CN114785493A - Quantum key distribution phase encoding method and device based on IQ (in-phase Quadrature) optical modulator - Google Patents
Quantum key distribution phase encoding method and device based on IQ (in-phase Quadrature) optical modulator Download PDFInfo
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Abstract
The invention provides a quantum key distribution phase encoding method and device based on an IQ optical modulator; the method comprises the following steps: splitting one path of input optical pulse into a first sub optical pulse and a second sub optical pulse, and respectively transmitting the first sub optical pulse and the second sub optical pulse along two optical paths; the first sub light pulse and the second sub light pulse are relatively delayed and then are combined into a pair of light pulses to be output; an IQ (in-phase quadrature) optical modulator is arranged on at least one of the two split optical paths or the optical path after beam combination output, and phase modulation is carried out on at least one optical pulse in the first sub optical pulse and the second sub optical pulse or at least one optical pulse in a pair of optical pulses output by the beam combination through the IQ optical modulator according to a quantum key distribution protocol in the process from beam splitting to beam combination; the two Mach-Zehnder modulators of the IQ optical modulator in-phase branch and the quadrature branch work in a push-pull mode.
Description
Technical Field
The invention relates to the technical field of optical transmission secret communication, in particular to a quantum key distribution phase coding method and a quantum key distribution phase coding device.
Background
The quantum secret communication technology is a leading-edge hotspot field combining quantum physics and information science. Based on quantum key distribution technology and the cryptographic principle of 'one-time pad', quantum secret communication can realize the safety of information in a public channel. The quantum key distribution is based on the physical principles of quantum mechanics Heisebauer uncertain relation, quantum unclonable theorem and the like, the key can be safely shared among users, potential eavesdropping behavior can be detected, and the quantum key distribution method can be applied to units with high safety requirements such as national defense, government affairs, finance, electric power and the like.
At present, the encoding scheme of quantum key distribution mainly adopts polarization encoding and phase encoding. The ground quantum key distribution is mainly based on optical fiber channel transmission, and in the optical fiber quantum channel transmission process, due to the non-ideal conditions that the section of the optical fiber is non-circular symmetrical, the refractive index of the fiber core is not uniformly distributed along the radial direction and the like in the optical fiber manufacturing process, and the optical fiber is influenced by temperature, strain, bending and the like in the actual environment, the random birefringence effect is generated. When polarization coding is adopted, the influence of random double refraction of optical fibers is received, when the quantum state of the polarization coding reaches a receiving end after being transmitted by long-distance optical fibers, the polarization state of light pulse is randomly changed, the error rate is increased, deviation rectifying equipment needs to be added, the complexity and the cost of a system are increased, and the stable application to the strong interference conditions of overhead optical cables, road and bridge optical cables and the like is difficult. Compared with polarization coding, phase coding adopts the phase difference of front and back light pulses to code information, and can be stably maintained in the long-distance optical fiber channel transmission process. When the phase coding scheme is used for interference decoding, the problem of polarization-induced fading exists due to the double refraction influence of the transmission optical fiber and the decoding interference ring optical fiber, and the problem is well solved. At present, the actual quantum key distribution application mainly adopts a BB84 protocol or an evolved BB84 protocol, phase encoding requires randomly generating four different phases (such as 0 degree, 90 degrees, 180 degrees, and 270 degrees), and it is a common practice to generate four different voltages through a digital-to-analog converter (DAC) to drive an electro-optical phase modulator to encode corresponding four phase values, which is limited by an analog bandwidth of the DAC, and this scheme is difficult to implement a high-speed quantum key distribution system.
Disclosure of Invention
A quantum key distribution phase coding method and a corresponding phase coding device are provided to solve the problem that in the prior art, phase coding needs to generate four different voltages to drive an electro-optic phase modulator to code four corresponding phase values and is limited by DAC analog bandwidth.
