JP2019021137A - Random number signal generator and random number signal generation method - Google Patents

Abstract

To generate a natural random number row with a simple device structure.SOLUTION: A random number signal generator comprises a single photon light source, a single photon detector and a random number generation part. The single photon light source outputs a photon in which an average output photon number in a unit time slot ΔT is less than 1. The single photon detector detects the photon which is output by the single photon light source. The random number generation part is configured so that, at a time Twhen M×ΔT≤T<(M+1)×ΔT (M is an integer of more than 0 and equal to or less than N-1) is satisfied, when the single photon detector detects the photon, the random number generation part sets a value in a M-th number of the random number row to 1, and when the single photon detector does not detect photon, the random number generation part generates a random number in which, a value in the M-th number of the random number is 0.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a random number signal generator and a random number signal generation method for generating a random number sequence used for a common key of cryptographic communication.

  Random number sequences are used in various industrial fields and science and technology fields such as simulation of secret keys and probabilistic models in cryptographic communication, and performance evaluation of communication systems and devices. Although the random number sequence can be generated mathematically using a mathematical logic circuit or the like, a physical (natural) random number sequence that is physically generated using a natural phenomenon is most desirable.

  As a random number signal generator for generating a natural random number sequence, there is one using a Zener diode (for example, see Non-Patent Document 1).

  On the other hand, recently, a random number signal generator using quantum mechanical superposition of photons has been reported (for example, see Non-Patent Document 2).

  In the random number signal generator disclosed in Non-Patent Document 2, for example, light attenuated to a single photon level is input to a beam splitter, and a single photon detector provided at each of two output ports of the beam splitter is used. A random number sequence very close to a natural random number can be generated by setting bit “1” when light is detected on one side and bit “0” when light is detected on the other side.

  The random number signal generator using the photon quantum mechanical superposition disclosed in Non-Patent Document 2 is expected to generate an ideal random number sequence close to a natural random number. A method has been proposed and demonstrated.

  In general, the desired mark ratio in a random number sequence (ratio of “1” in all bit sequences) is ½. However, a random number sequence such as a mark ratio of 1/4 or 1/8 is required in a test of a communication ultrahigh-speed logic circuit.

  Such a random number sequence having a mark rate other than 1/2 is generated by processing two types of random number sequences having a mark rate of 1/2 in a logic circuit composed of, for example, a shift register and an exclusive OR. (For example, refer to Patent Document 1).

JP 2003-198336 A

Tamura Yoshiho, Onodera Toru, Nakabata Masaya, Shimizu Takakuni, “Current Status of Physical Random Number Generators in Japan”, Journal of the Japan Statistical Society, Vol. 35, No. 2, March 2006, pp. 201-212 Thomas Jennewein, Ulrich Achleitner, Gregor Weihs, Harald Weinfurter and Anton Zeitner, “A Fast and Compact Quantum Randum Number.” 71, Issues 4, 10.1063 / 1.1150518, 2000

  However, in the random number generator disclosed in Patent Document 1 described above, the random number sequence is a mathematical random number and not a natural random number. Also, the mark ratio that can be realized is substantially fixed, such as 1/4 or 1/8.

  Further, the random number generator disclosed in Non-Patent Document 2 described above uses a plurality of photon detectors, and thus it is not easy to reduce the size of the apparatus configuration. Moreover, the mark rate that can be realized is ½, and even if it is combined with the above-described Patent Document 1, the mark rate that can be realized is substantially fixed, such as ¼ or ８.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to generate a random number sequence with a simple device configuration and easily change the mark rate. And providing a random number signal generation method.

  In order to achieve the above object, a random number signal generator for generating a random number sequence of N (N is an integer of 1 or more) bits according to the present invention includes a single photon light source, a single photon detector, and a random number generator. And configured.

The single photon light source outputs photons having an average output photon number of less than 1 in a unit time slot ΔT. The single photon detector detects photons output from the single photon light source. When the single photon detector detects a photon at time T _M that satisfies M × ΔT ≦ T _M <(M + 1) × ΔT (M is an integer of 0 to N−1), the random number generator When the Mth value of the sequence is “1” and the single photon detector does not detect a photon, a random number is generated with the Mth value of the random number sequence being “0”.

  The random number signal generation method for generating an N-bit random number sequence according to the present invention comprises the following steps.

  In the single photon generation process, the single photon light source generates photons having an average output photon number of less than 1 in a unit time slot ΔT. Next, photons are detected in the photon detection process.

