Laser phase noise quantum random number generation method and device without phase stabilization

Abstract

The present invention discloses a novel laser phase noise quantum random number generation method and device. Based on real-time monitoring of changes in the average output light intensity of an interferometer to determine the real-time phase difference between the interferometer's two arms, the method dynamically adjusts the extraction ratio of the current original random number sequence to obtain quantum random numbers through online estimation of minimum entropy. This method eliminates the need for a phase stabilization structure and ensures that, regardless of the phase difference between the two arms, quantum random numbers can be generated and output while meeting randomness requirements. This simplifies the internal structure and process flow of the interferometer, reduces the system's requirements for feedback algorithms and hardware drivers, and facilitates the miniaturization, modularization, and chip-based development of existing quantum random number devices.

Description

Technical Field

[0001] The present invention relates to the field of quantum communication technology, and in particular to a method and device for generating laser phase noise quantum random numbers without phase stabilization. Background Art

[0002] In quantum communication systems, random numbers are ubiquitous, and the requirements for randomness are extremely strict. The key generated by quantum communication equipment is a sequence of random numbers, and the quality of this sequence's randomness determines the security of the final key. Furthermore, random numbers have a wide range of applications beyond cryptography, playing a crucial role in statistical sampling, Monte Carlo simulations, and scientific computing. Unlike pseudo-random number generators based on mathematical algorithms, quantum random number generators (QNRGs) use a random source based on the principles of quantum mechanics to measure random variables and generate output information. The uncertainty inherent in quantum mechanics ensures that the process is truly unpredictable and non-replicable. Therefore, schemes based on quantum random sources are also called true random number generators. Among existing QNRGs, laser phase noise is a key noise source in continuous QNRGs, with a well-defined mechanism. Systematic analysis methods exist for the variance of phase noise, the optimal laser drive current, and the optimal generation rate, allowing for optimization by measuring appropriate values ​​for a number of parameters.

[0003] Chinese patent number CN 108762723 A discloses a quantum random number generator based on laser phase fluctuations. Figure 1 As shown, it uses an optical interferometer with a phase shifter to maintain phase stability, converts the phase fluctuation of the laser into laser intensity fluctuations, and uses conventional photodetectors for detection. It no longer relies on single-photon detectors, which can effectively improve the random number generation rate.

[0004] Chinese patent number CN 204759398 U discloses an ultra-high-speed quantum random number generator based on laser phase fluctuations. Figure 2 As shown, the light radiation output by the laser light source is interfered by a dual-beam interferometer. There is a predetermined access arm length difference between the two interference light paths of the dual-beam interferometer. A voltage-controlled phase shifter is provided on one of the interference light paths. The phase control system adjusts the voltage-controlled phase shifter to ensure that the phase difference between the two interference light paths is maintained at a predetermined value, thereby achieving a one-to-one correspondence between the phase fluctuation of the laser light source and the output light intensity of the interferometer. The original data of the random number is output through the photodetector and the analog-to-digital converter. The original data is post-processed to obtain the final quantum random number.

[0005] Chinese patent number CN 109240645 A also discloses a quantum random number generator and a quantum random number generation method to solve the problem of low generation rate and high cost of existing random number generators. Figure 3 As shown, a pulsed laser outputs a pulsed laser signal to an interferometer. The pulsed laser signal carries information about the phase fluctuations of spontaneously emitted photons. The interferometer causes interference between two pulsed laser signals whose optical path time difference meets a preset condition, thereby converting the phase fluctuations of the pulsed laser signal into intensity fluctuations of the interfering light signal. A photodetector converts the interfering light signal into an analog electrical signal. A signal processing module processes the analog electrical signal to generate a quantum random number. In this scheme, because pulsed light is used as the light source, specific timing control is implemented, eliminating the need for phase feedback control of the unequal-arm interferometer. In other words, the interferometer does not include a phase stabilization structure.

[0006] Existing quantum random number generation schemes based on the principle of laser phase noise generally adopt an interferometer structure. Through the principle of optical interference, the phase noise is first converted into a light intensity fluctuation signal, and then a conventional photodetector is used to detect the light intensity fluctuation signal. A single detection can generate multiple random number bits, which is conducive to improving the generation rate of quantum random numbers. In existing schemes based on laser phase noise, it is usually necessary to achieve phase stabilization through phase feedback or compensation devices such as phase shifters, so that the phase difference caused by the optical path of the two arms of the unequal-arm interferometer is maintained at 2mπ+π / 2 (m is an integer). In this way, the final detection voltage or current is approximately proportional to the phase noise, and the output voltage basically conforms to the normal distribution.

