WO2008015758A1 - Appareil, système et procédé de communication quantique - Google Patents
Appareil, système et procédé de communication quantique Download PDFInfo
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- WO2008015758A1 WO2008015758A1 PCT/JP2006/315490 JP2006315490W WO2008015758A1 WO 2008015758 A1 WO2008015758 A1 WO 2008015758A1 JP 2006315490 W JP2006315490 W JP 2006315490W WO 2008015758 A1 WO2008015758 A1 WO 2008015758A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
- H04L9/0852—Quantum cryptography
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/70—Photonic quantum communication
Definitions
- Quantum communication device Quantum communication device, quantum communication system, and quantum communication method
- the present invention relates to a quantum communication device, a quantum communication system, and a quantum communication method.
- the present invention particularly relates to a quantum cryptography communication device.
- a conventional quantum cryptography communication device using a single photon source with a messenger transmits a messenger signal output from a single photon source from a transmitting device to a receiving device, and the messenger signal is used as a trigger in the transmitting device.
- the signal modulation operation was performed, and the receiving device also performed the photon detection operation and the quantum signal demodulation operation using the transmitted messenger signal as a trigger (see, for example, Non-Patent Documents 1 and 2).
- a single photon source with a messenger is generated by generating a twin photon pair using parametric down-conversion and measuring one photon without measuring the presence of the other photon.
- This is a method used as a single photon source.
- the measured output of one photon is output as a messenger signal notifying the output of the other photon.
- CW Continuous' Wave
- a twin photon pair is generated as a probabilistic occurrence, so a single photon is generated at irregular time intervals as a photon source.
- a single-photon source with a messenger is used as the preferred one because it has a lower probability of generating a multi-photon state than a conventional one that attenuates laser light. This is because it is an excellent light source. If a typical photon detector currently used for quantum cryptography is used, it is impossible to guarantee safety at a communication distance of about 25 km (kilometers) with a laser using a single photon source. In the case of an attached single photon source, the single photon nature is excellent, so safety can be guaranteed even at a distance exceeding 50 km.
- the two-photon existence probability P (2) of the optical pulse specified by the messenger signal is generally reduced by reducing the pump light intensity. (1 ) Can be made arbitrarily small while maintaining the same level of quantum cryptography as when using an ideal single-photon source.
- Non-patent literature 1 A. Trifonov and A. Zavriyev, Secure communication with a heralded single— photon source, "Journal of Optics B: Quantum Semiclass.Opt. 7 No 12 (December 2005) S772-S777,
- Non-Patent Document 2 S. Fasel, O. Alibart, S. Tanzilli, P. Baldi, A. Be veratos, N. Gism and H. Zbinden, "High— quality asynchronous heralded single- photon source at telecom wavelength," New Journal of Physics 6 (November 2004) 163, 12 November 2004 Invention Disclosure
- a messenger signal is generated by measuring one of the twin photon pairs with a photon detector. Therefore, the accuracy of the messenger signal depends on the performance of the photon detector used for this measurement. There was a problem that would be limited.
- a photon measured as a messenger signal light with a short wavelength of 850 nm (nanometer) or less is used, and SiAPD (Silicon-Avalanche • Photodiode) is preferably used for detecting this photon. It is done.
- a photon detector called SPCM (Single Photon Couting Module) using SiAPD has a jitter fluctuation of about 500 ps (picoseconds). Therefore, for a single photon, the messenger signal has 500 ps of jitter.
- Quantum cryptography usually uses a single photon in the communication wavelength band of 1.55 m (micrometers), and the photon detector in this wavelength band (communication wavelength band photon detector) is a gate type Geiger mode.
- the jitter of the messenger signal Since it is operated in accordance with the timing of photon incidence, the jitter of the messenger signal has a non-negligible effect. Since the communication wavelength band photon detector actually realizes the optimum operation by setting the timing in the order of ⁇ s, the above-mentioned SPCM jitter cannot be ignored.
- An object of the present invention is to realize stable and highly efficient quantum communication regardless of jitter of a messenger signal. Means for solving the problem
- a quantum communication device includes:
- a quantum communication device that transmits a photon output as a quantum signal from a single photon source that is pulse-driven and outputs a photon via a quantum communication channel
- Timing of outputting a messenger signal indicating that a quantum signal output from the single photon source exists on the quantum communication path as a trigger signal in synchronization with a clock signal for driving the pulse of the single photon source An adjustment unit;
- a quantum signal modulation unit that performs signal modulation on the quantum signal in accordance with the timing of the trigger signal output from the timing adjustment unit, and transmits the quantum signal subjected to signal modulation via the quantum communication path;
- a messenger signal transmission unit configured to transmit the messenger signal via a messenger signal communication path.
- the quantum communication device further includes:
- a clock signal transmission unit that transmits the clock signal via a clock communication path is provided.
- the quantum communication device further includes:
- a clock signal receiving unit configured to receive the clock signal via a clock communication path, wherein the timing adjustment unit synchronizes the messenger signal with the clock signal received by the clock signal receiving unit; Is output as
- the quantum communication device further includes:
- a photon pair is generated by the single photon source, one photon of the photon pair is output as the quantum signal, and the other photon of the photon pair is output as the messenger signal.
- the quantum signal modulation unit performs signal modulation on the quantum signal output from the signal generation unit,
- the messenger signal transmitting unit transmits the messenger signal output from the signal generating unit.
- the signal generation unit generates the photon pair by parametric down conversion.
- the signal generation unit performs an AND operation on the messenger signal output from the single photon source and the clock signal, and outputs the result of the AND operation again as the messenger signal. To do.
- the signal generator controls the messenger signal output from the single photon source by the clock signal, and outputs a controlled messenger signal.
