replacing PPKTP crystals to generate collinear signal light and idler frequency light, a more compact optical structure can be allowed, miniaturization of the entangled photon source is facilitated, meanwhile, the overall optical stability is improved, and the system cost and the optical path modulation difficulty are reduced.
Description
Technical Field
The invention relates to the field of quantum information science, in particular to an entangled photon source.
Background
Quantum entanglement is one of the most important subjects in quantum information science, and there are many experimental methods for its preparation, the most common of which is parametric down-conversion using nonlinear crystals. For example, a typical entangled photon generation scheme is disclosed in chinese patent application No. 201210114481.X, as shown in fig. 1, in the generation scheme, a pump light with a wavelength of 518nm passes through an optical isolator 111, a polarization controller 112, a focusing lens 113, a dichroic mirror 114, enters a polarization beam splitter 115, a horizontal polarization component generated by the polarization beam splitter 115 is transmitted through a first mirror 116 to pump a PPKTP crystal 117, a vertical polarization component generated by the polarization beam splitter 115 passes through a half-wave plate 118, the polarization direction thereof becomes horizontal, the polarization direction thereof passes through a second mirror 119 to pump the PPKTP crystal 117, a nonlinear process is performed to generate pairs of photons with wavelengths of 780nm and 1550nm in clockwise and counterclockwise directions, respectively, and then the pairs of photons are returned to the polarization beam splitter 115, and finally photons with a wavelength of 780nm exit from the polarization beam splitter 115, photons with a wavelength of 1550nm exit from the dichroic mirror 114, the two photons are in an entangled relationship, thereby producing an entangled photon pair.
However, in the prior art, the entanglement source generated by the parametric down-conversion process based on the PPKTP crystal (as shown in fig. 1) or the PPLN waveguide is expensive, and the periodic polarization requirement based on the PPKTP crystal or the PPLN waveguide has a certain device length limitation, thereby causing a certain difficulty in optical circuit debugging and system integration.
Disclosure of Invention
To solve the problem, the invention provides an entangled photon source for generating entangled photons, which comprises a pumping light source, a dichroic mirror, a polarization beam splitting unit and a Sagnac loop; wherein the content of the first and second substances,
the pump light source is used for generating pump light;
the dichroic mirror is arranged to receive and transmit the pump light and to receive and reflect the entangled photons;
the polarization beam splitting unit is configured to split the pump light into a first pump light component and a second pump light component having polarization states perpendicular to each other, and to cause the first pump light component and the second pump light component to simultaneously enter the sagnac loop in different directions;
the sagnac loop is configured to: enabling the first pump light component to generate 90-degree polarization state inversion, enabling the first pump light component to enter a collinear BBO crystal to generate a first pair of signal light and idler frequency light, and enabling the first pair of signal light and idler frequency light to return to the polarization beam splitting unit at a first time; enabling the second pump light component to enter the collinear BBO crystal to generate a second pair of signal light and idler frequency light, and enabling the second pair of signal light and idler frequency light to return to the polarization beam splitting unit at the first time after the polarization state of the second pair of signal light and idler frequency light is reversed by 90 degrees;
the signal and idler of the first and second pairs of signal and idler are separated at the polarization beam splitting unit.
Further, the entangled-photon source further comprises a first polarization control unit disposed between the pump light source and the dichroic mirror. The first polarization control unit may be a wave plate or a polarization controller, or may be implemented by means of optical axis rotation alignment.
Further, the sagnac loop includes a first reflection unit, a second polarization control unit, and the collinear BBO crystal; the first reflection unit is configured to reflect the first pump light component into the collinear BBO crystal and reflect the second pair of signal light and idler light back to the polarization beam splitting unit; the second reflection unit is configured to reflect the second pump light component into the collinear BBO crystal and reflect the first pair of signal light and idler light back to the polarization beam splitting unit; the second polarization control unit is configured to implement the 90-degree polarization state flip.
Optionally, the second polarization control unit is a wave plate or a polarization controller, or is implemented by means of optical axis rotation alignment.
Optionally, the first reflecting unit is a plane or concave mirror, and/or the second reflecting unit is a plane or concave mirror.
Optionally, the pump light is continuous light or pulsed light.
Further, the entangled-photon source may further comprise a focusing unit for focusing the pump light before it enters the collinear BBO crystal. Wherein the focusing unit is a focusing lens; and/or the focusing unit is arranged in front of the dichroic mirror.
Further, the entangled-photon source may further comprise a phase modulator for modulating the phase of the pump light.
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 illustrates a prior art PPKTP crystal-based entangled-photon source;
FIG. 2 illustrates one example of an entangled-photon source according to the present invention;
FIG. 3 illustrates another example of an entangled-photon source according to the present invention.
Detailed Description
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples are provided by way of illustration in order to fully convey the spirit of the invention to those skilled in the art to which the invention pertains. Accordingly, the present invention is not limited to the embodiments disclosed herein.