[0007] However, optical interferometers are usually sensitive to environmental disturbances, such as temperature fluctuations and vibrations, which can affect the output stability of the interferometer. Stabilizing the phase within a preset range is not an easy task. First, in terms of hardware, not only does it require the design of a precise anti-vibration structure to resist the interference of external vibrations, but it is also necessary to combine software for active phase compensation. To this end, active phase control devices such as phase shifters need to be added to the interferometer arms, which increases the complexity of the interferometer optical path structure and process manufacturing. It is also necessary to increase software and hardware functions such as phase shifter control voltage and phase stabilization algorithm, which greatly reduces the robustness of the system and is not conducive to the miniaturization, modularization and chipization of products. In addition, although some quantum random number generation schemes that do not require phase feedback stabilization of the interferometer have been proposed in the prior art, these schemes require the use of pulsed light as the light source of the noise source, and require precise control of the pulse width, duty cycle, spectral linewidth, etc. of the pulsed light, and also require the optical path time difference between the two interfering pulsed lights to be adjusted, which undoubtedly increases the complexity of light source control and is also not conducive to improving the stability of the noise source system, making it difficult to truly put it into practical use. Summary of the Invention

[0008] In response to the above-mentioned problems existing in the prior art, the present invention discloses a laser phase noise quantum random number generation method and device. Based on the real-time monitoring of the change in the average output light intensity of the interferometer to determine the real-time phase difference between the two arms of the interferometer, the method dynamically adjusts the extraction ratio of the current original random number sequence to obtain quantum random numbers through online estimation of minimum entropy. This eliminates the need to set up a complex phase stabilization structure in the interferometer, ensuring that regardless of the state of the phase difference between the two arms, quantum random numbers can be generated and output while meeting the randomness requirements. Therefore, the internal structure and process of the interferometer can be simplified, the system's requirements for feedback algorithms and hardware drivers can be reduced, and it is conducive to the miniaturization, modularization and chipization of quantum random number devices.

[0009] Specifically, the first aspect of the present invention relates to a method for generating quantum random numbers using laser phase noise without phase stabilization, which includes a light emission step, an original random number sequence acquisition step, and a quantum random number generation step, wherein:

[0010] In the light emitting step, a driving current is used to drive the laser to output a laser signal;

[0011] In the step of acquiring the original random number sequence, an interferometer is used to convert the phase fluctuation noise in the laser signal into a light intensity fluctuation signal, and an original random number sequence is generated based on the light intensity fluctuation signal;

[0012] In the quantum random number generation step, quantum random numbers are extracted and generated from the original random number sequence according to an extraction ratio;

[0013] It is characterized in that it also includes a step of dynamically updating the extraction ratio, wherein the phase difference between the two arms of the interferometer is monitored within a time period corresponding to the light intensity fluctuation signal related to the original random number sequence, and the extraction ratio for the original random number sequence is dynamically updated when the phase difference changes.

[0014] Furthermore, the driving current is selected to be near a threshold current so that the phase fluctuation noise formed by spontaneous radiation in the laser signal has a maximum range; and / or, the laser is selected to be a continuous light laser or a pulsed light laser.

[0015] Furthermore, in the step of dynamically updating the extraction ratio, the phase difference is determined by monitoring the average output light intensity of the interferometer in the time period.

[0016] Furthermore, in the step of dynamically updating the extraction ratio, when the phase difference changes, the minimum entropy of the original random number sequence is estimated, and the extraction ratio is determined according to the minimum entropy for dynamic updating.

[0017] Furthermore, the quantum random number generation method of the present invention may further include a presetting step, wherein a plurality of light intensity ranges R(i) are preset, a minimum value H(i) in the minimum entropy of the original random number sequence corresponding to the average output light intensity falling within the light intensity range R(i) is estimated, and an extraction ratio P(i) is determined based on the minimum value H(i); and,

[0018] In the extraction ratio dynamic update step, when the average output light intensity changes, the extraction ratio is updated to the extraction ratio P(i) corresponding to the light intensity range R(i) that includes the average output light intensity.

[0019] Preferably, the plurality of light intensity ranges include a first light intensity range R(1), a second light intensity range R(2) and a third light intensity range R(3), wherein the first light intensity range R(1) is (P min , P 0.25 ), the second light intensity range R(2) is (P 0.25 , P 0.75 ), the third light intensity range R(3) is (P 0.75 , P max ), the P min and P max are the minimum and maximum values ​​of the average output light intensity of the interferometer, P 0.25 =(P 0.5 +P min ) / 2, P 0.75 =(P 0.4 +P max ) / 2, P 0.5 =(P max +P min ) / 2.

