CN116192279A - Transmitting end, receiving end and system for transmitting quantum light - Google Patents
Transmitting end, receiving end and system for transmitting quantum light Download PDFInfo
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- CN116192279A CN116192279A CN202310429735.5A CN202310429735A CN116192279A CN 116192279 A CN116192279 A CN 116192279A CN 202310429735 A CN202310429735 A CN 202310429735A CN 116192279 A CN116192279 A CN 116192279A
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- 238000004891 communication Methods 0.000 claims abstract description 19
- 239000013307 optical fiber Substances 0.000 claims abstract description 17
- 230000003287 optical effect Effects 0.000 claims abstract description 15
- 238000000034 method Methods 0.000 claims abstract description 13
- 230000005540 biological transmission Effects 0.000 claims description 29
- 238000006243 chemical reaction Methods 0.000 claims description 16
- 239000000835 fiber Substances 0.000 claims description 14
- 238000001514 detection method Methods 0.000 claims description 12
- 230000010287 polarization Effects 0.000 claims description 12
- 239000002070 nanowire Substances 0.000 claims description 10
- 238000002834 transmittance Methods 0.000 claims description 8
- 230000003044 adaptive effect Effects 0.000 claims description 4
- 230000008569 process Effects 0.000 abstract description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000005040 ion trap Methods 0.000 description 3
- 229910052769 Ytterbium Inorganic materials 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- -1 ytterbium ion Chemical class 0.000 description 2
- 238000012937 correction Methods 0.000 description 1
- 230000009365 direct transmission Effects 0.000 description 1
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/70—Photonic quantum communication
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/40—Transceivers
Abstract
The invention provides a transmitting end, a receiving end and a system for transmitting quantum light, and relates to the technical field of quantum computers. The system for transmitting the quantum light comprises an emitting end and a receiving end, wherein the emitting end converts first quantum light with a first wavelength into second quantum light with a second wavelength, and emits the second quantum light to the receiving end through a free space; the receiving end receives the second quantum light from the transmitting end through the free space; and transmitting the second quantum light by adopting a communication optical fiber at the internal optical path of the transmitting end and the internal optical path of the receiving end. By using the invention, the photon loss in the process of transmitting the quantum light can be reduced, the signal to noise ratio of the quantum light signal is improved, and the quantum entanglement quality is ensured.
Description
Technical Field
The present invention relates to the field of quantum computers, and in particular, to a transmitting end, a receiving end and a system for transmitting quantum light.
Background
In the technical field of quantum computers, in order to realize connection between quantum computers located in different position spaces in a distributed quantum computer network, remote quantum entanglement of the quantum computers is required to be realized. Quantum entanglement is achieved by using a photon medium as the entanglement medium, wherein factors affecting photon entanglement quality are numerous, such as signal-to-noise ratio, single photon purity, measurement entanglement scheme, etc. The number of photons directly affects the signal-to-noise ratio, so how to reduce the photon loss to improve the signal-to-noise ratio becomes a key issue for guaranteeing the quantum entanglement quality.
Disclosure of Invention
The invention aims to provide a transmitting end, a receiving end and a system for transmitting quantum light, which are used for reducing photon loss in the quantum light transmission process, improving the signal-to-noise ratio of a quantum light signal and guaranteeing the quantum entanglement quality of a distributed quantum computer network.
According to an aspect of the present invention, there is provided an emission end for transmitting quantum light, including: a first quantum light generator for preparing and outputting first quantum light having a first wavelength; a first optical fiber adapter for converting the first quantum light to a frequency conversion device; the frequency conversion device is used for receiving and converting the first quantum light into second quantum light with a second wavelength; a first communication fiber for transmitting the second quantum light from the frequency conversion device to the emission device; and the transmitting device is used for transmitting the second quantum light to the receiving end through the free space.
According to one embodiment of the present invention, a frequency translating apparatus includes: the polarization-preserving quantum frequency converter is used for converting the first quantum light into second quantum light; and the polarization analyzer is used for carrying out photon polarization detection on the second quantum light, and controlling the polarization-preserving quantum frequency converter to output the second quantum light after detecting single photons of the second quantum light meeting the quantum entanglement requirement.
According to one embodiment of the invention, the polarization maintaining sub-converter is a Sagnac interferometer.
According to one embodiment of the invention, the wavelength of the first quantum light is 369nm; the wavelength of the second quantum light is 1550nm; the frequency conversion device is also used for converting 369nm first quantum light into 780nm optical signals and converting 780nm optical signals into 1550nm second quantum light.
