Quantum entanglement source distribution apparatus and quantum key distribution system

Abstract

The application discloses a quantum entanglement source distribution device, comprising: a pump assembly configured to generate a pump pulse, the pump pulse carrying first sequence information through phase information, and the pump pulse comprising phase randomized laser pulses, the phase randomized laser pulses not carrying effective information; and a waveguide assembly coupled with the pump assembly and configured to receive the pump pulse and generate a photon pair of a time entangled quantum state. The quantum entanglement source distribution device provided by the application makes it impossible for unauthorized users to use the entangled photon pair to obtain quantum keys, realizes device-independent quantum key distribution, and can resist memory attacks at a very small cost; the structure can be reformed by adding some existing devices on the basis of a conventional entanglement source, compared with prior art, the structure can allow reuse of a single device, greatly reduces complexity of the system, and greatly reduces system cost.

Description

Technical Field

[0001] This invention relates to the field of quantum secure communication technology, and in particular to a quantum entanglement source distribution device, a quantum key distribution system, and a method for quantum entanglement source distribution using the quantum entanglement source distribution device. Background Technology

[0002] Modern society is based on reliable and secure communication. Current cryptographic systems rely on computational complexity to defend against eavesdropping and attacks, but they are vulnerable to attack with the development of quantum technology. Quantum key distribution (QKD) allows remote users to establish secret keys based on fundamental physical principles, regardless of the attacker's computational capabilities, thus ensuring information-theoretic security. In particular, entanglement-based QKD (EB-QKD) protocols stand out from standard QKD (such as the BB84 protocol) because they do not require intensity modulation and are naturally suitable for multi-user use. Furthermore, the ultimate form of quantum-secure communication—device-independent QKD (DI-QKD)—utilizes the strong correlations in quantum entanglement that transcend classical mechanisms, thereby completely eliminating the need for trust in QKD user devices. The main reason behind this is that the security requirement of DI-QKD excludes the existence of local hidden variable (LHV) models in devices, which can be viewed as pre-defined intrusion mechanisms that are indistinguishable in traditional QKD.

[0003] In fact, the lower the required level of trust, the higher the performance requirements for the actual equipment. High-quality entangled states are a prerequisite for defending against mass attacks in order to faithfully implement DI-QKD. Furthermore, high detection efficiency is required along the intermediate link from the distribution source to each user to ensure the unbiasedness of statistical data, thereby defending against detection efficiency attacks. Additionally, the measurement device should be memory-free, as attackers can steal information by tracking the historical statistics of reused devices; this is known as a memory attack.

[0004] Quantum entanglement is foreseeably to serve as an important resource in real-world quantum applications, much like electricity and natural gas in energy networks. Existing discussions assume that entangled resources are in a fixed form (typically one of the four Bell states), and users utilize received correlated photons (usually photons, as they are the best information carriers over long distances) to perform various tasks. While the control of entangled resources is clearly important, research on this is still limited. Summary of the Invention

[0005] In existing technologies, methods to address attacks on the measurement devices of one party in quantum secure communication primarily involve adding redundant devices. These devices participate in the protocol only once and do not participate in subsequent communications, thus ensuring that the device has no opportunity to leak information about the previous communication that may be secretly stored in its memory during subsequent communications. It can be seen that current solutions significantly increase the complexity of the system and also greatly increase the overall system construction cost.

[0006] In view of at least one deficiency of the prior art, in a first aspect, the present invention provides a quantum entanglement source distribution device, comprising:

[0007] A pumping component is configured to generate pump pulses, wherein the pump pulses carry first sequence information through phase information, and the pump pulses include phase-randomized laser pulses, wherein the phase-randomized laser pulses do not carry valid information.

[0008] A waveguide component, coupled to the pump component, is configured to receive the pump pulse and generate photon pairs of time-entangled quantum states based on the pump pulse.

[0009] According to a first aspect of the invention, the pump assembly comprises:

[0010] A first laser is configured to emit a first pulse, perform phase encoding on the first pulse according to the first sequence information, add a phase-randomized laser pulse to the encoded first pulse, and output a first encoded pulse.

[0011] A second laser, coupled to the first laser, is configured to emit a second pulse and receive the first coded pulse to modulate the second pulse and generate the pump pulse.

[0012] According to a first aspect of the invention, the first laser is further configured to:

[0013] The first pulse is phase-encoded by adjusting the driving voltage;

[0014] By reducing the driving voltage below the avalanche threshold, a phase-randomized laser pulse can be added to the encoded first pulse.

