CN216118325U - Efficient all-fiber entanglement source - Google Patents
Efficient all-fiber entanglement source Download PDFInfo
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- CN216118325U CN216118325U CN202122494899.5U CN202122494899U CN216118325U CN 216118325 U CN216118325 U CN 216118325U CN 202122494899 U CN202122494899 U CN 202122494899U CN 216118325 U CN216118325 U CN 216118325U
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Abstract
The utility model discloses an efficient all-fiber entanglement source, which comprises a PPKTP crystal packaging structure, a circulator/wavelength division multiplexer, a fiber polarization beam splitter and a 90-degree polarization rotation unit which are connected through a fiber channel and used for generating entangled photons. The PPTPK crystal and the optical coupling device thereof are packaged into a whole, the end face of the crystal is formed into an inclined plane and plated with an antireflection film, the phase modulator and the polarization controller are arranged at the output end of the laser, and the filter is arranged in front of the output end of the entanglement source to filter non-entangled light components, so that the light transmission efficiency and the pump light utilization efficiency can be effectively improved, the efficiency of the entanglement source is improved, optical noise is reduced, and the performance of the entanglement source is improved. Meanwhile, the entanglement source is strong in stability and easy to debug and integrate.
Description
Technical Field
The utility model relates to the technical field of quanta, in particular to an efficient all-fiber entanglement source.
Background
Quantum entanglement is one of the most important subjects in the science of quantum information, and there are many experimental methods for its preparation, the most common of which is parametric down-conversion using nonlinear crystals. Some entanglement source structures based on PPKTP crystals have been disclosed in the prior art, but these prior art often all utilize space optics to build under experimental environment, and the debugging degree of difficulty is great, and system stability and optical efficiency are not high, are unfavorable for carrying out system integration.
SUMMERY OF THE UTILITY MODEL
Aiming at the problems in the prior art, the utility model provides an efficient all-fiber entanglement source. The optical fiber channel is used for transmitting optical signals among different optical devices, optical alignment is easy to realize among the optical devices, the system stability is good, the efficiency of the entanglement source can be effectively improved, and meanwhile, the entanglement source is easier to integrate and regulate. In addition, the PPTPKP crystal and the related optical coupling device are packaged into a whole, the end structure of the PPTPKP crystal is optimized, a phase and polarization state regulation function is provided for pump light, an output filtering function is provided, the optical coupling efficiency can be further improved, the optical noise is reduced, and the efficiency and the performance of an entanglement source are improved.
Specifically, the utility model relates to an efficient all-fiber entanglement source, which comprises a laser for generating a pump light signal, an optical transmission device, a polarization beam splitter, a polarization rotation unit and a PPKTP crystal;
the PPKTP crystal is characterized in that the PPKTP crystal, the first coupling collimator and the second coupling collimator are packaged into a whole;
the optical transmission device is provided with a first port, a second port and a third port, wherein input light of the first port is output by the second port, and input light of the second port is output by the third port;
the laser is connected with the first port of the optical transmission device through a first optical fiber;
the polarization beam splitter is provided with a first port, a second port, a third port and a fourth port and is used for splitting the pump light signal into two pump light signal components to be output through the third port and the fourth port respectively, wherein the first port of the polarization beam splitter is connected with the second port of the optical transmission device through a second optical fiber;
the first coupling collimator is arranged to form optical coupling with one end of the PPKTP crystal, and a tail fiber of the first coupling collimator is connected with a third port of the polarization beam splitter through a third optical fiber;
the PPKTP crystal is arranged to enable the pump light signal component to generate a spontaneous parametric down-conversion process so as to generate a parametric down-conversion light signal, and two ends of the PPKTP crystal are plated with antireflection films;
the second coupling collimator is arranged to form optical coupling with the other end of the PPKTP crystal, and a tail fiber of the second coupling collimator is connected with a fourth port of the polarization beam splitter through a fourth optical fiber;
the polarization rotation unit is arranged on the third optical fiber or the fourth optical fiber and is used for enabling the light polarization state to rotate by 90 degrees;
and a filter is connected with the third port of the optical transmission device and/or the second port of the polarization beam splitter.
Further, the optical transmission device is a circulator.
