JP2009147432A - Quantum cryptography transmitter and quantum encryption device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quantum encryption device with a simpler device configuration than a conventional technology with respect to a device to be possessed by a regular user. <P>SOLUTION: This quantum encryption device is provided with: a light source for generating a photon as the information carrier of a quantum bit; a branch coupler for branching the photon generated by the light source at random to a plurality of transmission paths; a number of photon non-destructive measurement device for non-destructively detecting the presence/absence of the photon to be propagated for each of the plurality of transmission paths; and a photon pulse state preparation means for transmitting double photon pulses prepared in a non-orthogonal four states to a single transmission path depending on the propagation path on which the photon has passed among the plurality of propagation paths. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a quantum cryptography device, and more particularly to a quantum cryptography transmitter that performs quantum cryptography key distribution that shares an encryption secret key by optical fiber communication.

  With the explosive spread of the Internet and the commercialization of electronic commerce, there is an increasing social need for cryptographic technologies such as confidentiality and tampering prevention of communications and personal authentication.

  Currently, public key systems such as DES (Data Encryption Standard) cipher, public key systems such as RSA (R. Rivest, A. Shamir, L. Adelman) cipher and RAS cipher The key method is widely used. However, these are based on “computational safety”.

  In other words, current cryptosystems are constantly threatened by advances in computer hardware and decryption algorithms. In particular, in fields where extremely high security is required, such as transactions between banks and information related to military and diplomacy, the impact will be great if practically secure cryptographic methods become practical.

  There is a one-time pad method as an encryption method whose unconditional security is proved by information theory. The one-time pad method is characterized by using an encryption key with the same length as the message and throwing away the encryption key once.

  Non-Patent Document 1 (Bennett, Brassard, IEEE Computer, Systems, Signal Processing International Conference (IEEE Int. Conf. On Computers, Systems, and Signal Processing, Bangalore, India, p. 175 (1984)) ) And Bennett et al. Proposed for the first time a specific protocol that is widely known as the BB84 protocol and that securely distributes a cryptographic private key used in the one-time pad method. As a result, research on quantum cryptography has become active.

  In quantum cryptography, the laws of physics guarantee the security of cryptography, so it is possible to guarantee the ultimate security that does not depend on the limits of computer capabilities. In a quantum cryptography apparatus that is currently under much investigation, 1-bit information is encoded into a single photon state and transmitted. This is because photons are more resistant to environmental disturbances than other quantum systems, and at the same time, long-distance encryption key distribution can be expected by utilizing existing optical fiber communication technology.

  In the quantum cryptographic key distribution protocol (referred to as BB84) using the four non-orthogonal states described in Non-Patent Document 1, which is the basis of the present invention and theoretically proves its security, the sender is predetermined. Modulation by randomly selecting one of two non-orthogonal complementary bases of a given photon (a set of variables in an uncertain relationship: for example, position and momentum) as a modulation base and selecting key bit data Modulated and transmitted according to two orthogonal states (classically distinguishable states) belonging to the base.

  The receiver demodulates the arrival photon by a demodulation method suitable for a demodulation base that randomly selects the arrival photon, and records the demodulation result as a bit data candidate as a key. The sender / receiver verifies which of the complementary bases was used for modulation / demodulation using the public channel for all quantum keys (photons whose cryptographic keys are modulated), and selects only bit data related to photons whose modulation / demodulation bases match. To make a key candidate.

  An eavesdropping act disturbs the quantum mechanical state, and the protocol is designed so that the amount of leaked information can be estimated from the error in the selection key of the authorized sender / receiver. If there is no wiretapping, the amount of leaked information is zero, and the error in the selection key is zero. It is known that an error rate in a selection key is measured by a sampling method, and if the measured error rate is smaller than a threshold value, a secure secret key can be extracted from the selection key.

  The quantum state used for such information communication is often called quantum information. A quantum mechanical two-degree-of-freedom system carrying quantum information is called a qubit, which is mathematically equivalent to a spin 1/2 system. Hereinafter, the prior art will be described in the case where the physical system as a carrier is a photon.

  The prior art will be described below with respect to an encryption key distribution apparatus that uses photons as qubit carriers and optical fibers as transmission lines for long-distance transmission according to the present invention. Non-Patent Document 2 (Zbinden et al., “Experimental Quantum Cryptography”, “INTRODUCTION TO QUANTUM COMPUTATION AND INORMATION” (edited by Lo et al.)) (World Scientific, 1998) ), 120 pages), Non-Patent Document 3 (Ekert et al., “Quantum Cryptography”, “The Physics of Quantum Information (edited by Bouwmeester et al.)” (Springer, 2000), 15) Patent Document 4 (Gisin et al., “Quantum Cryptography” Review of Modern Physics (Rev. Mod. Phys.), 74 (2002), pages 145-195) has a detailed description.

  Non-Patent Document 1 proposes the implementation of a quantum cryptography device called polarization coding that encodes information into two polarization states that a photon can have. However, since polarization coding requires real-time control and compensation of polarization rotation in the transmission line, it is not often used as a mounting method for a long-distance encryption key distribution system using an optical fiber as a transmission line.

  As a long-distance encryption key distribution system, Bennet et al. Have proposed and realized an implementation of a quantum encryption device called phase coding that encodes information in a relative phase between two weak light pulses.

  FIG. 7 shows a typical implementation example of a quantum cryptography device based on phase coding using coherent weak light pulses described in Non-Patent Documents 2 to 4. In this apparatus, an optical interference system having a structure in which two asymmetric Mach-Zehnder interference systems are connected in series by an optical fiber transmission line is used.

  The weak short light pulse generated by the weak laser light source 71 provided in the transmission unit is incident on the asymmetric Mach-Zehnder interference system 72 on the transmission side, so that the difference between the long and short optical paths is spatially separated on the optical fiber transmission line. A coherent double weak light pulse 78 is prepared.

  Here, the term coherent means that the relative phase can be clearly defined between two pulses of the double weak light pulse 78 by the asymmetric Mach-Zehnder interference system 72 in which the long and short optical path differences are clearly defined.

  The double weak light pulses 78 are disturbed during transmission on the optical fiber transmission path 73, but their relative phase relationship and polarization plane relationship are preserved. By the asymmetric Mach-Zehnder interference system 74 on the reception side, the double weak light pulse 78 is converted into a triple pulse-like photon output 79 and output to two downstream ports.

  The photon detector 75 identifies and records whether the photon contained in the center optical pulse of the triple pulsed photon output 79 output to the two downstream ports of the asymmetric Mach-Zehnder interference system 74 is 0 or 1.

