A quantum random number generator based on laser phase fluctuations

Abstract

The present invention provides a quantum random number generator based on laser phase fluctuations. The quantum random number generator includes: a laser, an interferometer, a photodetector and an analog-to-digital converter; the laser is used to generate a signal light with phase fluctuations, and output the signal light to the interferometer; the interferometer is used to convert the phase fluctuations in the signal light into intensity fluctuations, and output the converted signal light to the photodetector; the photodetector is used to convert the light intensity in the received signal light into a current signal, and output the obtained current signal to the analog-to-digital converter; the analog-to-digital converter is used to convert the received current signal into a discrete digital signal and output it. The present invention can be used to generate random numbers using the phase fluctuations of the laser, greatly improving the generation rate of quantum random numbers and reducing costs.

Description

Technical Field

[0001] The present application relates to the field of quantum information communication technology, and in particular to a quantum random number generator based on laser phase fluctuations. Background Art

[0002] In modern society, random numbers play an important role in various fields such as economy, science, national defense, industrial production, etc. Specifically, random numbers have very important applications in statistical analysis, simulation in industrial and scientific fields, cryptography, etc.

[0003] Classic random number generation methods can only generate pseudo-random numbers. For example, the classic random number generation methods in the prior art are often based on certain algorithms to generate random numbers, but this algorithm-based software method can only generate pseudo-random numbers. From the perspective of its generation principle, a pseudo-random number actually just "looks like" a random number, that is, with the current level of science and technology, there is only a very small possibility of distinguishing the difference between a pseudo-random number and a true random number within a limited time. However, in essence, the entropy of pseudo-random numbers and true random numbers is different. Therefore, these pseudo-random numbers can actually be predicted, but they are not real random numbers. Therefore, in some specific fields or actual use scenarios (for example, in secure communications, quantum communications, and other fields that require absolute security, etc.), this pseudo-random number is unsafe and cannot be used directly.

[0004] There are also random number generators based on the randomness of physical processes in the prior art. For example, random number generators that use physical processes such as noise from electronic components, cosmic noise from nuclear fission, thermal noise from circuits, and radioactive decay to generate random numbers. Although random numbers generated in this way will not generate risks as computing power develops, since they are still classical systems, the randomness of the random numbers produced cannot be essentially guaranteed.

[0005] A quantum random number generator has also been proposed in the prior art. The quantum random number generator generates quantum random numbers based on the basic principles of quantum mechanics, and the quantum random number is a true random number. Many quantum random number generator schemes have been proposed in the prior art. For example, random number generators based on single-photon detection and random number generators based on quantum non-locality have been successfully tested. At the same time, commercial quantum random number generators, such as the ID-Quantique random number generator based on single-photon detection, have also entered the market. However, it is worth pointing out that these quantum random number generators inevitably rely on assumptions about the model and the requirement for perfection of the equipment.

[0006] The quantum random number generator in the prior art mainly uses the method of directly performing quantum measurement on a known source to generate true random numbers guaranteed by the principles of quantum mechanics. For example, the ID-Quantique random number generator based on single-photon detection uses a light-emitting diode to emit a single photon to a semi-transparent and semi-reflective mirror, and two single photodetectors are used to detect the transmitted or reflected photons respectively. Since whether a single photon will be transmitted or reflected is essentially a quantum effect, the resulting quantum random number is a true random number.

[0007] However, in the above-mentioned random number generator based on single-photon detection, the cost is high due to the use of a single photodetector, and the final random number generation rate is also restricted by the dead time of the single photodetector, so there is an upper limit, which greatly limits the generation rate of quantum random numbers in the prior art. Summary of the invention

[0008] In view of this, the present invention provides a quantum random number generator based on laser phase fluctuations, so that random numbers can be generated by utilizing the phase fluctuations of the laser, which greatly improves the generation rate of quantum random numbers and reduces costs.

[0009] The technical solution of the present invention is specifically achieved as follows:

[0010] A quantum random number generator based on laser phase fluctuations, the quantum random number generator comprising: a laser, an interferometer, a photodetector and an analog-to-digital converter;

[0011] The laser is used to generate signal light with phase fluctuations and output the signal light to the interferometer;

[0012] The interferometer is used to convert the phase fluctuation in the signal light into intensity fluctuation, and output the converted signal light to the photodetector;

[0013] The photoelectric detector is used to convert the light intensity of the received signal light into a current signal, and output the obtained current signal to the analog-to-digital converter;

[0014] The analog-to-digital converter is used to convert the received current signal into a discrete digital signal and output the signal.