[0015] According to a first aspect of the invention, the pump assembly further comprises:

[0016] An attenuator, coupled to the first laser, is configured to receive the first coded pulse, attenuate its power, and then output it.

[0017] A circulator having a first end, a second end, and a third end, wherein the first end is coupled to the attenuator, the second end is coupled to the second laser, and the circulator is configured as follows:

[0018] The attenuated first coded pulse is injected into the second laser to form modulation, and the pump pulse is output.

[0019] An erbium-doped fiber amplifier, coupled to the third terminal of the circulator, is configured to receive the pump pulse, amplify it, and then output it.

[0020] According to a first aspect of the invention, the device further comprises:

[0021] The beam splitter component is coupled to the waveguide component and configured as a photon partitioning channel in the photon pair of the time-entangled quantum state.

[0022] According to a first aspect of the invention, the device further comprises:

[0023] A receiving component, coupled to the beam splitting component, is configured to receive one photon from the photon pair of the time-entangled quantum state to obtain the original key.

[0024] According to a first aspect of the invention, the receiving component comprises:

[0025] An interferometer, coupled to the beam-splitting component, is configured to receive the photons and perform phase measurements;

[0026] A single-photon detector is positioned downstream of the interferometer's optical path and configured to receive the optical signal output by the interferometer and convert it into an electrical signal to output the original key.

[0027] According to a first aspect of the invention, wherein

[0028] The waveguide assembly includes a silicon waveguide chip configured to cause the pump pulse to undergo four-wave mixing.

[0029] The beam splitting component includes a wavelength division multiplexer;

[0030] The pumping component, the waveguide component, the beam splitter component, and the receiving component transmit optical signals via optical fiber.

[0031] According to a first aspect of the invention, the pump pulse includes a laser pulse with a preset ratio of phase randomization, the preset ratio being set based on safety requirements.

[0032] According to a first aspect of the invention, the first sequence information includes a pseudo-random number sequence, which is generated based on a classical random seed, and the communicating parties periodically share the classical random seed.

[0033] In a second aspect, the present invention also provides a quantum key distribution system, including a first user terminal and a second user terminal for quantum secure communication, wherein the quantum key distribution system further includes:

[0034] A third-party terminal, wherein the third-party terminal is equipped with a quantum entanglement source distribution device as described in the first aspect of the present invention; wherein

[0035] The first user terminal is coupled to the third-party terminal and configured to receive one photon from a photon pair of time-entangled quantum states distributed by the quantum entanglement source distribution device;

[0036] The second user terminal is coupled to the third-party terminal and configured to receive another photon from the photon pair of time-entangled quantum states distributed by the quantum entanglement source distribution device.

[0037] In a third aspect, the present invention also provides a method for distributing quantum entangled sources using a quantum entangled source distribution device as described in the first aspect of the present invention, comprising:

[0038] Pump pulses are generated by the pumping component. The pump pulses carry first sequence information through phase information, and the pump pulses include phase-randomized laser pulses, which do not carry valid information.

[0039] The waveguide component receives the pump pulses and generates photon pairs of time-entangled quantum states.

[0040] The quantum entanglement source distribution device provided by this invention prevents unauthorized users from obtaining quantum keys using entangled photon pairs, and achieves device-independent quantum key distribution, resisting memory attacks at minimal cost. Furthermore, the quantum entanglement source distribution device provided by this invention can be structurally modified by adding existing devices to a conventional entanglement source. Compared to existing technologies (which require replacing a batch of devices with each communication), the quantum entanglement source distribution device provided by this invention allows for the reuse of individual devices, greatly reducing system complexity and cost. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings, without exceeding the scope of protection claimed by this application.

[0042] Figure 1 An embodiment of the present invention provides a quantum entanglement source distribution apparatus;

[0043] Figure 2 The internal structure of a quantum entanglement source distribution device and its pumping assembly provided in one embodiment of the present invention is shown.

[0044] Figure 3 The internal structure of a quantum entanglement source distribution device and its pumping assembly provided in one embodiment of the present invention is shown.

[0045] Figure 4 An embodiment of the present invention provides a quantum entanglement source distribution apparatus;

[0046] Figure 5 An embodiment of the present invention provides a quantum entanglement source distribution apparatus;

[0047] Figure 6 The internal structure of a quantum entanglement source distribution device and its receiving component provided in one embodiment of the present invention is shown.

