CN109391471B - Hybrid waveguide integrated interferometer and quantum key distribution system - Google Patents
Hybrid waveguide integrated interferometer and quantum key distribution system Download PDFInfo
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- CN109391471B CN109391471B CN201811195947.7A CN201811195947A CN109391471B CN 109391471 B CN109391471 B CN 109391471B CN 201811195947 A CN201811195947 A CN 201811195947A CN 109391471 B CN109391471 B CN 109391471B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
- H04L9/0852—Quantum cryptography
- H04L9/0858—Details about key distillation or coding, e.g. reconciliation, error correction, privacy amplification, polarisation coding or phase coding
Abstract
The application discloses a hybrid waveguide integrated interferometer and a quantum key distribution system, wherein the hybrid waveguide integrated interferometer comprises a waveguide chip, a delayer and a reflection module, wherein the waveguide chip comprises a beam splitter, a first waveguide line and a second waveguide line; on one hand, the precision of the first waveguide line and the second waveguide line formed by manufacturing the waveguide chip can be controlled at a nanometer level, so that the arm length difference control precision of the interferometer is higher. On the other hand, the hybrid waveguide integrated interferometer has extremely small volume, is convenient for packaging vibration isolation and temperature control, is not easily influenced by external environment and has better stability; on the other hand, the optical waveguide has better polarization maintaining characteristic, and the polarization of the optical pulse is better maintained in the transmission process, so that the hybrid waveguide integrated interferometer is more stable. The arm length difference of the hybrid waveguide integrated interferometer is easier to control relative to the optical fiber interferometer in the three aspects, and therefore the quantum key distribution system works more stably.
Description
Technical Field
The invention relates to the technical field of quantum cryptography communication, in particular to a hybrid waveguide integrated interferometer and a quantum key distribution system.
Background
Quantum key distribution technology combines quantum physics principles with modern communication technologies. The quantum key distribution ensures the security of the key negotiation process and results in different places by virtue of a physical principle, and can realize secret communication independent of algorithm complexity by combining with a one-time pad encryption technology.
At present, quantum cryptography mainly uses light quanta as a carrier for realization, and the light quanta are distributed through free space or optical fiber channels. The quantum key distribution equipment loads classical random bits on physical quantities such as polarization, phase and the like of light quanta by utilizing various optical modulation equipment to transmit according to the requirements of different quantum key distribution protocols, thereby realizing the distribution of quantum keys. The interference module is used as a core device of a phase-coded quantum key distribution system, and an interferometer with excellent design can ensure the stability and the high efficiency of the quantum key distribution system.
In the prior art, an unequal-arm optical fiber Faraday Michelson interferometer is adopted to realize a quantum key distribution system, and the Faraday mirror is adopted to cause 90-degree rotation to the polarization state inside an optical fiber, so that the interferometer is used for immunizing the problem of reduced stability of the interferometer caused by different polarization changes in long and short arms due to different long and short arm paths of a common Mach-Zehnder interferometer. Moreover, quantum key distribution experiments over long distances between cities have been implemented in the prior art using faraday michelson interferometers.
However, the faraday michelson interferometer also has its disadvantages, such as that the arm length differences of the interferometers of the transmitting end and the receiving end are strictly consistent in the quantum key distribution system, while the arm length difference of the faraday michelson interferometer in the prior art is poor in control accuracy, and the interferometer itself also has the characteristic of instability, which causes that the control of the arm length difference consistency of the interferometers of the transmitting end and the receiving end is difficult.
Disclosure of Invention
In view of this, the present invention provides a hybrid waveguide integrated interferometer and a quantum key distribution system, so as to solve the problem in the prior art that it is difficult to control the interferometer arms with the same length difference between the sending end and the receiving end.
In order to achieve the purpose, the invention provides the following technical scheme:
a hybrid waveguide integrated interferometer, comprising:
the device comprises a waveguide chip, a delayer and a reflection module;
the waveguide chip comprises a first end face and a second end face which are oppositely arranged, and the first end face comprises an incident port and an emergent port of the light pulse;
the reflection module is positioned on the second end face;
the waveguide chip comprises a beam splitter, a first waveguide line and a second waveguide line;
the delayer is used for delaying the light pulse on the first waveguide line or the second waveguide line;
wherein the beam splitter splits one light pulse incident to the incident port into a first light pulse and a second light pulse, the first light pulse propagating along the first waveguide line, the second light pulse propagating along the second waveguide line;
the reflection module reflects a first light pulse on the first waveguide and returns along the first waveguide, and reflects a second light pulse on the second waveguide and returns along the second waveguide;
the beam splitter is further configured to split a first optical pulse returning along the first waveguide line and a second optical pulse returning along the second waveguide line, and output the split optical pulses to the exit port.