In a first aspect of the present application, there is provided a quantum key distribution phase encoding method, the method comprising: splitting one path of input optical pulse into a first sub optical pulse and a second sub optical pulse, and respectively transmitting the first sub optical pulse and the second sub optical pulse along two optical paths; the first sub light pulse and the second sub light pulse are relatively delayed and then are combined into a pair of light pulses to be output; an IQ (in-phase quadrature) optical modulator is arranged on at least one of the two split optical paths or the optical path after beam combination output, and phase modulation is carried out on at least one optical pulse in the first sub optical pulse and the second sub optical pulse or at least one optical pulse in a pair of optical pulses output by the beam combination through the IQ optical modulator according to a quantum key distribution protocol in the process from beam splitting to beam combination; the two Mach-Zehnder modulators of the IQ optical modulator in-phase branch and the quadrature branch work in a push-pull mode.
In an alternative of the present application, the modulation voltage of the in-phase branch mach-zehnder modulator of the IQ-optical modulator is randomly modulated by 0 or half-wave voltage, and the modulation voltage of the quadrature branch mach-zehnder modulator of the IQ-optical modulator is randomly modulated by 0 or half-wave voltage.
In an alternative aspect of the present application, the random modulation phase of the IQ-optical modulator comprises: 0 degrees, 90 degrees, 180 degrees, and 270 degrees.
In this application alternative, splitting one path of input light pulse into a first sub light pulse and a second sub light pulse includes: the input light pulse is split into a first sub light pulse and a second sub light pulse in a 50:50 ratio.
In a second aspect of the present application, there is also provided an IQ optical modulator-based quantum key distribution phase encoding apparatus; the method comprises the following steps: the beam splitter is used for receiving an input optical pulse and splitting the input optical pulse into two paths of sub optical pulses, namely a first sub optical pulse and a second sub optical pulse; the beam combiner is used for receiving the first sub optical pulse and the second sub optical pulse which are delayed relatively and outputting a pair of optical pulses; and the IQ optical modulator is arranged on an optical path of at least one of the first sub optical pulse and the second sub optical pulse or an output end of the beam combiner and is used for carrying out phase modulation on at least one of the first sub optical pulse and the second sub optical pulse transmitted through the optical path where the IQ optical modulator is arranged or at least one of a pair of combined optical pulses according to a quantum key distribution protocol. The in-phase and quadrature-branch Mach-Zehnder modulators of the IQ optical modulator are both operated in push-pull mode.
In an alternative of the present application, the modulation voltage of the in-phase branch mach-zehnder modulator of the IQ-optical modulator is randomly modulated by 0 or half-wave voltage, and the modulation voltage of the quadrature branch mach-zehnder modulator of the IQ-optical modulator is randomly modulated by 0 or half-wave voltage.
In an alternative aspect of the present application, the random modulation phase of the IQ-optical modulator comprises: 0 degrees, 90 degrees, 180 degrees, and 270 degrees.
In the alternative of the present application, the beam splitter, the beam combiner, the IQ optical modulator, and the optical devices on the optical path between the beam splitter and the beam combiner are all polarization maintaining optical devices.
In an alternative aspect of the present application, the apparatus further comprises: a first light reflector and a second light reflector; the first light reflector and the second light reflector are respectively positioned on the light paths of the first sub light pulse and the second sub light pulse and are respectively used for reflecting the first sub light pulse and the second sub light pulse back to the beam splitter; wherein, beam splitter and beam combiner are the same device.
In an alternative scheme of the application, the device further comprises an optical circulator, wherein the optical circulator is positioned at the front end of the beam splitter, one path of input optical pulse is input from a first port of the optical circulator and output to the beam splitter from a second port of the optical circulator, and a combined beam output from the beam combiner is input to the second port of the optical circulator and output from a third port of the optical circulator; the beam splitter and the beam combiner are the same device.
In summary, in the quantum key distribution phase encoding method and apparatus of the present invention, one input optical pulse is split into two sub optical pulses, that is, a first sub optical pulse and a second sub optical pulse, which are transmitted along two optical paths, respectively, and the two sub optical pulses are relatively delayed and then combined into a pair of optical pulses to be output, wherein an IQ optical modulator is configured on at least one of the two split optical paths or on an optical path after the combined optical pulse is output, and in a process from splitting to combining, at least one of the two sub optical pulses or at least one of the pair of optical pulses output by the combined optical pulse is phase-modulated according to a quantum key distribution protocol. The scheme uses digital level signal modulation, is easy to realize high-speed quantum key distribution phase modulation, and has the characteristics of simple method and low difficulty of implementation means.
