CN107070655A - One kind polarization and phase tangle coding method, device and quantum key dispatching system - Google Patents
One kind polarization and phase tangle coding method, device and quantum key dispatching system Download PDFInfo
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Abstract
The present invention proposes a kind of polarization and phase tangles coding method, device and quantum key dispatching system, and this method includes：First photon of the polarization-entangled photon centering that polarization-entangled light source is produced is converted to phase code by polarization encoder；It is converted into the first photon of phase code and the second photon formation polarization and phase entangled photon pairs of the polarization-entangled photon centering.The transmission advantage that the quantum key dispatching system for tangling code device composition based on polarization and phase can make full use of different coding in different channels, when realizing different channels transmission, photon is converted to phase code by polarization encoder.Using the quantum key dispatching system of the present invention, the quantum-key distribution demand of free space and fiber mix transmission can be met.
Description
Technical Field
The invention relates to the technical field of optical transmission secure communication, in particular to a polarization and phase entanglement encoding method and device and a quantum key distribution system.
Background
One of the main technical approaches for realizing wide area quantum secure communication is to establish a space-based quantum secure communication satellite network and a ground metropolitan area/inter-city quantum secure communication optical fiber network, and connect the main nodes of each metropolitan area/inter-city quantum secure communication network of a ground optical fiber channel through a free space channel quantum satellite network to realize the wide area quantum secure communication. In a wide-area quantum secret communication system, coded light quanta need to be transmitted in two channels, namely a free space channel and an optical fiber channel, and cannot be detected in the transmission process before reaching two communication parties. The optical quantum polarization encoding is a main encoding mode adopted by free space channel quantum key distribution, and the optical quantum phase encoding and the polarization encoding are two main encoding modes adopted by optical fiber channel quantum key distribution. The optical fiber channel adopts phase coding, particularly adopts phase coding of an unequal-arm Faraday-Michelson interferometer, can realize an optical fiber channel quantum key distribution system of environmental interference immunity, and has stable and long-range quantum key distribution capacity. If polarization encoding is adopted in a free space channel and phase encoding is adopted in a fiber channel, conversion between polarization encoding and phase encoding needs to be realized. At present, a conversion method between polarization encoding and phase encoding in quantum secure communication is rarely reported.
Disclosure of Invention
The invention mainly aims to provide a polarization and phase entanglement encoding method, a polarization and phase entanglement encoding device and a quantum key distribution system, which are used for solving the problem that the polarization encoding of the quantum key distribution system based on entangled photon pairs is converted into phase encoding, realizing the problem of polarization and phase entanglement and establishing the problem of the polarization and phase entanglement quantum key distribution system applicable to free space and optical fiber mixed channels.
To achieve the above object, the present invention provides a polarization and phase entanglement encoding method, comprising:
converting a first photon of a polarization-entangled photon pair generated by a polarization-entangled light source from polarization encoding to phase encoding;
forming a polarization and phase-entangled photon pair from the first photon converted into the phase encoding and a second photon of the polarization-entangled photon pair; wherein the second photon is polarization encoded;
a method of converting a first photon from polarization encoding to phase encoding, comprising:
the method comprises the steps of splitting a first photon into photons transmitted on two sub-light paths through a polarization beam splitter, carrying out phase encoding on the photons transmitted on the two sub-light paths through phase encoders respectively arranged on the two sub-light paths, combining the photons transmitted on the two sub-light paths after the phase encoding into photons output by one light path through a beam combiner, wherein the combined photons output by one light path have a determined polarization state.
Optionally, the phase difference of the phase encoder codes respectively arranged on the two sub-optical paths is 180 degrees.
Optionally, the photons transmitted on the two sub-optical paths arrive at the beam combiner synchronously, and are combined into photons output by one optical path.
Optionally, an eigen state of an orthogonal basis of the polarization beam splitter is the same as an orthogonal polarization state of the first photon, and the polarization beam splitter splits the orthogonal polarization state of the first photon onto the two sub-optical paths.
Optionally, when the polarization states of the photons transmitted on the two sub-optical paths incident to the beam combiner are the same, the beam combiner uses a polarization-independent beam combiner;
when the polarization state of the photons transmitted on the two sub-light paths and incident to the beam combiner is an orthogonal polarization state, the beam combiner adopts a polarization-independent beam combiner or a polarization beam combiner; when the beam combiner adopts a polarization beam combiner, the orthogonal polarization state of the photons transmitted on the two sub-light paths is the eigenstate of the orthogonal base of the polarization beam combiner.
Optionally, the phase encoder adopts any one of the following: unequal arm Mach-Zehnder interferometers, unequal arm Michelson interferometers, and unequal arm Faraday-Michelson interferometers.
Optionally, when the phase encoder uses an unequal-arm michelson interferometer or an unequal-arm faraday-michelson interferometer, the polarization beam combiner and the polarization beam splitter are the same device.
Optionally, the method for controlling the combined beam to be a photon output by one optical path to have a certain polarization state includes:
a polarizer is arranged behind the beam combiner; or,
polarizers are respectively arranged on two sub-light paths between the polarization beam splitter and the beam combiner; or,
and arranging a polarization controller on one or two sub-light paths between the polarization beam splitter and the beam combiner.
Optionally, the polarization beam splitter, the phase encoder, the beam combiner, the polarization controller, the polarizer, and the discrete devices and waveguide devices used for guiding light are all polarization-controlled devices, and control the polarization state of photons in an optical path, so that the photons output by the combined beam as one optical path have a certain polarization state.
Further, to achieve the above object, the present invention provides a polarization and phase entanglement encoding device including: the device comprises a polarization beam splitter, a beam combiner and a phase encoder;
the polarization beam splitter is used for splitting a first photon in the polarization-entangled photon pair generated by the polarization-entangled light source into photons transmitted on two sub-light paths;
the phase encoders are respectively arranged on the two sub-light paths and are used for carrying out phase encoding on photons transmitted on the two sub-light paths;
the beam combiner is used for combining the photons transmitted on the two sub-light paths after phase coding into photons output by one light path.
Optionally, the phase difference of the phase encoder codes respectively arranged on the two sub-optical paths is 180 degrees.
Optionally, the photons transmitted on the two sub-optical paths arrive at the beam combiner synchronously, and are combined into photons output by one optical path.
Optionally, an eigen state of an orthogonal basis of the polarization beam splitter is the same as an orthogonal polarization state of the first photon, and the polarization beam splitter splits the orthogonal polarization state of the first photon onto the two sub-optical paths.