[0048] Figure 7 An embodiment of the present invention provides a quantum entanglement source distribution apparatus;

[0049] Figure 8 This illustrates the theoretical relationship between the bit string entropy and the random mixing ratio;

[0050] Figure 9 The relationship between the control bit string entropy, random mixing ratio, and Bell inequality parameters obtained by a quantum entangled source distribution device provided using an embodiment of the present invention is shown.

[0051] Figure 10 An embodiment of the present invention provides a quantum key distribution system;

[0052] Figure 11 An embodiment of the present invention provides a method for distributing quantum entangled sources. Detailed Implementation

[0053] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0054] Traditionally, entanglement-based quantum key distribution involves a server continuously distributing the most entangled state to users. However, this method of providing entangled resources leaves the server without control over the distributed photons. This means that even unauthorized users could obtain entangled photons from the channel undetected to generate their own keys. This significantly impacts the ability of legitimate users to access entangled resources. Currently, there are no clearly proposed technologies to control the distribution of entangled resources.

[0055] Furthermore, controlling the entanglement source can also prevent memory attacks. Since memory attacks extract information retained from past communications to eavesdrop, the main approach of existing countermeasures is to prevent attackers from accessing used devices. Such countermeasures include destroying used measuring equipment, strictly isolating entanglement-generating devices, or using additional alternative devices. However, without exception, these countermeasures introduce considerable additional complexity to the system, not to mention the potentially high costs.

[0056] In the solution provided by this invention, the 0 and π phases are randomly assigned to the pump source used to generate entangled states. Thus, the entangled state actually distributed to the user by the entangled source will be φ. + and φ - One of them, specifically which one will be controlled by the bit string T C To decide, here φ ± =|00>±|11>. It can be seen that these two entangled states have opposite correlations.

[0057] Because the security analysis of the QKD protocol requires proving violations of Bell-type inequalities (e.g., the well-known Clauser-Horn-Shimoney-Holt (CHSH) inequality), and for users to observe violations of inequalities, they must know the exact entangled state φ corresponding to each conforming event. + or φ - .

[0058] Specifically, the parameter of the CHSH inequality can be written as S CHSH :=E(σ X ,σ X+Y )+E(σ Y ,σ X+Y )+E(σ X ,σ X-Y )-E(σ Y ,σ X-Y ),in The correlation function is composed of the probabilities of four possible outcomes, where α and β are the given measurement basis vectors. It can be seen that the correlation function E quantifies the correlation (correlation degree) of photon pairs; that is, "++" and "--" from the output port indicate positive correlation, while "+-" and "-+" indicate negative correlation. Under the classical locality assumption, S... CHSH There is an upper bound at point 2. However, in quantum systems, entangled states are strongly correlated and can transcend the limitations of locality theory. Therefore, if S CHSH If the value is >2, then we consider the entangled source to be a truly reliable quantum source and not manipulated by an attacker.

[0059] We use the mean of the correlation values ​​to characterize the effectiveness of the control, which is defined as a function of the control string:

[0060]

[0061] Where {T} N It is a valid control string (i.e., the decoded control bit string), that is... N is the length of T. For example, control string T C ="01010101", the decoded string T on the user side D If the value is "00000000", then U = 0. In this case, the user cannot fully distinguish whether a positive or negative association should be used, which will result in E = 0, therefore S... CHSH =0, so they will have to terminate the agreement to avoid security risks.

[0062] The current problem is how to effectively distribute the control string. A reasonable approach is for the entanglement source and the legitimate user to pre-share the control string. This can be achieved using a block cipher algorithm in stream cipher mode (such as AES). In this way, only a short random string is needed as a seed to achieve T. C Effective distribution.

[0063] While the above approach can prevent unauthorized users from accessing entangled photon resources, it cannot be directly applied to defend against memory attacks. This is because in such attacks, the attacker can completely obtain the user's measurement choices and results. Due to the correspondence between the measurement results and control bits, the attacker can immediately determine the control string by analyzing the original key.

[0064] This invention provides a quantum key distribution device that performs double randomization on entangled resources. The first randomization ensures that only authorized users can access entangled resources; unauthorized users, lacking the control string used for the first randomization, cannot obtain any. The second randomization adds redundancy to the transmitted information, preventing memory attackers from deciphering the control string even if they eavesdrop on the original key. Using this quantum key distribution device, the control string can be protected from exposure even when the original key is completely revealed, while also ensuring the device can be reused.