Additional features and advantages of embodiments of the present application will be described in the detailed description which follows.
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, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a flowchart of an example IQ-optical modulator-based quantum key distribution phase encoding method according to an embodiment of the present invention;
fig. 2 is an IQ optical modulator-based quantum key distribution phase encoding apparatus as an example in a second embodiment of the present invention;
fig. 3 is an IQ optical modulator-based quantum key distribution phase encoding apparatus as an example in the third embodiment of the present invention;
fig. 4 is an IQ-optical-modulator-based quantum key distribution phase encoding apparatus as an example in a fourth embodiment of the present invention; and
fig. 5 is a schematic block diagram of an IQ optical modulator-based phase-encoded quantum key distribution system according to a fifth embodiment of the present invention.
In the above figures, the list of components represented by the various reference numbers is as follows:
example two
100. A quantum key distribution phase encoding device; 201. A beam splitter;
202. an IQ optical modulator; 203. A beam combiner;
204a, a first light reflector; 204b, a second light reflector;
205. an optical circulator.
EXAMPLE III
100. Phase encoding means; 301. A first input port;
302. a second input port; 303. A beam splitter;
304. an IQ optical modulator; 305. A beam combiner;
306. a first output port; 307. A second output port.
Example four
100. Phase encoding means; 401. A first transmission port;
402. a second transmission port; 403. A beam splitter;
404. an IQ optical modulator; 405. A first light reflector;
406. a second light reflector.
EXAMPLE five
100. Phase encoding means; 200. A quantum key distribution system.
Detailed Description
In order to make the above and other features and advantages of the present invention more apparent, the present invention is further described below with reference to the accompanying drawings. It is understood that the specific embodiments described herein are for purposes of illustration only and are not intended to be limiting, as those of ordinary skill in the art will recognize.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless explicitly specified otherwise.
The first embodiment of the present invention provides a general inventive concept, which is a high-speed, simple and convenient quantum key distribution phase encoding method based on an IQ optical modulator, the method first splits one optical pulse into two sub-optical pulses, modulates the sub-optical pulses or the combined optical pulse by setting the IQ optical modulator, makes the two split sub-optical pulses have a time delay property by time delay encoding, and outputs the combined optical pulse as a pair of optical pulses to realize high-speed quantum key distribution phase modulation.
Referring to fig. 1, fig. 1 is a flowchart of an IQ optical modulator-based quantum key distribution phase encoding method according to an embodiment of the present invention; the method specifically comprises the following steps:
s101, splitting one path of input optical pulse into a first sub optical pulse and a second sub optical pulse, and transmitting the first sub optical pulse and the second sub optical pulse along two optical paths respectively;
s102, performing relative delay on the first sub-optical pulse and the second sub-optical pulse, and combining the first sub-optical pulse and the second sub-optical pulse into a pair of optical pulses to be output;
step S103, setting an IQ light modulator on at least one of the two split light paths or the light path after beam combination output, and performing phase modulation on at least one of the first sub light pulse and the second sub light pulse or at least one of a pair of light pulses output by beam combination through the IQ light modulator according to a quantum key distribution protocol in the process from beam splitting to beam combination.
It can be understood that one path of input optical pulse is split into two paths of sub optical pulses, that is, a first sub optical pulse and a second sub optical pulse, which are respectively transmitted along two optical paths, and the two paths of sub optical pulses are relatively delayed and then combined into a pair of optical pulses to be output.
Thus, it will be understood by those skilled in the art that splitting and combining can be achieved by optical means, such as a beam splitter (or "splitter") and a beam combiner (or "combiner"), that convert one beam of light into two or more beams of light and combine the beams of light into a pair of optical pulses, and that other devices, such as a beam splitting lens, can be used instead in some embodiments. All the above mentioned beam splitters and beam combiners are common instruments in optical devices, and are not described in too much detail in the embodiments of the present invention.
Specifically, in the above-mentioned splitting of one input light pulse into the first sub light pulse and the second sub light pulse, in this embodiment, one input light pulse is split into two light pulses according to the splitting ratio of 50:50, so as to maintain the consistency of the first sub light pulse and the second sub light pulse.