Optionally, when the polarization states of the photons transmitted on the two sub-optical paths incident to the beam combiner are the same, the beam combiner uses a polarization-independent beam combiner;
when the polarization state of the photons transmitted on the two sub-light paths and incident to the beam combiner is an orthogonal polarization state, the beam combiner adopts a polarization-independent beam combiner or a polarization beam combiner; when the beam combiner adopts a polarization beam combiner, the orthogonal polarization state of the photons transmitted on the two sub-light paths is the eigenstate of the orthogonal base of the polarization beam combiner.
Optionally, the phase encoder adopts any one of the following: unequal arm Mach-Zehnder interferometers, unequal arm Michelson interferometers, and unequal arm Faraday-Michelson interferometers.
Optionally, when the phase encoder uses an unequal-arm michelson interferometer or an unequal-arm faraday-michelson interferometer, the polarization beam combiner and the polarization beam splitter are the same device.
Optionally, the apparatus further comprises: a polarizer or polarization controller; the polarizer or the polarization controller is used for controlling the combined beam to be a photon output by a light path to have a determined polarization state;
when the device comprises polarizers, the polarizers are arranged behind the beam combiner, or the polarizers are respectively arranged on two sub-optical paths between the polarization beam splitter and the beam combiner;
when the device comprises a polarization controller, the polarization controller is arranged on one or two sub-light paths between the polarization beam splitter and the beam combiner.
Optionally, the polarization beam splitter, the phase encoder, the beam combiner, the polarization controller, the polarizer, and the discrete devices and waveguide devices used for guiding light are all polarization-controlled devices, and control the polarization state of photons in an optical path, so that the photons output by the combined beam as one optical path have a certain polarization state.
In addition, to achieve the above object, the present invention also provides a quantum key distribution system, including: a polarization entanglement light source, a phase decoder, a polarization decoder, a single photon detector and the polarization and phase entanglement encoding device introduced above;
the polarization-entangled light source is used for generating polarization-entangled photon pairs;
the polarization and phase entanglement encoding device is used for converting a first photon in the polarization entangled photon pair from polarization encoding to phase encoding;
the phase decoder is used for decoding the first photons converted into the phase codes;
the polarization decoder is used for decoding the second photon in the polarization entangled photon pair; wherein the second photon is polarization encoded;
the single photon detector is used for detecting the photons output by the phase decoder and the polarization decoder and carrying out quantum key distribution according to the detection result and a quantum key distribution protocol.
Optionally, the phase set in the phase decoder is identical to or differs by 90 degrees from the phase set in any one of the phase encoders in the polarization and phase entanglement encoding devices, and phase modulation is performed according to a quantum key distribution protocol.
Optionally, the system further includes: a quantum channel;
the quantum channel is used for transmitting photons; the quantum channel is composed of at least one of: optical waveguides, optical fibers, free space, discrete optical elements, planar waveguide optical elements, fiber optical elements.
Optionally, quantum channels between the polarization-entangled light source and the polarization and phase-entangled encoding device and quantum channels between the polarization-entangled light source and the polarization decoder are non-depolarized quantum channels.
Optionally, the system further includes: a polarization-independent beam splitter;
the polarization-independent beam splitter is used for receiving the photons transmitted by the polarization and phase entanglement encoding device and splitting the photons transmitted by the polarization and phase entanglement encoding device into two phase decoders in an equal probability manner;
the polarization-independent beam splitter is further used for receiving the second photon sent by the polarization-entangled light source and splitting the second photon into two polarization decoders in an equal probability manner.
Optionally, the phase decoder employs any one of the following: unequal arm Mach-Zehnder interferometers, unequal arm Michelson interferometers, and unequal arm Faraday-Michelson interferometers.
Optionally, when the phase decoder employs an unequal-arm mach-zehnder interferometer, two output ports of the phase decoder are respectively connected with the single photon detector;
when the phase decoder employs an unequal-arm michelson interferometer or an unequal-arm faraday-michelson interferometer, the system further comprises: an optical circulator;
the first port of the optical circulator receives photons sent by the polarization and phase entanglement coding device or the polarization-independent beam splitter, and the photons are output to the phase decoder from the second port of the optical circulator and sent to the single photon detector through the phase decoder; and the second port of the optical circulator receives the photons sent by the phase decoder and outputs the photons to another single photon detector through the third port of the optical circulator.
By adopting the technical scheme, the invention at least has the following advantages:
the polarization and phase entanglement encoding method, the polarization and phase entanglement encoding device and the quantum key distribution system convert the polarization encoding of the first photon in the polarization entanglement photon pair into the phase encoding so as to realize that the second photon in the polarization entanglement photon pair and the first photon converted into the phase encoding form the polarization and phase entanglement photon pair. The quantum key distribution system formed by the polarization and phase entanglement encoding devices can fully utilize the transmission advantages of different codes in different channels, and photons are converted from polarization codes into phase codes when the transmission of the different channels is realized, so that the technical foundation is laid for establishing a world-wide quantum secret communication network. For example, free space and fiber hybrid channel quantum key distribution can be realized by polarization and phase-entangled photon pairs generated by a polarization and phase-entangled encoding device, wherein the polarization-encoded photons are transmitted in a free space channel in the photon pairs, and the phase-encoded photons are transmitted in a fiber channel. For another example, one polarization-encoded photon of the polarization and phase-entangled photon pair is transmitted in a free space channel, and the other polarization-encoded photon is transmitted in the free space for a distance and then coupled into an optical fiber channel for transmission. The method is simple and easy to realize, and can effectively solve the problems of converting the polarization code of the entangled light source into the phase code, realizing polarization and phase entanglement, realizing quantum entanglement distribution and quantum key distribution applied to free space and optical fiber mixed channels and the like.
Drawings
FIG. 1 is a flow chart of a polarization and phase entanglement encoding method of a first embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a polarization and phase-entangled encoding device according to a second embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a polarization and phase-entangled encoding device according to a third embodiment of the present invention;
FIG. 4 is a schematic structural diagram of a polarization and phase-entangled encoding device according to a fourth embodiment of the present invention;
FIG. 5 is a schematic structural diagram of a polarization and phase-entanglement encoding device according to a fifth embodiment of the invention;
FIG. 6 is a schematic structural diagram of a polarization and phase-entangled encoding device according to a sixth embodiment of the present invention;
FIG. 7 is a schematic structural diagram of a polarization and phase-entangled encoding device according to a seventh embodiment of the present invention;
FIG. 8 is a schematic structural diagram of a polarization and phase-entanglement encoding device according to an eighth embodiment of the invention;
FIG. 9 is a schematic diagram of the structure of an unequal arm Mach-Zehnder interferometer according to a ninth embodiment of the present invention;
FIG. 10 is a schematic structural diagram of an unequal-arm Michelson interferometer according to a tenth embodiment of the invention;
FIG. 11 is a schematic structural diagram of an unequal arm Faraday-Michelson interferometer according to an eleventh embodiment of the present invention;
fig. 12 and 13 are schematic structural diagrams of components of a quantum key distribution system according to a twelfth embodiment of the present invention.