[0065] According to one embodiment of the present invention, such as Figure 1 As shown, the present invention provides a quantum entanglement source distribution device 100, comprising: a pump assembly 110 and a waveguide assembly 120. Wherein:

[0066] Pump component 110 is configured to generate pump pulses that carry first sequence information via phase information. The pump pulses include phase-randomized laser pulses that do not carry valid information. First, pump pulses are prepared, and then photon pairs in a time-entangled quantum state are prepared based on these pump pulses. Since photons in the photon pairs in the time-entangled quantum state need to be distributed to authorized users, first sequence information (i.e., the control string mentioned above) is introduced and shared in advance so that legitimate users of both communicating parties can obtain the first sequence information. The pump pulses are phase-encoded using the first sequence information, so that the pump pulses carry the first sequence information. Users can decode the photons in the photon pairs in the time-entangled quantum state using the pre-shared first sequence information.

[0067] For memory attackers who target user-end devices, they can obtain the original key by copying the decoding steps of legitimate users. To prevent the attacker from obtaining valid information, phase-randomized laser pulses are added to the encoded pulses carrying the first sequence information after phase encoding. This makes it impossible for the attacker to distinguish between valid and invalid information, thus protecting the valid information.

[0068] Waveguide component 120 is coupled to pump component 110 and configured to receive the pump pulse to generate a photon pair in a time-entangled quantum state. Waveguide component 120 includes, for example, a silicon waveguide chip. Before the pump pulse enters waveguide component 120, the photon is in a superposition state of two time-bins. After the pump pulse enters waveguide component 120, a photon pair (two single photons) in a time-entangled quantum state can be obtained through a series of processes, such as beam splitting, interference, single photon separation, and filtering.

[0069] The above embodiments of the present invention hide detectable binary pseudorandomness within true randomness. Operationally, a phase-randomized mixed state with probability p is chosen to be mixed with a maximally entangled state. This operation will destroy the phase correlation. Thus, the entangled source will randomly distribute three possible quantum states:

[0070] φ + φ - and Their probabilities are respectively and p.

[0071] Assuming each user's local state remains unchanged, a malicious device will be unable to deduce the control string (first sequence information) from the measurement results because it's impossible to recover a specific decomposition from a mixed state without sufficient auxiliary information. Furthermore, even if the malicious device records the original key and manages to send it out, an eavesdropper still cannot obtain the secure key generated in the previous session because the key generation process is encrypted with a truly random element in the control string. In other words, a valid original key is obtained by filtering truly random bits from the measurement results. The measurement results must be guaranteed to be transmitted to a trusted computer for post-processing.

[0072] According to one embodiment of the present invention, such as Figure 2 As shown, in the quantum entanglement source distribution device 100 provided by the present invention, the pumping component 110 includes: a first laser 111 and a second laser 112. Wherein:

[0073] The first laser 111 is configured to emit a first pulse, and to perform phase encoding on the first pulse according to the first sequence information, and to add a phase-randomized laser pulse to the encoded first pulse, and output the first encoded pulse.

[0074] The second laser 112 is coupled to the first laser and configured to emit a second pulse and receive the first coded pulse to modulate the second pulse and generate the pump pulse.

[0075] According to one embodiment of the present invention, the first laser 111 is further configured to:

[0076] The first pulse is phase-encoded by adjusting the driving voltage.

[0077] By reducing the driving voltage below the avalanche threshold, a phase-randomized laser pulse can be added to the encoded first pulse.

[0078] In the quantum entanglement source distribution device 100 provided by this invention, the entanglement source needs to be adjusted to three different quantum states. Therefore, when preparing the pump light pulse, at least three different phases should be assigned to the pump pulse. For example, according to the first sequence information (control string), a phase of 180° is assigned to the pulse corresponding to the number "1", and a phase of -180° is assigned to the pulse corresponding to the number "0". A phase-randomized laser pulse is then added to the encoded pulse. Optionally, the above-mentioned phase encoding and phase randomization process can be achieved by adjusting the driving voltage of the first laser. First, a pulse corresponding to the number "1" is emitted by applying a conventional first driving voltage. Then, a pulse corresponding to the number "0" is emitted by applying a second driving voltage lower than the conventional driving voltage, where the second driving voltage is still greater than the avalanche threshold of the first laser. During the pulse encoding process, by reducing the driving voltage of the first laser below the avalanche threshold, the phase of the emitted pulse of the first laser is randomized, thus realizing the addition of a "truly random" phase pulse to the pump light in the pulse phase-encoded according to the first sequence information. The entangled photon pairs obtained by the pump light have three different quantum states.