- a quantum communication device according to another aspect of the present invention provides:
- a quantum communication device that receives a photon output as a quantum signal from a single photon source that is pulse-driven and outputs a photon via a quantum communication channel
- a messenger signal receiving unit for receiving a messenger signal indicating that a quantum signal output from the single photon source is present on the quantum communication channel
- a timing adjustment unit that outputs a messenger signal received by the messenger signal reception unit as a trigger signal in synchronization with a clock signal for pulse driving the single photon source, and a trigger output from the timing adjustment unit
- a quantum signal detector configured to detect a quantum signal existing on the quantum communication path in accordance with a signal timing
- the quantum communication device further includes:
- a clock signal receiving unit that receives the clock signal via a clock communication path; and the timing adjustment unit receives the messenger signal received by the messenger signal receiving unit as a clock signal received by the clock signal receiving unit. Output as the trigger signal in synchronism with.
- the quantum communication device further includes:
- a clock signal transmission unit that transmits the clock signal via a clock communication path is provided.
- the quantum signal detection unit includes a quantum signal demodulation unit that performs signal demodulation on a quantum signal existing on the quantum communication path in accordance with the timing of the trigger signal output by the timing adjustment unit.
- the quantum signal demodulated by the quantum signal demodulation unit is detected in accordance with the timing of the trigger signal output from the adjustment unit.
- the quantum signal detection unit includes a quantum signal branching unit that branches the quantum communication channel, and is branched by the quantum signal branching unit in accordance with the timing of the trigger signal output from the timing adjustment unit. It is characterized by detecting a quantum signal present on a quantum communication channel.
- a quantum communication system includes:
- a messenger signal channel carrying a messenger signal indicating that the quantum signal is present on the quantum channel
- a first timing adjustment unit that outputs the messenger signal as a first trigger signal in synchronization with a clock signal for pulse driving the single photon source, and is output from the first timing adjustment unit.
- the quantum signal modulating unit that performs signal modulation on the quantum signal in accordance with the timing of the first trigger signal and transmits the quantum signal subjected to signal modulation via the quantum communication channel, and the messenger signal
- a first quantum communication device including a messenger signal transmitter that transmits the messenger signal via the messenger signal communication path
- the messenger signal receiver that receives the messenger signal transmitted by the messenger signal transmitter via the messenger signal communication path and the messenger signal received by the messenger signal receiver are synchronized with each other.
- the second timing adjustment unit that outputs the second trigger signal, and the second timing adjustment unit forces the quantum signal modulation unit on the quantum communication path according to the timing of the output second trigger signal.
- a second quantum communication device including a quantum signal detector that detects the quantum signal transmitted to
- the quantum communication system further includes:
- the first quantum communication device further includes a clock signal transmission unit that transmits the clock signal via the clock communication path,
- the second quantum communication device further includes a clock transmitted by the clock signal transmission unit.
- a clock signal receiving unit that receives a clock signal via the clock communication path, and the second timing adjustment unit receives the messenger signal received by the messenger signal receiving unit by the clock signal receiving unit.
- the second trigger signal is output in synchronization with the clock signal thus generated.
- the quantum communication system further includes:
- the second quantum communication device further includes a clock signal transmission unit that transmits the clock signal via the clock communication path,
- the first quantum communication device further includes a clock signal reception unit that receives the clock signal transmitted by the clock signal transmission unit via the clock communication path, and the first timing adjustment unit includes: The messenger signal is output as the first trigger signal in synchronization with the clock signal received by the clock signal receiver.
- the quantum communication channel is characterized in that a dispersion compensating fiber is used in the subsequent stage of the optical fiber.
- a quantum communication method includes:
- a messenger signal indicating that the quantum signal is present on the quantum communication path is synchronized with a clock signal for driving the pulse of the single photon source to generate a first trigger. Output as a signal,
- the quantum signal is subjected to signal modulation in accordance with the timing of the first trigger signal output by the output of the first trigger signal, and the signal is subjected to signal modulation.
- the quantum channel Via the quantum channel,
- the messenger signal is transmitted via the messenger signal communication path
- the messenger signal transmitted by the transmission of the messenger signal is received via the messenger signal communication path
- the messenger signal received by the reception of the messenger signal is synchronized with the clock signal and output as a second trigger signal
- the quantum signal transmitted on the quantum communication path by transmitting the quantum signal is synchronized with the timing of the second trigger signal output by the output of the second trigger signal. It is characterized by detecting.
- the timing adjustment unit outputs the messenger signal as a trigger signal in synchronization with the clock signal for pulse driving the single photon source.
- the quantum signal modulation unit modulates the quantum signal in accordance with the timing of the trigger signal, transmits the quantum signal via the quantum communication path, and the messenger signal transmission unit transmits the messenger signal via the messenger signal communication path. Therefore, stable and highly efficient quantum communication can be realized without being influenced by jitter of the messenger signal.
- FIG. 1 is a block diagram showing a configuration of quantum communication system 100 according to the present embodiment.
- a quantum communication system 100 (also referred to as “quantum cryptography communication system”) includes a quantum cryptography transmission device 200, a quantum cryptography reception device 300, and a quantum communication path 101 (which connects these devices). (Also called “quantum signal communication channel”), messenger signal communication channel 102 and clock communication channel 103 (also known as “pulse / clock signal communication channel” or “pulse / clock signal communication channel”).
- Quantum communication channel 101 is a communication channel that carries photons as quantum signals.
- a dispersion compensation fiber 104 is connected to the subsequent stage to compensate for the optical pulse waveform distortion caused by the chromatic dispersion inherent in the optical fiber. Also good.
- the messenger signal communication path 102 is a communication path that carries a messenger signal to be described later.
- the clock communication path 103 is a communication path that carries a clock signal (also referred to as “pulse“ clock signal ”) described later.
- the messenger signal communication path 102 and the clock communication path 103 may be optical communication paths or electrical signal communication paths.
- the quantum cryptography transmission device 200 is an example of a quantum communication device, and includes a single-photon source 201 with a pulse-driven messenger, a quantum signal modulation unit 203, a messenger signal transmission unit 205, a clock signal transmission unit 206, A timing adjuster 202.
- the single photon source 201 with a pulse drive instruction is an example of a signal generation unit.
- the quantum signal modulator 203 includes a quantum signal modulator 204 that applies signal modulation to the quantum state of a single photon output from the single photon source 201 with a pulse drive command.
- the messenger signal transmission unit 205 is a transceiver or transmitter that transmits the messenger signal output from the single photon source 201 with a pulse drive messenger to the messenger signal communication path 102.