Further, the optical transmission device is a wavelength division multiplexer, the first port allows transmission of the pump optical signal but not the parametric down-converted optical signal, the third port allows transmission of the parametric down-converted optical signal but not the pump optical signal, and the second port allows transmission of the pump optical signal and the parametric down-converted optical signal.
Further, the polarization beam splitter is a fiber polarization beam splitter.
Further, the polarization rotation unit is a polarization controller.
Further, the first optical fiber is a single-mode polarization maintaining optical fiber, and the second optical fiber, the third optical fiber and the fourth optical fiber are full-wavelength polarization maintaining optical fibers.
Further, the polarization rotation unit is realized by rotationally aligning the third optical fiber and/or the fourth optical fiber with the optical axis of the polarization beam splitter.
Optionally, the laser is a pulsed laser or a continuous light laser.
Further, one or more of an optical isolator, a phase modulator and a polarization controller are arranged on the first optical fiber.
Preferably, two end faces of the PPKTP crystal are inclined planes.
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 shows a schematic structural view of a high efficiency all-fiber entanglement 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 utility model to those skilled in the art to which the utility model pertains. Accordingly, the present invention is not limited to the embodiments disclosed herein.
Fig. 1 shows a schematic structural view of a high efficiency all-fiber entanglement source according to the present invention.
As shown in fig. 1, the all-fiber entanglement source includes a laser 1, an optical transmission device 2, a polarization beam splitter 3, a polarization rotation unit 4, and a PPKTP crystal 6.
In this entanglement source, a laser 1 is connected to a first port 2-1 of an optical transmission device 2 by a first optical fiber. Thus, the pump light signal generated by the laser 1 can be transmitted via the fibre channel to the optical transmission device 2, input via its first port 2-1 and output by the second port 2-2. The laser 1 may be a pulse laser or a continuous light laser.
The second port 2-2 of the optical transmission device 2 is connected to the first port 3-1 of the fiber polarization splitter 3 through a second optical fiber, so that the pump light signal can continue to be transmitted through the optical fiber channel and input into the fiber polarization splitter 3.
At the fiber polarization splitter 3, the pump light signal input by the first port 3-1 will be split into two pump light signal components, i.e., a vertically polarized pump light signal component and a horizontally polarized pump light signal component. For example, a horizontally polarized pump light signal component may be output from the third port 3-3 of the fiber polarization beam splitter 3 via transmission, and a vertically polarized pump light signal component may be output from the fourth port 3-4 of the fiber polarization beam splitter 3 via reflection.
In the utility model, the PPKTP crystal 6, the first coupling collimator 5 and the second coupling collimator 7 are packaged into an integral structure, wherein the tail fibers of the first coupling collimator 5 and the second coupling collimator 7 are used as optical fiber connecting ends at two ends of the integral structure for receiving the pumping optical signal component and outputting the parametric down-conversion optical signal.
As shown in fig. 1, the pigtail of the first coupling collimator 5 may be connected to the third port 3-3 of the fiber polarization beam splitter 3 through a third optical fiber, and the pigtail of the second coupling collimator 7 may be connected to the fourth port 3-4 of the fiber polarization beam splitter 3 through a fourth optical fiber.
In the integral structure for the PPKTP crystal 6, the first coupling collimator 5 is set to form good optical coupling with one end of the PPKTP crystal 6, while the second coupling collimator 7 forms good optical coupling with the other end of the PPKTP crystal 6, and antireflection films are plated on both ends of the PPKTP crystal 6, thereby ensuring that the pump light signal component can efficiently enter the PPKTP crystal 6 and allowing the parametric down-conversion light signal generated in the PPKTP crystal 6 to be efficiently output, thereby improving the optical efficiency of the entanglement source.
In a preferred example, two end faces of the PPKTP crystal 6 may also be formed as slopes to effectively suppress reflected light of the pump light signal from entering the coupling collimator, thereby reducing the noise effect of the pump light signal and improving the efficiency of the entanglement source.
The polarization rotation unit 4 is disposed on the third optical fiber or the fourth optical fiber for rotating the polarization state of light by 90 degrees.