According to another aspect of the present invention, there is also provided a receiving terminal for transmitting quantum light, including: the receiving device is used for receiving the second quantum light from the emitting end through the free space; a second fiber optic adapter for transferring a second quantum light from the receiving device to the beam splitter; the beam splitter is used for splitting the second quantum light into one or more paths of second quantum light; one or more second communication fibers for transmitting the one or more second quantum lights from the beam splitter to the single photon detector; and one or more single photon detectors for receiving and detecting the second quantum light from the beam splitter and outputting a detection electrical signal.
According to one embodiment of the invention, the receiving means is an adaptive optical receiving subsystem.
According to one embodiment of the invention, the single photon detector is a photomultiplier tube, or an avalanche photodiode, or a superconducting nanowire single photon detector.
According to another aspect of the present invention, there is also provided a system for transmitting quantum light, including the transmitting end and the receiving end for transmitting quantum light.
According to one embodiment of the invention, the photon transmission loss of the system for transmitting quantum light comprises a fixed loss and a variable loss, wherein the variable loss comprises the transmission loss of the second quantum light in free space between the transmitting end and the receiving end; the method for acquiring the transmission loss of the second quantum light in the free space between the transmitting end and the receiving end comprises the following steps: according to the formula
Obtaining the atmospheric attenuation coefficientαThe method comprises the steps of carrying out a first treatment on the surface of the According to the transmission distanceLAnd the atmospheric attenuation coefficientαCalculating to obtain the transmissivity of the second quantum light in the atmosphere>
The method comprises the steps of carrying out a first treatment on the surface of the According to the transmittanceTCalculating the transmission loss value of the second quantum light in the free space as +.>
； wherein ,λ0 At a wavelength of 550nm,λfor the wavelength of the second quantum light,Vin order for the visibility to be good, qfor visibility ofVA corresponding visibility constant.
According to one embodiment of the invention, when the second quantum light is transmitted obliquely in the free space between the emitting end and the receiving end, the transmittance of the second quantum light in the atmosphere is calculated by adopting the following integral form
T：
The method comprises the steps of carrying out a first treatment on the surface of the According to the transmittanceTCalculating to obtain the transmission loss value of the second quantum light in the free space atmosphere when the second quantum light is transmitted obliquely>
； wherein ,λfor the wavelength of the second quantum light,αfor the atmospheric attenuation coefficient,Has the vertical height of the ramp path,φis the zenith angle of the oblique path,hin order to represent the variation of the vertical height,secrepresenting a secant function.
According to the transmitting end, the receiving end and the system for transmitting the quantum light, photon loss in the process of transmitting the quantum light is reduced by converting the first quantum light into the second quantum light which is suitable for being transmitted in the communication optical fiber and the atmosphere of free space. On one hand, the attenuation loss of the photon quantity of the quantum light in the optical fiber can be reduced to the maximum extent, and on the other hand, the transmission loss in the atmosphere of the free space can be reduced, so that the signal-to-noise ratio of the quantum light signal is finally improved. At the same time, the second quantum light converted to fiber optic communication frequency allows for more economical implementation of distributed quantum computer network links using existing telecommunications infrastructure after photon transmission. Further, photon state detection is performed in the process of converting the first quantum light into the second quantum light, so that high-quality second quantum light preparation and output are ensured, and the level of polarization-preserving fidelity of photons is ensured, and therefore, the quantum entanglement quality is improved.
Drawings
The above objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.
Fig. 1 is a schematic block diagram illustrating a system for transmitting quantum light according to an exemplary embodiment of the present invention.
Fig. 2 is a schematic block diagram illustrating a frequency translating apparatus of a transmitting end according to an exemplary embodiment of the present invention.
Detailed Description
The invention has the conception that: in order to realize the transmission of quantum light among quantum computers positioned at different spatial positions in a distributed quantum computer network and reduce photon transmission loss in the transmission process, the technical scheme of the invention converts first quantum light into second quantum light, and the converted second quantum light can be transmitted through the existing optical fiber communication network; meanwhile, a calculation mode of the transmission loss of the second quantum light in the atmosphere of the free space is provided, and the photon transmission of the free space can be carried out by selecting proper atmosphere transmission conditions according to the actual transmission condition, so that the photon transmission loss in the atmosphere of the free space is reduced.