Further, the arrival times of the different sub-light pulses may be made different by delay coding either of the first sub-light pulse and the second sub-light pulse.
And an IQ optical modulator is configured on at least one of the two split optical paths or the optical path after beam combination output, and phase modulation is carried out on at least one optical pulse of the two paths of sub optical pulses or at least one optical pulse of a pair of optical pulses output by beam combination according to a quantum key distribution protocol in the process from beam splitting to beam combination.
According to the preferable scheme of the foregoing embodiment, in step S103, the IQ optical modulator performs phase modulation according to the quantum key distribution protocol, and the random modulation phase of the IQ optical modulator includes four phases of 0 degree, 90 degrees, 180 degrees, and 270 degrees, that is, four phase modulations required for phase encoding can be randomly generated.
Specifically, Mach-Zehnder modulators (Mach-Zehnder modulators) of the in-phase branch and the quadrature branch of the IQ optical modulator are both operated in a push-pull mode, i.e., when the upper and lower arm phase shifts of the Mach-Zehnder modulators are opposite.
It can be understood that, in the invention, the in-phase shunt and the orthogonal shunt of the IQ optical modulator work in a push-pull mode, the in-phase shunt and the orthogonal shunt of the IQ optical modulator respectively and randomly generate (0, pi) and (pi/2, 3 pi/2) phase modulation through digital signal modulation, and four phase modulations required by phase encoding can be randomly generated after the two branches of light are combined.
More specifically, the modulation voltage of the in-phase shunt mach-zehnder modulator of the IQ-optical modulator is randomly modulated by 0 or half-wave voltage, and the modulation voltage of the quadrature shunt mach-zehnder modulator of the IQ-optical modulator is randomly modulated by 0 or half-wave voltage.
Further, the optical device split on the beam combining optical path and the IQ optical modulator are polarization maintaining optical devices.
In summary, the quantum key distribution phase encoding method based on the IQ optical modulator provided by the embodiments of the present invention uses digital level signal modulation, is easy to implement high-speed quantum key distribution phase modulation, and has the characteristics of simple method and low implementation difficulty. Therefore, the technical problem that four different voltages are required to be generated for driving the electro-optic phase modulator to encode four corresponding phase values and are limited by DAC analog bandwidth in phase encoding is solved.
Referring to fig. 2, fig. 2 is a schematic structural diagram of a quantum key distribution phase encoding device based on an IQ optical modulator according to a second embodiment of the present invention. A second embodiment of the present invention provides an IQ-optical modulator-based quantum key distribution phase encoding apparatus, where the phase encoding apparatus 100 includes:
a beam splitter 201, configured to receive an input optical pulse and split the input optical pulse into two sub optical pulses, which are a first sub optical pulse and a second sub optical pulse respectively;
a beam combiner 203 for receiving and outputting the first sub optical pulse and the second sub optical pulse;
between the beam splitter 201 and the beam combiner 203, two optical paths are included, and the first sub optical pulse and the second sub optical pulse are transmitted respectively.
The phase encoding apparatus 100 further includes:
and the IQ optical modulator 202 is arranged on at least one of the transmission optical paths of the first sub optical pulse and the second sub optical pulse, or the output end of the beam combiner 203, and is configured to perform phase modulation on at least one of the first sub optical pulse and the second sub optical pulse transmitted through the optical path thereof, or at least one optical pulse of a pair of combined optical pulses according to a quantum key distribution protocol.
In a preferred embodiment of the present invention, the IQ-optical modulator 202 is disposed on an optical path of at least one of transmission optical paths of the first sub-optical pulse and the second sub-optical pulse.
The connection relationship is that the input end of the beam splitter 201 is connected with an input optical pulse, and after the input optical pulse is divided into a first sub optical pulse and a second sub optical pulse in the beam splitter 201, the input optical pulse is optically coupled with the beam combiner 203 through two optical paths where the first sub optical pulse and the second sub optical pulse are located;
further, the upper and lower optical paths shown in fig. 2 are used for respectively transmitting two paths of sub-optical pulses and for realizing the relative delay of the two paths of sub-optical pulses, the beam combiner 203 is used for combining and outputting the two paths of sub-optical pulses, and the optical pulses output by combining are a pair of optical pulses.