- the clock signal transmission unit 206 is a transceiver or a transmitter that transmits a clock signal of a pulse laser serving as a pump source of the single photon source 201 with a pulse drive command to the clock communication path 103.
- the timing adjuster 202 is an example of a first timing adjuster.
- the timing adjuster 202 is a first trigger signal (simply referred to as a “trigger signal”) that is supplied to the quantum signal modulator 204 in synchronization with a pulse clock signal. , U).
- the messenger signal is a signal that is output at irregular time intervals in synchronization with a single photon, but there is a non-negligible jitter between the single photon.
- the pulse clock signal is a clock signal of the pulse laser of the pump light source, it is output even in a time slot where a single photon is not output regularly.
- the jitter between single photons is very small.
- the jitter is less than lps.
- the quantum cryptography reception device 300 is an example of a quantum communication device, and includes a quantum signal detection unit 304, an messenger signal reception unit 301, a clock signal reception unit 302, and a timing adjuster 303.
- the quantum signal detection unit 304 includes a photon detector 306 that detects a photon transmitted through the quantum communication channel 101, and a quantum signal demodulator 305 that performs signal demodulation on the quantum state of the photon transmitted through the quantum communication channel 101. Including.
- the quantum signal demodulator 305 is an example of a quantum signal demodulator.
- the messenger signal receiving unit 301 is a receiver or transceiver that receives the messenger signal transmitted through the messenger signal communication path 102.
- the clock signal receiving unit 302 is a receiver or a transceiver that receives the pulse clock signal transmitted through the clock communication path 103.
- the timing adjuster 303 is an example of a second timing adjusting unit, and synchronizes the messenger signal received by the messenger signal receiving unit 301 with the pulse clock signal received by the clock signal receiving unit 302, thereby detecting the photon detector. 306 and the second trigger signal applied to the quantum signal demodulator 305 (simply “trigger” Signal ").
- the transmitter (ie, clock signal transmission unit 206) and receiver (ie, clock signal reception unit 302) used in the clock communication path 103 are required to operate at low jitter and at high speed. For this reason, in some cases, a part of the pulsed laser light output from the pump light source of the single-photon source 201 with a pulse-driven messenger is branched, and if necessary, the wavelength is converted to an appropriate wavelength for the communication path,
- the clock communication path 103 may be configured to transmit using an optical fiber.
- quantum cryptography secure communication is realized by randomly selecting measurement means conjugate to each other.
- this measuring means is actively selected on the receiving side, the quantum signal demodulator 305 is used in the quantum signal detection unit 304, but when it is passively selected, the quantum signal demodulator 305 is used instead.
- the photon detector 306 used for the measurement is increased.
- the former configuration is as shown in Fig. 1.
- the latter configuration will be described in the third and subsequent embodiments.
- FIG. 2 is a diagram illustrating an example of a quantum cryptography optical system that actively performs measurement unit selection on the reception side.
- the control system is omitted for simplicity.
- FIG. 2 particularly shows an example of the configuration of the quantum signal modulation unit 203 and the quantum signal detection unit 304.
- the quantum cryptography transmission device 200 actively specifies and transmits the quantum state using the phase modulator 208, and the quantum cryptography reception device 300 also actively uses the phase demodulator 307 to actively quantize the quantum state. Measure. Further, after the phase demodulator 307, there is an asymmetric Matsuhsunder interferometer 308 corresponding to a preset and fixed measuring means, which leads to photon detectors 306a, b corresponding to the measuring means. In this example, the quantum signal modulation unit 203 of the quantum cryptography transmission device 200 also uses an asymmetric Mach-Zehnder interferometer 207 before the phase modulator 208 in order to perform signal modulation processing.
- a polarization modulator or the like may be used instead of the force using the phase modulator 208.
- the phase demodulator 307 is used as an example of the quantum signal demodulation unit, but a polarization demodulator or the like may be used instead. ! /
- the quantum cryptography transmitter 200 An input device (not shown) inputs the 2-bit information to a processing device (not shown).
- a storage device (not shown) may store the 2-bit information, and the processing device may read the 2-bit information from the storage device.
- the processing device converts this 2-bit information into an electric signal and inputs it to the quantum signal modulation unit 203.
- the quantum signal modulation unit 203 inputs one photon of the photon pair output from the single-photon source 201 with a pulse drive command using an asymmetric Mach-Zehnder interferometer 207 and a phase modulator 208 and inputs it from the processing device.
- the signal is modulated by the electrical signal.
- the phase modulator 208 performs phase modulation of the photon with four types of phase differences ⁇ 0, ⁇ / 2, ⁇ , (3/2) ⁇ , so that a 2-bit value is added to the photon. Apply signal modulation. Photons subjected to such signal modulation are transmitted from the quantum cryptography transmission device 200 to the quantum cryptography reception device 300 via the quantum communication channel 101.
- the quantum signal detection unit 304 In the quantum cryptography receiving device 300, the quantum signal detection unit 304 generates a 1-bit random number using a random number generator (not shown), and inputs the generated 1-bit random number to the phase demodulator 307.
- the quantum signal detection unit 304 uses a phase demodulator 307 to demodulate a photon transmitted through the quantum communication channel 101 using an input 1-bit random electrical signal.
- the phase demodulator 307 performs phase modulation (that is, phase demodulation) of photons 0 or ⁇ 2 according to the value of the 1-bit random number (for example, the value 1 of the 1-bit random number 1). Phase modulation of ⁇ ⁇ 2 at the time, and the photon is demodulated.
- the phase demodulator 307 is connected to a photon detector 306a and a photon detector 306b via an asymmetric Matsuhsunder interferometer 308.
- the quantum signal detection unit 304 specifies the 1-bit value of the 2-bit information depending on which of the photon detector 306a and the photon detector 306b detects the photon subjected to signal demodulation.
- the identified bit is effective when the remaining 1 bit of the 2-bit information has the same value as the 1-bit random number, for example, the photon detector 306a detects a photon with a phase difference of 0 and detects the photon.