[0020] The second aspect of the present invention relates to a laser phase noise quantum random number generator without phase stabilization, which includes a noise source module, a signal acquisition and processing module, and a light intensity monitoring module;

[0021] The noise source module includes a laser light source, an interferometer and a photoelectric detection unit;

[0022] The laser light source is configured to generate a laser signal;

[0023] The interferometer is configured to convert phase fluctuation noise in the laser signal into a light intensity fluctuation signal;

[0024] The photoelectric detection unit is configured to convert the light intensity fluctuation signal into an electrical signal;

[0025] The light intensity monitoring module is configured to monitor the average output light intensity of the interferometer within a time period corresponding to the light intensity fluctuation signal;

[0026] The signal acquisition and processing module is configured to generate an original random number sequence based on the electrical signal, and to extract and generate quantum random numbers from the original random number sequence according to an extraction ratio, and to update the extraction ratio for the original random number sequence when the average output light intensity changes.

[0027] Furthermore, the driving current of the laser light source is set near its threshold current so that the phase fluctuation noise formed by spontaneous radiation in the laser signal has a maximum range, and / or the laser is a continuous light laser or a pulsed light laser.

[0028] Furthermore, the signal acquisition and processing module is also configured to estimate the minimum entropy of the original random number sequence when the average output light intensity changes, and determine the extraction ratio according to the minimum entropy for dynamic updating.

[0029] Furthermore, the signal acquisition and processing module also stores multiple light intensity ranges R(i) and corresponding extraction ratios P(i), and the extraction ratio P(i) is determined based on the minimum value H(i) in the minimum entropy of the original random number sequence corresponding to the average output light intensity falling within the light intensity range R(i); and when the average output light intensity changes, the extraction ratio used for the original random number sequence is updated to the extraction ratio P(i) corresponding to the light intensity range R(i) including the average output light intensity.

[0030] Optionally, the interferometer is an unequal-arm Mach-Zehnder interferometer or an unequal-arm Michelson interferometer without a phase stabilization structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1-3 The structural principle diagrams of several quantum random number generating devices in the prior art are shown respectively;

[0034] Figure 4-6 The distribution characteristics of the detector detection current I(t) related to the laser light source phase fluctuation noise are shown respectively when the phase difference between the two arms of the interferometer is in different states;

[0035] Figure 7 An exemplary flow chart of a method for generating laser phase noise quantum random numbers without phase stabilization according to the present invention is shown;

[0036] Figure 8 The schematic diagram of the laser phase noise quantum random number generator without phase stabilization according to the present invention is shown;

[0037] Figure 9 An example of an interferometer used in the quantum random number generating device of the present invention is shown;

[0038] Figure 10 Another example of an interferometer used in the quantum random number generating device of the present invention is shown. DETAILED DESCRIPTION

[0039] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so as to fully convey the spirit of the present invention to those skilled in the art to which the present invention belongs. Therefore, the present invention is not limited to the embodiments disclosed herein.

[0040] Those skilled in the art know that the light field E(t) of a continuous laser signal at time t can be given by the following formula:

[0041] E(t)=E0exp(i(ω0t+θ(t))) (1)

[0042] Where E0 is the amplitude of the light field, ω0 is the angular frequency, and θ(t) is the light phase at time t.

[0043] After the laser signal is interfered by an interferometer with a splitting ratio of 1:1 and an arm length difference of ΔT, the output light intensity of the interferometer is:

[0044]

[0045] The phase fluctuation of the laser light source is represented by the phase difference between time t and time t+ΔT, which is expressed as:

[0046] Δθ(t)=θ(t+ΔT)-θ(t) (3)

[0047] Then, after removing the DC part of the detection signal, the detection current of the photodetector is:

[0048] I(t)∝Pcos(ω0ΔT+Δθ(t))

[0049] =P(cos(ω0ΔT)cos(Δθ(t))-sin(ω0ΔT)sin(Δθ(t))) (4)

[0050] Where ω0ΔT is the phase difference between the two arms of the interferometer, which is a relatively slowly varying quantity. Prior art usually requires a phase stabilization structure to be set up in the interferometer, and by adjusting the phase shifter in real time, ω0ΔT satisfies the following conditions:

[0051] ω0ΔT→(2mπ+π / 2) (5)