[0079] According to one embodiment of the present invention, since the QKD protocol involved in the present invention requires three basic states, in order to accurately introduce the designed phase shift or phase randomization into the time-bank entangled states, this embodiment uses direct phase modulation technology. Its basic setup is to use a 2.5 GHz signal to modulate a pair of gain-switched distributed feedback lasers (DFBs) to achieve optical injection locking. A significant advantage of this setup is that phase randomization can be easily achieved by switching the main drive signal at the laser threshold of the master laser (i.e., the first laser mentioned above). Operationally, state φ + This corresponds to applying a conventional driving voltage to the main laser; state φ - A shallower driving voltage is applied accordingly; state This corresponds to applying a reverse voltage. The slave laser (i.e., the second laser mentioned above) uses a 2.5 GHz square signal for pulse generation. The slave laser's bias voltage is just above its lasing threshold, resulting in an optical power of 30 μW. The main laser, centered at 1550.52 nm, has an optical power of approximately 80 μW; the actual power varies with the modulation signal.

[0080] According to one embodiment of the present invention, such as Figure 3 As shown, in the quantum entanglement source distribution device 100 provided by the present invention, the pump component 110 further includes: an attenuator 113, a circulator 114, and an erbium-doped fiber amplifier 115. Wherein:

[0081] The attenuator 113 is coupled to the first laser 111 and configured to receive the first coded pulse, attenuate the power, and then output it.

[0082] Circulator 114 has a first end, a second end, and a third end, wherein the first end is coupled to attenuator 113, the second end is coupled to second laser 112, and circulator 114 is configured to:

[0083] The attenuated first coded pulse is injected into the second laser 112 to form modulation, and the pump pulse is output.

[0084] The erbium-doped fiber amplifier 115 is coupled to the third terminal of the circulator 114 and configured to receive the pump pulse, amplify it, and then output it. Optionally, the output power of the erbium-doped fiber amplifier (EDFA) is 10mW. The pump pulse is then sent to a silicon waveguide chip to generate entangled photon pairs through spontaneous four-wave mixing (SFWM).

[0085] The above-described one or more embodiments of the present invention are one implementation of the pump component 110 in the quantum entanglement source distribution device 100 provided by the present invention. Other arrangements of the laser source, and / or the use of other optical components to encode and randomize the first pulse, and / or the use of other optical components to modulate the second pulse, thereby generating the pump pulse, are all within the protection scope of the present invention.

[0086] According to one embodiment of the present invention, such as Figure 4 As shown, the quantum entanglement source distribution device 100 provided by the present invention further includes: a beam splitter 130. Wherein:

[0087] The beam splitter 130 is coupled to the waveguide 120 and configured as a photon partitioning channel in the photon pair of the time-entangled quantum state.

[0088] The pump pulse input waveguide component 120 generates entangled states consisting of a cluster of paired photons distributed across a relatively wide frequency spectrum. By guiding all generated entangled photon pairs into the beam splitter component 130, the individual photons can be divided into multiple channels. Optionally, in some embodiments of the invention, channels C30 and C37 (ITU grid standard, full width at half maximum (FWHM) 25 GHz) are selected. Those skilled in the art will readily understand that the quantum entanglement source distribution device 100 provided by this invention, in which the beam splitter component 130 can support more channels, is also within the scope of protection of this invention.

[0089] According to one embodiment of the present invention, such as Figure 5 As shown, the quantum entanglement source distribution device 100 provided by the present invention further includes: a receiving component 140. Wherein:

[0090] The receiving component 140 is coupled to the beam splitting component 130 and configured to receive one photon from the photon pair of the time-entangled quantum state to obtain the original key.

[0091] According to one embodiment of the present invention, such as Figure 6 As shown, the receiving component 140 further includes an interferometer 141 and a single-photon detector 142. Wherein:

[0092] Interferometer 141 is coupled to beam splitter 130 and configured to receive the photons and perform phase measurement.

[0093] A single-photon detector 142 is positioned downstream of the optical path of the interferometer 141 and is configured to receive the optical signal output by the interferometer and convert it into an electrical signal to output the original key.