- phase difference of the photons transmitted through the communication channel 101 is 0 or ⁇ and the phase demodulator 307 performs phase modulation of 0 (ie, phase modulation is not performed)
- the quantum signal detection unit 304 On the other hand, the phase difference of the photons transmitted through the quantum channel 101 is ⁇ ⁇ 2 or (3 ⁇ 2) ⁇ , and the phase demodulator 307 performs phase modulation of ⁇ ⁇ 2.
- the bit specified by the quantum signal detection unit 304 is valid.
- the bit detected by the number detection unit 304 is output.
- a processing device may perform predetermined processing using this bit. This bit can be used, for example, as key information or a part of key information.
- FIG. 3 is a timing chart showing an example of quantum cryptography communication according to the present embodiment.
- a pulse clock signal (“transmission side clock signal”) is regularly output from the single photon source 201 with a pulse drive message included in the quantum cryptography transmitter 200.
- transmission side clock signal the pulse clock signal
- the generation of single photons occurs stochastically, the output of single photons and accompanying messenger signals (“transmitting messenger signals”) occurs irregularly.
- the generation timing of the single photon is very accurately synchronized with the pulse clock signal.
- the power messenger signal is synchronized with the single photon generation timing and the pulse clock signal in the order of 500 ps. Has jitter.
- the timing adjuster 202 included in the quantum cryptography transmission device 200 takes in the messenger signal and the pulse 'clock signal, and only when the messenger signal is input, the first trigger that is accurately synchronized with the pulse' clock signal.
- a signal (“quantum signal modulation trigger signal”) is output, and the quantum signal modulator 204 is operated.
- the single photon output from the single photon source 201 with a pulse drive command is accurately subjected to signal modulation.
- the clock communication path 103 and the messenger signal communication path 102 are respectively set to the pulse'clock signal and the messenger signal power. And transmitted to the quantum cryptography receiver 300. At this time, the single photon that has undergone signal modulation is transmitted to the quantum cryptography receiving device 300 via the quantum communication channel 101.
- the pulse clock signal (“reception side clock signal”) and the message signal (“reception side message signal”) transmitted to the quantum cryptography reception device 300 are the clock signal reception unit 302 and the message signal reception unit 301, respectively. And input to the timing adjuster 303 included in the quantum cryptography receiving device 300.
- the timing adjuster 303 outputs the second trigger signal (“photon detection trigger signal”) that is accurately synchronized with the NORSE clock signal only when the messenger signal is input, and operates the photon detector 306.
- photon detection trigger signal the second trigger signal that is accurately synchronized with the NORSE clock signal only when the messenger signal is input, and operates the photon detector 306.
- the timing adjuster 303 can detect the second trigger signal accurately synchronized with the pulse clock signal only when the messenger signal is input (" Quantum signal demodulation trigger signal ”) is output, and the quantum signal demodulator 305 is operated. For this reason, the signal demodulation operation can be performed in precise synchronization with the single photon transmitted to the quantum cryptography receiver 300.
- the unit time of the clock is 12.5 ns. Therefore, if the jitter of the messenger signal is suppressed to about 5 ns, it is considered possible to synchronize the messenger signal with the pulse clock signal. As described above, since the jitter of the messenger signal is about 500 ps, it is sufficiently possible to synchronize the messenger signal with the pulse clock signal. In addition, as described above, the jitter of the pulse 'clock signal can be suppressed to about lps, so the jitter of the trigger signal generated by synchronizing the messenger signal with the pulse' clock signal can be suppressed to about lOOps. It is. This makes it possible to reduce the influence of the performance of the photon detector 306 on the stability and efficiency of quantum communication.
- the quantum signal modulation timing in the quantum cryptography transmission device 200, the quantum signal demodulation timing and the photon detection timing in the quantum cryptography reception device 300 can be set to a message in which jitter cannot be ignored with respect to the single photon transmission timing.
- the jitter is much smaller than the signal alone, and it is designed to be synchronized with the pulse clock signal. Therefore, for each single photon transmitted, each of quantum signal modulation, quantum signal demodulation, and photon detection Operation can be stabilized and highly efficient.
- single photons are generated randomly in a random manner, they are generated in precise synchronization with a regularly output pulse'clock signal, so that photons generated from other photon sources are generated.
- Two-photon measurement such as Bell measurement can be easily realized.
- the communication distance limit of existing quantum cryptography communication is around 100 km, and that the quantum repeater and quantum relay based on Bell measurement can be realized, the communication distance can be greatly extended.
- the communication system 100 is suitable for using a quantum repeater and a quantum relay. The communication distance can be greatly extended.
- FIG. 4 is a diagram showing an example of hardware resources of the quantum communication device (that is, the quantum cryptography transmission device 200 or the quantum cryptography reception device 300) in the present embodiment.
- the quantum communication device is a computer, a display device 901 having a CRT (Cathode-Ray-Tube) or LCD (liquid crystal display) display screen, a keyboard 902 (K ZB), a mouse 903, FDD904 Hardware resources such as (Flexible-Disk-Drive), CDD905 (Compact-Disc • Drive), and printer device 906 are provided, and these are connected by cables and signal lines. It is connected to the Internet via a LAN (local area network) and gateway.
- LAN local area network
- the quantum communication device includes a CPU 911 (Central 'Prosssing' Unit) that executes a program.
- the CPU 911 is an example of a processing device.
- CPU911 via ROM 912 ROM913 (Read 'Only' Memory) ⁇ RAM914 (Random 'Access Memory), communication board 915, display device 901, keyboard 902, mouse 903, FDD904, CDD905, printer device 906, It is connected to the magnetic disk unit 920 and controls these hardware devices.
- a storage medium such as an optical disk device or a memory card reader / writer may be used instead of the magnetic disk device 920.
- the RAM 914 is an example of a volatile memory.
- the storage media of the ROM 913, the FDD 904, the CDD 905, and the magnetic disk device 920 are examples of nonvolatile memories. These are examples of storage devices.
- Communication board 915, keyboard 902, FDD904, etc. are examples of input devices. Further, the communication board 915, the display device 901, the printer device 906, and the like are examples of output devices.
- the communication board 915 is connected to a LAN or the like.