In the invention, an entangled photon source structure realized based on a barium metaborate (BBO) crystal is provided, wherein a two-photon polarization entanglement source is prepared by adopting a spontaneous parameter down-conversion process of a II-type collinear BBO crystal and a Sagnac interference ring structure and is used for generating entangled photons with a second wavelength.
Figure 2 shows an example of an entangled-photon source based on a BBO crystal according to the present invention.
As shown in fig. 2, the entangled-photon source may include a pumping light source 1, a first polarization control unit 2, a dichroic mirror 3, a polarization beam splitting unit 4, a first reflection unit 5, a second reflection unit 6, a collinear BBO crystal 7, and a second polarization control unit 8. The polarization beam splitting unit 4, the first reflecting unit 5 and the second reflecting unit 6 form a sagnac loop.
The pump light source 1 is used to generate pump light, which may be continuous light or pulsed light. Wherein the pump light has a first wavelength that is different from a second wavelength.
The first polarization control unit 2 is configured to receive the pump light generated by the pump light source 1 and adjust its polarization state, for example, so that the pump light can be equally divided into two pump light components having polarization states perpendicular to each other at the polarization beam splitting unit 4.
As an example, the first polarization control unit 2 may be a wave plate or a polarization controller, and may also be implemented by means of optical axis rotational alignment.
A dichroic mirror 3 is arranged after the first polarization control unit 2 and is arranged to allow transmission of pump light having a first wavelength and to reflect entangled photons having a second wavelength.
Therefore, the pump light adjusted in polarization state will be transmitted from the dichroic mirror 3 to reach the polarization beam splitting unit 4.
As described above, the polarization beam splitting unit 4 is configured to split the pump light into the first pump light component and the second pump light component having the same size and having the polarization states perpendicular to each other, for example, the pump light horizontal polarization component and the pump light vertical polarization component. As an example, the polarization beam splitting unit 4 may be a polarization beam splitter.
The horizontally polarized component of the pump light and the vertically polarized component of the pump light output from the two ports of the polarization beam splitting unit 4 enter the sagnac loop at the same time, and propagate in the sagnac loop in the clockwise direction and the counterclockwise direction, respectively.
As shown in fig. 2, a second polarization control unit 8 is further disposed in the sagnac loop, and is used for, for example, reversing the polarization state of the horizontal polarization component of the pump light by 90 degrees, and then reflecting the horizontal polarization component of the pump light by the first reflection unit 5 to enter the collinear BBO crystal 7, so as to generate a type-II parametric down-conversion process | V>p→|H>s|V>iA first pair of signal and idler lights with polarization directions perpendicular to each other is generated with a certain probability. The vertical polarization component of the pump light is reflected by the second reflection unit 6 to enter the collinear BBO crystal 7, and the type-II parametric down-conversion process | V occurs>p→|H>s|V>iA second pair of signal and idler lights with polarization directions perpendicular to each other is generated with a certain probability. Those skilled in the art will appreciate that at this point, the first pair of signal and idler (i.e., the first pair of entangled photons) will be identical to the second pair of signal and idler (i.e., the second pair of entangled photons).
The first pair of signal light and idler light generated clockwise is reflected by the second reflecting unit 6 to return to the polarization beam splitting unit 4; the second pair of signal light and idler light generated along the counterclockwise direction is reflected by the first reflection unit 5, and after the polarization state is reversed by 90 degrees under the action of the second polarization control unit 8, the second pair of signal light and idler light and the first pair of signal light and idler light return to the polarization beam splitting unit 4 at the same time.
At this time, the signal light of the first pair of signal light and idler light and the signal light of the second pair of signal light and idler light will be output from one port of the polarization beam splitting unit 4, for example, from the port connected to the optical detector 10 in fig. 2, and will be detected by the optical detector 10; the idler of the first pair of signal and idler and the idler of the second pair of signal and idler will be output from another port of the polarization beam splitting unit 4, e.g. the port connected to the dichroic mirror 3 in fig. 2 and output towards the photo detector 9 by means of the dichroic mirror 3, and will be detected by the photo detector 9. Those skilled in the art will appreciate that the first and second pairs of entangled photons will be identical and will not be distinguishable by the photodetector.
As an example, the first and second reflecting units may be plane or concave mirrors.
As an example, the second polarization control unit 8 may also be a wave plate or a polarization controller, which may also be realized by means of optical axis rotational alignment.
In a preferred example, the entangled-photon source may further comprise a focusing unit for focusing the pump light before it enters the collinear BBO crystal 7, thereby increasing the pump light power density incident on the collinear BBO crystal 7. For example, in the example of fig. 3, the focusing unit 11 is disposed between the first polarization control unit 2 and the dichroic mirror 3.
As an example, the focusing unit 11 may be a focusing lens.