Preferably, the reflecting module is a reflecting mirror or a faraday rotator mirror.
Preferably, the reflector includes a plane reflector disposed on the second end surface or a reflective film formed on the second end surface by a plating process.
Preferably, the faraday rotator comprises a reflector, a magneto-optical crystal and a magnetic ring;
the magneto-optical crystal is positioned on the incident light side of the reflector;
the magnetic ring is arranged around the magneto-optical crystal.
Preferably, the faraday rotator further comprises a collimating lens located at a side of the magneto-optical crystal facing away from the mirror.
Preferably, the delayer is arranged inside the waveguide chip, and is positioned on the first waveguide line or the second waveguide line.
Preferably, the delayer is a delayer with constant delay time or an adjustable delay time.
Preferably, the optical fiber coupler further comprises a phase modulation module, wherein the phase modulation module is arranged on the first waveguide line and/or the second waveguide line and is used for modulating the phase difference of the optical pulses transmitted on the first waveguide line and the optical pulses transmitted on the second waveguide line.
The present invention also provides a quantum key distribution system comprising a transmitting end and a receiving end connected by a channel, wherein,
the transmitting end comprises a pulse light source, a first interferometer, a first phase modulation module and an attenuator;
the receiving end comprises a first detector, a second phase modulation module and a second interferometer;
wherein the first interferometer and the second interferometer have the same arm length difference, and the first interferometer and/or the second interferometer is the hybrid waveguide integrated interferometer of any one of claims 1 to 7;
the pulse light source emits light pulses, the light pulses are coupled to the first interferometer, then emitted to the first phase modulation module, transmitted to the channel through the attenuator, transmitted to the second phase modulation module through the channel, and then transmitted to the second interferometer and the first detector respectively; and the light pulse after passing through the second interferometer is output to the second detector.
Preferably, the first phase modulation module is disposed inside the first interferometer;
and/or;
the second phase modulation module is disposed inside the second interferometer.
According to the technical scheme, the hybrid waveguide integrated interferometer comprises a waveguide chip, a delayer and a reflection module, wherein the waveguide chip comprises a beam splitter, a first waveguide line and a second waveguide line; on one hand, the first waveguide line and the second waveguide line are formed in the manufacturing process of the waveguide chip, and the accuracy of forming the first waveguide line and the second waveguide line in the manufacturing process of the waveguide chip can be controlled at a nanometer level, and is a micrometer level relative to the control accuracy of the optical fiber interferometer, so that the arm length difference control accuracy of the interferometer is higher. On the other hand, the waveguide chip interferometer has extremely small volume, is convenient for packaging vibration isolation and temperature control, is not easily influenced by external environment and has better stability; on the other hand, the optical waveguide has better polarization maintaining property, and compared with the optical fiber, the polarization of the optical pulse is better maintained in the transmission process, so that the hybrid waveguide integrated interferometer is more stable. The arm length difference of the hybrid waveguide integrated interferometer is easier to control relative to an optical fiber interferometer in the three aspects, and the hybrid waveguide integrated interferometer is further applied to a quantum key distribution system, so that the quantum key distribution system works more stably.
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 embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a hybrid waveguide integrated interferometer according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a hybrid waveguide integrated interferometer with a common reflector as a reflection module;
FIG. 3 is a schematic diagram of a hybrid waveguide integrated interferometer with a Faraday rotator mirror as a reflection module;
FIG. 4 is a schematic cross-sectional view of a Faraday rotator mirror according to an embodiment of the present invention;
FIG. 5 is a schematic cross-sectional view of another Faraday rotator provided in the embodiments of the present invention;
FIG. 6 is a schematic diagram of a hybrid waveguide integrated interferometer according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a hybrid waveguide integrated interferometer according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of a hybrid waveguide integrated interferometer according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of a hybrid waveguide integrated interferometer according to an embodiment of the present invention;
fig. 10 is a schematic structural diagram of a quantum key distribution system according to an embodiment of the present invention.