[0052] Where m is a positive integer, → means equal to or infinitely close to, in which case cos(ω0ΔT)→0, sin(ω0ΔT)→1, and Δθ(t) is a small quantity, so sin(Δθ(t))→Δθ(t). In this case, equation (4) can be simplified to:

[0053] I(t)∝P·sin(ω0ΔT)·sin(Δθ(t))=P sin(Δθ(t))=PΔθ(t) (6)

[0054] Formula (6) is the theoretical basis for the generation of random numbers by most existing quantum random number generators based on the principle of laser phase noise. P is regarded as the input power of the interferometer and is a fixed value. Under this condition, the phase fluctuation noise Δθ(t) with Gaussian distribution based on spontaneous radiation can be linearly converted into the detection current I(t) of the detector. By collecting and quantifying the detection current, the original random number that conforms to the normal distribution is obtained. When Δθ(t) conforms to the normal distribution, the distribution characteristics of I(t) can be obtained from Formula (6), as follows: Figure 4 shown.

[0055] It can be seen that the existing quantum random number generation scheme based on the laser phase noise principle requires that the phase difference between the two arms of the interferometer be stably maintained to satisfy equation (5) so that the original random number obtained by sampling better conforms to the normal distribution, thereby allowing the final random number that meets the requirements to be obtained through further post-processing.

[0056] Based on the above theoretical analysis, the present invention further analyzes the impact of different arm length difference phase stability ranges on the quality of random number output. As in the prior art, a beam of light is split at the output end of the interferometer and its output light intensity change is detected to indirectly reflect the phase change. The light intensity detected at the light intensity monitoring port is usually the average light intensity over a period of time, and is therefore not affected by the instantaneous phase fluctuation Δθ(t) of the laser. The (average) output light intensity can be described as:

[0057]

[0058] When equation (5) is strictly satisfied, ω0ΔT→(2mπ+π / 2), cos(ω0ΔT)→0, the output light intensity of the detection port is It is half of the maximum output light intensity, that is, the middle value of the output light intensity (P 0.5 ), which is the ideal situation.

[0059] When the phase difference between the two arms deviates from the ideal phase difference, for example, ω0ΔT→(2mπ+0) or ω0ΔT→(2mπ+π), cos(ω0ΔT)→±1, and the output light intensity at the light intensity monitoring end reaches its maximum and minimum values, and sin(ω0ΔT)→0. Ignoring the sign of the noise fluctuation, Equation (4) can be simplified to:

[0060] I(t)∝Pcos(ω0ΔT)cos(Δθ(t))=Pcos(Δθ(t))=P[1-2sin 2 (Δθ(t) / 2)]

[0061] ≈P[1-Δθ(t) 2 / 2] (8)

[0062] At this time, when Δθ(t) conforms to the normal distribution, the detection current I(t) roughly conforms to the chi-square distribution, as shown in Figure 5 shown.

[0063] contrast Figure 4 and Figure 5 It can be seen that when the phase difference of the unequal-arm interferometer gradually deviates from the preset ideal value (the middle value of the output light intensity) to the maximum or minimum value, the laser phase noise gradually evolves from the ideal normal distribution characteristics to the pure chi-square distribution characteristics after detection, and the data that conforms to the chi-square distribution also has randomness.

[0064] The randomness of the original data is quantified by the minimum entropy, which is defined as H ∞ = -log2(P_max), where P_max is the probability of the most likely outcome. When gradually transitioning from normal distribution to chi-square distribution, Figure 4 and Figure 5 It can be seen that as P_max gradually increases, the minimum entropy gradually decreases accordingly, and the proportion of original random numbers that meet security requirements is decreasing. Therefore, when the final random number is output, the proportion of original random numbers extracted by the post-processing algorithm must also be reduced. More generally, when active phase control is not performed, the phase difference caused by the interferometer arm length difference changes randomly over time. Therefore, in most cases, after the noise signal output by the interferometer is detected, its detection signal is a superposition of the normal distribution and the chi-square distribution. For example, in some cases, the deviation of ω0ΔT makes cos(ω0ΔT) = ±1 / 2, that is, when the monitored average output light intensity deviates from 50% of its middle value, the distribution characteristics of the detection current I(t) at this time are as follows: Figure 6 shown.

[0065] Based on the above theoretical analysis, the present invention proposes a new quantum random number generation device and method, which is different from the existing technology and does not require the setting of a phase stabilization structure to stably maintain the phase difference between the two arms of the interferometer at a specific value (for example, 2mπ+π / 2).

[0066] The quantum random number generation method according to the present invention may include a light emitting step, an original random number sequence acquisition step, an extraction ratio dynamic updating step, and a quantum random number generation step.