  Of the triplet-like photon output 79, the central optical pulse includes an optical pulse that has passed through the length of the asymmetric Mach-Zehnder interference system at the transmitter and a short path at the receiver, and a receiver that passes through the short length at the transmitter. The optical pulse that has passed through a long length contributes, and due to the interference of these two contributions, the intensity ratio to the two output ports is sinusoidally related to the optical delay (relative phase) of the double weak light pulse 78. Dependent.

  In the above-described optical interference system, by modulating the optical delay (relative phase) to the double weak light pulse 78, encryption key distribution based on the principle of quantum cryptography can be performed. For this purpose, the optical modulator 73 performs quaternary phase modulation of {0, π / 2, π, 3π / 2} with the phase modulator 76 included while the optical pulse passes through the asymmetric Mach-Zehnder interference system 72. The binary pulse after transmission is subjected to binary phase modulation of {0, π / 2} by the phase modulator 77 included while passing through the asymmetric Mach-Zehnder interference system 74.

  By appropriately adjusting the optical delay in the asymmetric Mach-Zehnder interferometers 72 and 74, the quantum cryptographic key distribution protocol using the non-orthogonal four states proposed in Non-Patent Document 1 can be executed to perform secure key distribution. Is possible.

  Quantum cryptography devices based on phase coding have the advantage of good compatibility with optical fiber transmission lines and the ability to distribute long-distance keys. However, the relative optical delay of the asymmetric Mach-Zehnder interference system of each transmitter / receiver is considered to be less than the optical wavelength. There is a problem that it must be maintained with an accuracy of.

  Since the optical delay of the interference system distributed to these transmitters and receivers fluctuates and drifts independently due to temperature changes and other causes, the optical interference effect is easily lost. In order to solve this problem, an active control device that measures the relative optical delay change of both interference systems and feeds back the measurement result to keep the relative optical delay constant is required. Such a measuring apparatus not only complicates the system itself, but the reference light used for the measurement increases system noise and causes the performance degradation of the quantum cryptography apparatus.

  In recent years, Non-Patent Document 5 (Nanbu et al., “BB84 Quantum Key Distribution System Based on Silica-Based Planar Lightwave Circuits”, Japan Journal of Applied Physics (Jpn J. Appl. Phys.), 43 (published in 2004), page L1109), Non-Patent Document 6 (Kimura et al., “Single-photon Interference over 150 km Transmission Using Silica-based Integrated-optic Interferometers for Quantum Cryptography”, Japan Journal of・ Applied Physics (Jpn J. Appl. Phys.), No. 43 (published in 2004), page L1217), Non-Patent Document 7 (by Nambu et al. “One-way Quantum Key Distribution System based on Planar Lightwave Circuit” Japan Journal of Applied Physics, No. 45, Volume 6A (2006), 5344-534 Pages) and as mentioned in Patent Document 1 (JP 2003-249928), the planar lightwave circuit (PLC: Photonic Lightwave Circuit) quantum cryptography device that applies techniques have been devised developed.

  By fabricating an asymmetric Mach-Zehnder interference system with an optical waveguide formed by patterning on a silicon substrate, a stable optical interference system that is not affected by disturbance can be realized only by passive control such as temperature control. There is an advantage that a low noise system can be constructed.

  In the case of implementation using a PLC, it is not easy with the current technology to manufacture a low-loss asymmetric Mach-Zehnder interference system including a phase modulator as shown above. Even if an increase in cost is not a problem, an increase in optical loss of the receiving device is an unacceptable problem because it directly leads to performance degradation of the quantum cryptography device that uses weak light as an information carrier. In order to solve this problem, a quantum cryptography device as shown in FIG. 8 in which a phase modulator is disposed outside the asymmetric Mach-Zehnder interference system has been devised and developed.

  In the example of the quantum cryptography device shown in FIG. 8, a weak short light pulse generated by a weak laser light source 81 provided in a transmission unit is incident on an asymmetric Mach-Zehnder interference system 82 constituted by a PLC on the transmission side. A coherent double weak light pulse 89 spatially separated by the difference between the long and short optical path is prepared on the optical fiber transmission path.

  The double weak light pulse 89 is transmitted on the optical fiber transmission line 83. The double weak light pulse 89 is converted into a triple light pulse 90 by the asymmetric Mach-Zehnder interference system 84 on the reception side, and is output to two ports on the downstream side. The photon detector 85 identifies and records the presence or absence of a photon contained in the center optical pulse of the triple pulsed photon output 90 output to the two downstream ports of the asymmetric Mach-Zehnder interference system 84.

  Applying a pulse-like modulation signal to the phase modulators 86 and 87 inserted in series downstream of the asymmetric Mach-Zehnder interference system 82 on the transmission side in synchronization with the passage of the double weak light pulse 89 of each modulator. Thus, one of the double weak light pulses 89 is selectively subjected to four-level phase modulation of {0, π / 2, π, 3π / 2}, so that the optical delay (relative) of the double weak light pulses 89 is obtained. (4) modulation is applied to (phase).

  By applying a pulse-like modulation signal to the phase modulator 88 inserted in series upstream of the asymmetric Mach-Zehnder interference system 84 on the receiving side in synchronization with the passage of the double weak light pulse 89, the double weak light pulse is applied. A binary phase modulation of {0, π / 2} is selectively given to one pulse of 89, so that a binary modulation is given to the optical delay (relative phase) of the double weak light pulse 89.

  By adjusting the optical delay in the asymmetric Mach-Zehnder interference systems 82 and 84, the quantum encryption key distribution protocol using the non-orthogonal four states proposed in Non-Patent Document 1 is executed in the same manner as the quantum encryption apparatus of FIG. Key distribution is possible.

  On the other hand, in the example of the quantum cryptography device shown in FIG. 9 known in Non-Patent Document 5 and Patent Document 1, a weak short light pulse generated by the weak laser light source 91 provided in the transmission unit is transmitted to the PLC on the transmission side. Coherent that is spatially separated by a long and short optical path difference of the asymmetric Mach-Zehnder interference system 93 on the optical fiber transmission line by being incident on the asymmetric Mach-Zehnder interference system 93 connected in cascade with the symmetrical Mach-Zehnder interference system 92 Two weak light pulses 98 or advanced or delayed weak light pulses 98 which are their constituent elements are prepared.