[0015] Preferably, the interferometer comprises: a first beam splitter, a phase shifter and a second beam splitter;

[0016] The first beam splitter is used to split the received signal light into two light signals, which are output to the phase shifter and the second beam splitter through two different optical paths respectively;

[0017] The phase shifter is used to adjust the phase of the received optical signal and output the phase-adjusted optical signal to the second beam splitter;

[0018] The second beam splitter is used to combine the optical signals received through the two optical paths and output the combined optical signals to the photodetector.

[0019] Preferably, the interferometer comprises: a beam splitter, a first Faraday rotator mirror, a phase shifter and a second Faraday rotator mirror;

[0020] The beam splitter is used to split the received signal light into two light signals, output them to the first Faraday rotator mirror and the phase shifter through two different optical paths respectively; and combine the light signals reflected back by the first Faraday rotator mirror and the second Faraday rotator mirror and output them to the photodetector;

[0021] The first Faraday rotator is used to rotate the polarization state of the received optical signal by a preset angle and then reflect it back to the beam splitter;

[0022] The phase shifter is used to adjust the phase of the received optical signal and output the phase-adjusted optical signal to the second Faraday rotator mirror;

[0023] The second Faraday rotator is used to rotate the polarization state of the received optical signal by a preset angle and then reflect it back to the beam splitter through a phase shifter.

[0024] Preferably, the interferometer comprises: a beam splitter and an optical fiber ring;

[0025] The beam splitter is used to split the received signal light into two light signals and output them to the optical fiber ring through two different optical paths;

[0026] The two optical signals are respectively returned to the beam splitter through the optical fiber ring;

[0027] The beam splitter combines the two optical signals returned through the optical fiber ring and outputs the combined signals to the photoelectric detector.

[0028] Preferably, the quantum random number generator further comprises: a post-processor;

[0029] The post-processor is connected to the analog-to-digital converter and is used to post-process the digital signal to generate a processed digital signal.

[0030] Preferably, the laser is a laser diode.

[0031] As can be seen from the above, in the quantum random number generator based on laser phase fluctuation in the present invention, since the above-mentioned laser, interferometer, photodetector and analog-to-digital converter are used, the random phase fluctuation brought by the spontaneous radiation of the laser internal medium can be used to generate random numbers, so that the true randomness and reliability of the generated quantum random numbers can be guaranteed. Moreover, since the phase fluctuation of the signal light output by the laser is a continuous variable, when the continuous variable is used to transmit information, the amount of information carried by each photon is increased, so that the random number generation rate can be effectively increased, and random numbers can be generated at a relatively high code rate. In addition, the quantum random number generator in the technical solution of the present invention uses a photodetector instead of a single photon detector in the prior art, and a laser diode can be used as a light source, so the cost of the entire device can be greatly reduced, and it has a very high practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the structure of a quantum random number generator based on laser phase fluctuations in an embodiment of the present invention.

[0033] Figure 2 It is a schematic diagram of the structure of an interferometer in a specific embodiment of the present invention.

[0034] Figure 3 It is a schematic structural diagram of an interferometer in another specific embodiment of the present invention.

[0035] Figure 4 It is a schematic structural diagram of an interferometer in another specific embodiment of the present invention. DETAILED DESCRIPTION

[0036] In order to more clearly demonstrate the technical solutions and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0037] Figure 1 FIG. 1 is a schematic diagram of the structure of a quantum random number generator based on laser phase fluctuations in an embodiment of the present invention. Figure 1 As shown, the quantum random number generator based on laser phase fluctuation in the embodiment of the present invention includes:

[0038] Laser 11, interferometer 12, photodetector 13 and analog-to-digital converter 14;

[0039] The laser 11 is used to generate a signal light with phase fluctuation and output the signal light to the interferometer 12;

[0040] The interferometer 12 is used to convert the phase fluctuation in the signal light into intensity fluctuation, and output the converted signal light to the photodetector 13;

[0041] The photodetector 13 is used to convert the light intensity of the received signal light into a current signal, and output the obtained current signal to the analog-to-digital converter 14;

[0042] The analog-to-digital converter 14 is used to convert the received current signal into a discrete digital signal and output it.

[0043] The discrete digital signal output by the analog-to-digital converter 14 can be used as a quantum random number or raw data of a quantum random number.

[0044] As can be seen from the above, in the above-mentioned quantum random number generator of the present invention, a laser is used as a light source. The laser can be driven by a pump current, and its gain medium is composed of a semiconductor PN structure. There is a threshold relationship between the pump current of the laser and the gain medium and the resonant cavity of the laser. When the pump current intensity of the laser is lower than this threshold relationship, there is only weak spontaneous radiation inside the laser and no laser output. Only when the pump current intensity of the laser is higher than this threshold will there be laser output, and stimulated radiation is dominant. In the technical solution of the present invention, when the above-mentioned quantum random number generator works normally, the pump current intensity of the laser can be set to be slightly higher than the threshold, so that the proportion of spontaneous radiation can be as high as possible under the condition of laser output.