Detailed Description
As described in the background section, the arm length difference of the faraday michelson interferometer in the prior art is poor in control accuracy, and the interferometer itself has an unstable characteristic, which makes it difficult to control the arm length difference of the sending end and the receiving end to be consistent.
The inventor finds that the main reason for the above situation is that the faraday michelson interferometer in the prior art is an optical fiber interferometer, on one hand, the length difference between two arms of the interferometer is controlled by the length of the optical fiber, but the process precision in the prior art can only control the tolerance of the arm length of the interferometer at the micrometer level, so that the control precision of the arm length difference of the interferometer at the transmitting end and the receiving end is poor; moreover, the fiber interferometer is relatively susceptible to external environmental disturbances, such as changes caused by temperature, vibration, etc., which may cause the fiber interferometer to be unstable.
Based on this, the present invention provides a hybrid waveguide integrated interferometer comprising:
the device comprises a waveguide chip, a delayer and a reflection module;
the waveguide chip comprises a first end face and a second end face which are oppositely arranged, and the first end face comprises an incident port and an emergent port of the light pulse;
the reflection module is positioned on the second end face;
the waveguide chip comprises a beam splitter, a first waveguide line and a second waveguide line;
the delayer is used for delaying the light pulse on the first waveguide line or the second waveguide line;
wherein the beam splitter splits one light pulse incident to the incident port into a first light pulse and a second light pulse, the first light pulse propagating along the first waveguide line, the second light pulse propagating along the second waveguide line;
the reflection module reflects a first light pulse on the first waveguide and returns along the first waveguide, and reflects a second light pulse on the second waveguide and returns along the second waveguide;
the beam splitter is further configured to split a first optical pulse returning along the first waveguide line and a second optical pulse returning along the second waveguide line, and output the split optical pulses to the exit port.
The invention provides a hybrid waveguide integrated interferometer which comprises a waveguide chip, a delayer and a reflection module, wherein the waveguide chip comprises a beam splitter, a first waveguide line and a second waveguide line; on one hand, the first waveguide line and the second waveguide line are formed in the manufacturing process of the waveguide chip, and the accuracy of forming the first waveguide line and the second waveguide line in the manufacturing process of the waveguide chip can be controlled at a nanometer level, and is a micrometer level relative to the control accuracy of the optical fiber interferometer, so that the arm length difference control accuracy of the interferometer is higher. On the other hand, the waveguide chip interferometer has extremely small volume, is convenient for packaging vibration isolation and temperature control, is not easily influenced by external environment and has better stability; on the other hand, the optical waveguide has better polarization maintaining property, and compared with the optical fiber, the polarization of the optical pulse is better maintained in the transmission process, so that the hybrid waveguide integrated interferometer is more stable. The arm length difference of the hybrid waveguide integrated interferometer is easier to control relative to an optical fiber interferometer in the three aspects, and the hybrid waveguide integrated interferometer is further applied to a quantum key distribution system, so that the quantum key distribution system works more stably.
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a hybrid waveguide integrated interferometer according to an embodiment of the present invention, where the hybrid waveguide integrated interferometer includes: the device comprises a waveguide chip 1, a delayer 2 and a reflection module 3; the waveguide chip 1 comprises a first end face 11 and a second end face 12 which are oppositely arranged, wherein the first end face 11 comprises an incident port 111 and an emergent port 112 of the light pulse; the reflection module 3 is positioned on the second end face 12; the waveguide chip 1 comprises a beam splitter 13, a first waveguide line 14 and a second waveguide line 15; the delayer 2 is used to delay the light pulse on the first waveguide 14 or the second waveguide 15.
Wherein the beam splitter 13 splits one light pulse incident to the incident port 111 into a first light pulse traveling along the first waveguide line 14 and a second light pulse traveling along the second waveguide line 15; the reflection module 3 reflects the first light pulse on the first waveguide 14 and returns along the first waveguide 14, and reflects the second light pulse on the second waveguide 15 and returns along the second waveguide 15; the beam splitter 13 is also configured to split the first optical pulse returning along the first waveguide 14 and the second optical pulse returning along the second waveguide 15, and output the split optical pulses to the exit port 112.