Detailed Description
The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with the embodiments of the invention serve to explain the principles of the invention. For the purpose of clarity and simplicity, a detailed description of known functions and configurations in the devices described herein will be omitted when it may obscure the subject matter of the present invention.
It is a primary object of embodiments of the present invention to provide a polarization and phase entanglement encoding method, a polarization and phase entanglement encoding device constructed according to the method, and a quantum key distribution system composed of such encoding devices. The invention converts the first photon of a polarization-entangled photon pair generated by an entanglement light source from polarization encoding to phase encoding. The method for converting the first photon from polarization coding to phase coding comprises the following steps: the first photon is split into photons transmitted on two sub-light paths through a polarization beam splitter, the photons transmitted on the two sub-light paths are respectively subjected to phase coding modulation, the photons transmitted on the two sub-light paths are combined into a photon output by one light path, and the photon output by the combined beam which is one light path has a determined polarization state. The first photon converted to phase encoding is formed into a polarization and phase-entangled photon pair with a second photon of the polarization-entangled photon pair. And (3) establishing a quantum key distribution system meeting the transmission requirements of different channels by utilizing the transmission advantages of different codes in different channels. The method is simple and easy to implement.
The technical solution of the present invention will be described in detail by means of several specific examples.
A first embodiment of the present invention, a polarization and phase entanglement encoding method, as shown in fig. 1, includes the following specific steps:
step S101: the first photon of the polarization-entangled photon pair generated by the polarization-entangled light source is converted from polarization encoding to phase encoding.
In particular, a polarization-entangled light source generates a pair of polarization-entangled photons. The polarization state of the polarization entangled photon pair is a set of orthogonal polarization states, commonly used orthogonal polarization states are a set of linear polarization states polarized horizontally and vertically, a set of linear polarization states polarized at 45 degrees and-45 degrees, and a set of circular polarization states polarized left-hand and right-hand. Taking a set of linear polarization states of horizontal and vertical polarization as an example, a pair of polarization-entangled photons generated by the polarization-entangled light source are four Bell statesWherein H and V represent the horizontal and vertical polarization states, respectively, and subscripts 1 and 2 represent the first and second photons, respectively.
Further, a method of converting a first photon from polarization encoding to phase encoding, comprising:
the method comprises the steps of splitting a first photon into photons transmitted on two sub-light paths through a polarization beam splitter, carrying out phase encoding on the photons transmitted on the two sub-light paths through phase encoders respectively arranged on the two sub-light paths, combining the photons transmitted on the two sub-light paths after the phase encoding into photons output by one light path through a beam combiner, wherein the combined photons output by one light path have a determined polarization state.
And the phase difference of the two phase encoder codes respectively arranged on the two sub-optical paths is 180 degrees.
And the photons transmitted on the two sub-light paths synchronously reach the beam combiner, and are combined into photons output by one light path.
Wherein the eigen state of the orthogonal basis of the polarization beam splitter is the same as the orthogonal polarization state of the first photon, and the polarization beam splitter splits the orthogonal polarization state of the first photon onto the two sub-optical paths.
For example, a common polarization beam splitter can transmit and reflect horizontal and vertical polarization states, convert left and right circular polarization states into horizontal and vertical polarization states using 90 degree glass slides and half glass slides, and inject the polarization beam splitter, and convert 45 degree and-45 degree polarization states into horizontal and vertical polarization states, and inject the polarization beam splitter into the polarization beam splitter, or rotate the polarization beam splitter by 45 degrees, which transmits and reflects the horizontal and vertical polarization states, respectively.
Wherein, the beam combiner includes: a polarization-independent beam combiner or polarization beam combiner; when the polarization states of the photons transmitted on the two sub-light paths and incident to the beam combiner are the same, the beam combiner adopts a polarization-independent beam combiner; when the polarization state of the photons transmitted on the two sub-light paths and incident to the beam combiner is an orthogonal polarization state, the beam combiner adopts a polarization-independent beam combiner or a polarization beam combiner; when the beam combiner adopts a polarization beam combiner, the orthogonal polarization state of the photons transmitted on the two sub-light paths is the eigenstate of the orthogonal base of the polarization beam combiner.
Wherein, the phase encoder adopts any one of the following: unequal arm Mach-Zehnder interferometers, unequal arm Michelson interferometers, and unequal arm Faraday-Michelson interferometers.
When the phase encoder adopts an unequal-arm michelson interferometer or an unequal-arm faraday-michelson interferometer, the polarization beam combiner and the polarization beam splitter are the same device.
Furthermore, the method for controlling the photons output by the combined beam into one optical path to have a determined polarization state comprises the following steps:
a polarizer is arranged behind the beam combiner; or,
polarizers are respectively arranged on two sub-light paths between the polarization beam splitter and the beam combiner; or,
and arranging a polarization controller on one or two sub-light paths between the polarization beam splitter and the beam combiner.
In addition, the polarization beam splitter, the phase encoder, the beam combiner, the polarization controller, the polarizer, and the discrete devices and waveguide devices used by the transmitted light are all polarization control type devices, and the polarization state of photons in an optical path is controlled, so that the photons output by the combined beam as one optical path have a determined polarization state.
Step S102: forming a polarization and phase-entangled photon pair from the first photon converted into the phase encoding and a second photon of the polarization-entangled photon pair; wherein the second photon is polarization encoded.
In this embodiment, the polarization-entangled light source generates a pair of polarization-entangled photons, any one of the pair of polarization-entangled photons is incident on the polarization beam splitter, the polarization beam splitter splits the photons into photons transmitted on two sub-optical paths, the photons transmitted on the two sub-optical paths are respectively phase-encoded by the phase encoder, and the phase-encoded photons transmitted on the two sub-optical paths are combined into a photon output by an optical path by the beam combiner. The phase difference of the phase encoder codes arranged on the two sub-optical paths is 180 degrees. In order to make the polarization state of the photons output after combination not be related to the phase, the combined photon beam transmitted on the two sub-optical paths is the photons output by one optical path and then has a determined polarization state. The method for enabling the photons transmitted on the two sub-optical paths to have a determined polarization state after being combined and output comprises the following steps: outputting the photons output after the beam combination to a transmitted quantum channel through a polarizer; or polarizers are arranged in the two sub-optical paths between the polarization beam splitter and the beam combiner, so that the photons of the two sub-optical paths have the same polarization state and are combined and output to the transmitted quantum channel; or a polarization controller is arranged in one or two sub-optical paths between the polarization beam splitter and the beam combiner, and the photons of the two sub-optical paths are modulated into the same polarization state and then combined and output to a transmitted quantum channel. The other photon of the pair of entangled photons generated by the entanglement light source remains polarization encoded, thus generating a pair of polarization and phase entangled photons, one photon employing phase encoding and the other employing polarization encoding.