  These weak light pulses 98 are transmitted on the optical fiber transmission line 94, and after passing through the asymmetric Mach-Zehnder interference system 95 on the receiving side, the photon arrival times at the two downstream ports operate in synchronization with the transmitter. The photon detector 96 recognizes and records which of the three separated time slots is equivalent to the time corresponding to the long / short optical path difference.

  A phase modulator 97 is inserted in one optical path of the symmetric Mach-Zehnder interference system 92 on the transmission side, and weak light pulses incident from the weak laser light source 91 are {0, π / 2, π, 3π / 2}. Are subjected to phase modulation selected from the four values.

  When the applied phase modulation is {0, π}, the optical pulse propagates only in the long or short length of the asymmetric Mach-Zehnder interference system 93, and either the front or rear optical pulse 98 depends on the phase modulation value. Prepared on the transmission line 94.

  When the applied phase modulation is {π / 2, 3π / 2}, the weak light pulse propagates both the long and short lengths of the asymmetric Mach-Zehnder interference system 93, and the relative phase changes by π depending on the phase modulation value. A coherent duplex optical pulse 98 is prepared on the optical fiber transmission line 94.

  When the phase modulation value in the phase modulator 97 is {0, π}, the output port of the photon appearing in the central time slot correlates with the phase modulation value, and the phase modulation value in the phase modulator 97 is {π / 2 and 3π / 2}, the optical delays in the asymmetric Mach-Zehnder interference systems 93 and 95 are appropriately set so that the time modulation of the photons appearing in the first and third time slots correlates with the phase modulation value. By adjusting, it is possible to execute the quantum encryption key distribution protocol using the non-orthogonal four states proposed in Non-Patent Document 1 and perform secure key distribution.

  The quantum cryptography device shown in FIGS. 7 and 8 has the following problems.

  Phase modulation randomly selected from four values by the phase modulators 76, 86, 87 of the transmitter for selecting key data and modulation base, and random from binary values by the phase modulator 77, 88 of the receiver for selecting demodulation base It is necessary to perform the phase modulation selected. This requires a 2-bit random number sequence at the transmitter and a 1-bit random number sequence at the receiver.

  In order to perform secure secret key sharing, these random number sequences need to be true random number sequences. Such a true random number sequence can be generated by a device using a physical phenomenon such as thermal noise.

  For high-speed key sharing, for example, it is necessary to increase the system operation speed. For this purpose, it is necessary to generate a high-speed intrinsic random number sequence. Unfortunately, because the current technology's true random number generators do not have a high random number generation speed, the only way to increase the generation speed is to use multiple devices in parallel, which increases system size and costs. Increased heat generation and power consumption.

  Also, when collating the basis for the arriving photon according to the protocol, which photon arrives at the receiver is a stochastic event and cannot be predicted, so it must be stored for a while until the basis is collated in the transceiver. is there. For this reason, it is necessary to prepare a storage device of enormous size and repeat burst system operation for a short time, which is also a factor of system size enlargement, cost increase, and heat generation / power consumption increase. It was.

  Some of the above problems of the quantum cryptography apparatus are solved by the system configuration shown in FIG.

  In FIG. 9, the transmitter includes four sets of weak laser light sources 91 that generate photons serving as information carriers of qubits, an optical waveguide 92 having a pair of long and short optical paths, and an asymmetric Mach-Zehnder interference system 93. Are coupled to a common optical transmission line 95.

  In the receiver, an optical waveguide 96 having a pair of long and short optical paths and an asymmetric Mach-Zehnder interference system 97 similar to those of the transmitter are coupled to a common optical fiber transmission path 95 by an optical coupler 98. Is connected to a photon detector 99.

  The regular transmitter randomly selects one light source from the four sets of weak laser light sources 91 that generate coherent light of the same wavelength λ, and emits a weak short light pulse from the selected light source. When LD00 or LD01 is selected in the weak laser light source 91, the short optical pulses incident on the two input ports of the asymmetric Mach-Zehnder interference system 93 are coherent with different relative phases by π depending on the selection of the input port. Two continuous weak light pulses (two light pulses whose relative phases are clearly defined) are output on the output port.

  On the other hand, when LD10 or LD11 is selected, by appropriately adjusting the waveguide length of the optical waveguide 92 having a pair of long and short optical paths, the input port can be connected at the same time as the coherent double weak light pulse. A weak light pulse whose emission time is modulated according to the selection can be prepared on the output port.

  By coupling the output ports of these two optical circuits to a common optical transmission line 95 with an optical coupler, depending on the selection of the weak laser light source 91, they are complementary to each other required to execute the quantum encryption key distribution protocol. A non-orthogonal optical pulse 9A composed of any one of the coherent double weak light pulses belonging to the basis system or the weak light pulses constituting them can be prepared on the optical transmission line 95 at random.

  On the other hand, the receiver has an optical waveguide 96 having a pair of long and short optical paths similar to the transmitter and an asymmetric Mach-Zehnder interference system 97, and their input ports are connected to a common optical fiber transmission path 95 by an optical coupler 98. Combined, the four output ports are connected to four sets of photon detectors 99.

  Of these four output ports, of the triplet optical pulse 9B output from the asymmetric Mach-Zehnder interference system 97, the arrival photon included in the central optical pulse contributing to the optical interference, the double series after propagation through the long optical waveguide Of the optical pulses, the arrival photons included in the forward pulse and the arrival photons included in the rear pulse among the double light pulses after propagation through the short optical waveguide are detected by four sets of photon detectors 99 operating in synchronization with the transmitter. Detected and recorded.

  At this time, when the selected light source 91 is {LD00 or LD01} and the arrival photon of the photon detector 99 is {D00 or D01} (1/4 of all events), and the selected light source 91 is {LD10 or LD11} and asymmetric Mach-Zehnder interferometer so that the selected light source and the detected detector are perfectly correlated when the photon arrival at photon detector 99 is {D10 or D11} (1/4 of all events) The optical path delay amount 93 or 97 can be controlled by a method such as temperature control.

  Regarding combinations of light source selection and photon-detected detectors other than those described above, there is no complete correlation between them, and they are not used for secret key generation. The above operation satisfies the necessary and sufficient conditions of the quantum cryptography device using the non-orthogonal four states proposed in Non-Patent Document 1, and shares the unconditionally secure secret key between the sender and the receiver according to the proposed protocol. Is possible.

  In the quantum cryptography apparatus shown above, the transmitter performs random selection of four light sources for key data and modulation basis selection. At this time, a 2-bit true random number sequence is required. At the same time, a huge sized storage device for selective base storage is necessary.