It should be noted that the incident port and the exit port of the waveguide chip are only distinguished for convenience of description, and in an actual use process, the waveguide chip includes two optical pulse coupling ports, and the positions of the two optical pulse coupling ports are equivalent, and both the two optical pulse coupling ports can be used as the incident port and the exit port, which is not limited in this embodiment.
In this embodiment, the specific structure of the reflection module is not limited, the reflection module in the embodiment of the present invention is a reflector, please refer to fig. 2, and fig. 2 is a schematic structural view of a hybrid waveguide integrated interferometer in which the reflection module is a common reflector; the reflecting module may also be a faraday rotator, please refer to fig. 3, and fig. 3 is a schematic structural view of a hybrid waveguide integrated interferometer with the reflecting module being a faraday rotator. The reflecting mirror is a common reflecting mirror which only reflects the light pulse, and the Faraday rotator mirror is a reflecting mirror which rotates the polarization of the light pulse by 90 degrees. Because the waveguide has certain polarization maintaining characteristic, which is the characteristic of keeping the polarization state of light unchanged in the process of transmitting the light pulse, the embodiment of the invention can adopt a common reflector to reflect the light pulse. In other embodiments of the present invention, in order to further ensure the polarization state of light, a faraday rotator may be used to reflect the light pulse, which is not limited in this embodiment.
When the reflection module is a common reflection mirror, the specific arrangement manner of the reflection mirror is not limited in the embodiment of the present invention, please refer to fig. 2, the reflection mirror may be a plane reflection mirror 31 directly disposed on the second end face 12; with the reflective surface of the plane mirror facing the second end face 12. In addition, when the second end surface 12 is a plane, a reflective film may be directly formed on the second end surface 12 by a plating process in this embodiment, so as to further reduce the volume of the hybrid waveguide integrated interferometer.
When the reflecting module is a faraday rotator, the embodiment of the present invention does not limit the specific structure of the faraday rotator, and in an embodiment of the present invention, as shown in fig. 4, fig. 4 is a schematic cross-sectional structure diagram of a faraday rotator provided in the embodiment of the present invention; the Faraday rotator mirror 32 comprises a reflector 321, a magneto-optical crystal 322 and a magnetic ring 323; the magneto-optical crystal 322 is positioned on the incident light side of the reflector 321; a magnetic ring 323 is disposed around the magneto-optical crystal 322. The magneto-optical crystal 322 faces the second end face of the waveguide chip and is in contact with the first waveguide line and the second waveguide line.
In another embodiment of the present invention, in order to ensure that the optical pulses transmitted by the first waveguide line and the second waveguide line can return along the original path, as shown in fig. 5, fig. 5 is a schematic cross-sectional structure diagram of another faraday rotator provided in the embodiment of the present invention; faraday rotator mirror 32 further comprises a collimating lens 324, collimating lens 324 being located on the side of magneto-optical crystal 322 facing away from mirror 321.
It should be noted that, in the embodiment of the present invention, an external faraday rotator may be directly disposed outside the waveguide chip, see fig. 3, and a groove may be dug on the second end surface of the waveguide chip, so as to embed the magneto-optical crystal in the faraday rotator inside the waveguide chip, and then a reflector and other structures are disposed, see fig. 6.
In the embodiment of the present invention, the optical pulses transmitted on the first waveguide line and the second waveguide line in the hybrid waveguide integrated interferometer need to have relative time delay, and it should be noted that, in this embodiment, the specific form of the time delay is not limited, in an embodiment of the present invention, the time delay may be a time delay with constant time delay, and in another embodiment of the present invention, the time delay may also be a time delay with adjustable time delay. The invention is not limited in this regard. When the delayer is a delayer with constant delay time, the delayer may be disposed inside the waveguide chip, and located on the first waveguide line or the second waveguide line. In the manufacturing process of the waveguide chip, a delayer is drawn in the process of forming a first waveguide line or a second waveguide line; or the waveguide chip is arranged outside the waveguide chip and is realized by adopting a time delay piece; when the delayer is a delayer with adjustable delay time, the delayer with variable delay can be obtained by setting a micro-cavity or a multi-stage cascade mode.