A second embodiment of the present invention, a polarization and phase-entangled encoding device, as shown in fig. 2, specifically includes the following components: a polarization beam splitter 201, two phase encoders 202 and 203, and a beam combiner 204;
1) the polarization beam splitter 201 is used to split the first photon of the polarization-entangled pair of photons generated by the polarization-entangled light source into photons that are transmitted on two sub-optical paths.
Specifically, the eigenstate of the orthogonal base of the polarization beam splitter 201 is the same as the orthogonal polarization state of the first photon, and the polarization beam splitter 201 splits the orthogonal polarization state of the first photon onto the two sub-optical paths.
2) The phase encoders 202 and 203 are respectively disposed on two sub-optical paths between the polarization beam splitter 201 and the beam combiner 204, and the phase encoders 202 and 203 are configured to perform phase encoding on photons transmitted on the two sub-optical paths.
Specifically, the phases encoded by the phase encoder 202 and the phase encoder 203 are different by 180 degrees.
Specifically, the phase encoders 202 and 203 perform phase encoding on photons, and the phase encoders 202 and 203 adopt any one of the following: unequal arm Mach-Zehnder interferometers, unequal arm Michelson interferometers, and unequal arm Faraday-Michelson interferometers.
3) The beam combiner 204 is configured to combine the phase-coded photons transmitted on the two sub-optical paths into a photon output by one optical path.
Specifically, the beam combiner 204 includes: a polarization-independent beam combiner or polarization beam combiner; when the polarization states of the photons incident to the beam combiner 204 and transmitted on the two sub-optical paths are the same, the beam combiner 204 adopts a polarization-independent beam combiner; when the polarization state of the photons transmitted on the two sub-optical paths incident to the beam combiner 204 is a set of orthogonal polarization states, the beam combiner 204 is a polarization-independent beam combiner or a polarization beam combiner; when the polarization beam combiner 204 uses the polarization beam combiner, the orthogonal polarization states of the photons transmitted on the two sub-optical paths are eigenstates of an orthogonal basis of the polarization beam combiner.
Further, when the unequal-arm michelson interferometer or the unequal-arm faraday-michelson interferometer is used in the phase encoders 202 and 203, the polarization beam combiner 204 and the polarization beam splitter 201 are the same device.
Further, the photons split by the polarization beam splitter 201 and transmitted on the two sub-optical paths synchronously reach the beam combiner 204 and are combined into one output path.
Further, a first photon of the polarization-entangled photon pair that passes through the polarization and phase-entangled encoding device is formed into a polarization and phase-entangled photon pair with a second photon of the polarization-entangled photon pair.
Still further, the apparatus further comprises: a polarizer or polarization controller; the polarizer or the polarization controller is used for controlling the combined beam to be a photon output by a light path to have a determined polarization state;
when the device comprises polarizers, the polarizers are arranged behind the beam combiner 204, or the polarizers are respectively arranged on two sub-optical paths between the polarization beam splitter 201 and the beam combiner 204; or
When the apparatus comprises a polarization controller, the polarization controller is disposed on one or two sub-optical paths between the polarization beam splitter 201 and the beam combiner 204.
In addition, the polarization beam splitter 201, the phase encoders 202 and 203, the beam combiner 204, the polarization controller, the polarizer, and the discrete devices and waveguide devices used for guiding light are all polarization control devices, and control the polarization state of photons in an optical path, so that the photons output by the combined beam as one optical path have a determined polarization state.
A third embodiment of the present invention, a polarization and phase-entangled encoding device, as shown in fig. 3, specifically includes the following components: a polarizing beam splitter 301, two phase encoders 302 and 305, two mirrors 303 and 304, a beam combiner 306, and a polarizer 307.
Any one photon in the polarization-entangled photon pair generated by the polarization-entangled light source is input to the polarization beam splitter 301, and the polarization beam splitter 301 splits two orthogonal polarization states of the incident photon into two sub-optical paths for transmission. One path is subjected to phase encoding by a phase encoder 302 and then reflected to an input port of a beam combiner 306 by a reflector 303; the other path is reflected by the mirror 304, phase-encoded by the phase encoder 305, and output to the other input port of the beam combiner 306. The two sub-optical paths synchronously reach the beam combiner 306, and the beam combiner 306 combines the photons transmitted by the two sub-optical paths and outputs the combined photons to the polarizer 307. The polarizer 307 allows both polarization states of the incident photon to pass through and output with the same probability. The beam combiner 306 may use a polarization beam combiner or a polarization-independent beam combiner. The mirrors 303 and 304 are used to adjust the propagation direction of the optical path, and a waveguide device may be used instead to transmit photons and adjust the propagation direction of the optical path. In the polarization and phase entanglement encoding device, discrete devices and waveguide devices used by conducted light, a phase encoder, a polarization beam splitter, a beam combiner, a polarizer and the like are all polarization control type devices.
A fourth embodiment of the present invention, a polarization and phase-entangled encoding device, as shown in fig. 4, specifically includes the following components: a polarizing beam splitter 401, two phase encoders 402 and 403, and a polarizer 404.
Any one photon in the polarization entangled photon pair generated by the entanglement light source is input through the first port A of the polarization beam splitter 401, and the polarization beam splitter 401 splits two orthogonal polarization states of the incident photon into two sub-optical paths for transmission. One of the two paths is output from the third port C of the polarization beam splitter 401 to the phase encoder 402 for phase encoding, and is output from the input port of the phase encoder 402 to the polarization beam splitter 401 after being reflected. The other route is that the fourth port D of the polarization beam splitter 401 outputs to the phase encoder 403 for phase encoding, and the reflected route is output to the polarization beam splitter 401 from the input port of the phase encoder 403. Phase encoders 402 and 403 employ unequal-arm faraday-michelson interferometers. The two reflected photons synchronously reach the polarization beam splitter 401 to combine into one path, and are output to the polarizer 404 through the second port B of the polarization beam splitter 401, and the polarizer 404 enables the two polarization states of the incident photons to pass through and output with the same probability. In the polarization and phase entanglement encoding device, discrete devices and waveguide devices used by conducted light, a phase encoder, a polarization beam splitter, a polarizer and the like are all polarization control devices.