On the other hand, since the demodulation base is randomly and passively selected by the optical coupler 98 in the receiver, an intrinsic random number sequence is unnecessary. In addition, since the arrival photon recording recorded in each photon detector simultaneously records the information on the demodulation basis, a huge storage device is not necessary. Therefore, the problems related to the receiver of the quantum cryptography apparatus described above are solved by the system configuration shown in FIG.
International Conference on IEEE Computers, Systems, and Signal Processing by Bennett and Brassard (IEEE Int. Conf. On Computers, Systems, and Signal Processing, Bangalore, India, p. 175 (1984)) Zbinden et al., “Experimental Quantum Cryptography”, “INTRODUCTION TO QUANTUM COMPUTATION AND INORMATION” (World Scientific, 1998), 120 pages Ekert et al., “Quantum Cryptography”, “The Physics of Quantum Information (edited by Bouwmeester et al.)” (Springer, 2000), 15 pages Gisin et al. “Quantum Cryptography” Review of Modern Phys., 74 (2002), pages 145-195 Nanbu et al. “BB84 Quantum Key Distribution System Based on Silica-Based Planar Lightwave Circuits” Japan Journal of Applied Physics, No. 43 (published in 2004), L1109 pages Kimura et al., “Single-photon Interference over 150 km Transmission Using Silica-based Integrated-optic Interferometers for Quantum Cryptography”, Japan Journal of Applied Physics (Jpn J. Appl. Phys.), 43 (published in 2004) , L1217 page Nambu et al. “One-way Quantum Key Distribution System based on Planar Lightwave Circuit” Japan Journal of Applied Phys. 45 (2006), 5344 pages

  The quantum cryptography device using the phase modulator shown in Non-Patent Documents 2 to 7 described above requires a true random number generation device and a selection base storage device in both the transmitter and the receiver, and the system size is enlarged. , Increase costs, and increase heat generation and power consumption.

  Some of this problem is solved by the apparatus shown in FIG. That is, the true random number generator of the receiver and the storage device of the selection base are not necessary. However, the transmitter's true random number generator and the selected base storage device are still necessary, and it has been difficult to completely solve the increase in system size, cost increase, and heat generation / power consumption increase.

  The present invention has been made in view of the above-described problems of the prior art, and its purpose is to realize a technique for realizing a quantum cryptography device, particularly a transmitter thereof, that requires a simpler device configuration for a device that a regular user should have. The purpose is to provide.

The quantum cryptography transmitter of the present invention includes a light source that generates a photon serving as an information carrier of qubits,
A branch coupler that randomly branches photons generated by the light source into a plurality of propagation paths;
A photon number nondestructive measuring device for nondestructively detecting the presence or absence of photons propagating for each of the plurality of propagation paths;
Photon pulse state preparation means for sending a double photon pulse prepared in a non-orthogonal four state depending on a propagation path through which a photon of a plurality of propagation paths has passed, to a single transmission line.

  The quantum cryptography apparatus of the present invention includes the above quantum cryptography transmitter.

  A common feature of the quantum cryptography transmitter that is a constituent element of the quantum cryptography devices disclosed in Patent Documents 1 to 3 is that a pair of non-orthogonal four states required for the quantum cryptography key distribution protocol in the optical circuit used are paired. There are four corresponding optical paths. By using passive branching of light by an optical coupler, photons are randomly sent to four optical paths without a random number generator. At this time, the presence or absence of photons propagating in the four optical paths is observed without breaking the photons by the conventional technique of quantum nondestructive measurement of the number of photons, and the photon propagation ports are recorded only for the positive results. By doing so, it is known which state of the four non-orthogonal states is prepared for each photon from the correspondence. This information is necessary for secret key generation and modulation / demodulation basis verification. As a result, the true random number generator and the enormous storage device, which were the economical and technical load of the device, can be eliminated from the transmitter.

  According to the present invention, the structure of a device that a regular user should have can be simplified, and problems such as an increase in system size, an increase in cost, and an increase in heat generation and power consumption can be solved. Therefore, as compared with the quantum cryptography devices disclosed in Non-Patent Documents 2 to 7, it is possible to greatly reduce the economic and technical burden of the authorized user's device and device operation.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a first embodiment of a quantum cryptography transmitter according to the present invention.

  The quantum cryptography transmitter of the present embodiment is based on the transmitter included in the quantum cryptography device disclosed in Patent Document 1, and includes a light source 11 that generates a photon serving as an information carrier of qubits, and propagation of four photons. A four-branch coupler 12 that randomly branches into a path, a photon number nondestructive measuring device 13 that observes and records the presence or absence of photon propagation in each optical path, and two sets of asymmetric Mach-Zehnder interference systems 14 and 15 that are correlated photon pulse generating means , And an optical coupler 16 that couples them to a common optical transmission line 17.

  FIG. 2 is a block diagram showing the configuration of the second embodiment of the quantum cryptography transmitter according to the present invention.

  The transmission device of the present embodiment is based on a transmitter included in the quantum cryptography device disclosed in Patent Document 2, and includes a light source 21 that generates photons serving as information carriers of qubits, and random photons in four propagation paths. A four-branch coupler 22, a photon number nondestructive measuring device 23 for observing / recording the presence or absence of photon propagation in each optical path, an asymmetric Mach-Zehnder interference system 24, which is a correlated photon pulse generating means, The optical delay circuit 25 has a structure in which an optical waveguide having a short optical path is coupled by an optical coupler, and an optical coupler 26 that couples these to a common optical transmission path 27.

  FIG. 3 is a block diagram showing the configuration of the third embodiment of the quantum cryptography transmitter according to the present invention.

  The transmission device of the present embodiment is based on a transmitter included in the quantum cryptography device disclosed in Patent Document 2, and includes a light source 31 that generates photons serving as information carriers of qubits, and photons in four propagation paths. A four-branch coupler 32 that branches randomly, a photon number nondestructive measuring device 33 that observes and records the presence or absence of photon propagation in each optical path, and a long and short optical path, which is a correlated photon pulse generating means, are coupled to an optical waveguide. It comprises an asymmetric Mach-Zehnder interference system 34 and is connected to a receiver by an optical transmission line 35.

  FIG. 4 is a block diagram showing the configuration of the fourth embodiment of the quantum cryptography transmitter according to the present invention.