[0067] Figure 7 An exemplary flow chart of a method for generating laser phase noise quantum random numbers without phase stabilization according to the present invention is shown.

[0068] See also Figure 7 In the light emitting step, a suitable driving current can be provided to the laser to drive it to output a laser signal to provide a spontaneous radiation noise source.

[0069] In order to obtain the maximum range of phase fluctuation noise formed by spontaneous emission, the driving current of the laser can be controlled to operate near the threshold current.

[0070] In the present invention, the laser used as the spontaneous emission noise source can be a continuous light laser or a pulsed light laser. Moreover, the wavelength range of the laser can cover the ultraviolet band to the near infrared band, for example, a wavelength of 1550 nm.

[0071] In the step of acquiring the original random number sequence, similar to the prior art, a laser signal is input into an interferometer, causing interference to generate an interference signal. This converts the phase fluctuation noise in the laser signal into a light intensity fluctuation signal represented by the interference signal. Unlike the prior art, the interference process of the present invention eliminates the need for feedback and active adjustment of the phase difference between the two arms of the interferometer to maintain it at a predetermined value.

[0072] Then, a high-speed photodetector is used to detect the light intensity fluctuation signal output by the interferometer to convert it into an electrical signal, and then the electrical signal is sampled and converted into a sequence of original random numbers with the help of an analog-to-digital converter.

[0073] In order to adapt to the unstable phase difference between the two arms of the interferometer, different from the prior art, the present invention introduces a step of dynamically updating the extraction ratio.

[0074] To dynamically update the extraction ratio, the interferometer's output intensity is monitored simultaneously with the original random number sequence acquisition step to obtain its average output intensity over the time period corresponding to the interference signal used for the original random number sequence. Based on the previous theoretical analysis, this average output intensity reflects the phase difference between the two arms of the interferometer.

[0075] By obtaining this average output light intensity, changes in the average output light intensity (i.e., the phase difference between the two arms) can be monitored, allowing the extraction ratio for the original random number sequence to be updated online in real time when such changes occur, so that the quantum random numbers generated based on the original random number sequence can meet the specified randomness requirements.

[0076] Specifically, in one embodiment, when the average output light intensity of the interferometer is monitored to change, the minimum entropy of the original random number sequence corresponding to the average output light intensity can be estimated online in real time. Figure 4-6 The distribution characteristics shown are used to obtain the probability of the most likely result in the original random number sequence, and then the corresponding minimum entropy is calculated according to the minimum entropy formula. Finally, the corresponding extraction ratio is determined based on the minimum entropy and used for subsequent processing of the original random number sequence.

[0077] For example, in one example, a continuous light laser with a wavelength of 1550 nm operating near the threshold current is used as a spontaneous emission noise source. The light intensity fluctuation signal generated by the laser signal passing through an interferometer is detected and sampled, and then converted into a raw random number sequence using a 12-bit analog-to-digital converter.

[0078] While generating the original random number sequence, the average output light intensity of the interferometer is monitored in real time (that is, the phase difference between the two arms of the interferometer is monitored in real time), where P min 、P max and P 0.5 are the minimum, maximum and middle values ​​of the average output light intensity of the interferometer, and P 0.25 =(P 0.5 +P min ) / 2, P 0.75 =(P 0.5 +P max ) / 2, P 0.5 =(P max +P min ) / 2. When the current average output light intensity is the middle value P of the average output light intensity 0.5 Transformed to maximum value P maxWhen , based on the current original random number sequence, it can be estimated that its minimum entropy is 3.09, and the extraction ratio can be determined to be 0.25 (<3.09 / 12) accordingly. At this time, the extraction ratio for the original random number sequence can be dynamically updated to 0.25 to adapt to the randomness requirements under the current phase difference state.

[0079] Therefore, in the subsequent quantum random number generation step, the updated extraction ratio (eg, 0.25) can be used to extract and generate quantum random numbers from the original random number sequence.

[0080] In another embodiment, a preset step may be further provided in the method of the present invention.

[0081] In this preset step, multiple light intensity ranges R(i) can be preset in advance, and the minimum value H(i) in the minimum entropy of the original random number sequence corresponding to the average output light intensity falling within each light intensity range R(i) can be estimated one by one, and the extraction ratio P(i) for each light intensity range R(i) can be determined based on the minimum value H(i).

[0082] Accordingly, in the step of dynamically updating the extraction ratio, when the average output light intensity is monitored to change, it is possible to determine in which light intensity range R(i) the current average output light intensity falls, and update the current extraction ratio to the extraction ratio P(i) corresponding to the light intensity range R(i) that includes the current average output light intensity.