In an optional scheme, the IQ optical modulator 202 is configured on one of two optical paths between the beam splitter 201 and the beam combiner 203 or at a rear end (output end) of the beam combiner 203, and is configured to perform phase modulation on at least one of two optical pulses transmitted through the optical path where the IQ optical modulator is located or at least one optical pulse of a pair of combined optical pulses according to a quantum key distribution protocol.
Specifically, the random modulation phase of the IQ optical modulator 202 includes: 0 degree, 90 degrees, 180 degrees, 270 degrees.
In this embodiment, the mach-zehnder modulators on both the in-phase and quadrature branches of IQ-optical modulator 202 operate in push-pull mode. The in-phase and quadrature branches mentioned above refer to one of the two branches, and as an example, the in-phase branch randomly modulates the phases of 0 ° and 180 °, and the quadrature branch randomly modulates the phases of 90 ° and 270 °, which are denoted as I-branch and Q-branch, and the I-branch and the Q-branch refer to the in-phase branch and the quadrature branch proposed in the embodiment of the present invention.
To sum up, the quantum key distribution phase encoding apparatus 100 provided in the embodiment of the present invention implements phase modulation on at least one optical pulse of the two sub optical pulses or at least one optical pulse of a pair of optical pulses output by beam combination according to a quantum key distribution protocol by using a simple structure, such as the beam splitter 201 and the beam combiner 203 which are the same device, and arranging the IQ optical modulator 202 on optical paths of the beam splitter 201 and the beam combiner 203, thereby implementing high-speed quantum key distribution phase modulation.
An embodiment three is a modification of the embodiment two, please refer to fig. 3, fig. 3 is a schematic structural diagram of a quantum key distribution phase encoding device based on an IQ optical modulator according to the embodiment three of the present invention; the phase encoding apparatus 100 specifically includes the following components: a beam splitter 303, an IQ optical modulator 304, a beam combiner 305;
in this embodiment, the first input port 301 or the second input port 302 on the side of the beam splitter 303 is used as an input terminal of the device, the first output port 306 or the second output port 307 on the side of the beam combiner 305 away from the beam splitter 303 is used as an output terminal of the device, the beam splitter 303 and the beam combiner 305 constitute an unequal arm mach-zehnder interferometer, and the IQ optical modulator 304 is inserted into either arm of the two arms of the unequal arm mach-zehnder interferometer.
During operation, one optical pulse is input from the first input port 301 or the second input port 302 on one side of the beam splitter 303, the beam splitter 303 splits the input optical pulse into two sub optical pulses, one of the two sub optical pulses is subjected to phase modulation by the IQ optical modulator 304 and then transmitted to the beam combiner 305, the other sub optical pulse is directly transmitted to the beam combiner 305, and the two sub optical pulses are relatively delayed and then combined into one optical pulse by the beam combiner 305 and output by the first output port 306 or the second output port 307.
Further, in this embodiment, the optical devices used in the optical paths of the beam splitter 303, the beam combiner 305, the IQ optical modulator 304, and the beam splitter 303 to the beam combiner 305 are all polarization maintaining optical devices.
The fourth embodiment is another modification of the second embodiment, and fig. 4 is a quantum key distribution phase encoding device based on an IQ optical modulator illustrated in the fourth embodiment of the present invention; the quantum key distribution phase encoding device based on the IQ optical modulator specifically comprises the following components: a beam splitter 403, an IQ light modulator 404, a first light mirror 405 and a second light mirror 406;
in this embodiment, the first transmission port 401 and the second transmission port 402 on one side of the beam splitter 403 are respectively used as an input end and an output end of the phase encoding device, the beam splitter 403, the first light reflector 405, and the second light reflector 406 constitute an unequal-arm michelson interferometer, and the IQ light modulator 404 is inserted into either arm of the two arms of the unequal-arm michelson interferometer.
During operation, one optical pulse is input from the first transmission port 401 on one side of the beam splitter 403, the beam splitter 403 splits the input one optical pulse into two sub optical pulses, that is, a first sub optical pulse and a second sub optical pulse, the first sub optical pulse is reflected back by the first light reflector 405 after being phase-modulated by the IQ optical modulator 404, the second sub optical pulse is directly transmitted to the second light reflector 406 and is also reflected back, and the two reflected sub optical pulses that are relatively delayed are combined into one optical pulse by the beam splitter 403 and output by the second transmission port 402.