In the random number sequence generation process, when the single photon detector detects a photon at time T _M satisfying M × ΔT ≦ T _M <(M + 1) × ΔT, the Mth value of the random number sequence is set to “1”. When the single photon detector does not detect a photon, a random number sequence with the Mth value of the random number sequence set to “0” is generated.

  According to the random number signal generator and the random number signal generation method of the present invention, the random number is generated based on the time when the single photon detector detects the photon generated by the single photon light source. Therefore, a simple device configuration can be realized, for example, a random number signal generator can be configured with one single photon detector without using a plurality of single photon detectors. Further, the mark rate can be easily changed to a desired value by changing the attenuation of the variable attenuator provided in the single photon light source or the unit time slot.

It is a schematic diagram which shows the structural example of the random number signal generator of this invention. It is a schematic diagram for demonstrating operation | movement of the random number signal generator of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the shape, size, and arrangement relationship of each component are merely schematically shown to the extent that the present invention can be understood. In the following, a preferred configuration example of the present invention will be described, but it is merely a preferred example. Therefore, the present invention is not limited to the following embodiments, and many changes or modifications that can achieve the effects of the present invention can be made without departing from the scope of the configuration of the present invention.

(Constitution)
A random signal generator according to the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram showing a configuration example of a random number signal generator according to the present invention. FIG. 2 is a schematic diagram for explaining the operation of the random number signal generator of the present invention. FIGS. 2A to 2C each show a state where a single photon is detected.

  The random number signal generator generates an N-bit random number sequence. The random number signal generator includes a single photon light source 10, a single photon detector 20, and a random number generation unit 30.

  The single photon light source 10 includes, for example, a continuous light source 12 and a variable optical attenuator 14. The continuous light source 12 is composed of a laser light source or the like, and generates continuous light. The variable optical attenuator 14 attenuates the continuous light generated by the continuous light source 12 by a desired attenuation amount. Continuous light is attenuated to light intensity at a so-called single photon level, and becomes weak continuous light. Thus, the single photon light source 10 generates a single photon having an average output photon number of less than 1 in a certain unit time slot ΔT.

  The single photon detector 20 is composed of, for example, an avalanche photodiode (APD). The single photon detector 20 detects a photon generated by the single photon light source 10 and sends an electric signal in response to the detection of the photon to the random number generation unit 30.

  The random number generation unit 30 includes, for example, an A / D conversion unit (not shown) and a digital signal processing circuit. When the output of the single photon detector 20 is an analog signal, it is converted into a digital signal by an A / D converter and sent to a digital signal processing circuit. If the application is used to determine whether photons are detected, the A / D converter outputs “1” when the intensity of the analog signal exceeds a certain threshold, and “0” otherwise. As long as it has a function of outputting.

  The digital signal processing circuit includes a detection time string recording unit 32 and a determination unit 34.

The detection time sequence recording unit 32 uses the time at which the single photon detector 20 detects photons during the time T as the time sequence {t _i }, for example, a RAM (Random Access Memory) provided in the digital signal processing circuit, or the like. Is stored in the storage unit 36.

The determination unit 34 reads the time sequence from the storage unit 36, and if there is a time t _i that satisfies M × ΔT ≦ t _i <(M + 1) × ΔT, M × ΔT ≦ T _M <(M + 1) × ΔT. at time T _M is satisfied, the single photon detector 20 determines that it has detected a photon, the M-th value of the random number sequence is set to "1". On the other hand, if there is no time t _i that satisfies M × ΔT ≦ t _i <(M + 1) × ΔT, the determination unit 34 simply sets the time T _M that satisfies M × ΔT ≦ T _M <(M + 1) × ΔT. It is determined that the one-photon detector 20 has not detected a photon, and the Mth value of the random number sequence is set to “0”. If this determination is performed for each of M from 0 to N−1, an N-bit random number sequence is generated (see FIG. 2A).

  Here, when the average number of photons per unit time of weak continuous light having a single photon level input to the single photon detector 20 is μ, the average value of the number of photons contained in the unit time slot is μΔT. It becomes. Now, when 1 / (μΔT) time slots divided every time ΔT are prepared, since the input light is continuous light, the photon detection probability in each time slot is constant at μΔT. As a result, on average, a photon is included in any one of 1 / (μΔT) time slots.

  At this time, it is not known in which time slot of the 1 / (μΔT) time slots the photon is included. In other words, assuming that a state in which a photon is included in the kth time slot is | k>, a superposition state represented by the following expression (1) is obtained.

  This indicates that the information indicating which time slot contains the photon is a natural random number. That is, the detection time when the photon is detected by the single photon detector 20 is a natural random number.