Thus, after the horizontally polarized pump light signal component enters the third optical fiber from the third port 3-3 of the fiber polarization beam splitter 3, the pump light signal component will enter the pigtail of the first coupling collimator 5 along the fiber channel and be coupled into the PPKTP crystal 6 by the first coupling collimator 5, so that a spontaneous parametric down-conversion process occurs in the PPKTP crystal 6 to generate a first parametric down-converted light signal comprising the signal photon | Hs>And idler photon | Vi>. The first parametric down-conversion optical signal enters the fourth optical fiber through the second coupling collimator 7, is input to the polarization rotation unit 4 along the optical fiber channel, and is subjected to 90-degree polarization state rotation under the action of the polarization rotation unit. At this point, the first parametrically down-converted optical signal will include signal photons | Vs>And idler photon | Hi>It will continue to travel in the fourth fiber to the fourth port 3-4 of the fiber polarization splitter 3.
After the vertically polarized pump light signal component enters the fourth optical fiber from the fourth port 3-4 of the optical fiber polarization beam splitter 3, the pump light signal component is input to the polarization rotation unit 4 along the optical fiber channel, and the polarization rotation unit rotates the polarization state by 90 degrees under the action of the pump light signal component, so that the pump light signal component becomes horizontally polarized light. The horizontally polarized pump light signal component continues to enter the tail fiber of the second coupling collimator 7 along the fourth optical fiber and is coupled into the PPKTP crystal 6 by the second coupling collimator 7, so that a spontaneous parametric down-conversion process occurs in the PPKTP crystal 6 to generate a second parametric down-converted light signal comprising signal photons | Hs>And idler photon | Vi>. The second parametric down-conversion optical signal enters a third optical fiber through the first coupling collimator 5, and is transmitted along an optical fiber channel to reach a third port 3-3 of the optical fiber polarization beam splitter 3.
Thus, a signal photon | V is output at the first port 3-1 of the fiber polarization splitter 3s>And | Hs>Which is to be inputted into the second port 2-2 of the optical transmission device 2 and from the third port2-3, emitting; the second port 3-2 of the optical fiber polarization beam splitter 3 can directly output the idler photon | Hi>And | Vi>。
Due to the homologies of photons, when a photon is detected at the third port 2-3 of the optical transmission device 2 and the second port 3-2 of the fiber polarization beam splitter 3 at the same time, it is not possible to distinguish which path the down-converted photon comes from, and at this time, the two photons are in an entangled state.
In the utility model, a filter 8 can be further arranged at the third port 2-3 of the optical transmission device 2 and the second port 3-2 of the fiber polarization beam splitter 3 to filter out the components of non-signal photons and idler photons and improve the performance of the entanglement source.
Further, an optical isolator 9 may also be provided at the output of the laser 1 (i.e. on the first fibre) to provide protection to the laser.
Further, a phase modulator 11 and a polarization controller 10 may be further disposed at the output end of the laser 1 (i.e., on the first optical fiber) for adjusting the phase and the polarization state of the pump light, so as to improve the optical transmission efficiency of the pump light in the entanglement source and the working efficiency of the spontaneous parameter down-conversion process, thereby implementing an efficient entanglement source.
In the present invention, the first optical fiber may be a single-mode polarization maintaining optical fiber, and the second optical fiber, the third optical fiber, and the fourth optical fiber may be full-wavelength polarization maintaining optical fibers.
According to the present invention, the optical transmission device 2 may employ a circulator, such as that shown in fig. 1.
Alternatively, the optical transmission device 2 may be implemented by a wavelength division multiplexer. At this time, the wavelength division multiplexer 2 may be configured such that the first port 2-1 thereof allows only the transmission of the pump optical signal and does not allow the transmission of the parametric down-converted optical signal, the third port 2-3 allows only the transmission of the parametric down-converted optical signal and does not allow the transmission of the pump optical signal, and the second port 2-2 allows both the transmission of the pump optical signal and the parametric down-converted optical signal. Thus, in the entanglement source of the present invention, the pump optical signal output by the laser 1 may be input by the first port 2-1 of the wavelength division multiplexer 2 and output by the second port 2-2, and the parametrically down-converted optical signal output by the polarization beam splitter 3 may be input by the second port 2-2 of the wavelength division multiplexer 2 and output by the third port 2-3.
According to the present invention, the polarization rotation unit 4 may be implemented using a polarization controller, such as that shown in fig. 1.