[0094] According to one embodiment of the present invention, in the quantum entanglement source distribution device 100 provided by the present invention:

[0095] Waveguide assembly 120 includes a silicon waveguide chip configured to cause the pump pulses to undergo four-wave mixing. According to one embodiment of the invention, at the entanglement source, a series of phase-modulated pump pulses are sent to a silicon waveguide chip. Before entering the chip, photons are in a superposition state of two time-bins, meaning that when a measurement is applied, the photons have a 50% probability of appearing at the earlier time point and a 50% probability of appearing at the later time point. The time difference between the two time points is set to 400 ps, ​​corresponding to a 2.5 GHz signal frequency. After entering the chip, the photons undergo spontaneous four-wave mixing (SFWM), which transforms the original time-bin superposition state into a time-bin entangled state, specifically a modulated entangled state.

[0096] The beam splitter 130 includes a wavelength division multiplexer. According to one embodiment of the present invention, by guiding all the generated entangled photon pairs into a dense wavelength division multiplexer (DWDM), each photon can be divided into multiple channels, such as channels C30 and C37 (ITU grid standard, half-height 25 GHz). The quantum entanglement source distribution device provided by the present invention can also directly support more channels.

[0097] Both communicating parties are equipped with a receiving component 140. Optionally, each communicating party's terminal holds an asymmetric Mach-Zehnder interferometer (AMZI), which achieves active phase stabilization based on temperature and can also control the phase by changing the temperature—setting the measurement base. A continuous-wave reference laser is stabilized at a center wavelength of 1550.52 nm, which propagates along the same path as the entangled photon pair and provides feedback control for the AMZI.

[0098] Optical signals are transmitted between the pump assembly 110, waveguide assembly 120, beam splitter assembly 130 and receiver assembly 140 via optical fiber.

[0099] According to one embodiment of the present invention, in the quantum entanglement source distribution device 100 provided by the present invention:

[0100] The pump pulse includes a laser pulse with a preset ratio of phase randomization, the preset ratio being set based on safety requirements.

[0101] In the prepared pump pulses, the more mixed-state phase randomization pulses there are, the more redundant information in the original key obtained from decoding, and the more difficult it is to read the truly effective control string information. Therefore, depending on the security level requirements, the pump pulses can be set to have a preset proportion of phase randomization laser pulses.

[0102] According to one embodiment of the present invention, in the quantum entanglement source distribution device 100 provided by the present invention:

[0103] The first sequence information includes a pseudo-random number sequence, which is generated based on a classic random seed, and the two communicating parties periodically share the classic random seed.

[0104] Defense against memory attacks relies primarily on classic encryption; the QKD protocol does not generate additional permanent security data. Therefore, while the entanglement source does not participate in the QKD process between users and cannot obtain any information about the user's security key, it needs to communicate with the user periodically (e.g., for a small portion of each day) to update the classic random seed.

[0105] The following is for reference. Figure 7 Experimental verification was conducted on the quantum entanglement source distribution device 100 provided by the present invention.

[0106] According to one embodiment of the present invention, such as Figure 7 As shown, the master laser and slave laser are 2.5GHz gain-switched distributed feedback lasers (DFBs), and phase randomization is achieved by switching the master drive signal at the laser threshold of the master laser. Wherein, state φ +This corresponds to applying a conventional driving voltage (denoted as signal "0") to the main laser; state φ - A shallow driving voltage (denoted as signal "1") is applied accordingly; state This corresponds to applying a reverse voltage (denoted as signal "2"). That is, the numbers "0" and "1" in the control bit string refer to pseudo-random phase, while the number "2" refers to true random phase. The optical power of the master laser centered at 1550.52nm is approximately 80μW, with the actual power varying with the modulation signal. The slave laser uses a 2.5GHz square signal for pulse preparation, with the slave laser bias voltage just above its lasing threshold, resulting in an optical power of 30μW.

[0107] Each end user possesses an asymmetric Mach-Zehnder interferometer (AMZI) that achieves active phase stabilization based on temperature, and the phase can also be controlled by changing the temperature—setting the measurement basis. A continuous-wave reference laser (not shown in the figure) is stabilized at a center wavelength of 1550.52 nm, which propagates along the same path as the entangled photon pairs and provides feedback control for the AMZI.

[0108] To simulate a scenario where an unauthorized user or malicious device obtains partial control string information in a certain way, this experiment sets different control bit string entropies. And the maximum mixed-state ratio p used for interference. Operationally, multiple control bit strings are first generated, each containing 5000 random classical trits, corresponding to a set of B and p settings respectively. These sequences are then loaded onto an arbitrary waveform generator to produce a modulated signal. Figure 8 It shows the theoretical S CHSH The relationship between the value of and B and p, Figure 9 The experimental results of this experiment are shown.