A fifth embodiment of the present invention, a polarization and phase-entangled encoding device, as shown in fig. 5, specifically includes the following components: an optical circulator 501, a polarization beam splitter 502, two phase encoders 503 and 504, and a polarizer 505.
Any one photon in the polarization-entangled photon pair generated by the entanglement light source is input through the first port a of the optical circulator 501 and output to the polarization beam splitter 502 through the second port B of the optical circulator 501. The polarization beam splitter 502 splits the two orthogonal polarization states of the incident photons into two sub-paths for transmission. One path is phase-encoded by the phase encoder 503, and is output to the polarization beam splitter 502 by the input port of the phase encoder 503 after being reflected. The other path is phase-encoded by the phase encoder 504, and is reflected and output to the polarization beam splitter 502 through the input port of the phase encoder 504. The phase encoders 503 and 504 employ an unequal arm michelson interferometer. The two reflected photons synchronously reach the polarization beam splitter 502 to be combined into one path, and are output to the second port B of the optical circulator 501 through the input port of the polarization beam splitter 502, the optical circulator 501 transmits the photons input by the second port B to the third port C of the optical circulator and outputs the photons to the polarizer 505, and the polarizer 505 enables the two polarization states of the incident photons to pass through and output with the same probability. In the polarization and phase entanglement encoding device, discrete devices and waveguide devices used for transmitting light, a phase encoder, a polarization beam splitter, an optical circulator, a polarizer and the like are all polarization control type devices.
A sixth embodiment of the present invention, a polarization and phase-entangled encoding device, as shown in fig. 6, specifically includes the following components: a polarizing beam splitter 601, two phase encoders 602 and 606, two mirrors 604 and 605, two polarizers 603 and 607, and a beam combiner 608.
Any one photon in the polarization entangled photon pair generated by the entanglement light source is input to the polarization beam splitter 601, and the polarization beam splitter 601 splits two orthogonal polarization states of the incident photon into two sub-optical paths. One path is subjected to phase encoding by a phase encoder 602, then exits to a reflector 604 through a polarizer 603, and is reflected to an incident port of a beam combiner 608 through the reflector 604; the other path is reflected by the reflecting mirror 605, then is subjected to phase encoding by the phase encoder 606 and output to the polarizer 607, and is output to the other input port of the beam combiner 608 through the polarizer 607. The two sub-paths arrive synchronously at the combiner 608. Polarizers 603 and 607 make the polarization state of the photons output from the two sub-paths the same and have the same probability to pass through polarizers 603 and 607, respectively. In the polarization and phase entanglement encoding device, discrete devices and waveguide devices used by conducted light, a phase encoder, a polarization beam splitter, a beam combiner, a polarizer and the like are all polarization control type devices. The mirrors 604 and 605 are used to adjust the propagation direction of the optical path, and a waveguide device may be used instead to transmit photons and adjust the propagation direction of the optical path. Changing the order between the phase encoder 602 and the polarizer 603 and changing the order between the phase encoder 606 and the polarizer 607 results unaffected.
A seventh embodiment of the present invention, a polarization and phase entanglement encoding device, as shown in fig. 7, specifically includes the following components: a polarization beam splitter 701, two phase encoders 702 and 706, two mirrors 704 and 705, two polarization controllers 703 and 707, and a beam combiner 708.
Any one photon in the polarization entangled photon pair generated by the entanglement light source is input to the polarization beam splitter 701, and the polarization beam splitter 701 splits two orthogonal polarization states of the incident photon into two sub-optical paths for transmission. One path is subjected to phase encoding by a phase encoder 702, modulated in polarization state by a polarization controller 703, and then emitted to a reflector 704, and reflected to an incident port of a beam combiner 708 by the reflector 704; the other path is reflected by the mirror 705, phase-encoded by the phase encoder 706 and output to the polarization controller 707, and the polarization state is modulated by the polarization controller 707 and output to the other input port of the beam combiner 708. The two sub-lightpaths arrive synchronously at the combiner 708. The modulation polarization controllers 703 and 707 make the photons transmitted by the two sub-optical paths in the same polarization state incident to the beam combiner 708. In the polarization and phase entanglement encoding device, discrete devices and waveguide devices used for transmitting light, phase encoders, polarization beam splitters, beam combiners, polarization controllers and the like are all polarization control type devices. The mirrors 704 and 705 are used to adjust the propagation direction of the optical path, and a waveguide device may be used instead to transmit photons and adjust the propagation direction of the optical path. The order between the phase encoder 702 and the polarization controller 703 is changed, and the order between the phase encoder 706 and the polarization controller 707 is changed, with the result that the results are not affected.
An eighth embodiment of the present invention, a polarization and phase entanglement encoding device, as shown in fig. 8, specifically includes the following components: a polarization beam splitter 801, two phase encoders 802 and 806, two mirrors 804 and 805, a polarization controller 803, and a beam combiner 807.
Any one photon in the polarization entangled photon pair generated by the entanglement light source is input to the polarization beam splitter 801, and the polarization beam splitter 801 splits two orthogonal polarization states of the incident photon into two sub-optical paths. One path is subjected to phase encoding by a phase encoder 802, modulated in polarization state by a polarization controller 803, and then emitted to a reflector 804, and reflected to an incident port of a beam combiner 807 by the reflector 804; the other path is reflected by the mirror 805, phase-encoded by the phase encoder 806, and output to the other input port of the beam combiner 807. The two sub-paths arrive synchronously at the beam combiner 807. The polarization controller 803 modulates the polarization state of the light path input to the beam combiner 807 to be consistent with the polarization state of the other light path input to the beam combiner 807. In the polarization and phase entanglement encoding device, discrete devices and waveguide devices used for transmitting light, phase encoders, polarization beam splitters, beam combiners, polarization controllers and the like are all polarization control type devices. The mirrors 804 and 805 are used to adjust the propagation direction of the optical path, and a waveguide device may be used instead to transmit photons and adjust the propagation direction of the optical path. The order between the phase encoder 802 and the polarization controller 803 is changed and the result is not affected. When the polarization controller 803 is placed in the other optical path, the result is not affected.
In a ninth embodiment of the present invention, an unequal arm mach-zehnder interferometer, as shown in fig. 9, specifically includes the following components: two 2 x 23 dB polarization maintaining beam splitters 903 and 906, a polarization maintaining delay line 904, and one polarization maintaining phase modulator 905.