Alternatively, the polarization rotation unit 4 may also be implemented by rotationally aligning the fourth fiber (or the third fiber) with the optical axis of the fiber polarization beam splitter 3.
Therefore, the utility model provides an entanglement source realized based on an all-fiber structure, wherein optical signals are transmitted among different optical devices through an optical fiber channel, optical alignment is easy to realize among the optical devices, and the system stability is good, so that the efficiency of the entanglement source can be effectively improved, and meanwhile, the entanglement source is easier to integrate and regulate. In addition, the PPTPK crystal and the related optical coupling device are packaged into a whole, and the end structure of the PPTPK crystal is optimized, so that the optical coupling efficiency can be further improved, the optical noise can be reduced, and the efficiency of an entanglement source can be improved. And, through setting up polarization controller and phase modulator in order to provide the regulation and control function of pump light, can allow to optimize pump light parameter to improve the utilization ratio of pump light, and then improve the efficiency of entanglement source.
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 efficient all-fiber entanglement source comprises a laser for generating a pump light signal, an optical transmission device, a polarization beam splitter, a polarization rotation unit and a PPKTP crystal;
the PPKTP crystal is characterized in that the PPKTP crystal, the first coupling collimator and the second coupling collimator are packaged into a whole;
the optical transmission device is provided with a first port, a second port and a third port, wherein input light of the first port is output by the second port, and input light of the second port is output by the third port;
the laser is connected with the first port of the optical transmission device through a first optical fiber;
the polarization beam splitter is provided with a first port, a second port, a third port and a fourth port and is used for splitting the pump light signal into two pump light signal components to be output through the third port and the fourth port respectively, wherein the first port of the polarization beam splitter is connected with the second port of the optical transmission device through a second optical fiber;
the first coupling collimator is arranged to form optical coupling with one end of the PPKTP crystal, and a tail fiber of the first coupling collimator is connected with a third port of the polarization beam splitter through a third optical fiber;
the PPKTP crystal is arranged to enable the pump light signal component to generate a spontaneous parametric down-conversion process so as to generate a parametric down-conversion light signal, and two ends of the PPKTP crystal are plated with antireflection films;
the second coupling collimator is arranged to form optical coupling with the other end of the PPKTP crystal, and a tail fiber of the second coupling collimator is connected with a fourth port of the polarization beam splitter through a fourth optical fiber;
the polarization rotation unit is arranged on the third optical fiber or the fourth optical fiber and is used for enabling the light polarization state to rotate by 90 degrees;
and a filter is connected with the third port of the optical transmission device and/or the second port of the polarization beam splitter.
2. The entanglement source of claim 1, wherein the optical transmission device is a circulator.
3. The entanglement source of claim 1, wherein the optical transmission device is a wavelength division multiplexer, the first port allowing transmission of the pump optical signal but not the parametric down-converted optical signal, the third port allowing transmission of the parametric down-converted optical signal but not the pump optical signal, the second port allowing transmission of the pump optical signal and the parametric down-converted optical signal.
4. The entanglement source of claim 1, wherein the polarizing beam splitter is a fiber polarizing beam splitter.
5. The entanglement source of claim 1, wherein the polarization rotation unit is a polarization controller.
6. The entanglement source of claim 1, wherein the first optical fiber is a single-mode polarization-maintaining fiber, and the second, third, and fourth optical fibers are full-wavelength polarization-maintaining fibers.
7. The entanglement source of claim 6, wherein the polarization rotation unit is implemented by rotational alignment of the third and/or fourth optical fibers with an optical axis of a polarizing beam splitter.
8. The entanglement source of claim 1, wherein the laser is a pulsed laser or a continuous light laser.
9. The entanglement source of claim 1, wherein the first fiber has one or more of an optical isolator, a phase modulator, and a polarization controller disposed thereon.
10. The entanglement source of claim 1, wherein the PPKTP crystal has beveled ends.
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| CN202122494899.5U CN216118325U (en) | 2021-10-15 | 2021-10-15 | Efficient all-fiber entanglement source |
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| CN202122494899.5U CN216118325U (en) | 2021-10-15 | 2021-10-15 | Efficient all-fiber entanglement source |
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