Here, by changing the attenuation amount of the variable optical attenuator 14, the value of the average photon number μ changes. As described above, photons are included in any one of 1 / (μΔT) time slots on average. For this reason, when the value of μ decreases, the value of 1 / (μΔT) increases, and as a result, the probability that there exists a time t _i that satisfies M × ΔT ≦ t _i <(M + 1) × ΔT decreases. That is, the mark rate is reduced (see FIG. 2B). Conversely, as the value of μ increases, the mark rate increases.

  In this manner, the desired mark rate can be easily changed by changing the attenuation amount of the variable optical attenuator 14.

Similarly, the mark rate may be changed by changing the width of the time slot. If the time slot width is reduced, the value of 1 / (μΔT) increases, and as a result, the probability that a time t _i that satisfies M × ΔT ≦ t _i <(M + 1) × ΔT exists is reduced. That is, the mark rate is reduced (see FIG. 2C). Conversely, as the value of ΔT increases, the mark rate increases.

  According to the random number signal generator and the random number signal generation method of the present invention, the random number is generated based on the time when the single photon detector detects the photon generated by the single photon light source. Therefore, a simple device configuration can be realized, for example, a random number signal generator can be configured with one single photon detector without using a plurality of single photon detectors. Further, the mark rate can be easily changed to a desired value by changing the attenuation amount of the variable optical attenuator provided in the single photon light source or the unit time slot.

DESCRIPTION OF SYMBOLS 10 Single photon light source 12 Continuous light source 14 Variable optical attenuator 20 Single photon detector 30 Random number generation part 32 Detection time sequence recording part 34 Judgment part 36 Memory | storage part

Claims (9)

A random number signal generator for generating a random number sequence of N (N is an integer of 1 or more) bits,
A single photon light source having an average output photon number of less than 1 in a unit time slot ΔT;
A single photon detector for detecting photons output by the single photon light source;
When the single photon detector detects a photon at a time T _M that satisfies M × ΔT ≦ T _M <(M + 1) × ΔT (M is an integer of 0 to N−1), A random number generation unit that generates a random number that sets the Mth value of the random number sequence to “0” when the Mth value is “1” and the single photon detector does not detect a photon. Random number signal generator characterized. The random number generator
A detection time sequence recording unit that records a time when the single photon detector detects a photon as a photon detection time sequence; and
A determination unit that reads out the photon detection time sequence and determines whether or not there is a time T _M that satisfies M × ΔT ≦ T _M <(M + 1) × ΔT (M is an integer of 0 or more and N−1 or less). The random number signal generator according to claim 1. The single photon light source is
A continuous light source that generates continuous light;
The random signal generator according to claim 1, further comprising a variable optical attenuator that attenuates the continuous light to a single photon level. 4. The random number signal generator according to claim 3, wherein a mark rate which is a ratio of “1” in the random number sequence can be changed by changing an attenuation amount of the variable optical attenuator. 5. 5. The random number signal generator according to claim 1, wherein a mark rate that is a ratio of “1” in the random number sequence can be changed by changing the unit time slot ΔT. 6. A random number signal generation method for generating a random number sequence of N (N is an integer of 1 or more) bits,
A single-photon light source generation process in which a single-photon light source generates photons having an average output photon number of less than 1 in a unit time slot ΔT;
A photon detection process in which a single photon detector detects the photons;
When the single photon detector detects a photon at a time T _M that satisfies M × ΔT ≦ T _M <(M + 1) × ΔT (M is an integer of 0 to N−1), A random number sequence generating step of generating a random number with an Mth value of “1” and when the single photon detector does not detect a photon, an Mth value of the random number sequence is set to “0”. A random number signal generation method characterized by the above. The random number sequence generation process includes:
A detection time sequence recording process for recording a time when the single photon detector detects a photon as a photon detection time sequence;
A determination step of reading the photon detection time sequence and determining whether or not there is a time T _M that satisfies M × ΔT ≦ T _M <(M + 1) × ΔT (M is an integer of 0 to N−1). The random number signal generation method according to claim 6. The single photon light source is
A continuous light source that generates continuous light;
A variable optical attenuator that attenuates the continuous light to a single photon level;
8. The random number signal generation method according to claim 6, wherein a mark rate which is a ratio of “1” in the random number sequence can be changed by changing an attenuation amount in the variable optical attenuator. 9. 9. The random number signal generation method according to claim 6, wherein a mark rate that is a ratio of “1” in the random number sequence can be changed by changing the unit time slot ΔT. 10.

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