  The transmission device of this embodiment is based on a transmitter included in the quantum cryptography device disclosed in Patent Document 1, and includes a light source 41 that generates photons serving as information carriers of qubits, and photons in four propagation paths. 4-branch coupler 42 that branches randomly, photon number nondestructive measuring device 43 that observes and records the presence or absence of photon propagation in each optical path, four sets of polarization plane controllers 44 that are correlated photon pulse generation means, and maintains polarization However, the optical transmission path 48 includes two sets of polarization maintaining couplers or polarization beam splitters 45 coupled to a common optical transmission path, an asymmetric Mach-Zehnder interference plane optical circuit 46, a polarization plane scrambler or a polarizer 47. Is connected to the receiver.

  FIG. 5 is a block diagram showing the configuration of the fifth embodiment of the quantum cryptography transmitter according to the present invention.

  The transmission device of the present embodiment is based on a transmitter included in the quantum cryptography device disclosed in Patent Document 3, and includes a light source 51 that generates photons serving as information carriers of qubits, and random photons in four propagation paths. A four-branch coupler 52, a photon number nondestructive measuring device 53 for observing and recording the presence or absence of photon propagation in each optical path, four sets of polarization plane controllers 54 that are correlated photon pulse generating means, and holding polarization. 2 sets of polarization maintaining couplers or polarization beam splitters 55 coupled to a common optical transmission line, a polarization controller 56, an asymmetric Mach-Zehnder interference system planar optical circuit 57, a polarization controller 58, and a polarization selection element 59. And connected to the receiver by the optical transmission line 5A.

  FIG. 6 is a block diagram showing the configuration of the sixth embodiment of the quantum cryptography transmitter according to the present invention.

  The transmission apparatus according to the present embodiment is based on a transmitter included in the quantum cryptography apparatus disclosed in Patent Document 3, and includes a light source 61 that generates a photon serving as a qubit information carrier, a polarization controller 62, an asymmetric Mach-Zehnder. Interferometric optical circuit 63, four-branch coupler 64 for randomly branching photons into four propagation paths, photon number nondestructive measuring device 65 for observing and recording the presence or absence of photon propagation in each optical path, polarization selection elements 66, 4 It is composed of a four-multiplexed optical coupler 67 that couples two propagation paths to a common propagation path, and is connected to a receiver by an optical transmission line 68.

  Each of the photon number nondestructive measuring apparatuses 13, 23, 33, 43, 53, and 65 includes QNDs (Quantum Non Demolition) 1 to 4 that perform nondestructive measurement on photons propagating through the respective optical paths.

  Hereinafter, operations of the six embodiments of the present invention will be sequentially described with reference to the drawings.

  In the first embodiment of the present invention shown in FIG. 1, a regular sender emits a photon pulse as an information carrier by a light source 11. Photons are randomly branched into four propagation paths by the four-branch coupler 12. The presence or absence of photon pulse propagation in each optical path is observed and recorded by the photon number nondestructive measuring device 13.

  Photons are incident on one of the four input ports of two downstream asymmetric Mach-Zehnder interferometers 14 and 15. When a photon pulse is incident on two input ports of a single asymmetric Mach-Zehnder interferometer system, a coherent double photon pulse having a relative phase different by π depending on the selection of the input port (the relative phase is clearly defined 2 Two photon pulses) can be prepared on the output port.

  When m is an integer and n is the effective refractive index of the interference waveguide, the long and short optical path differences are different from each other by (m + 1/2) λ / 2n, that is, the long and short optical path difference of one interference system is ΔL. Two sets of interference systems 14 and 15 having a long / short optical path difference of ΔL + (m + 1/2) λ / 2n (the propagation optical phase difference of the long / short optical path is different by π / 2) are transmitted through the output ports of the interference system. Coupled to a common optical transmission line 17 by a coupler.

  Interferers 14 and 15 were characterized by 0 basis sets: {0, π} and π / 2 basis sets: {π / 2, 3π / 2}, depending on the four choices of photon input ports, respectively. Two photon pulses having relative phases belonging to mutually complementary basis sets are prepared on the optical transmission line. Therefore, the propagation path of the photon pulse observed and recorded by the photon number nondestructive measuring device 13 and the non-orthogonal four states prepared on the optical transmission path are correlated.

  Since the propagation path of the photon pulse is passively and randomly selected by the four-branch coupler 12, the relative phases required for quantum cryptography using a non-orthogonal four state without a random number generator are {0, π / 2, π A non-orthogonal photon pulse 18 composed of four types of coherent double photon pulses offset by 3π / 2} can be prepared on the optical transmission line 17 at random. At the same time, by comparing with the record of the photon number nondestructive measuring device 13, it is possible to know which state the prepared state was.

  Next, the operation of the quantum cryptography transmitter according to the second embodiment of the present invention shown in FIG. 2 will be described.

  The regular sender emits a photon pulse as an information carrier by the light source 21. Photons are randomly branched into four propagation paths by the four-branch coupler 22. The presence or absence of photon pulse propagation in each optical path is observed and recorded by the photon number nondestructive measuring device 23.

  The photon is incident on one of four input ports of an optical delay circuit 25 having a structure in which a downstream asymmetric Mach-Zehnder interference system 24 and an optical waveguide having a pair of long and short optical paths are coupled by an optical coupler.

  When photon propagation is recorded in QND1 or QND2 of the photon number nondestructive measuring device 23, the photon pulse incident on the two input ports of the asymmetric Mach-Zehnder interference system 24 is only π depending on the selection of the input port. Coherent double photon pulses with different relative phases (two photon pulses with clearly defined relative phases) are output on the output port.

  On the other hand, when photon propagation is recorded in QND3 or QND4, the photon pulses incident on the two input ports of the optical delay circuit 25 are emitted at the same time as the coherent double photon pulse by the action of the optical delay circuit 25. A photon pulse modulated in time depending on the selection of the input port is output on the output port.

  The output ports of the asymmetric Mach-Zehnder interference system 24 and the optical delay circuit 25 are coupled to a common optical transmission line 27 by an optical coupler 26, and belong to mutually complementary basis systems depending on the selection of four photon input ports. A photon pulse is prepared on the optical transmission line.

  Therefore, the propagation optical path of the photon pulse observed and recorded by the photon number nondestructive measuring device 23 and the non-orthogonal four states prepared on the optical transmission path are correlated. Since the propagation path of the photon pulse is passively and randomly selected by the four-branch coupler 22, the non-orthogonal photons belonging to the mutually complementary basis sets are necessary for quantum cryptography using the non-orthogonal four states without a random number generator. The pulses 28 can be prepared on the optical transmission line 27 at random. At the same time, by comparing with the record of the photon number nondestructive measuring device 23, it is possible to know which state the prepared state was.