When it is necessary to modulate the phase of the optical pulse on the first waveguide line or the second waveguide line, the hybrid waveguide integrated interferometer in this embodiment may further include a phase modulation module, where the phase modulation module is disposed on the first waveguide line and/or the second waveguide line, and is configured to modulate a phase difference between the optical pulse transmitted on the first waveguide line and the optical pulse transmitted on the second waveguide line. Referring to fig. 7-9, fig. 7 shows the phase modulation module 16 disposed on the first waveguide 14, fig. 8 shows the phase modulation module 16 disposed on the second waveguide 15, and fig. 9 shows the phase modulation module 16 disposed on the first waveguide 14 and the second waveguide 15. In this embodiment, the specific form of the phase modulation module is not limited, and the phase modulation module may be a phase modulator or a phase shifter.
It should be noted that, in this embodiment, the specific structure of the beam splitter 13 is not limited, and may be a 50:50 beam splitter, which is used to split one optical pulse into two identical optical pulses; or two light pulses may be combined to form one light pulse, which is not limited in this embodiment.
The hybrid waveguide integrated interferometer provided in the embodiment of the present invention may be applied to a transmitting end and/or a receiving end of a quantum key distribution system, and the working principle of the hybrid waveguide integrated interferometer in the embodiment is described by taking the case where the hybrid waveguide integrated interferometer is applied to the transmitting end of the quantum key distribution system as an example, and may be described by taking the hybrid waveguide integrated interferometer shown in fig. 1 as an example, and the working principle is specifically as follows:
the light pulse is incident from an incident port 111 of the waveguide chip, and is divided into a first light pulse and a second light pulse through a 50:50 beam splitter 13, wherein the first light pulse is transmitted along a first waveguide line 14, passes through a delayer 2, reaches a reflection module 3, is reflected, and returns to the beam splitter 13 along a first waveguide line 14; the second optical pulse is transmitted along the second waveguide line 15, reaches the reflection module 3, is reflected, and returns to the beam splitter 13 along the original path of the second waveguide line 15; the reflected first optical pulse and second optical pulse are also divided into two optical pulses at the beam splitter 13, and the first optical pulse and the second optical pulse are both divided into two, one of the optical pulses is emitted from the incident port 111 of the waveguide chip, and the other optical pulse is emitted from the emission port 112 of the waveguide chip. The optical pulse emitted from the incident port 111 is discarded, and the optical pulse emitted from the exit port 112 is used for quantum key distribution.
The invention provides a hybrid waveguide integrated interferometer which comprises a waveguide chip, a delayer and a reflection module, wherein the waveguide chip comprises a beam splitter, a first waveguide line and a second waveguide line; on one hand, the first waveguide line and the second waveguide line are formed in the manufacturing process of the waveguide chip, and the accuracy of forming the first waveguide line and the second waveguide line in the manufacturing process of the waveguide chip can be controlled at a nanometer level, and is a micrometer level relative to the control accuracy of the optical fiber interferometer, so that the arm length difference control accuracy of the interferometer is higher. On the other hand, the waveguide chip interferometer has extremely small volume, is convenient for packaging vibration isolation and temperature control, is not easily influenced by external environment and has better stability; on the other hand, the optical waveguide has better polarization maintaining property, and compared with the optical fiber, the polarization of the optical pulse is better maintained in the transmission process, so that the hybrid waveguide integrated interferometer is more stable. The arm length difference of the hybrid waveguide integrated interferometer is easier to control relative to an optical fiber interferometer in the three aspects, and the hybrid waveguide integrated interferometer is further applied to a quantum key distribution system, so that the quantum key distribution system works more stably.
Fig. 10 shows a schematic structural diagram of a quantum key distribution system provided in an embodiment of the present invention, where fig. 10 is a schematic structural diagram of a quantum key distribution system provided in an embodiment of the present invention; the quantum key distribution system comprises a sending end Alice and a receiving end Bob which are connected through a channel C, wherein the sending end Alice comprises a pulse light source A1, a first interferometer A2, a first phase modulation module A3 and an attenuator A4; the receiving end Bob includes a first detector B1, a second detector B2, a second phase modulation block B3, and a second interferometer B4.
Wherein the arm length difference of the first interferometer a2 and the second interferometer B4 is the same, and the first interferometer a2 and/or the second interferometer B4 is any one of the hybrid waveguide integrated interferometers provided in the above embodiments.