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Fig. 1 shows a schematic diagram of a system for transmitting quantum light according to an exemplary embodiment of the present invention. Referring to fig. 1, a system for transmitting quantum light includes an emitting end 100 and a receiving end 200, the emitting end emitting a quantum light signal to the receiving end via free space.
The transmitting end 100 for transmitting quantum light shown in fig. 1 includes a first quantum light generator 101, a first optical fiber adapter 102, a frequency conversion device 103, a first communication optical fiber 104, and a transmitting device 105, wherein: the first quantum light generator 101 is configured to prepare and output first quantum light having a first wavelength; the first optical fiber adapter 102 is used for transferring the first quantum light to the frequency conversion device 103; the frequency conversion device 103 is configured to receive and convert the first quantum light into a second quantum light with a second wavelength; the first communication fiber 104 is used for transmitting the second quantum light from the frequency conversion device to the emitting device 105; the emitting device 105 is configured to emit the second quantum light to the receiving end via free space.
The first quantum light generator 101 may be an ion trap quantum computer. In some examples, the ion trap of the ion trap quantum computer may be an ytterbium ion pin trap, and the first quantum light emitted by the ytterbium ion pin trap has a wavelength of 369nm, i.e., the first wavelength is 369nm. The 369nm first quantum light has extremely large loss when transmitted in the free space atmosphere and the communication optical fiber, and is not suitable for direct transmission in the free space atmosphere and the communication optical fiber, and therefore, the first quantum light needs to be converted into the second quantum light with smaller loss. The wavelength of the second quantum light may be 850nm, or 1310nm, or 1550nm. In some examples, the wavelength of the second quantum light is 1550nm, i.e., the second wavelength is 1550nm.
As shown in fig. 2, in some examples, the frequency conversion device 103 at the transmitting end includes an polarization-preserving sub-converter 1031 and a polarization analyzer 1032, where: an polarization-preserving quantum converter 1031 for converting the first quantum light into a second quantum light having a second wavelength; the polarization analyzer 1032 is configured to perform photon polarization detection on the second quantum light to determine whether a single photon of the second quantum light is detected, and if so, control the polarization-preserving quantum frequency converter 1031 to output the second quantum light to the emitting device 105.
Specific ways of converting the first quantum light into the second quantum light by the frequency conversion device 103 include: first, 369nm of first quantum light is converted into 780nm of optical signals, and then 780nm of optical signals are converted into 1550nm of second quantum light. In some examples, the polarization maintaining quantum converter may be a Sagnac interferometer that converts incident 369nm first quantum light into 1550nm second quantum light by difference frequency. For example, in specific implementation, first quantum light of 369nm is converted into quantum light of 780 and nm, and then polarization-preserving quantum frequency conversion of second quantum light of a telecom S-band 1522 and nm is realized by a difference frequency generation mode in a built-in Periodically Polarized Lithium Niobate (PPLN) waveguide. For this purpose, the quantum light of 780nm is mixed with a strong continuous pumping field of 1600 nm in the waveguide in a Sagnac type device. The input polarized light is split into two arms by a Polarizing Beam Splitter (PBS), one of which incorporates a Half Wave Plate (HWP) such that the two counter propagating beams have the same polarization as they enter the waveguide, creating 1550nm quantum light in the waveguide at the difference frequency from the other beam wavelength.
The receiving end 200 for transmitting quantum light shown in fig. 1 comprises a receiving device 201, a second optical fiber adapter 202, a beam splitter 203, one or more second communication optical fibers 204 (204A, 204B), one or more single photon detectors 205 (205A, 205B), wherein: the receiving device 201 is configured to receive, via free space, the second quantum light having the second wavelength from the emitting end; the second optical fiber adapter 202 is used for transferring the second quantum light from the receiving device to the beam splitter 203; the beam splitter 203 is configured to split the second quantum light into one or more paths of second quantum light; one or more second communication fibers 204 are used to transmit one or more second quantum lights from the beam splitter 203 to the single photon detector 205; one or more single photon detectors 205 are configured to receive and detect the second quantum light from beam splitter 203 and output a detection electrical signal.
In some examples, the receiving device 201 may be specifically an adaptive optical receiving subsystem, which may implement correction of wavefront distortion caused by atmospheric turbulence in the atmospheric environment in free space, so as to achieve the purpose of correcting the phase of the optical wavefront. The adaptive optical receiving subsystem may improve the quality of reception of the second quantum light.