  Next, the quantum cryptography transmitter according to the third embodiment shown in FIG. 3 will be described.

  The regular sender emits a photon pulse as an information carrier by the light source 31. Photons are randomly branched into four propagation paths by the four-branch coupler 32. The presence or absence of photon pulse propagation in each optical path is observed and recorded by the photon number nondestructive measuring device 33.

  The photon is incident on one of the four input ports of the asymmetric Mach-Zehnder interference system 34 in which the optical waveguide is coupled to the downstream long and short optical paths. When photon propagation is recorded in QND1 or QND2 of the photon number nondestructive measuring device 33, the photon pulses incident on the corresponding two input ports are coherent with different relative phases by π depending on the selection of the input ports. Are output as two consecutive photon pulses (two photon pulses whose relative phases are clearly defined) on the output port.

  On the other hand, when photon propagation is recorded in QND3 or QND4, the photon pulses incident on the corresponding two input ports have the same time as the coherent dual photon pulses and the emission time depends on the input port selection. A modulated photon pulse is output on the output port.

  The output port of the asymmetric Mach-Zehnder interference system 34 is coupled to the optical transmission line 35, and depending on the selection of the four photon input ports, photon pulses belonging to mutually complementary basis systems are prepared on the optical transmission line. Therefore, the propagation optical path of the photon pulse observed and recorded by the photon number nondestructive measuring apparatus 33 and the non-orthogonal four states prepared on the optical transmission path are correlated.

  Since the propagation path of the photon pulse is passively and randomly selected by the four-branch coupler 32, non-orthogonal photons belonging to mutually complementary basis sets, which are necessary for quantum cryptography using non-orthogonal four states without a random number generator, are used. The pulse 36 can be prepared on the optical transmission line 35 at random. At the same time, by comparing with the record of the photon number nondestructive measuring device 33, it is possible to know which state the prepared state was.

  Next, the quantum cryptography transmitter of the fourth embodiment shown in FIG. 4 will be described.

  The regular sender emits a photon pulse serving as an information carrier by the light source 41. Photons are randomly branched into four propagation paths by the four-branch coupler 42. The presence or absence of photon pulse propagation in each optical path is observed and recorded by the photon number nondestructive measuring device 43.

  The photon is adjusted by the downstream polarization plane controller 44 so that the plane of polarization becomes TE polarization or TM polarization. The photon pulse is incident on one of the two input ports of the asymmetric Mach-Zehnder interference planar optical circuit 46 via the polarization beam splitter 45.

  The polarization beam splitter 45 uses the birefringence characteristics of the silica waveguide that forms the planar optical circuit, and the difference between the long and short optical paths is (m + 1/2) λ / 2n different from the TE polarized light and the TM polarized light ( That is, the propagation phase difference between the long and short optical paths is different by π / 2 between the two polarizations (m is an integer, n is the average refractive index of the PLC waveguide), and is controlled by rough temperature adjustment.

  Thus, depending on the polarization plane of the input photon pulse of the asymmetric Mach-Zehnder interference system planar optical circuit 46, 0 basis systems: {0, π} and π / 2 basis systems: {π / 2, 3π / 2} Coherent dual photon pulses belonging to any of the mutually complementary basis sets with the characterized relative phase are prepared on the optical transmission line (base selection). At the same time, depending on the input port of the asymmetric Mach-Zehnder interference system planar optical circuit 46, the relative phase differs by π (data selection).

  As a result, the polarization beam splitter 45 and the asymmetric Mach-Zehnder interferometer plane optical circuit 46 depend on the four selections of the photon input ports, and 0 basis systems: {0, π} and π / 2 basis systems: {π / 2 and 3π / 2} are prepared on the optical transmission line as two-photon pulses belonging to a mutually complementary basis set having a relative phase characterized by 2/2, 3π / 2}.

  Accordingly, the propagation optical path of the photon pulse observed and recorded by the photon number nondestructive measuring device 43 and the four non-orthogonal states prepared on the optical transmission path are correlated. The remaining correlation between the polarization plane of the prepared dual photon pulse and the selected basis is canceled by passing through a polarizer 47 that transmits only a linearly polarized wave tilted 45 degrees with respect to the polarization plane scrambler or TE / TM. To the optical transmission line 48.

  Since the propagation path of the photon pulse is passively and randomly selected by the four-branch coupler 42, the relative phases required for the quantum cryptography using the non-orthogonal four states without the random number generator are {0, π / 2, π A non-orthogonal photon pulse 49 composed of four types of coherent duplex optical pulses offset by 3π / 2} can be prepared on the optical transmission line 48 at random. At the same time, by comparing with the record of the photon number nondestructive measuring device 43, it is possible to know which state the prepared state was.

  Next, the quantum cryptography transmitter of the fifth embodiment shown in FIG. 5 will be described.

  The regular sender emits a photon pulse as an information carrier by the light source 51. Photons are randomly branched into four propagation paths by a four-branch coupler 52. The presence or absence of photon pulse propagation in each optical path is observed and recorded by the photon number nondestructive measuring device 53.

  The photon is adjusted by the downstream polarization plane controller 54 so that the plane of polarization becomes TE polarization or TM polarization. The photon pulse propagated through QND1 or QND2 of the photon number nondestructive measuring device 53 passes through the polarization maintaining coupler or the polarization beam splitter 55, and its polarization is changed to the oblique polarization (TE + TM, TE-TM). After being adjusted by the polarization controller 56, the light is incident on one input port of the asymmetric Mach-Zehnder interference system planar optical circuit 57.

  The photon pulse that has propagated through QND3 or QND4 of the photon number nondestructive measuring device 53 passes through the polarization maintaining coupler or the polarization beam splitter 55 and maintains its polarization plane, and the other input of the asymmetric Mach-Zehnder interference system 57. It is incident on the port.

  The asymmetric Mach-Zehnder interferometer planar optical circuit 57 uses the birefringence characteristics of the silica waveguide constituting the planar optical circuit, where m is an integer and n is the average refractive index of the PLC waveguide. And the TM polarized light are controlled by rough temperature adjustment so that the difference between the long and short optical paths is different by (m + 1/2) λ / n (that is, the propagation phase difference between the long and short optical paths is different by π between both polarizations).

  At this time, if the polarization of the input photon pulse of the asymmetric Mach-Zehnder interference system planar optical circuit 57 is a TE polarization or a TM polarization, the coherent 2 having the same polarization plane as the input polarization at the output side port. A continuous light pulse is output.