[0045] In the technical solution of the present invention, the phase fluctuation of the signal light output by the above-mentioned laser can be converted into the fluctuation of light intensity after appropriate interference, and then the fluctuation of the light intensity can be conveniently detected by a high-speed photodetector and converted into a current signal. Therefore, the intrinsic random characteristics of the photons generated by spontaneous radiation can be extracted and converted into the original quantum random number. That is to say, in the technical solution of the present invention, the randomness of the quantum random number generated by the above-mentioned quantum random number generator is actually the random phase fluctuation brought about by the spontaneous radiation extracted from the internal medium of the laser, thereby ensuring the true randomness and reliability of the generated quantum random number.

[0046] In addition, since the phase fluctuation of the signal light output by the above-mentioned laser is a continuous variable, when the continuous variable is used to transmit information, the amount of information carried by each photon is increased, thereby effectively increasing the random number generation rate and generating random numbers at a relatively high code rate. The random number generation rate of the quantum random number generator in the technical solution of the present invention is much greater than the random number generation rate of the quantum random number generator in the prior art. For example, the quantum random number generator in the technical solution of the present invention can reach the Gbps level.

[0047] In addition, the quantum random number generator in the technical solution of the present invention uses a photodetector instead of a single photon detector in the prior art, and can use a laser diode as a light source, thereby greatly reducing the cost of the entire device and having a high practical value.

[0048] In addition, preferably, in a specific embodiment of the present invention, the laser may be a laser diode.

[0049] In addition, in the technical solution of the present invention, considering that in an actual application environment, the above-mentioned quantum random number generator may introduce some classical randomness due to the influence of the surrounding environment, making it possible for an eavesdropper to steal this part of the randomness, therefore, it is possible to further consider post-processing the digital signal output by the analog-to-digital converter to eliminate the bias term and the correlation between adjacent random numbers, thereby further improving the randomness of the obtained digital signal.

[0050] For example, preferably, in a specific embodiment of the present invention, the quantum random number generator may further include: a post-processor (not shown in the figure);

[0051] The post-processor is connected to the analog-to-digital converter 14 and is used to post-process the digital signal to generate a processed digital signal.

[0052] Through the above-mentioned post-processor, the digital signal after analog-to-digital conversion can be post-processed, and the classical randomness that may be introduced into the quantum random number generator can be eliminated from the total randomness, thereby obtaining a true quantum random number (i.e., the processed digital signal).

[0053] In addition, in the technical solution of the present invention, the above-mentioned post-processor can use a post-processing device commonly used in the art for post-processing digital signals, so it will not be described in detail here.

[0054] In addition, in the technical solution of the present invention, the above-mentioned interferometer can be realized by a variety of specific implementation methods.

[0055] For example, preferably, Figure 2 As shown, in a specific embodiment of the present invention, the interferometer may include: a first beam splitter 21, a phase shifter 22, and a second beam splitter 23;

[0056] The first beam splitter 21 is used to split the received signal light into two light signals, which are output to the phase shifter and the second beam splitter 23 through two different optical paths;

[0057] The phase shifter 22 is used to adjust the phase of the received optical signal and output the phase-adjusted optical signal to the second beam splitter 23;

[0058] The second beam splitter 23 is used to combine the optical signals received through the two optical paths and output the combined optical signals to the photodetector 13 .

[0059] Specifically, in a preferred embodiment of the present invention, the interferometer may be a Mach-Zehnder interferometer.

[0060] For example, preferably, Figure 3 As shown, in another specific embodiment of the present invention, the interferometer may include: a beam splitter 31, a first Faraday rotator mirror 32, a phase shifter 33 and a second Faraday rotator mirror 34;

[0061] The beam splitter 31 is used to split the received signal light into two light signals, which are respectively output to the first Faraday rotator 32 and the phase shifter 33 through two different optical paths; and combine the light signals reflected by the first Faraday rotator 32 and the second Faraday rotator 34 and output them to the photodetector 13;

[0062] The first Faraday rotator 32 is used to rotate the polarization state of the received optical signal by a preset angle (for example, 90°) and then reflect it back to the beam splitter 31;

[0063] The phase shifter 33 is used to adjust the phase of the received optical signal and output the phase-adjusted optical signal to the second Faraday rotator 34;

[0064] The second Faraday rotator 34 is used to rotate the polarization state of the received optical signal by a preset angle (for example, 90°) and then reflect it back to the beam splitter 31 through the phase shifter 33 .