The single photon detector 205 may be a photomultiplier tube, or an avalanche photodiode, or a superconducting nanowire single photon detector (SNSPD, superconducting nanowire single-photon detector). In some examples, single photon detector 205 is a superconducting nanowire single photon detector. The superconducting nanowire single photon detector utilizes photon energy to realize the disassembly of a superconducting nanowire cooper pair, so that superconducting-non-superconducting phase transformation occurs in the local area of the superconducting nanowire, and quantum limit sensitivity optical detection is realized based on the phase transformation of a superconducting material with micro-nano scale. Compared with the traditional semiconductor single photon detector, the superconducting nanowire single photon detector has the advantages of high detection efficiency, low dark count, small time jitter, short dead time, wide spectral response, free running and the like. For 1550nm wavelength light, the detection efficiency of the photomultiplier tube and avalanche photodiode is about 20-35%. Typical detection efficiency of superconducting nanowire single photon detectors exceeds 80%, and optimal device detection efficiency is as high as 90%.
In the system for transmitting quantum light shown in fig. 1, the first and second communication fibers are polarization-maintaining communication fibers; the first and second optical fiber adapters are polarization maintaining optical fiber adapters. And the communication optical fiber is used for transmitting second quantum light with the second wavelength in the internal optical paths of the transmitting end and the receiving end.
In the system for transmitting quantum light shown in fig. 1, there is a photon loss in each link of photon transmission, and the photon loss includes a fixed loss and a variable loss. The fixed loss specifically includes: the first and second fiber optic adapters typically have a fixed photon pass loss, e.g., 3 dB; the loss efficiency of the first and second communication fibers is typically 1dB/km, and the photon passing loss of the communication fibers is the product of the transmission length and the loss efficiency. The variable losses include transmission losses of the second quantum light in the atmosphere of free space and photon transit losses within the frequency conversion device.
In the system for transmitting quantum light shown in fig. 1, the method for acquiring the transmission loss of the second quantum light in the atmosphere of the free space specifically includes: according to the formula
Obtaining the atmospheric attenuation coefficientαThe method comprises the steps of carrying out a first treatment on the surface of the According to the transmission distanceLAnd the atmospheric attenuation coefficientαObtaining the transmittance of the second quantum light in the atmosphere>
The method comprises the steps of carrying out a first treatment on the surface of the According to the transmittanceTCalculating the loss value of the second quantum light in the atmosphere as +.>
； wherein ,λ 0 at a wavelength of 550nm,λfor the wavelength of the second quantum light,Vin order for the visibility to be good,qfor visibility ofVThe corresponding visibility constant is lower. At a known visibilityVIn the case of (in km), the visibility constant is determined according to the following equationq. For example, when the visibility is 10km, the visibility constant can be calculatedqThe number of (2) is 1.3.
When the second quantum light is transmitted obliquely in the free space between the transmitting end and the receiving end, the transmissivity of the second quantum light in the atmosphere is calculated by adopting an integral form as shown belowT。
According to the transmittanceTCalculating to obtain loss value of second quantum light in the oblique transmission in atmosphere as +.>
； wherein ,λfor the wavelength of the second quantum light,αfor the atmospheric attenuation coefficient, H is the vertical height of the ramp path,φis the zenith angle of the oblique path,hin order to represent the variation of the vertical height,secrepresenting a secant function.
While the present application has been shown and described with reference to the preferred embodiments, it will be understood by those skilled in the art that various modifications and changes may be made to these embodiments without departing from the spirit and scope of the present application as defined by the appended claims.
Claims (10)
1. An emitter for transmitting quantum light, comprising:
a first quantum light generator for preparing and outputting first quantum light having a first wavelength;
a first optical fiber adapter for converting the first quantum light to a frequency conversion device;
the frequency conversion device is used for receiving and converting the first quantum light into second quantum light with a second wavelength;
a first communication fiber for transmitting the second quantum light from the frequency conversion device to the emission device;
and the transmitting device is used for transmitting the second quantum light to the receiving end through the free space.
2. The transmitting terminal for transmitting quantum light according to claim 1, wherein the frequency converting means comprises:
the polarization-preserving quantum frequency converter is used for converting the first quantum light into second quantum light;
and the polarization analyzer is used for carrying out photon polarization detection on the second quantum light, and controlling the polarization-preserving quantum frequency converter to output the second quantum light after detecting single photons of the second quantum light meeting the quantum entanglement requirement.
3. The transmitting end for transmitting quantum light of claim 2, wherein the polarization maintaining quantum frequency converter is a Sagnac interferometer.