  On the other hand, when the polarization of the input photon pulse is in an oblique polarization state (TE + TM, TE-TM) perpendicular to each other, it consists of superposition of TE and TM polarization isobaric ratios. The coherent double light pulses that are held are sequentially output.

  The polarization controller 58 and the polarization selection element 59 are adjusted so as to cut out only one of these double pulses. As a result, the optical system from the polarization beam splitter 55 to the polarization selection element 59 belongs to mutually complementary basis systems necessary for executing the quantum key distribution protocol depending on the selection of four photon input ports. , A coherent double photon pulse whose relative phase is different by π, or a photon pulse whose emission time is modulated depending on the selection of the input port is prepared on the optical transmission line.

  Therefore, the propagation path of the photon pulse observed and recorded by the photon number nondestructive measuring device 53 and the non-orthogonal four states prepared on the optical transmission path are correlated. Since the propagation path of the photon pulse is passively and randomly selected by the four-branch coupler 52, non-orthogonal photons belonging to mutually complementary basis sets, which are necessary for quantum cryptography using non-orthogonal four states without a random number generator, are used. The pulse 5B can be prepared on the optical transmission line 59 at random. At the same time, by comparing with the record of the photon number nondestructive measuring device 53, it is possible to know which state was prepared.

  Finally, the quantum cryptography transmitter according to the sixth embodiment of the present invention shown in FIG. 6 will be described.

  The regular sender emits a photon pulse as an information carrier by the light source 61. The polarization controller 62 adjusts the polarization of the photon pulse so that the polarization is in an oblique polarization state (TE + TM or TE-TM), which is a linear combination of the TE polarization and TM polarization of the intrinsic optical axis of the waveguide. The wave is adjusted and incident on the input port of the asymmetric Mach-Zehnder interference system planar optical circuit 63.

  The asymmetric Mach-Zehnder interferometer plane optical circuit 63 uses the birefringence characteristics of the silica optical waveguide, and when m is an integer and n is the average refractive index of the PLC waveguide, the long and short optical paths that are constituent elements of the optical waveguide 63 are used. The optical path length difference is controlled by rough device temperature adjustment so that the TE-polarized light and the TM-polarized light are different by (m + 1/2) λ / n (that is, the propagation optical phase difference between the long and short optical paths is π different for both polarizations). .

  As a result, the photon state output to the output port of the asymmetric Mach-Zehnder interference system planar optical circuit 63 is approximately the state mode (Time-bin mode) stretched between the polarization mode and the photon wave packet state of the double pulse. It becomes the maximum sympathy state. Utilizing this fact, it is possible to prepare an arbitrary time-bin state corresponding one-to-one by appropriately selecting a polarization mode of photons and filtering a specific polarization component.

  The four-branch optical coupler 64, the photon number nondestructive measuring device 65, the polarization selection element 66, and the four-multiplexed optical coupler 67 are passive polarization filters used for this purpose. Each of the four sets of polarization selection elements 66 is set to select and transmit one of the four types of non-orthogonal polarization states (TE / TM / TE + TM / TE-TM) of the output pulsed light. Yes.

  Therefore, depending on the photon propagation optical path, the corresponding polarization component of the output pulse light is selectively transmitted. The 4-multiplex optical coupler 67 outputs the output pulse light on the optical transmission line 68 after appropriately converting the polarization plane so that the photon pulses have the same polarization (for example, TE polarization).

  The polarization plane conversion as described above can be performed by appropriately rotating and coupling the polarization-maintaining optical fiber end faces constituting the 4-multiplex optical coupler 67. Alternatively, a polarization controller can be used. The presence or absence of photon pulse propagation in each optical path is observed and recorded by the photon number nondestructive measuring device 65. Since there is a correlation between the photon propagation optical path of the passive polarization filter and the polarization plane to be filtered, there is also a correlation between the photon propagation optical path and the generated time-bin photon.

  Accordingly, the propagation optical path of the photon pulse observed and recorded by the photon number nondestructive measuring device 65 correlates with the four non-orthogonal states prepared on the optical transmission path. Since the propagation path of photon pulses is passively and randomly selected by the four-branch coupler 64, non-orthogonal photons belonging to mutually complementary basis sets, which are necessary for quantum cryptography using non-orthogonal four states without a random number generator, are used. Pulses 69 can be prepared on the optical transmission line 68 at random. At the same time, by comparing with the record of the photon number nondestructive measuring device 65, it is possible to know which state the prepared state was.

  The common features of the above embodiments of the present invention are as follows.

  The true random number modulator and the large-scale storage device can be excluded from the transmitter of the quantum cryptography device. In addition to this, when a conventional quantum cryptography receiver is used, the true random number modulator and the storage device can be completely eliminated from the quantum cryptography device. As a result, the structure of the device that the authorized user should have can be simplified, and problems such as an increase in system size, an increase in cost, and an increase in heat generation and power consumption can be solved. Therefore, as compared with the prior art quantum cryptography devices disclosed in Non-Patent Documents 2 to 7, it is possible to significantly reduce the economic and technical burden of the authorized user's device and device operation.

  In addition, although only the part which transmits quantum cryptography was demonstrated as embodiment, naturally the quantity encryption apparatus provided with the transmitter of each embodiment and the receiver which receives quantum cryptography is also contained in this invention.