[0109] like Figure 9 As shown, the overall prediction efficiency of the experimental setup was 1.6%, including losses from the waveguide chip (-6.5 dB), transmission and coupling (-7 dB), spectral filtering (-4 dB), and photon detection (-0.5 dB). The maximum coincidence rate obtained exceeded 2 kHz, and the coincidence-to-accidental coincidence ratio (CAR) was 50.

[0110] The quantum entanglement source distribution device provided by one or more embodiments of the present invention prevents unauthorized users from obtaining quantum keys using entangled photon pairs, and achieves device-independent quantum key distribution, resisting memory attacks at minimal cost. The quantum entanglement source distribution device provided by one or more embodiments of the present invention can achieve structural modification by adding some existing devices to a conventional entanglement source. Compared with existing technical solutions (replacing a batch of devices with each communication), the quantum entanglement source distribution device provided by the present invention allows for the reuse of individual devices, greatly reducing system complexity and significantly lowering system costs.

[0111] According to one embodiment of the present invention, such as Figure 10 As shown, the present invention also provides a quantum key distribution system 200, including a first user terminal 210 and a second user terminal 220 for quantum secure communication, and a third-party terminal 230. Wherein:

[0112] The third-party terminal 230 is equipped with a quantum entanglement source distribution device 100 as described in one or more embodiments above.

[0113] The first user terminal 210 is coupled to the third-party terminal 230 and configured to receive a photon from a photon pair of time-entangled quantum states distributed by the quantum entanglement source distribution device 100.

[0114] The second user terminal 220 is coupled to the third-party terminal 230 and configured to receive another photon from the photon pair of time-entangled quantum states distributed by the quantum entanglement source distribution device 100.

[0115] According to one embodiment of the present invention, such as Figure 11 As shown, the present invention also provides a method 10 for distributing a quantum entangled source using a quantum entangled source distribution device 100 as described in one or more embodiments above, comprising: steps S101 and S102. Wherein:

[0116] In step S101, a pump pulse is generated by the pump component. The pump pulse carries first sequence information through phase information. Furthermore, the pump pulse includes a phase-randomized laser pulse, which does not carry valid information.

[0117] In step S102, the pump pulse is received through the waveguide component to generate photon pairs of time-entangled quantum states.

[0118] According to an embodiment of the present invention, in the method 10 for distributing quantum entangled sources provided by the present invention, the pumping assembly further includes a first laser and a second laser coupled to each other, and the method 10 further includes:

[0119] The first pulse is emitted by the first laser, and the first pulse is phase-encoded according to the first sequence information. A phase-randomized laser pulse is added to the encoded first pulse to output the first encoded pulse.

[0120] The second laser is configured to emit a second pulse and receive the first coded pulse to modulate the second pulse, thereby generating the pump pulse.

[0121] According to one embodiment of the present invention, the method 10 for distributing quantum entangled sources provided by the present invention further includes:

[0122] The first pulse is phase-encoded by adjusting the driving voltage of the first laser.

[0123] By reducing the driving voltage of the first laser below the avalanche threshold, a phase-randomized laser pulse is added to the encoded first pulse.

[0124] According to an embodiment of the present invention, in the method 10 for distributing a quantum entangled source provided by the present invention, the quantum entangled source distribution device further includes a beam splitter and a receiving component, wherein the beam splitter is coupled to the waveguide component, and the receiving component is coupled to the beam splitter. The method 10 further includes:

[0125] The beam splitter divides the photons in the photon pair of the time-entangled quantum state into channels.

[0126] The original key is obtained by receiving one photon from the photon pair of the time-entangled quantum state through the receiving component.

[0127] According to an embodiment of the present invention, in the method 10 for distributing quantum entangled sources provided by the present invention, the pump pulse includes a laser pulse with a preset proportion of phase randomization, and the method 10 further includes:

[0128] The preset ratio is set according to safety requirements.

[0129] According to an embodiment of the present invention, in the method 10 for distributing quantum entangled sources provided by the present invention, the first sequence information includes a pseudo-random number sequence, the pseudo-random number sequence being generated based on a classical random seed, and the method 10 further includes:

[0130] The two communicating parties periodically share the classic random seed.

[0131] The specific limitations in the above-described method 10 for distributing quantum entanglement sources are similar to those in the quantum entanglement source distribution device 100 described above. Please refer to the previous description of the quantum entanglement source distribution device 100, which will not be repeated here.