[0083] For example, in one example, the entire average output light intensity range can be divided into a first light intensity range R(1), a second light intensity range R(2), and a third light intensity range R(3), wherein: the first light intensity range R(1) is (P min , P 0.25 ), the second light intensity range R(2) is (P 0.25 , P 0.75 ), the third light intensity range R(3) is (P 0.75 , P max ).

[0084] By estimation, it can be determined that the minimum entropy variation range of the original random number sequence obtained within the first light intensity range R(1) is (3.09, 9.34), where 3.09 and 9.34 correspond to P min and P 0.25 , the minimum value of minimum entropy H(1) is 3.09, and the corresponding extraction ratio P(1) = 0.25 (<3.09 / 12); the minimum entropy variation range of the original random number sequence obtained within the second light intensity range R(2) is (9.33, 9.56), where 9.33 and 9.56 correspond to P 0.75 and P 0.5, the minimum value of the minimum entropy H(2) is 9.33, and the corresponding extraction ratio P(2) = 0.75 (<9.33 / 12); the minimum entropy variation range of the original random number sequence obtained in the third light intensity range R(3) is (3.09, 9.33), where 3.09 and 9.33 correspond to P max and P 0.75 , the minimum value of its minimum entropy H(3) is 3.09, and the corresponding extraction ratio P(3) = 0.25 (<3.09 / 12).

[0085] Therefore, while generating the original random number sequence, the average output light intensity of the interferometer is monitored in real time. When the current average output light intensity falls within the first or third light intensity range R(1) or R(3), the extraction ratio for the original random number sequence can be dynamically updated to 0.25; when the current average output light intensity falls within the second light intensity range R(2), the extraction ratio for the original random number sequence can be dynamically updated to 0.75.

[0086] In the subsequent quantum random number generation step, the updated extraction ratio (eg, 0.25, 0.75, etc.) can be used to extract and generate quantum random numbers from the original random number sequence.

[0087] Thus, in the quantum random number generation method disclosed in the present invention, the real-time phase difference between the two arms of the interferometer is determined by real-time monitoring of the change in the average output light intensity of the interferometer. By online estimation of the minimum entropy, the extraction ratio of the current original random number sequence to obtain the quantum random number can be dynamically adjusted in real time. There is no need to set a complex phase stabilization structure in the interferometer to ensure that no matter what state the phase difference between the two arms is in, quantum random numbers can be generated and output while meeting the randomness requirements. Therefore, the internal structure and process of the interferometer can be simplified, the system's requirements for the feedback algorithm and the hardware drive are reduced, which is conducive to the miniaturization, modularization and chipization of quantum random number equipment.

[0088] Figure 8 The schematic diagram of the laser phase noise quantum random number generator without phase stabilization according to the present invention is shown.

[0089] like Figure 8 As shown, the quantum random number generating device may include a noise source module, a signal acquisition and processing module, and a light intensity monitoring module (not shown).

[0090] The noise source module includes a laser light source, an interferometer and a photoelectric detection unit.

[0091] The laser light source is used to generate a laser signal, which may be a continuous light laser or a pulsed light laser, and the wavelength range may cover the ultraviolet band to the near infrared band, such as 1550 nm.

[0092] The interferometer is used to convert the phase fluctuation noise in the laser signal into a light intensity fluctuation signal. In the present invention, the interferometer is not provided with a phase stabilization structure such as that achieved by a phase shifter.

[0093] The photoelectric detection unit is used to convert the light intensity fluctuation signal into an electrical signal, and it can be, for example, a high-speed photoelectric detector.

[0094] The light intensity monitoring module can monitor the output light intensity of the interferometer, so as to obtain, for example, the average output light intensity of the interferometer in the time period corresponding to the light intensity fluctuation signal.

[0095] The signal acquisition and processing module is used to acquire electrical signals and generate an original random number sequence based on the electrical signals, as well as to extract and generate quantum random numbers from the original random number sequence according to an extraction ratio, and to update the extraction ratio used for the original random number sequence when the average output light intensity changes.

[0096] In one example, the signal acquisition and processing module may include an analog-to-digital conversion unit and a post-processing unit.

[0097] The analog-to-digital conversion unit is used to convert the electrical signal into an original random number sequence. For example, the analog-to-digital conversion unit can be a 12-bit analog-to-digital converter, thereby converting the electrical signal into a 12-bit random number, thereby generating an original random number sequence.