The connection relationship of the above structures includes: the pulse light source A1 emits light pulses, which are coupled to the first interferometer A2, emitted to the first phase modulation module A3, transmitted to the channel C through the attenuator A4, transmitted to the second phase modulation module B3 through the channel C, and transmitted to the second interferometer B4 and the first detector B1 respectively; the light pulse after passing through the second interferometer B4 is output to the second detector B2.
It should be noted that the quantum key distribution system includes a sending end Alice and a receiving end Bob, both of which include interferometers, in this embodiment, the sending end Alice or the receiving end Bob may use the hybrid waveguide integrated interferometer provided in the above embodiment of the present invention, or both of the sending end and the receiving end may use the hybrid waveguide integrated interferometer described in the above embodiment of the present invention. Because the arm length difference of the sending end Alice and the receiving end Bob needs to be kept strictly consistent, in order to conveniently control the arm length difference to be consistent, optionally, the interferometers of the sending end Alice and the receiving end Bob both adopt hybrid waveguide integrated interferometers, so that the problem of unstable work of the quantum key distribution system caused by inconsistent arm length is solved.
In this embodiment, the connection relationship between the input port and the output port of the first interferometer a2 and other components is not limited, and alternatively, the optical pulse of the pulsed light source a1 is coupled to the input port of the first interferometer a2 through an optical fiber and an optical fiber coupler; the optical pulse at the exit port of the first interferometer a2 is also coupled to external light through an optical fiber coupler and an optical fiber for transmission. The same connection relationship between the second interferometer B4 and other components is also realized by an optical fiber and an optical fiber coupler, which is not described in detail in this embodiment.
It should be noted that, in the embodiment of the present invention, the position of the phase modulation module is not limited, and the first phase modulation module A3 may also be disposed inside the first interferometer a 2; and/or; a second phase modulation block B3 may also be disposed inside the second interferometer B4. The phase modulation module is located in the first waveguide line and/or the second waveguide line of the interferometer, and specific arrangement modes can be shown in fig. 7 to 9, which are not described in detail in this embodiment.
At a receiving end Bob, the optical pulse after passing through the second phase modulation module B3 is divided into two paths, where one path is directly incident to the first detector B1, and the other path is incident to the second interferometer B4, where in this embodiment, the specific manner of implementing beam splitting is not limited, and optionally, as shown in fig. 10, the receiving end Bob further includes a circulator B5, the circulator B5 includes a port 1, a port 2, and a port 3, light at the three ports passes through the mode that the port 1 receives the optical pulse input, and the port 2 and the port 3 output the optical pulse respectively.
In this embodiment, the first phase modulation block a3 and the second phase modulation block B3 are both disposed outside the interferometer, and the operation principle of the quantum key distribution system includes:
(1) at the transmitting end Alice, light emitted from the pulsed light source a1 is coupled to an entrance port of the first interferometer a2, and is coupled into the waveguide chip through the coupler.
(2) The optical pulses travel along a waveguide line in the waveguide chip and are then split into two optical pulses after passing through a 50:50 splitter, one traveling along a first waveguide line in the waveguide chip and the other traveling along a second waveguide line in the waveguide chip.
(3) And then the two light pulses are respectively incident into a 90-degree Faraday rotation mirror and then enter the waveguide chip again after polarization rotation and reflection.
(4) These two pulses are again transmitted along the first and second waveguide lines, respectively. And then passes through the 50:50 beam splitter again to be emitted from the exit port of the waveguide chip. The emergent pulse is a front pulse and a rear pulse with the interval time corresponding to the arm length difference of the interferometer.
(5) The two pulses emitted by the first interferometer A2 then pass through a first phase modulation module A3, the first phase modulation module A3 performs phase modulation on any one of the pulses according to a BB84 protocol, and then the two pulses pass through an attenuator A4 and enter a channel C after being attenuated to a single photon magnitude.
(6) After receiving end Bob receives the optical pulses, the second phase modulation module B3 is also used to perform phase modulation on any one of the pulses according to BB84 protocol, and the phase-modulated pulses pass through port 1 and port 2 of the optical circulator and enter the second interferometer B4 having the same arm length difference with sending end Alice. After the two pulses are reflected by a 50:50 beam splitter and a Faraday rotator, a third pulse sequentially passing through a long arm of a first interferometer A2 in sending end Alice and a short arm of a second interferometer B4 in receiving end Bob and a fourth pulse sequentially passing through a short arm of a first interferometer A2 in sending end Alice and a long arm of a second interferometer B4 in receiving end Bob interfere at the 50:50 beam splitter, and then a first detector B1 and a second detector B2 are used for measuring an interference result. The two pulses interfere with each other, thereby extracting phase-encoded information.