One of two ports 901 and 902 of one side of the 3dB polarization maintaining beam splitter 903 is used as an input terminal of the phase encoder, one of two ports 907 and 908 of the other side of the 3dB polarization maintaining beam splitter 906 is used as an output terminal of the phase encoder, and a polarization maintaining delay line 904 and a polarization maintaining phase modulator 905 are respectively inserted into two arms of the mach-zehnder interferometer. During operation, photons enter the polarization maintaining beam splitter 903 through the port 901 or 902 of the polarization maintaining beam splitter 903 and are transmitted in two paths, one path is delayed by the polarization maintaining delay line 904, the other path is subjected to phase modulation by the polarization maintaining phase modulator 905, and the photons transmitted on the two light paths after the relative delay are combined into one routing port 907 or 908 for output through the polarization maintaining beam splitter 906. When the polarization maintaining delay line 904 and the polarization maintaining phase modulator 905 are located on the same arm of the mach-zehnder interferometer, the above result is not affected.
A tenth embodiment of the present invention is an unequal-arm michelson interferometer, as shown in fig. 10, which specifically includes the following components: a 2 x 23 dB polarization maintaining beam splitter 1003, two mirrors 1005 and 1007, a polarization maintaining phase modulator 1006, and a polarization maintaining delay line 1004.
Two ports 1001 and 1002 on one side of the 3dB polarization maintaining beam splitter 1003 are respectively used as an input end and an output end of the phase encoder, one of the two ports on the other side of the 3dB polarization maintaining beam splitter 1003 is sequentially connected with a polarization maintaining delay line 1004 and a reflecting mirror 1005, and the other port on the same side is sequentially connected with a polarization maintaining phase modulator 1006 and a reflecting mirror 1007. During operation, photons enter the polarization maintaining beam splitter 1003 through a port 1001 of the polarization maintaining beam splitter 1003 and are transmitted in two paths, one path is delayed through a polarization maintaining delay line 1004 and is reflected by a reflecting mirror 1005, the other path is subjected to phase modulation through a polarization maintaining phase modulator 1006 and then is reflected by a reflecting mirror 1007, and the reflected photons transmitted on the two light paths are combined into one path through the polarization maintaining beam splitter 1003 and are output through a port 1002. When the polarization maintaining delay line 1004 and the polarization maintaining phase modulator 1006 are connected in series at the same port, the above result is not affected. Photons are input by 1002 port, output by 1001 port and the same result with either port 1001 or 1002 as both input and output.
An eleventh embodiment of the present invention, an unequal-arm faraday-michelson interferometer, as shown in fig. 11, specifically includes the following components: a 2 x 23 dB splitter 1103, two 90 degree rotating faraday mirrors 1105 and 1107, a delay line 1104, and a phase modulator 1106.
Two ports 1101 and 1102 on one side of the 3dB splitter 1103 are respectively used as an input end and an output end of the phase encoder, one of the two ports on the other side of the 3dB splitter 1103 is sequentially connected to the delay line 1104 and the 90-degree rotating faraday mirror 1105, and the other port on the same side is sequentially connected to the phase modulator 1106 and the 90-degree rotating faraday mirror 1107. During operation, photons enter the beam splitter 1103 through the port 1101 of the beam splitter 1103 and are transmitted in two paths, one path is delayed through the delay line 1104 and reflected by the 90-degree rotating faraday mirror 1105, the other path is subjected to phase modulation through the phase modulator 1106 and then reflected by the 90-degree rotating faraday mirror 1107, and the reflected photons transmitted on the two light paths are combined into one path and output through the port 1102 through the beam splitter 1103. When the phase modulator 1104 and the delay line 1106 are connected in series at the same port, the result is not affected. Photons are input from port 1102, output from port 1101, and the same result occurs when either port 1101 or 1102 is both input and output.
A twelfth embodiment of the present invention provides a quantum key distribution system, as shown in fig. 12, which specifically includes the following components: a polarization-entangled light source 1201, quantum channels 1202, 1204, and 1212, two polarization-independent beam splitters 1205 and 1213, two phase decoders 1206 and 1209, two polarization beam splitters 1214 and 1217, eight single-photon detectors 1207, 1208, 1210, 1211, 1215, 1216, 1218, and 1219, and the polarization and phase-entangled encoding apparatus 1203 described above.
A polarization-entangled light source 1201 is used to generate polarization-entangled photon pairs.
Quantum channels 1202, 1204, and 1212 are used to transmit photons.
The polarization and phase-entanglement encoding means 1203 is configured to convert the first photon of the polarization-entangled photon pair from polarization encoding to phase encoding.
Phase decoders 1206 and 1209 are used to perform a decoding operation on the first photon converted to phase encoding;
polarizing beam splitters 1214 and 1217 are used to decode the second photon of the polarization entangled photon pair; wherein the second photon is polarization encoded;
single photon detectors 1207, 1208, 1210 and 1211 are used to detect photons output by phase decoders 1206 and 1209, respectively, and single photon detectors 1215, 1216, 1218 and 1219 are used to detect photons output by polarizing beam splitters 1214 and 1217, respectively; and quantum key distribution is carried out according to the detection result and the quantum key distribution protocol.
A first photon in a polarization-entangled photon pair generated by the polarization-entangled light source 1201 sequentially passes through the quantum channel 1202, the polarization and phase-entangled encoding device 1203 and the quantum channel 1204 and is incident to the polarization-independent beam splitter 1205 to be divided into two optical paths for transmission, one optical path is decoded by the phase decoder 1206 and output to the single-photon detector 1207 or the single-photon detector 1208, and the other optical path is decoded by the phase decoder 1209 and output to the single-photon detector 1210 or the single-photon detector 1211; the second photon of the polarization entangled photon pair enters the polarization independent beam splitter 1213 through the quantum channel 1212 and is split into two optical paths for transmission, one of the two optical paths is decoded by the polarization beam splitter 1214 and output to the single photon detector 1215 or the single photon detector 1216, and the other optical path is decoded by the polarization beam splitter 1217 and output to the single photon detector 1218 or the single photon detector 1219.
The quantum channels 1202, 1204, and 1212 may be optical waveguides, optical fibers, free space, discrete optical elements, planar waveguide optical elements, fiber optical elements, or optical propagation channels combined from any two or more of the above. Preferably, quantum channels 1202 and 1204 are non-depolarizing quantum channels.
Further, the phase decoder employs any one of: unequal arm Mach-Zehnder interferometers, unequal arm Michelson interferometers, and unequal arm Faraday-Michelson interferometers.
The phases set in the phase decoders 1206 and 1209 coincide with or differ by 90 degrees from the phase set by any one of the phase encoders in the polarization and phase entanglement encoding device 1203, and are phase-modulated in accordance with the quantum key distribution protocol.