[0098] The post-processing unit can extract and generate quantum random numbers from the original random number sequence according to the extraction ratio.

[0099] In the present invention, the post-processing unit may also dynamically update the extraction ratio for the original random number sequence according to the average output light intensity provided by the light intensity monitoring module.

[0100] In one example, the post-processing unit can estimate the minimum entropy of the original random number sequence corresponding to a change in the current average output light intensity. Based on this minimum entropy, the post-processing unit can determine an extraction ratio for extracting and generating quantum random numbers from the current original random number sequence. The specific process is described above and will not be repeated here.

[0101] In another example, multiple light intensity ranges R(i) and corresponding extraction ratios P(i) may be pre-set in the post-processing unit, and when the current average output light intensity changes, the extraction ratio used for the current original random number sequence is updated to the extraction ratio P(i) corresponding to the light intensity range R(i) that includes the current average output light intensity. In the pre-setting process, the extraction ratio P(i) may be determined based on the minimum value H(i) in the minimum entropy of the original random number sequence corresponding to the average output light intensity falling within the light intensity range R(i). The specific process can be found above and will not be repeated here.

[0102] Figure 9 An example of an interferometer that can be used in the quantum random number generating device of the present invention is shown, which adopts an unequal-arm Mach-Zehnder interferometer structure.

[0103] like Figure 9 As shown, the interferometer includes a beam splitter for an input end, a beam combiner for an output end, and a first arm and a second arm formed therebetween, wherein no phase stabilizing structure such as a phase shifter is provided in the interferometer.

[0104] The beam splitter can be a 1×2 or 2×2 polarization-maintaining fiber splitter, and the beam combiner can be a 2×2 polarization-maintaining fiber splitter. Therefore, the laser signal at the input end is split into two components after passing through the beam splitter. These components travel along the first and second arms of unequal lengths and arrive at the beam combiner at different times (with a time difference of ΔT).

[0105] Since the phases of the light field at time t and time t+ΔT are θ(t) and θ(t+ΔT) respectively, the random phase fluctuations generated are θ(t+ΔT)-θ(t), which are converted into random light intensity fluctuations after interference.

[0106] One output port of the beam combiner can be connected to a high-speed photodetector to allow the light intensity fluctuation signal to be detected and sampled as a random source for the quantum random number generator; the other port can be connected to a light intensity monitoring module to monitor the average output light intensity of the interferometer to analyze its working status.

[0107] Figure 10 Another example of an interferometer that can be used in the quantum random number generating device of the present invention is shown, which adopts an unequal-arm Michelson interferometer structure.

[0108] like Figure 10 As shown, the interferometer includes a 2×2 single-mode fiber beam splitter, which connects first and second arms of unequal length, respectively. The other ends of the first and second arms are respectively provided with Faraday rotator mirrors. Similarly, the interferometer can also be provided without a phase stabilization structure such as a phase shifter.

[0109] Therefore, the laser signal is split into two components after passing through the beam splitter. The two components are respectively transmitted along the first and second arms of unequal lengths and respectively reflected by the Faraday rotator mirror and arrive at the beam splitter at different times (with a time difference of ΔT).

[0110] Since the light field phases at time t and time t+ΔT are θ(t) and θ(t+ΔT) respectively, the random phase fluctuations generated are θ(t+ΔT)-θ(t), which are converted into random light intensity fluctuations after interference.

[0111] One port of the beam combiner can be connected to a high-speed photodetector to allow the light intensity fluctuation signal to be detected and sampled as a random source for the quantum random number generator; the other port is connected to a light intensity monitoring module via a circulator to monitor the average output light intensity of the interferometer to analyze its working status.

[0112] It can be seen that in the laser phase noise quantum random number generator according to the present invention, the phase stabilization structure used to stably maintain the phase difference between the two arms of the interferometer at a preset value is allowed to be omitted, which can greatly simplify the physical structure of the generator and the software structure such as the control algorithm, which is conducive to the miniaturization, modularization and chipization of quantum random number equipment.

[0113] Although the present invention has been described above through specific embodiments in conjunction with the accompanying drawings, it is easy for those skilled in the art to recognize that the above embodiments are merely exemplary and are used to illustrate the principles of the present invention. They do not limit the scope of the present invention. Those skilled in the art can make various combinations, modifications and equivalent substitutions to the above embodiments without departing from the spirit and scope of the present invention.