The optical pulses are input from the second transmission port 402, output from the first transmission port 401, and the same result when the first transmission port 401 or the second transmission port 402 is input and output at the same time.
Specifically, when the first transmission port 401 or the second transmission port 402 is used as both input and output, the input port may be connected to an optical circulator (not shown), the optical pulse input by the first port of the optical circulator is output from the second port of the optical circulator to the beam splitter 403, and the optical pulse output from the beam splitter 403 to the second port of the optical circulator is output from the third port of the optical circulator.
Where in embodiments of the present invention the beam splitter and the beam combiner are the same device (i.e., 403 in the figure), the terms "beam splitter" and "beam combiner" may be used interchangeably herein, and a beam splitter may also be referred to and used as a beam combiner, and vice versa.
Further, the beam splitter 403, the IQ optical modulator 404, and the optical device on the optical path split into a combined beam by the beam splitter 403 are polarization maintaining optical devices.
It should be noted that the third embodiment and the fourth embodiment are modifications based on the second embodiment, the structural configuration is relatively simpler, and the beneficial effects of the second embodiment can be inherited.
The embodiment of the present invention further provides a quantum key distribution system 200, which includes the above-mentioned quantum key distribution phase encoding device 100, and the quantum key distribution phase encoding device 100 is disposed at the transmitting end of the quantum key distribution system 200 for phase encoding. In addition, the quantum key distribution phase encoding device 100 may be used for phase decoding, and when the phase decoding is performed, the quantum key distribution phase encoding device 100 is installed at a receiving end of the quantum key distribution system 200, and in this case, the IQ optical modulator is disposed at a front end of the beam splitter or on an optical path on which the first sub optical pulse and the second sub optical pulse are transmitted between the beam splitter and the beam combiner.
It is understood that, as will be understood by those skilled in the art, if the quantum key distribution system 200 provided by the embodiment of the present invention, all or some of the involved sub-modules are combined and replaced by fusing, simple change, mutual transformation, etc., the connection of the modules moves positions; or some modules are integrated; it is within the scope of the present invention to replace the corresponding components of the present invention with such a device/apparatus/system.
It should be noted that in the description of the present specification, reference to the description of "one embodiment", "some embodiments", "an example", "a specific example", or "some examples", etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
To sum up, the embodiment described above is consistent with the fifth embodiment, and the quantum key distribution phase encoding method, the quantum key distribution phase encoding device, and the quantum key distribution system including the quantum key distribution phase encoding device introduced in the embodiments of the present invention are based on a general inventive concept, split one path of input optical pulse into two paths of sub optical pulses, that is, a first sub optical pulse and a second sub optical pulse, transmit the two paths of sub optical pulses along two optical paths, respectively, perform relative delay on the two paths of sub optical pulses, and then combine the two paths of sub optical pulses into a pair of optical pulses to be output, where an IQ optical modulator is configured on at least one of the two split optical paths or on the optical path after the combination output, and perform phase modulation on at least one of the two paths of sub optical pulses or on at least one of a pair of optical pulses output by the combination in a process of splitting to the combination according to a quantum key distribution protocol. The invention enables the in-phase shunt and the orthogonal shunt of the IQ optical modulator to work in a push-pull mode through the Mach-Zehnder modulator of the in-phase shunt and the orthogonal shunt to respectively and randomly generate (0, pi) phase modulation and (pi/2, 3 pi/2) phase modulation, and four phase modulations required by phase coding can be randomly generated after the two shunts of light are combined.
It should be noted that, based on the embodiment of the method, the method may be implemented by replacing components in the apparatus by other components, and the apparatus may not bring other effects obvious to those skilled in the art, which are also continued to utilize the core idea in the embodiment of the method, and thus should still fall within the protection scope covered by the embodiment of the present invention.