4. The emitter for transmitting quantum light according to claim 1, wherein,
the wavelength of the first quantum light is 369nm; the wavelength of the second quantum light is 1550nm;
the frequency conversion device is also used for converting 369nm first quantum light into 780nm optical signals and converting 780nm optical signals into 1550nm second quantum light.
5. A receiving end for transmitting quantum light, comprising:
the receiving device is used for receiving the second quantum light from the emitting end through the free space;
a second fiber optic adapter for transferring a second quantum light from the receiving device to the beam splitter;
the beam splitter is used for splitting the second quantum light into one or more paths of second quantum light;
one or more second communication fibers for transmitting the one or more second quantum lights from the beam splitter to the single photon detector; and
one or more single photon detectors for receiving and detecting the second quantum light from the beam splitter and outputting a detection electrical signal.
6. The receiver for transmitting quantum light according to claim 5, wherein,
the receiving device is an adaptive optical receiving subsystem.
7. The receiver for transmitting quantum light according to claim 5, wherein,
the single photon detector is a photomultiplier, an avalanche photodiode or a superconducting nanowire single photon detector.
8. A system for transmitting quantum light, characterized by comprising the transmitting end for transmitting quantum light according to any one of claims 1 to 4 and the receiving end for transmitting quantum light according to any one of claims 5 to 7.
9. The system for transmitting quantum light of claim 8, wherein the quantum light is transmitted through the quantum light source,
the photon transmission loss of the system for transmitting quantum light comprises a fixed loss and a variable loss, wherein the variable loss comprises the transmission loss of a free space between a transmitting end and a receiving end of second quantum light; the method for acquiring the transmission loss of the second quantum light in the free space between the transmitting end and the receiving end comprises the following steps:
according to the formula
Obtaining the atmospheric attenuation coefficientαThe method comprises the steps of carrying out a first treatment on the surface of the According to the transmission distanceLAnd the atmospheric attenuation coefficientαCalculating to obtain the transmissivity of the second quantum light in the atmosphere>
The method comprises the steps of carrying out a first treatment on the surface of the According to the transmittanceTCalculating the transmission loss value of the second quantum light in the free space as +.>
； wherein ,λ0 At a wavelength of 550nm,λfor the wavelength of the second quantum light,Vin order for the visibility to be good, qfor visibility ofVA corresponding visibility constant.
10. The system for transmitting quantum light of claim 8, wherein the quantum light is transmitted through the quantum light source,
when the second quantum light is transmitted obliquely in the free space between the transmitting end and the receiving end, the transmissivity of the second quantum light in the atmosphere is calculated by adopting an integral form shown as follows
T：
According to the transmittanceTCalculating to obtain the transmission loss value of the second quantum light in the free space atmosphere when the second quantum light is transmitted obliquely>
； wherein ,λfor the wavelength of the second quantum light,αfor the atmospheric attenuation coefficient, Has the vertical height of the ramp path,φis the zenith angle of the oblique path,hin order to represent the variation of the vertical height,secrepresenting a secant function. />
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104737491A (en) * | 2012-10-15 | 2015-06-24 | 诺基亚技术有限公司 | Quantum key distribution |
| US20170331560A1 (en) * | 2016-05-12 | 2017-11-16 | Shanxi University | Single photons communication method and system |
| CN113078950A (en) * | 2021-03-23 | 2021-07-06 | 中国科学技术大学 | Single photon source and single photon preparation method |
| CN215912100U (en) * | 2022-01-25 | 2022-02-25 | 国开启科量子技术(北京)有限公司 | Transmitting end, receiving end and system for quantum communication |
| CN115208479A (en) * | 2022-06-21 | 2022-10-18 | 华北电力大学（保定） | Star warship quantum downlink vertical transmission model based on different weather conditions |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104737491A (en) * | 2012-10-15 | 2015-06-24 | 诺基亚技术有限公司 | Quantum key distribution |
| US20170331560A1 (en) * | 2016-05-12 | 2017-11-16 | Shanxi University | Single photons communication method and system |
| CN113078950A (en) * | 2021-03-23 | 2021-07-06 | 中国科学技术大学 | Single photon source and single photon preparation method |
| CN215912100U (en) * | 2022-01-25 | 2022-02-25 | 国开启科量子技术(北京)有限公司 | Transmitting end, receiving end and system for quantum communication |
| CN115208479A (en) * | 2022-06-21 | 2022-10-18 | 华北电力大学（保定） | Star warship quantum downlink vertical transmission model based on different weather conditions |
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