- the communication board 915 is not limited to a LAN, and may be connected to the Internet, a WAN (wide area network) such as ISDN (Integrated 'Services' Digital' Network), or the like.
- a gateway When connected to a WAN, a gateway is not required.
- the magnetic disk device 920 stores an operating system 921 (OS), a program group 923, and a file group 924.
- Programs in program group 923 are executed by CPU 911 and operating system 921.
- Program group 923 contains data and information.
- a program for processing information is stored.
- the program is read and executed by the CPU911.
- data described as “ ⁇ data”, “ ⁇ information”, “ ⁇ ID (IDentifier)”, “ ⁇ flag”, “ ⁇ result” Information, signal values, variable values, and parameter forces are stored as items of " ⁇ file", " ⁇ database”, and " ⁇ table".
- the “ ⁇ file”, “ ⁇ database”, and “ ⁇ table” are stored in a storage medium such as a disk or a memory.
- Data, information, signal values, variable values, and parameters stored in a storage medium such as a disk or memory are read into the main memory or cache memory by the CPU911 via a read / write circuit, and extracted and searched.
- data, information, signal value, variable value and parameter are temporarily stored in main memory, cache memory and buffer memory Memorized.
- FIG. 5 shows a quantum communication on the transmission side in which the quantum cryptography transmission apparatus 200 transmits photons output as quantum signals from a single photon source that is pulse-driven and outputs photons via the quantum communication channel 101.
- 3 is a flowchart illustrating a method.
- the single-photon source 201 with a pulse-driven messenger generates a photon pair by, for example, a norametric down-conversion, and outputs one photon of the photon pair as a quantum signal.
- the other photon of the photon pair is output as a messenger signal (step S101).
- Timing adjuster 202 is output from single photon source 201 with a pulse drive command.
- the messenger signal indicating that the received quantum signal is present on the quantum channel 101 is output as the first trigger signal in synchronization with the clock signal for pulse driving the single photon source 201 with pulse drive messenger. (Step S102).
- the quantum signal modulation unit 203 performs signal modulation on the quantum signal output from the single photon source 201 with a pulse drive instruction in accordance with the timing of the first trigger signal output from the timing adjuster 202 (step S103). Then, the signal-modulated quantum signal is transmitted via the quantum communication channel 101 (step S104).
- the message signal transmitting unit 205 transmits the message signal output from the single photon source 201 with a pulse drive message via the message signal communication path 102 (step S105).
- the clock signal transmission unit 206 transmits the clock signal via the clock communication path 103 (step S106).
- FIG. 6 shows a quantum signal from a single-photon source in which the quantum cryptography receiving device 300 outputs a photon by being pulse-driven (that is, a single-photon source 201 with a pulse drive message included in the quantum cryptography transmission device 200).
- 2 is a flowchart showing a quantum communication method on the receiving side for receiving photons output as, from the quantum cryptography transmission device 200 via the quantum communication channel 101.
- the messenger signal receiving unit 301 transmits a messenger signal indicating that the quantum signal output from the single photon source exists on the quantum communication channel 101, and the quantum cryptography transmitting device 200. Is received via the messenger signal communication path 102 (step S201).
- the clock signal receiving unit 302 receives a clock signal for pulse driving the single photon source from the quantum cryptography transmission device 200 via the clock communication path 103 (step S 202).
- the timing adjuster 303 synchronizes the messenger signal received by the messenger signal receiver 301 with the clock signal received by the clock signal receiver 302 and outputs it as a second trigger signal (step S203).
- the quantum signal demodulator 305 included in the quantum signal detection unit 304 performs signal demodulation on the quantum signal existing on the quantum communication channel 101 in accordance with the timing of the second trigger signal output from the timing adjuster 303. (Step S204).
- the quantum signal detector 304 detects the quantum signal demodulated by the quantum signal demodulator 305 in accordance with the timing of the second trigger signal output from the timing adjuster 303 (step S205).
- quantum cryptography using a single-photon source 201 with a pulse-driven messenger that outputs a messenger signal generated by parametric down-conversion or the like is used.
- the quantum communication system 100 that performs communication transmits the pulse signal of the pulse laser used as a pump source for parametric down conversion and the like.
- a clock communication path 103 for transmission from the cryptographic transmitter 200 to the quantum cryptographic receiver 300 is provided.
- the quantum cryptography transmission device 200 includes a single photon source 201 with a pulse drive message, a quantum signal modulator 204 that applies signal modulation to the quantum state of a single photon, and a single photon source 201 with a pulse drive message.
- a transmission unit 206 and a timing adjuster 202 that generates a trigger signal to the quantum signal modulator 204 by synchronizing the messenger signal with the pulse clock signal with high accuracy are provided.
- the quantum cryptography receiving device 300 includes a photon detector 306 that detects a photon transmitted through the quantum communication channel 101, and a messenger signal receiving unit 301 that receives a messenger signal transmitted through the messenger signal communication channel 102.
- the clock signal receiving unit 302 that receives the pulse clock signal transmitted through the clock communication path 103, and the messenger signal are synchronized with the pulse clock signal with high accuracy to generate a trigger signal to the photon detector 306.
- a timing adjuster 303 is provided.
- the quantum cryptography receiving device 300 includes a quantum signal demodulator 305 that performs signal demodulation on a photon transmitted through the quantum communication channel 101, and a quantum signal demodulation by synchronizing a messenger signal with a pulse clock signal with high accuracy. And a timing adjuster 303 for generating a trigger signal to the device 305.
- the quantum communication system 100 is characterized in that the dispersion compensating fiber 104 is used in the subsequent stage of the optical fiber that is the quantum communication path 101.
- the quantum communication device As described above, by using the quantum communication device according to the present embodiment, it is possible to realize stable and highly efficient quantum communication without being influenced by jitter of the messenger signal. Further, since the quantum communication device on the receiving side has a configuration with a small number of photon detectors, the configuration is relatively compact. And the cost is also relatively low.
- Embodiment 2 The difference between the present embodiment and the first embodiment will be mainly described.
- the power having a configuration in which a pulse laser that is a pump light source of the single photon source 201 with a pulse drive messenger is used as a master clock.
- two quantities are used.