The figure which shows the structure of 1st Embodiment of the quantum cryptography transmitter by this invention. The figure which shows the structure of 2nd Embodiment of the quantum cryptography transmitter by this invention. The figure which shows the structure of 3rd Embodiment of the quantum cryptography transmitter by this invention. The figure which shows the structure of 4th Embodiment of the quantum cryptography transmitter by this invention. The figure which shows the structure of 5th Embodiment of the quantum cryptography transmitter by this invention. The figure which shows the structure of 6th Embodiment of the quantum cryptography transmitter by this invention. The block diagram of a quantum cryptography apparatus. The block diagram of a quantum cryptography apparatus. The block diagram of a quantum cryptography apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Light source 12 4-branch coupler 13 Photon number nondestructive measuring device 14 Asymmetric Mach-Zehnder interference system 15 Asymmetric Mach-Zehnder interference system 16 Optical coupler 17 Optical transmission line 18 Non-orthogonal photon pulse 21 Light source 22 Four-branch coupler 23 Photon number nondestructive measuring device 24 Asymmetric Mach-Zehnder Interference System 25 Optical Delay Circuit 26 Optical Coupler 27 Optical Transmission Path 28 Non-Orthogonal Photon Pulse 31 Light Source 32 Four-Branch Coupler 33 Photon Number Nondestructive Measuring Device 34 An Asymmetric Mach with an Optical Waveguide Coupled to Long and Short Optical Paths Zender interference system 35 Optical transmission path 36 Non-orthogonal photon pulse 41 Light source 42 Four-branch coupler 43 Photon number nondestructive measuring device 44 Polarization plane controller 45 Polarization maintaining coupler or polarization beam splitter 46 Symmetric Mach-Zehnder interference plane optical circuit 47 Wave front Rambler or polarizer 48 Optical transmission line 49 Non-orthogonal photon pulse 51 Light source 52 Four-branch coupler 53 Photon number nondestructive measuring device 54 Polarization plane controller 55 Polarization maintaining coupler or polarization beam splitter 56 Polarization controller 57 Asymmetric Mach-Zehnder interference system Planar optical circuit 58 Polarization controller 59 Polarization selection element 5A Optical transmission line 5B Non-orthogonal photon pulse 61 Light source 62 Polarization controller 63 Asymmetric Mach-Zehnder interferometer optical circuit 64 Four-branch coupler 65 Photon number nondestructive measurement device 66 Polarization selection Element 67 Four-coupled optical coupler 68 Optical transmission path 69 Non-orthogonal photon pulse 71 Weak laser light source 72 Asymmetric Mach-Zehnder interference system 73 Optical transmission path 74 Asymmetric Mach-Zehnder interference system 75 Photon detector 76 Phase modulator 77 Phase modulator 78 Coherent Double light pulse 79 triple light pulse 81 weak laser light source 82 asymmetric Mach-Zehnder interference system planar optical circuit 83 optical transmission path 84 asymmetric Mach-Zehnder interference system planar optical circuit 85 photon detector 86 phase modulator 87 phase modulator 88 phase Modulator 89 Coherent double light pulse 8A Triple light pulse 91 Weak laser light source 92 Optical waveguide having long and short optical paths 93 Asymmetric Mach-Zehnder interference system 94 Optical coupler 95 Optical transmission path 96 Optical waveguide having long and short optical paths 97 Asymmetric Mach-Zehnder interference system 98 Optical coupler 99 Photon detector 9A Non-orthogonal optical pulse 9B Triple light pulse

Claims (8)

A light source that generates photons that are information carriers of qubits;
A branch coupler that randomly branches photons generated by the light source into a plurality of propagation paths;
A photon number nondestructive measuring device for nondestructively detecting the presence or absence of photons propagating for each of the plurality of propagation paths;
Photon pulse state preparation means for sending a double photon pulse prepared in a non-orthogonal four state depending on the propagation path through which a photon of a plurality of propagation paths has passed, to a single transmission line;
A quantum cryptography transmitter. The quantum cryptography transmitter according to claim 1,
The photon pulse state preparation means is provided between the plurality of propagation paths and a single transmission path;
When m is an integer and n is the effective refractive index of the interference waveguide, the long and short optical path differences are different from each other by (m + 1/2) λ / 2n, that is, the long and short optical path difference of one interference system is ΔL. A quantum cryptography transmitter configured by an optical circuit in which two sets of asymmetric Mach-Zehnder interference system planar optical circuits whose long and short optical path differences of the interference system are ΔL + (m + 1/2) λ / 2n are connected in parallel. The quantum cryptography transmitter according to claim 1,
The photon pulse state preparation means is provided between the plurality of propagation paths and a single transmission path;
A quantum cryptography transmitter comprising an asymmetric Mach-Zehnder interference system composed of a planar optical circuit, an optical delay circuit, and an optical coupler for coupling them. The quantum cryptography transmitter according to claim 1,
The photon pulse state preparation means is provided between the plurality of propagation paths and a single transmission path;
A quantum cryptography transmitter comprising an asymmetric Mach-Zehnder interferometer plane optical circuit in which independent propagation paths are coupled to long and short optical paths. The quantum cryptography transmitter according to claim 1,
The photon pulse state preparation means is provided between the plurality of propagation paths and a single transmission path;
A polarization plane controller that adjusts the polarization plane of photons output from the plurality of propagation paths to be TE polarization or TM polarization;
Two sets of polarization beam splitters for coupling the TE polarized light and TM polarized light to two input ports of the asymmetric Mach-Zehnder interferometric planar optical circuit;
An asymmetric Mach-Zehnder interferometer plane in which the output optical paths of the polarization beam splitter are combined and the long / short optical path difference for the TE polarized light and the long / short optical path difference for the TM polarized light are controlled to be different from each other by (m + 1/2) λ / 2n. A quantum cryptography transmitter composed of optical circuits. The quantum cryptography transmitter according to claim 1,
The photon pulse state modulation means is provided between the plurality of propagation paths and a single transmission path;
A polarization controller that adjusts the polarization plane of photons output from the plurality of propagation paths to be TE polarization or TM polarization;
Two sets of polarization beam splitters that combine TE polarized light and TM polarized light output from the polarization controller into one output optical path;
A polarization controller that converts the polarization of the output light of the output optical path of the polarization beam splitter into oblique polarization (TE + TM or TE-TM);
The TE and TM polarized photons output from the polarization beam splitter and the obliquely polarized photon output from the polarization controller are input, and the long and short optical path difference for the TE polarized light and the long and short optical path difference for the TM polarized light are (M + 1/2) λ / n asymmetric Mach-Zehnder interferometric planar optical circuit controlled to be different,
Quantum cryptography transmission which is connected to the output port of the asymmetric Mach-Zehnder interferometer planar optical circuit, and which comprises a polarization plane controller for controlling the polarization plane of the output light and a polarization selection element for selectively transmitting only the specific polarization light vessel. The quantum cryptography transmitter according to claim 1,
The photon pulse state preparation means is provided before the plurality of propagation paths and transmission lines,
A polarization controller that controls the polarization of photons generated by the light source to be in an oblique polarization state (TE + TM or TE-TM);
The asymmetrical Mach, in which the obliquely polarized photons output from the polarization controller are input and the long / short optical path difference for the TE polarized light and the long / short optical path difference for the TM polarized light are controlled to be different by (m + 1/2) λ / n A Zehnder interference planar optical circuit;
And four types of polarization selection elements that select and transmit non-orthogonal polarization states (TE / TM / TE + TM / TE-TM) downstream of the plurality of propagation paths;
An optical coupler for multiplexing the polarization selection element outputs;
A quantum cryptography transmitter. A quantum cryptography apparatus comprising the quantum cryptography transmitter according to any one of claims 1 to 7.

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