Further, when the phase decoders 1206 and 1209 use the unequal arm mach-zehnder interferometer, two output ports of the phase decoder 1206 are connected to the single-photon detectors 1207 and 1208, respectively, and two output ports of the phase decoder 1209 are connected to the single-photon detectors 1210 and 1211, respectively.
When phase decoders 1206 and 1209 use an unequal-arm michelson interferometer or an unequal-arm faraday-michelson interferometer, the input port of phase decoders 1206 and 1209 is also one of the output ports, and in this case, the system further includes: an optical circulator. Optical circulators are located between polarization independent beam splitter 1205 and phase decoder 1206, and between polarization independent beam splitter 1205 and phase decoder 1209.
The connection mode of the optical circulator is as shown in fig. 13, a first port a of the optical circulator 1301 receives photons transmitted by the polarization-independent beam splitter, the photons are output to the phase decoder 1302 from a second port B of the optical circulator 1301, and one output port of the phase decoder 1302 is connected with the single photon detector 1303; the other output port of the phase decoder 1302 is an input port thereof, and the second port B of the optical circulator 1301 receives the photon sent by the phase decoder 1302 and outputs the photon to the single photon detector 1304 through the third port C of the optical circulator 1301.
The polarization and phase entanglement encoding device 1203 performs phase setting according to a quantum key distribution protocol, and the phase decoders 1206 and 1209 and the polarization beam splitters 1214 and 1217 decode photon phases and polarization states according to a Bell inequality inspection form and the quantum key distribution protocol, respectively, and perform quantum key distribution according to the quantum key distribution protocol.
The polarization and phase entanglement encoding method, the polarization and phase entanglement encoding device and the quantum key distribution system introduced in the embodiment of the invention convert the polarization encoding of any one photon in the polarization entanglement photon pair into the phase encoding, realize the phase entanglement of one photon polarization state and the other photon, and generate the polarization and phase entanglement photon pair. The quantum key distribution system formed by the polarization and phase entanglement encoding devices can fully utilize the transmission advantages of different codes in different channels, and photons are converted from polarization codes into phase codes when the transmission of the different channels is realized, so that the technical foundation is laid for establishing a world-wide quantum secret communication network. For example, free space and fiber hybrid channel quantum key distribution can be realized by polarization and phase-entangled photon pairs generated by a polarization and phase-entangled encoding device, wherein the polarization-encoded photons are transmitted in a free space channel in the photon pairs, and the phase-encoded photons are transmitted in a fiber channel. For another example, one polarization-encoded photon of the polarization and phase-entangled photon pair is transmitted in a free space channel, and the other polarization-encoded photon is transmitted in the free space for a distance and then coupled into an optical fiber channel for transmission. The method is simple and easy to realize, and can effectively solve the problems of converting the polarization code of the entangled light source into the phase code, realizing polarization and phase entanglement, realizing quantum entanglement distribution and quantum key distribution applied to free space and optical fiber mixed channels and the like.
While the invention has been described in connection with specific embodiments thereof, it is to be understood that it is intended by the appended drawings and description that the invention may be embodied in other specific forms without departing from the spirit or scope of the invention.
Claims (25)
1. A polarization and phase entanglement encoding method, comprising:
converting a first photon of a polarization-entangled photon pair generated by a polarization-entangled light source from polarization encoding to phase encoding;
forming a polarization and phase-entangled photon pair from the first photon converted into the phase encoding and a second photon of the polarization-entangled photon pair; wherein the second photon is polarization encoded;
a method of converting a first photon from polarization encoding to phase encoding, comprising:
the method comprises the steps of splitting a first photon into photons transmitted on two sub-light paths through a polarization beam splitter, carrying out phase encoding on the photons transmitted on the two sub-light paths through phase encoders respectively arranged on the two sub-light paths, combining the photons transmitted on the two sub-light paths after the phase encoding into photons output by one light path through a beam combiner, wherein the combined photons output by one light path have a determined polarization state.
2. The polarization and phase-entanglement encoding method of claim 1, wherein the phase encoders respectively disposed on the two sub-optical paths encode phases that are different by 180 degrees.
3. The polarization and phase-entanglement encoding method of claim 1, wherein the photons transmitted on the two sub-optical paths arrive at the combiner synchronously and are combined into photons output by one optical path.
4. The polarization and phase-entanglement encoding method of claim 1, wherein an eigenstate of an orthogonal basis of the polarization beam splitter splitting the orthogonal polarization state of the first photon onto the two sub-optical paths is the same as the orthogonal polarization state of the first photon.
5. The polarization and phase-entanglement encoding method according to claim 1, wherein the beam combiner employs a polarization-independent beam combiner when polarization states of photons transmitted on the two sub-optical paths incident to the beam combiner are the same;
when the polarization state of the photons transmitted on the two sub-light paths and incident to the beam combiner is an orthogonal polarization state, the beam combiner adopts a polarization-independent beam combiner or a polarization beam combiner; when the beam combiner adopts a polarization beam combiner, the orthogonal polarization state of the photons transmitted on the two sub-light paths is the eigenstate of the orthogonal base of the polarization beam combiner.
6. The polarization and phase entanglement encoding method of claim 1, wherein the phase encoder employs any one of: unequal arm Mach-Zehnder interferometers, unequal arm Michelson interferometers, and unequal arm Faraday-Michelson interferometers.
7. The polarization and phase entanglement encoding method of claim 6, wherein the polarization beam combiner and the polarization beam splitter are the same device when the phase encoder employs an unequal-arm Michelson interferometer or an unequal-arm Faraday-Michelson interferometer.
8. The polarization and phase-entangled encoding method according to claim 1, wherein the method for controlling the polarization state of the photons outputted from the combined beam into one optical path comprises:
a polarizer is arranged behind the beam combiner; or,
polarizers are respectively arranged on two sub-light paths between the polarization beam splitter and the beam combiner; or,
and arranging a polarization controller on one or two sub-light paths between the polarization beam splitter and the beam combiner.
9. The polarization and phase entanglement encoding method of any one of claims 1-8, wherein the polarization beam splitter, the phase encoder, the beam combiner, the polarization controller, the polarizer, and the discrete devices and waveguide devices used for guiding light are all polarization-controlled devices, and the polarization state of photons in the optical path is controlled so that the photons output by the combined beam as one optical path have a certain polarization state.
10. A polarization and phase entanglement encoding device, comprising: the device comprises a polarization beam splitter, a beam combiner and a phase encoder;
the polarization beam splitter is used for splitting a first photon in the polarization-entangled photon pair generated by the polarization-entangled light source into photons transmitted on two sub-light paths;
the phase encoders are respectively arranged on the two sub-light paths and are used for carrying out phase encoding on photons transmitted on the two sub-light paths;
the beam combiner is used for combining the photons transmitted on the two sub-light paths after phase coding into photons output by one light path.