- the encryption communication device shares a clock with low jitter, and uses this shared clock as a master to synchronize and drive a pulse laser that is a pump light source.
- the clock signal for synchronizing the messenger signal to generate the trigger signal is transmitted from the quantum cryptography transmission device 200 to the quantum cryptography reception device 300.
- the quantum cryptography reception device 300 transmits to the quantum cryptography transmission device 200.
- FIG. 7 is a block diagram showing a configuration of quantum communication system 100 according to the present embodiment.
- the quantum cryptography transmission device 200 includes a clock signal reception unit 209 instead of the clock signal transmission unit 206, and the quantum cryptography reception device 300.
- a clock signal transmission unit 309 is provided instead of the clock signal reception unit 302.
- the clock signal transmission unit 309 is a transceiver or a transmitter that transmits a clock signal generated by, for example, a clock incorporated in the timing adjuster 303 to the clock communication path 103.
- the timing adjuster 303 synchronizes the messenger signal received by the messenger signal receiving unit 301 with the clock signal generated by the self-contained clock and supplies it to the photon detector 306 and the quantum signal demodulator 305. Generate a trigger signal.
- the clock signal receiving unit 209 is a receiver or a transceiver that receives the clock signal transmitted through the clock communication path 103.
- the timing adjuster 202 synchronizes the message signal output from the single photon source 201 with a pulse drive message 201 with the clock signal received by the clock signal receiving unit 209, and supplies the signal to the quantum signal modulator 204.
- the trigger signal is generated.
- FIG. 8 is a flowchart showing a quantum communication method on the transmission side.
- the clock signal reception unit 209 has a pulse drive instruction.
- the clock signal for driving the pulsed single photon source 201 is also received by the quantum cryptography receiving device 300 via the clock communication path 103 (step S 111).
- the single photon source 201 with a pulse drive command is driven in synchronization with the clock signal received by the clock signal receiving unit 209, and generates a photon pair by parametric down conversion or the like (step S112). Then, one photon of the photon pair is output as a quantum signal, and the other photon of the photon pair is output as a messenger signal.
- the timing adjuster 202 synchronizes the message signal indicating that the quantum signal output from the single photon source 201 with a pulse-driven message exists on the quantum communication channel 101 with the clock signal received by the clock signal receiving unit 209. And output as the first trigger signal (step S113).
- the quantum signal modulation unit 203 performs signal modulation on the quantum signal output from the single photon source 201 with a pulse drive instruction in accordance with the timing of the first trigger signal output from the timing adjuster 202 (step S114). ),
- the quantum signal subjected to signal modulation is transmitted via the quantum communication channel 101 (step S115).
- the messenger signal transmission unit 205 transmits the messenger signal output from the single-photon source 201 with a pulse drive messenger via the messenger signal communication path 102 (step S116).
- FIG. 9 is a flowchart showing a quantum communication method on the receiving side.
- the clock signal transmission unit 309 transmits a clock signal for pulse driving the single photon source via the clock communication path 103 (step S211).
- the messenger signal receiving unit 301 receives a messenger signal indicating that the quantum signal output from the single photon source exists on the quantum communication channel 101 from the quantum cryptography transmission device 200 via the messenger signal communication channel 102.
- the timing adjuster 303 outputs the messenger signal received by the messenger signal receiving unit 301 as a second trigger signal in synchronization with the clock signal (step S213).
- the quantum signal demodulator 305 included in the quantum signal detection unit 304 performs signal demodulation on the quantum signal existing on the quantum communication channel 101 in accordance with the timing of the second trigger signal output from the timing adjuster 303.
- the quantum signal detection unit 304 detects the quantum signal demodulated by the quantum signal demodulator 305 in accordance with the timing of the second trigger signal output from the timing adjuster 303 (step S215).
- a message is transmitted. It is possible to realize stable and highly efficient quantum communication regardless of signal jitter.
- a clock signal supply source used for that purpose can be provided in addition to the quantum communication device on the transmission side.
- the quantum signal detection unit 304 of the quantum cryptography reception device 300 is configured to use the quantum signal demodulator 305, and the means for measuring the quantum state of photons transmitted from the quantum cryptography transmission device 200 is provided.
- the configuration is such that the number of photon detectors 306 used for measurement is increased, and the quantum state measuring means is passively selected. .
- FIG. 10 is a block diagram showing a configuration of quantum communication system 100 according to the present embodiment.
- the quantum signal detector 304 of the quantum cryptography receiver 300 includes a beam splitter 310 instead of the quantum signal demodulator 305.
- beam splitter 310 passively and randomly selects the optical path of photons transmitted from quantum cryptography transmission device 200 via quantum communication channel 101.
- the photon detector 306 detects photons on the optical path selected by the beam splitter 310. Since the quantum signal detection unit 304 does not include the quantum signal demodulator 305, the timing adjuster 303 only needs to supply the second trigger signal to the photon detector 306 only.
- FIG. 11 is a diagram illustrating an example of a quantum cryptography optical system that passively selects a measurement unit on the receiving side.
- the control system is omitted for simplicity.
- FIG. 11 particularly shows an example of the configuration of the quantum signal modulation unit 203 and the quantum signal detection unit 304.
- the quantum cryptography transmission device 200 actively designates and transmits a quantum state using the phase modulator 208, but the quantum cryptography reception device 300 passively and randomly uses the beam splitter 310. Select the optical path. In each optical path, there are asymmetric Mach-Zehnder interferometers 308a, b corresponding to preset and fixed measuring means, which lead to photon detectors 306a-d corresponding to each measuring means. In this example, the quantum cryptography transmitter 200
- the quantum signal modulation unit 203 also uses an asymmetric Mach-Zehnder interferometer 207 in front of the phase modulator 208 in order to perform signal modulation processing.
- the quantum signal modulator 204 as an example of the quantum signal modulator 204, a polarization modulator or the like may be used instead of the force using the phase modulator 208.
- the beam splitter 310 is used as an example of the quantum signal branching unit.
- an input device inputs the 2-bit information to a processing device (not shown).
- a storage device may store the 2-bit information, and the processing device may read the 2-bit information from the storage device.