[0065] For example, preferably, Figure 4 As shown, in another specific embodiment of the present invention, the interferometer may include: a beam splitter 41 and an optical fiber ring 42;

[0066] The beam splitter 41 is used to split the received signal light into two light signals and output them to the optical fiber ring 42 through two different optical paths;

[0067] The two optical signals are respectively returned to the beam splitter 41 through the optical fiber ring 42;

[0068] The beam splitter 41 combines the two optical signals returned through the optical fiber ring 42 and outputs the combined signals to the photodetector 13 .

[0069] In addition, in the technical solution of the present invention, the current signal output by the photodetector may contain both quantum signals and classical noise, which change differently with the laser power, and are respectively a linear function and a quadratic function of power. Therefore, preferably, in a specific embodiment of the present invention, when the above-mentioned quantum random number generator is working normally, the power of the laser is changed, and the quadratic function of the total noise and the ratio of the quantum signal to the classical noise are fitted, and the variance of the quantum signal is calculated by the variance of the total noise. Since the quantum signal is Gaussian distributed, the variance of the quantum signal can be calculated by calculating the variance of the total signal, and finally the randomness in the produced quantum random number can be calculated according to the minimum entropy formula.

[0070] In summary, in the technical solution of the present invention, since the above-mentioned laser, interferometer, photodetector and analog-to-digital converter are used, the random phase fluctuations caused by the spontaneous radiation of the medium inside the laser can be used to generate random numbers, thereby ensuring the true randomness and reliability of the generated quantum random numbers. Moreover, since the phase fluctuation of the signal light output by the laser is a continuous variable, when the continuous variable is used to transmit information, the amount of information carried by each photon is increased, thereby effectively increasing the random number generation rate and generating random numbers at a relatively high code rate. The random number generation rate of the quantum random number generator in the technical solution of the present invention is much greater than the random number generation rate of the quantum random number generator in the prior art. For example, the quantum random number generator in the technical solution of the present invention can reach the Gbps level. In addition, the quantum random number generator in the technical solution of the present invention uses a photodetector instead of a single photon detector in the prior art, and a laser diode can be used as a light source, so the cost of the entire device can be greatly reduced, and it has a high practical value.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A quantum random number generator based on laser phase fluctuations, characterized in that: The quantum random number generator includes: a laser, an interferometer, a photodetector and an analog-to-digital converter; The laser is used to generate signal light with phase fluctuations and output the signal light to the interferometer; The interferometer is used to convert the phase fluctuation in the signal light into intensity fluctuation, and output the converted signal light to the photodetector; The photoelectric detector is used to convert the light intensity of the received signal light into a current signal, and output the obtained current signal to the analog-to-digital converter; The analog-to-digital converter is used to convert the received current signal into a discrete digital signal and output the signal; The quantum random number generator further comprises: a post-processor; The post-processor is connected to the analog-to-digital converter and is used to remove the classical randomness introduced into the quantum random number generator from the total randomness by post-processing the digital signal to generate a processed digital signal; Wherein, the interferometer comprises: a first beam splitter, a phase shifter and a second beam splitter; The first beam splitter is used to split the received signal light into two light signals, which are output to the phase shifter and the second beam splitter through two different optical paths respectively; The phase shifter is used to adjust the phase of the received optical signal and output the phase-adjusted optical signal to the second beam splitter; The second beam splitter is used to combine the optical signals received through the two optical paths and output the combined optical signals to the photodetector.

2. The quantum random number generator according to claim 1, characterized in that The interferometer comprises: a beam splitter, a first Faraday rotator mirror, a phase shifter and a second Faraday rotator mirror; The beam splitter is used to split the received signal light into two light signals, output them to the first Faraday rotator mirror and the phase shifter through two different optical paths respectively; and combine the light signals reflected back by the first Faraday rotator mirror and the second Faraday rotator mirror and output them to the photodetector; The first Faraday rotator is used to rotate the polarization state of the received optical signal by a preset angle and then reflect it back to the beam splitter; The phase shifter is used to adjust the phase of the received optical signal and output the phase-adjusted optical signal to the second Faraday rotator mirror; The second Faraday rotator is used to rotate the polarization state of the received optical signal by a preset angle and then reflect it back to the beam splitter through a phase shifter.

3. The quantum random number generator according to claim 1, characterized in that The interferometer comprises: a beam splitter and an optical fiber ring; The beam splitter is used to split the received signal light into two light signals and output them to the optical fiber ring through two different optical paths; The two optical signals are respectively returned to the beam splitter through the optical fiber ring; The beam splitter combines the two optical signals returned through the optical fiber ring and outputs the combined signals to the photoelectric detector.

4. The quantum random number generator according to claim 1, characterized in that: The laser is a laser diode.

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