(7) And recording the measurement result, and then completing the distribution of the quantum key by the base pair, error correction, secret amplification and the like by the transmitting end Alice and the receiving end Bob.
It should be noted that, the above description is only given by taking an example of a hybrid waveguide integrated interferometer structure, and the using method of the hybrid waveguide integrated interferometer structure with other structures is similar to the working principle in the embodiment of the present invention, and details thereof are not described in detail in this embodiment.
The arm length difference of the hybrid waveguide integrated interferometer is easier to control, so that the quantum key distribution system consisting of the hybrid waveguide integrated interferometer works more stably.
It should be noted that, in the present specification, the embodiments are all described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other.
It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in an article or device that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (9)
1. A hybrid waveguide integrated interferometer, comprising:
the optical waveguide module comprises a waveguide chip, a delayer and a reflecting module, wherein the reflecting module is a reflecting mirror or a Faraday rotator mirror;
the waveguide chip comprises a first end face and a second end face which are oppositely arranged, and the first end face comprises an incident port and an emergent port of the light pulse;
the reflection module is positioned on the second end face;
the waveguide chip comprises a beam splitter, a first waveguide line and a second waveguide line;
the delayer is used for delaying the light pulse on the first waveguide line or the second waveguide line;
wherein the beam splitter splits one light pulse incident to the incident port into a first light pulse and a second light pulse, the first light pulse propagating along the first waveguide line, the second light pulse propagating along the second waveguide line;
the reflection module reflects a first light pulse on the first waveguide and returns along the first waveguide, and reflects a second light pulse on the second waveguide and returns along the second waveguide;
the beam splitter is further configured to split a first light pulse returning along the first waveguide and a second light pulse returning along the second waveguide, and output the split light pulses to the exit port and the entrance port for exit.
2. The hybrid waveguide integrated interferometer of claim 1, wherein the mirror comprises a planar mirror disposed on the second end face or a reflective film formed on the second end face using a coating process.
3. The hybrid waveguide integrated interferometer of claim 1, wherein the faraday rotator comprises a mirror, a magneto-optical crystal, and a magnetic ring;
the magneto-optical crystal is positioned on the incident light side of the reflector;
the magnetic ring is arranged around the magneto-optical crystal.
4. The hybrid waveguide integrated interferometer of claim 3, wherein the Faraday rotator mirror further comprises a collimating lens located on a side of the magneto-optical crystal facing away from the mirror.
5. The hybrid waveguide integrated interferometer of claim 1, wherein the retarder is disposed inside the waveguide chip on the first waveguide line or the second waveguide line.
6. The hybrid waveguide integrated interferometer of claim 5, wherein the delay is a constant delay or an adjustable delay.
7. The hybrid waveguide integrated interferometer of claim 1, further comprising a phase modulation module disposed on the first waveguide line and/or the second waveguide line for modulating a phase difference between optical pulses transmitted on the first waveguide line and optical pulses transmitted on the second waveguide line.
8. A quantum key distribution system comprising a transmitting end and a receiving end connected by a channel, characterized in that,
the transmitting end comprises a pulse light source, a first interferometer, a first phase modulation module and an attenuator;
the receiving end comprises a first detector, a second phase modulation module and a second interferometer;
wherein the first interferometer and the second interferometer have the same arm length difference, and the first interferometer and/or the second interferometer is the hybrid waveguide integrated interferometer of any one of claims 1 to 7;
the pulse light source emits light pulses, the light pulses are coupled to the first interferometer, then emitted to the first phase modulation module, transmitted to the channel through the attenuator, transmitted to the second phase modulation module through the channel, and then transmitted to the second interferometer and the first detector respectively; and the light pulse after passing through the second interferometer is output to the second detector.
9. The quantum key distribution system of claim 8, wherein the first phase modulation module is disposed inside the first interferometer;
and/or;
the second phase modulation module is disposed inside the second interferometer.
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