Further, the entangled-photon source may further include a phase modulator for modulating a phase of the pump light.
Based on the above description, in the entangled photon source provided by the present invention, the collinear BBO crystal is used to replace the PPKTP crystal to generate the collinear signal light and the collinear idler light, which allows a more compact optical structure, facilitates miniaturization of the entangled photon source, improves the overall optical stability, and reduces the system cost and the difficulty of optical path modulation.
Although the present invention has been described in connection with the embodiments illustrated in the accompanying drawings, it will be understood by those skilled in the art that the embodiments described above are merely exemplary for illustrating the principles of the present invention and are not intended to limit the scope of the present invention, and that various combinations, modifications and equivalents of the above-described embodiments may be made by those skilled in the art without departing from the spirit and scope of the present invention.
Claims (10)
1. An entanglement photon source for generating entangled photons, comprising a pump light source, a dichroic mirror, a polarizing beam splitting unit, and a sagnac loop; wherein the content of the first and second substances,
the pump light source is used for generating pump light;
the dichroic mirror is arranged to receive and transmit the pump light and to receive and reflect the entangled photons;
the polarization beam splitting unit is configured to split the pump light into a first pump light component and a second pump light component having polarization states perpendicular to each other, and to cause the first pump light component and the second pump light component to simultaneously enter the sagnac loop in different directions;
the sagnac loop is configured to: enabling the first pump light component to generate 90-degree polarization state inversion, enabling the first pump light component to enter a collinear BBO crystal to generate a first pair of signal light and idler frequency light, and enabling the first pair of signal light and idler frequency light to return to the polarization beam splitting unit at a first time; enabling the second pump light component to enter the collinear BBO crystal to generate a second pair of signal light and idler frequency light, and enabling the second pair of signal light and idler frequency light to return to the polarization beam splitting unit at the first time after the polarization state of the second pair of signal light and idler frequency light is reversed by 90 degrees;
the signal and idler of the first and second pairs of signal and idler are separated at the polarization beam splitting unit.
2. The entangled-photon source as recited in claim 1 further comprising a first polarization control unit disposed between the pump light source and the dichroic mirror.
3. The entangled photon source as claimed in claim 2 wherein the first polarization control unit is a wave plate or polarization controller or is implemented with optical axis rotational alignment.
4. The entangled-photon source of claim 1, wherein the sagnac loop comprises a first reflection unit, a second polarization control unit, and the collinear BBO crystal;
the first reflection unit is configured to reflect the first pump light component into the collinear BBO crystal and reflect the second pair of signal light and idler light back to the polarization beam splitting unit;
the second reflection unit is configured to reflect the second pump light component into the collinear BBO crystal and reflect the first pair of signal light and idler light back to the polarization beam splitting unit;
the second polarization control unit is configured to implement the 90-degree polarization state flip.
5. An entangled-photon source as claimed in claim 4 wherein the second polarization control unit is a wave plate or polarization controller or is implemented by means of optical axis rotational alignment.
6. The entangled photon source as claimed in claim 4 wherein the first reflecting unit is a planar or concave mirror and/or the second reflecting unit is a planar or concave mirror.
7. The entangled-photon source of claim 1 wherein the pump light is continuous light or pulsed light.
8. The entangled-photon source of any one of claims 1-7, further comprising a focusing unit to focus the pump light before it enters the collinear BBO crystal.
9. The entangled-photon source as recited in claim 8, wherein the focusing unit is a focusing lens; and/or the focusing unit is arranged in front of the dichroic mirror.
10. The entangled photon source of claim 1 further comprising a phase modulator for modulating the phase of the pump light.
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| CN202110022151.7A CN114740669A (en) | 2021-01-08 | 2021-01-08 | Entangled photon source |
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| CN202110022151.7A CN114740669A (en) | 2021-01-08 | 2021-01-08 | Entangled photon source |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115730665A (en) * | 2022-11-29 | 2023-03-03 | 北京百度网讯科技有限公司 | Entanglement source simulation method and device and electronic equipment |
| CN116149110A (en) * | 2023-04-20 | 2023-05-23 | 中国科学技术大学 | Device for generating multiphoton GHZ entangled state |
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2021
- 2021-01-08 CN CN202110022151.7A patent/CN114740669A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115730665A (en) * | 2022-11-29 | 2023-03-03 | 北京百度网讯科技有限公司 | Entanglement source simulation method and device and electronic equipment |
| CN115730665B (en) * | 2022-11-29 | 2023-08-18 | 北京百度网讯科技有限公司 | Entanglement source simulation method and device and electronic equipment |
| CN116149110A (en) * | 2023-04-20 | 2023-05-23 | 中国科学技术大学 | Device for generating multiphoton GHZ entangled state |
| CN116149110B (en) * | 2023-04-20 | 2023-08-29 | 中国科学技术大学 | Device for generating multiphoton GHZ entangled state |
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