The above are merely examples of the present application and are not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (10)
1. A quantum key distribution phase encoding method, the method comprising:
splitting one path of input optical pulse into a first sub optical pulse and a second sub optical pulse, and transmitting the first sub optical pulse and the second sub optical pulse along two optical paths respectively;
performing relative time delay on the first sub-optical pulse and the second sub-optical pulse, and combining the first sub-optical pulse and the second sub-optical pulse into a pair of optical pulses to be output;
an IQ (in-phase quadrature) optical modulator is arranged on at least one of the two split optical paths or the optical path after beam combination output, and phase modulation is carried out on at least one optical pulse in the first sub optical pulse and the second sub optical pulse or at least one optical pulse in a pair of optical pulses output by beam combination through the IQ optical modulator according to a quantum key distribution protocol in the process of splitting to beam combination; the two Mach-Zehnder modulators of the IQ optical modulator in-phase branch circuit and the quadrature branch circuit work in a push-pull mode.
2. The quantum key distribution phase encoding method of claim 1, wherein the modulation voltage of the in-phase shunt mach-zehnder modulator of the IQ optical modulator is randomly modulated 0 or half-wave voltage, and the modulation voltage of the quadrature shunt mach-zehnder modulator of the IQ optical modulator is randomly modulated 0 or half-wave voltage.
3. The quantum key distribution phase encoding method according to any one of claims 1 or 2, wherein the random modulation phase of the IQ light modulator comprises: 0 degrees, 90 degrees, 180 degrees, and 270 degrees.
4. The quantum key distribution phase encoding method of claim 1, wherein the splitting one path of input optical pulse into a first sub optical pulse and a second sub optical pulse comprises: splitting the input light pulse into a first sub light pulse and a second sub light pulse according to a 50:50 beam.
5. An IQ light modulator-based quantum key distribution phase encoding apparatus, the apparatus comprising:
the beam splitter is used for receiving an input optical pulse and splitting the input optical pulse into two paths of sub optical pulses, namely a first sub optical pulse and a second sub optical pulse;
the beam combiner is used for receiving the first sub optical pulse and the second sub optical pulse which are delayed relatively and outputting a pair of optical pulses;
the IQ optical modulator is arranged on an optical path of at least one of the first sub optical pulse and the second sub optical pulse or the output end of the beam combiner and is used for carrying out phase modulation on at least one of the first sub optical pulse and the second sub optical pulse transmitted through the optical path where the IQ optical modulator is arranged or at least one of a pair of combined optical pulses according to a quantum key distribution protocol; the Mach-Zehnder modulators of the in-phase branch and the quadrature branch of the IQ optical modulator work in a push-pull mode.
6. The IQ-optical-modulator-based quantum key distribution phase encoding apparatus according to claim 5, wherein the modulation voltage of the in-phase branch Mach-Zehnder modulator of the IQ optical modulator is randomly modulated by 0 or half-wave voltage, and the modulation voltage of the quadrature branch Mach-Zehnder modulator of the IQ optical modulator is randomly modulated by 0 or half-wave voltage.
7. The IQ-light-modulator-based quantum key distribution phase encoding apparatus according to any one of claims 5 or 6, characterized in that the random modulation phase of the IQ-light modulator comprises: 0 degrees, 90 degrees, 180 degrees, and 270 degrees.
8. The IQ optical modulator-based quantum key distribution phase encoding apparatus according to claim 5, wherein the beam splitter, the beam combiner, the IQ optical modulator, and the optical devices on the optical path from the beam splitter to the beam combiner are all polarization maintaining optical devices.
9. The IQ-light-modulator-based quantum key distribution phase encoding apparatus according to claim 5, characterized in that the apparatus further comprises: a first light reflector and a second light reflector;
the first light reflector and the second light reflector are respectively positioned on the light paths of the first sub light pulse and the second sub light pulse and are respectively used for reflecting the first sub light pulse and the second sub light pulse back to the beam splitter; wherein the beam splitter and the beam combiner are the same device.
10. The IQ-optical-modulator-based quantum key distribution phase encoding apparatus according to claim 5, characterized in that the apparatus further comprises an optical circulator located in front of the beam splitter, the one input optical pulse being input from a first port of the optical circulator and output from a second port of the optical circulator to the beam splitter, a combined beam output from the beam combiner being input to the second port of the optical circulator and output from a third port of the optical circulator; wherein, the beam splitter and the beam combiner are the same device.
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