- the processing device converts this 2-bit information into an electric signal and inputs it to the quantum signal modulation unit 203.
- the quantum signal modulation unit 203 inputs one photon of the photon pair output from the single-photon source 201 with a pulse drive command using an asymmetric Mach-Zehnder interferometer 207 and a phase modulator 208 and inputs it from the processing device.
- the signal is modulated by the electrical signal.
- the phase modulator 208 performs phase modulation of the photon with four types of phase differences ⁇ 0, ⁇ / 2, ⁇ , (3/2) ⁇ , so that a 2-bit value is added to the photon. Apply signal modulation. Photons subjected to such signal modulation are transmitted from the quantum cryptography transmission device 200 to the quantum cryptography reception device 300 via the quantum communication channel 101.
- the quantum signal detection unit 304 causes the beam splitter 310 to branch the optical path of the photon transmitted through the quantum communication path 101 into two optical paths.
- beam splitter 310 is a 50 to 50 non-polarizing beam splitter.
- a photon detector 306a and a photon detector 306b are connected to one optical path branched by the beam splitter 310 via an asymmetric Matsuhzander interferometer 308a, and a photon is connected to the other optical path via an asymmetric Matsuhzander interferometer 308a.
- a detector 306c and a photon detector 306d are connected.
- the quantum signal detection unit 304 specifies the 2-bit value of the 2-bit information depending on whether the photons transmitted through the quantum communication channel 101 are detected by the deviation of the photon detectors 310a to 310d. Of the 2 bits specified here, 1 bit is effective when the remaining 1-bit value matches the corresponding optical path with the optical path selected by the beam splitter 310.
- the asymmetric Mach-Zehnder interferometer 308a is adjusted to output photons with a phase difference of 0 or ⁇
- the asymmetric Mach-Zehnder interferometer 308b is adjusted to output photons with a phase difference of ⁇ ⁇ 2 or (3 ⁇ 2) ⁇ . Shall.
- the photon detector 306a detects a photon with a phase difference of 0, the photon detector 306b detects a photon with a phase difference of ⁇ , the photon detector 306c detects a photon with a phase difference of ⁇ ⁇ 2, and the photon detector 306d Detect photons with phase difference (3 ⁇ 2) ⁇ .
- the phase difference of the photons transmitted through the quantum communication path 101 is 0 or ⁇ , and the beam splitter 310 selects the optical path to which the asymmetric Matsuhatsu interferometer 308a is connected, the quantum signal detector The bit specified by 304 is valid.
- the beam splitter 310 selects the optical path for connecting the asymmetric Matsuhenda interferometer 308b
- the bit specified by the signal detection unit 304 is valid.
- An output device (not shown) outputs the bits specified by the quantum signal detection unit 304.
- a processing device (not shown) may perform a predetermined process using this bit. This bit can be used as, for example, key information or a part of key information.
- FIG. 12 is a timing chart showing an example of quantum cryptography communication according to the present embodiment.
- FIG. 12 is the same as FIG. 3 described in the first embodiment except that the second trigger signal (“quantum signal demodulation trigger signal”) for operating the quantum signal demodulator 305 is unnecessary on the reception side. It is.
- FIG. 13 is a flowchart showing a quantum communication method on the receiving side.
- the quantum communication method on the transmission side is the same as that shown in FIG.
- the messenger signal receiving unit 301 sends an messenger signal indicating that the quantum signal output from the single photon source exists on the quantum communication channel 101, to the quantum cryptography transmitting device 200. Is received via the messenger signal communication path 102 (step S221).
- the clock signal receiving unit 302 receives a clock signal for pulse driving the single photon source from the quantum cryptography transmission device 200 via the clock communication path 103 (step S222).
- the timing adjuster 303 synchronizes the messenger signal received by the messenger signal receiver 301 with the clock signal received by the clock signal receiver 302 and outputs it as a second trigger signal (step S223).
- the beam splitter 310 included in the quantum signal detection unit 304 branches the quantum communication path 101 (step S224).
- the quantum signal detector 304 uses the beam splitter 310 to synchronize with the timing of the second trigger signal output from the timing adjuster 303.
- a quantum signal existing on the branched quantum communication channel 101 is detected (step S225).
- the quantum communication device As described above, by using the quantum communication device according to the present embodiment, it is possible to realize stable and highly efficient quantum communication without being influenced by jitter of the messenger signal. In addition, since the quantum communication device on the receiving side does not use the quantum signal demodulator, a trigger signal to be given to the quantum signal demodulator is unnecessary, and control becomes relatively easy.
- the clock signal for synchronizing the messenger signal to generate the trigger signal is transmitted from the quantum cryptography transmission device 200 to the quantum cryptography reception device.
- the quantum cipher receiver 300 transmits to the quantum cipher transmitter 200 as in the second embodiment.
- FIG. 14 is a block diagram showing a configuration of quantum communication system 100 according to the present embodiment.
- the quantum cryptography transmission device 200 includes a clock signal reception unit 209 instead of the clock signal transmission unit 206, and the quantum cryptography reception device 300.
- a clock signal transmission unit 309 is provided instead of the clock signal reception unit 302.
- the functions of the clock signal transmission unit 309 and the clock signal reception unit 209 are the same as those shown in FIG.
- FIG. 15 is a flowchart showing a quantum communication method on the receiving side.
- the quantum communication method on the transmission side is the same as that shown in FIG.
- clock signal transmission section 309 transmits a clock signal for pulse driving the single photon source via clock communication path 103 (step S2 31).
- the messenger signal receiving unit 301 receives a messenger signal indicating that the quantum signal output from the single photon source exists on the quantum communication channel 101 from the quantum cryptography transmission device 200 via the messenger signal communication channel 102.
- the timing adjuster 303 outputs the messenger signal received by the messenger signal receiving unit 301 as a second trigger signal in synchronization with the clock signal (step S233).
- Beam splitter included in quantum signal detector 304 310 branches the quantum communication channel 101 (step S234).
- the quantum signal detection unit 304 detects a quantum signal present on the quantum communication path 101 branched by the beam splitter 310 in accordance with the timing of the second trigger signal output from the timing adjuster 303 ( Step S235).