Claims

1. A method for generating quantum random numbers using laser phase noise without phase stabilization, comprising a light emission step, an original random number sequence acquisition step, and a quantum random number generation step, wherein: In the light emitting step, a driving current is used to drive the laser light source to output a laser signal; In the step of acquiring the original random number sequence, an interferometer is used to convert the phase fluctuation noise in the laser signal into a light intensity fluctuation signal, and an original random number sequence is generated based on the light intensity fluctuation signal; In the quantum random number generation step, quantum random numbers are extracted and generated from the original random number sequence according to an extraction ratio; It is characterized in that it also includes a step of dynamically updating the extraction ratio, wherein the phase difference between the two arms of the interferometer is monitored within a time period corresponding to the light intensity fluctuation signal related to the original random number sequence, and the extraction ratio for the original random number sequence is dynamically updated when the phase difference changes.

2. The quantum random number generation method according to claim 1, wherein: The driving current is selected to be near a threshold current so that the phase fluctuation noise formed by spontaneous emission in the laser signal has a maximum range; and / or, the laser light source is selected to be a continuous light laser or a pulsed light laser.

3. The quantum random number generation method according to claim 1, wherein: In the step of dynamically updating the extraction ratio, the phase difference is determined by monitoring the average output light intensity of the interferometer during the time period.

4. The quantum random number generation method according to claim 1 or 3, wherein: In the step of dynamically updating the extraction ratio, when the phase difference changes, the minimum entropy of the original random number sequence is estimated, and the extraction ratio is determined according to the minimum entropy for dynamic updating.

5. The method for generating quantum random numbers as claimed in claim 3, further comprising a presetting step, wherein: Preset multiple light intensity ranges R(i), estimate the minimum value H(i) in the minimum entropy of the original random number sequence corresponding to the average output light intensity falling within the light intensity range R(i), and determine the extraction ratio P(i) based on the minimum value H(i); and In the extraction ratio dynamic update step, when the average output light intensity changes, the extraction ratio is updated to the extraction ratio P(i) corresponding to the light intensity range R(i) that includes the average output light intensity.

6. The quantum random number generation method according to claim 5, wherein: The plurality of light intensity ranges include a first light intensity range R(1), a second light intensity range R(2) and a third light intensity range R(3), wherein the first light intensity range R(1) is (P min , P 0.25 ), the second light intensity range R(2) is (P 0.25 , P 0.75 ), the third light intensity range R(3) is (P 0.75 , P max ), the P min and P max are the minimum and maximum values ​​of the average output light intensity of the interferometer, P 0.25 =(P 0.5 +P min ) / 2, P 0.75 =(P 0.5 +P max ) / 2, P 0.5 =(P max +P min ) / 2.

7. A laser phase noise quantum random number generator without phase stabilization, comprising a noise source module, a signal acquisition and processing module, and a light intensity monitoring module; The noise source module includes a laser light source, an interferometer and a photoelectric detection unit; The laser light source is configured to generate a laser signal; The interferometer is configured to convert phase fluctuation noise in the laser signal into a light intensity fluctuation signal; The photoelectric detection unit is configured to convert the light intensity fluctuation signal into an electrical signal; The light intensity monitoring module is configured to monitor the average output light intensity of the interferometer within a time period corresponding to the light intensity fluctuation signal; The signal acquisition and processing module is configured to generate an original random number sequence based on the electrical signal, and to extract and generate quantum random numbers from the original random number sequence according to an extraction ratio, and to update the extraction ratio for the original random number sequence when the average output light intensity changes.

8. The quantum random number generator according to claim 7, wherein: The driving current of the laser light source is set near its threshold current so that the phase fluctuation noise formed by spontaneous radiation in the laser signal has a maximum range, and / or the laser light source is a continuous light laser or a pulsed light laser.

9. The quantum random number generator according to claim 7, wherein: The signal acquisition and processing module is further configured to estimate the minimum entropy of the original random number sequence when the average output light intensity changes, and determine the extraction ratio according to the minimum entropy for dynamic updating.

10. The quantum random number generator according to claim 7, wherein: The signal acquisition and processing module also stores multiple light intensity ranges R(i) and corresponding extraction ratios P(i), and the extraction ratio P(i) is determined based on the minimum value H(i) in the minimum entropy of the original random number sequence corresponding to the average output light intensity falling within the light intensity range R(i); and when the average output light intensity changes, the extraction ratio used for the original random number sequence is updated to the extraction ratio P(i) corresponding to the light intensity range R(i) that includes the average output light intensity.

11. The quantum random number generator according to claim 7, wherein: The interferometer is an unequal-arm Mach-Zehnder interferometer or an unequal-arm Michelson interferometer without a phase stabilization structure.

Images