11. The polarization and phase-entanglement encoding device of claim 10, wherein the phase encoders respectively disposed on the two sub-optical paths encode phases that are different by 180 degrees.
12. The polarization and phase-entangled encoding device of claim 10 wherein photons transmitted on said two optical sub-paths arrive at said combiner synchronously and are combined into photons output by one optical path.
13. The polarization and phase-entanglement encoding device of claim 10, wherein an eigenstate of an orthogonal basis of the polarization beam splitter splits an orthogonal polarization state of the first photon onto the two sub-optical paths, the eigenstate being the same as the orthogonal polarization state of the first photon.
14. The polarization and phase-entanglement encoding device of claim 10, wherein the beam combiner employs a polarization-independent beam combiner when the polarization states of the photons transmitted on the two sub-optical paths incident to the beam combiner are the same;
when the polarization state of the photons transmitted on the two sub-light paths and incident to the beam combiner is an orthogonal polarization state, the beam combiner adopts a polarization-independent beam combiner or a polarization beam combiner; when the beam combiner adopts a polarization beam combiner, the orthogonal polarization state of the photons transmitted on the two sub-light paths is the eigenstate of the orthogonal base of the polarization beam combiner.
15. The polarization and phase entanglement encoding device of claim 10, wherein the phase encoder employs any one of: unequal arm Mach-Zehnder interferometers, unequal arm Michelson interferometers, and unequal arm Faraday-Michelson interferometers.
16. The polarization and phase-entangled encoding device of claim 15, wherein the polarization beam combiner and the polarization beam splitter are the same device when the phase encoder uses an unequal-arm michelson interferometer or an unequal-arm faraday-michelson interferometer.
17. The polarization and phase-entanglement encoding device of claim 10, further comprising: a polarizer or polarization controller; the polarizer and the polarization controller are used for controlling the combined beam to be a photon output by a light path to have a determined polarization state;
when the device comprises polarizers, the polarizers are arranged behind the beam combiner, or the polarizers are respectively arranged on two sub-optical paths between the polarization beam splitter and the beam combiner;
when the device comprises a polarization controller, the polarization controller is arranged on one or two sub-light paths between the polarization beam splitter and the beam combiner.
18. The polarization and phase entanglement encoding device of any one of claims 10 to 17, wherein the polarization beam splitter, the phase encoder, the beam combiner, the polarization controller, the polarizer, and the discrete devices and waveguide devices used for guiding light are polarization-controlled devices, and control the polarization state of photons in the optical path such that the photons output from the combined beam as one optical path have a certain polarization state.
19. A quantum key distribution system, comprising: a polarization-entangled light source, a phase decoder, a polarization decoder, a single-photon detector, and the polarization-and-phase-entangled encoding device of any one of claims 10-18;
the polarization-entangled light source is used for generating polarization-entangled photon pairs;
the polarization and phase entanglement encoding device is used for converting a first photon in the polarization entangled photon pair from polarization encoding to phase encoding;
the phase decoder is used for decoding the first photons converted into the phase codes;
the polarization decoder is used for decoding the second photon in the polarization entangled photon pair; wherein the second photon is polarization encoded;
the single photon detector is used for detecting the photons output by the phase decoder and the polarization decoder and carrying out quantum key distribution according to the detection result and a quantum key distribution protocol.
20. The quantum key distribution system of claim 19, wherein the phase set in the phase decoder is identical to or 90 degrees different from the phase set by any one of the phase encoders in the polarization and phase entanglement encoding device, and is phase modulated according to a quantum key distribution protocol.
21. The quantum key distribution system of claim 19, wherein the system further comprises: a quantum channel;
the quantum channel is used for transmitting photons; the quantum channel is composed of at least one of: optical waveguides, optical fibers, free space, discrete optical elements, planar waveguide optical elements, fiber optical elements.
22. A quantum key distribution system as claimed in claim 21 wherein the quantum channel between the polarization-entangled light source and the polarization and phase-entangled encoding device and the quantum channel between the polarization-entangled light source and the polarization decoder are all non-depolarized quantum channels.
23. The quantum key distribution system of claim 19, wherein the system further comprises: a polarization-independent beam splitter;
the polarization-independent beam splitter is used for receiving the photons transmitted by the polarization and phase entanglement encoding device and splitting the photons transmitted by the polarization and phase entanglement encoding device into two phase decoders in an equal probability manner;
the polarization-independent beam splitter is further used for receiving the second photon sent by the polarization-entangled light source and splitting the second photon into two polarization decoders in an equal probability manner.
24. The quantum key distribution system of claim 19, wherein the phase decoder employs any one of: unequal arm Mach-Zehnder interferometers, unequal arm Michelson interferometers, and unequal arm Faraday-Michelson interferometers.
25. The quantum key distribution system of claim 24, wherein when the phase decoder employs an unequal arm mach-zehnder interferometer, two output ports of the phase decoder are respectively connected to a single photon detector;
when the phase decoder employs an unequal-arm michelson interferometer or an unequal-arm faraday-michelson interferometer, the system further comprises: an optical circulator;
the first port of the optical circulator receives photons sent by the polarization and phase entanglement coding device or the polarization-independent beam splitter, and the photons are output to the phase decoder from the second port of the optical circulator and sent to the single photon detector through the phase decoder; and the second port of the optical circulator receives the photons sent by the phase decoder and outputs the photons to another single photon detector through the third port of the optical circulator.
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| CN201710374340.4A CN107070655A (en) | 2017-05-24 | 2017-05-24 | One kind polarization and phase tangle coding method, device and quantum key dispatching system |
| PCT/CN2018/087913 WO2018214888A1 (en) | 2017-05-24 | 2018-05-22 | Polarization and phase entangled coding method and apparatus, and quantum key distribution system |
| CN201810497144.0A CN108712249B (en) | 2017-05-24 | 2018-05-22 | Phase entanglement encoding method and device |
| CN201820765186.3U CN208190665U (en) | 2017-05-24 | 2018-05-22 | Phase for photon pair tangles code device |
| PCT/CN2018/088089 WO2018214922A1 (en) | 2017-05-24 | 2018-05-23 | Method and device for phase-entangled encoding |
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Also Published As
| Publication number | Publication date |
|---|---|
| CN108712249A (en) | 2018-10-26 |
| WO2018214888A1 (en) | 2018-11-29 |
| CN108712249B (en) | 2023-07-04 |
| CN208190665U (en) | 2018-12-04 |
| WO2018214922A1 (en) | 2018-11-29 |
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