- a clock signal supply source used for that purpose can be provided in addition to the quantum communication device on the transmission side.
- the messenger signal output from the single photon source 201 with a pulse drive messenger is used as it is as the messenger signal.
- the pulse signal output from the single-photon source 201 with a pulse-driven messenger is output to the AND gate and the signal output from the gate is used as the messenger signal. Use.
- FIG. 16 is a block diagram showing a configuration of quantum communication system 100 according to the present embodiment.
- the quantum cryptography transmission apparatus 200 has only a single photon source 201 with a pulse drive message as a signal generation unit.
- AND gate 210 (logical product) An arithmetic gate).
- the signal generation unit generates a photon pair by the single photon source 201 with a pulse drive instruction, outputs one photon of the photon pair as a quantum signal, and outputs the photon pair by the AND gate 210.
- the logical product operation of the other photon (ie, messenger signal) and the clock signal is performed, and the result of the logical product operation is output again as a messenger signal.
- the AND gate 210 performs an AND operation between the messenger signal and the pulse clock signal, and the result is changed to a messenger signal, so that the influence of such an error of the messenger signal is changed to the pulse clock. It is possible to limit the timing of the signal. That is, by using the quantum communication device according to this embodiment, the influence of the error of the messenger signal can be reduced. As a result, the SZN ratio (signal-to-noise ratio) increases.
- the difference between the present embodiment and the first embodiment may be applied to the above-described second to fourth embodiments.
- the messenger signal output from the single photon source 201 with a pulse drive messenger is used as it is as the messenger signal.
- the clock signal output from the single-photon source 201 with a pulse-driven messenger output in the same manner (or received from the quantum cryptography receiver 300) is input to the AND gate.
- the signal output from may be used as a command signal.
- the AND gate 210 is used to perform an AND operation between the messenger signal output from the single-photon source 201 with a pulse drive messenger and the pulse clock signal.
- the messenger signal force S pulse ' is output (from the signal generator) only at the rising edge of the clock signal.
- the signal generator uses a means other than the AND gate 210 to perform AND operation between the messenger signal and the pulse clock signal. An arithmetic operation may be performed and the result of the logical product operation may be output again as a messenger signal.
- the signal generator controls the messenger signal using a pulse clock signal by a method other than the logical product operation (for example, a negative logical sum operation, a negative logical product operation, a logical sum operation, or any combination thereof).
- a controlled messenger signal may be output.
- each quantum communication device may include both the transmission side and the reception side configurations.
- FIG. 1 is a block diagram showing a configuration of a quantum communication system according to a first embodiment.
- FIG. 2 is a diagram showing an example of a configuration of a quantum signal modulation unit and a quantum signal detection unit in the first embodiment.
- FIG. 3 is a timing chart showing an example of quantum cryptography communication in the first embodiment.
- ⁇ 4] is a diagram showing an example of hardware resources of the quantum communication device in the first embodiment.
- ⁇ 5] is a flowchart showing a quantum communication method (transmission side) according to the first embodiment.
- FIG. 7 is a block diagram showing a configuration of a quantum communication system according to a second embodiment.
- FIG. 10 is a block diagram showing a configuration of a quantum communication system according to a third embodiment.
- FIG. 11 is a diagram illustrating an example of a configuration of a quantum signal modulation unit and a quantum signal detection unit in the third embodiment.
- FIG. 12 is a timing chart showing an example of quantum cryptography communication in the third embodiment.
- 13 A flowchart showing the quantum communication method (receiving side) according to the third embodiment.
- FIG. 14 is a block diagram showing a configuration of a quantum communication system according to a fourth embodiment.
- FIG. 15 is a flowchart showing a quantum communication method (receiving side) according to the fourth embodiment.
- FIG. 16 is a block diagram showing a configuration of a quantum communication system according to a fifth embodiment.
- 100 quantum communication system 101 quantum communication channel, 102 message signal communication channel, 103 clock communication channel, 104 dispersion compensating fiber, 200 quantum cryptography transmitter, 201 single photon source with pulse drive command, 202 timing adjuster, 203 Quantum signal modulator, 204 quantum signal modulator, 205 messenger signal transmitter, 206 clock signal transmitter, 207 asymmetric Mach-Zehnder interferometer, 208 phase modulator, 209 clock signal receiver, 210 AND gate, 300 quantum cryptography reception Device, 301 Message signal receiver, 302 Clock signal receiver, 303 Timing adjuster, 304 Quantum signal detector, 305 Quantum signal demodulator, 306 Photon detector, 307 Phase demodulator, 308 Asymmetric Mach-Zehnder interferometer, 309 clock Signal transmitter, 310 beam splitter, 901 display, 902 keyboard, 903 mouse, 90 4 FDD, 905 CDD, 906 printer, 911 CPU, 912, 913 ROM, 91 4 RAM, 915 communication board, 920 magnetic disk unit, 921 operating
Description
Claims
Priority Applications (4)
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US12/376,343 US8270841B2 (en) | 2006-08-04 | 2006-08-04 | Quantum communication apparatus, quantum communication system and quantum communication method |
PCT/JP2006/315490 WO2008015758A1 (fr) | 2006-08-04 | 2006-08-04 | Appareil, système et procédé de communication quantique |
EP06782348A EP2051411B1 (en) | 2006-08-04 | 2006-08-04 | Quantum communication apparatus, quantum communication system and quantum communication method |
JP2008527629A JP4775919B2 (ja) | 2006-08-04 | 2006-08-04 | 量子通信装置及び量子通信システム及び量子通信方法 |
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PCT/JP2006/315490 WO2008015758A1 (fr) | 2006-08-04 | 2006-08-04 | Appareil, système et procédé de communication quantique |
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Also Published As
Publication number | Publication date |
---|---|
EP2051411B1 (en) | 2012-03-07 |
EP2051411A4 (en) | 2010-11-24 |
US20100226659A1 (en) | 2010-09-09 |
JP4775919B2 (ja) | 2011-09-21 |
US8270841B2 (en) | 2012-09-18 |
EP2051411A1 (en) | 2009-04-22 |
JPWO2008015758A1 (ja) | 2009-12-17 |
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