[0132] The quantum key distribution (QKD) involved in this invention refers to the ability of a remote user to establish a secret key without considering the computing power of an attacker, based on the fundamental principles of quantum mechanics (including the uncertainty principle, the no-cloning principle for unknown quantum states, etc.), thereby ensuring information-theoretic security.

[0133] The device-independent (DI) concept involved in this invention refers to the assumption that the measuring device inputs and outputs information according to a preset mechanism, that is, the measurement device may be modified or eavesdropped on by an attacker.

[0134] The embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this application. Furthermore, any changes or modifications made by those skilled in the art based on the ideas of this application, and on the specific implementation methods and application scope of this application, are all within the scope of protection of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A quantum entanglement source distribution device, characterized in that, include: A pumping component is configured to generate pump pulses, wherein the pump pulses carry first sequence information through phase information, and a phase-randomized laser pulse is added to the pump pulses carrying the first sequence information, wherein the first sequence information is a control string; A waveguide component, coupled to the pump component, is configured to receive the pump pulse and generate photon pairs of time-entangled quantum states based on the pump pulse.

2. The apparatus of claim 1, wherein the pump assembly comprises: A first laser is configured to emit a first pulse, perform phase encoding on the first pulse according to the first sequence information, add a phase-randomized laser pulse to the encoded first pulse, and output a first encoded pulse. A second laser, coupled to the first laser, is configured to emit a second pulse and receive the first coded pulse to modulate the second pulse and generate the pump pulse.

3. The apparatus of claim 2, wherein the first laser is further configured to: The first pulse is phase-encoded by adjusting the driving voltage; By reducing the driving voltage below the avalanche threshold, a phase-randomized laser pulse can be added to the encoded first pulse.

4. The apparatus of claim 2 or 3, wherein the pump assembly further comprises: An attenuator, coupled to the first laser, is configured to receive the first coded pulse, attenuate its power, and then output it. A circulator having a first end, a second end, and a third end, wherein the first end is coupled to the attenuator, the second end is coupled to the second laser, and the circulator is configured as follows: The attenuated first coded pulse is injected into the second laser to form modulation, and the pump pulse is output. An erbium-doped fiber amplifier, coupled to the third terminal of the circulator, is configured to receive the pump pulse, amplify it, and then output it.

5. The apparatus according to any one of claims 1-3, further comprising: The beam splitter component is coupled to the waveguide component and configured as a photon partitioning channel in the photon pair of the time-entangled quantum state.

6. The apparatus of claim 5, further comprising: A receiving component, coupled to the beam splitting component, is configured to receive one photon from the photon pair of the time-entangled quantum state to obtain the original key.

7. The apparatus of claim 6, wherein the receiving component comprises: An interferometer, coupled to the beam-splitting component, is configured to receive the photons and perform phase measurements; A single-photon detector is positioned downstream of the interferometer's optical path and configured to receive the optical signal output by the interferometer and convert it into an electrical signal to output the original key.

8. The apparatus of claim 6 or 7, wherein The waveguide assembly includes a silicon waveguide chip configured to cause the pump pulse to undergo four-wave mixing. The beam splitting component includes a wavelength division multiplexer; The pumping component, the waveguide component, the beam splitter component, and the receiving component transmit optical signals via optical fiber.

9. The apparatus of any one of claims 1-3, wherein the pump pulse includes a laser pulse with a preset ratio of phase randomization, the preset ratio being set based on safety requirements.

10. The apparatus of any one of claims 1-3, wherein the first sequence information comprises a pseudo-random number sequence, the pseudo-random number sequence being generated based on a classical random seed, and the communicating parties periodically sharing the classical random seed.

11. A quantum key distribution system, comprising a first user terminal and a second user terminal for quantum secure communication, characterized in that, The quantum key distribution system also includes: A third-party terminal, wherein the third-party terminal is equipped with a quantum entanglement source distribution device as described in any one of claims 1-10; wherein The first user terminal is coupled to the third-party terminal and configured to receive one photon from a photon pair of time-entangled quantum states distributed by the quantum entanglement source distribution device; The second user terminal is coupled to the third-party terminal and configured to receive another photon from the photon pair of time-entangled quantum states distributed by the quantum entanglement source distribution device.

12. A method for distributing a quantum entangled source using the quantum entangled source distribution device as described in any one of claims 1-10, characterized in that, include: Pump pulses are generated by the pumping component. The pump pulses carry first sequence information through phase information, and phase-randomized laser pulses are added to the pump pulses carrying the first sequence information. The first sequence information is a control string. The waveguide component receives the pump pulses and generates photon pairs of time-entangled quantum states.

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