Secure classical optical communication using quantum technology

Abstract

Systems and methods for detecting attacks on optical communication channels are presented. Techniques can include transmitting, from a sender to a receiver and through an optical communication channel, an optical signal, where the optical signal includes a classical optical signal representing first information and a quantum optical signal representing second information. Techniques can include detecting, by the receiver, third information from at least a portion of the quantum optical signal, and transmitting, by the receiver to the sender, the third information. Techniques can include determining, by the sender, an indication of an attack on the optical communication channel based on the second information and at least a portion of the third information. Techniques can include triggering an alarm based on the determination.

Description

Technical Field

[0001] This disclosure relates to secure optical communications, for example, detecting attacks on optical communication channels (such as fiber optic lines). Background Technology

[0002] Optical communication uses light to transmit information, for example, through fiber optic lines. Security is becoming increasingly important for optical communication infrastructure. The prevalence of attacks necessitates continuous monitoring of fiber optic lines. However, classical optical communication physical layer security relies on active fiber optic monitoring techniques, typically based on network power monitoring and proactive diagnostics, such as measuring the average optical power of optical signals in the communication line. However, such classical methods have practical flaws and security vulnerabilities. For example, existing techniques cannot protect against intercept-retransmission attacks. As another example, sophisticated tapping attacks can reduce transmission by less than 1%, which may be undetectable by existing classical techniques.

[0003] Quantum optical communication technology has been used to detect information intruders where classical detection methods fail. However, such techniques are typically limited to distributing encryption keys within quantum optical signals. They cannot be used to detect attacks on classical optical communication channels that encode information within classical optical signals. Furthermore, quantum key distribution systems are expensive to implement and are "overkill" for most applications. Moreover, these techniques are largely limited to demonstrations in laboratory settings. Existing quantum optical communication technologies are generally impractical for real-world implementation. Summary of the Invention

[0004] This disclosure provides examples under the following terms.

[0005] Clause 1: A method for detecting an attack on an optical communication channel, the method comprising: transmitting an optical signal from a transmitter to a receiver and through the optical communication channel, wherein the optical signal includes a classical optical signal representing first information and a quantum optical signal representing second information; detecting third information from at least a portion of the quantum optical signal by the receiver; transmitting the third information from the receiver to the transmitter; determining, by the transmitter, an indication of an attack on the optical communication channel based on at least a portion of the second information and the third information; and triggering an alarm based on the determination.

[0006] Clause 2: The method described in Clause 1, wherein the indication of the attack includes at least one of transmission loss or increased noise.

[0007] Clause 3: The method according to any one of Clauses 1 or 2, wherein the indication of the attack includes a transmission loss of less than 1% of that of the unattacked transmission.

[0008] Clause 4: The method according to any one of Clauses 1-3, wherein the indication of the attack comprises a noise increase of at least 0.5 shot noise units.

[0009] Clause 5: The method according to any one of Clauses 1-4, wherein the transmission of the third information from the receiver to the sender includes transmitting classical optical signals through the optical communication channel.

[0010] Clause 6: The method according to any one of Clauses 1-5, wherein the classical optical signal is interleaved with the quantum optical signal.

[0011] Clause 7: The method according to any one of Clauses 1-6, wherein the attack includes at least one of eavesdropping attack, interference attack, related interference attack, or interrupt-retransmission attack.

[0012] Clause 8: The method according to any one of Clauses 1-7, wherein the optical communication channel comprises a distance of at least 50 km, and wherein the method has a sensitivity of less than or equal to 0.04 dB.

[0013] Clause 9: The method according to any one of Clauses 1-8, wherein the detection includes measurement using homodyne detection.

[0014] Clause 10: The method according to any one of Clauses 1-9, wherein the detection includes measurement using heterodyne detection.

[0015] Clause 11: A system for detecting attacks on an optical communication channel, the system comprising: a transmitter operable to transmit an optical signal to a receiver via the optical communication channel, the optical signal including a classical optical signal representing first information and a quantum optical signal representing second information; a receiver operable to detect third information from at least a portion of the quantum optical signal; wherein the receiver is operable to transmit the third information to the transmitter; and wherein the transmitter is operable to determine an indication of an attack on the optical communication channel based on at least a portion of the second information and the third information and to trigger an alarm indicating the attack.

[0016] Clause 12: The system pursuant to Clause 11, wherein the indication of the attack includes at least one of transmission loss or increased noise.

[0017] Clause 13: A system pursuant to any one of Clauses 11 or 12, wherein the indication of said attack includes a transmission loss of less than 1% of that of an unattacked transmission.

[0018] Clause 14: A system pursuant to any one of Clauses 11-13, wherein the indication of said attack comprises a noise increase of at least 0.5 shot noise units.

[0019] Clause 15: A system according to any one of Clauses 11-14, wherein the receiver is operable to transmit the third information as a classical optical signal to the sender via the optical communication channel.

[0020] Clause 16: A system according to any one of Clauses 11-15, wherein the classical optical signal is interleaved with the quantum optical signal.

[0021] Clause 17: A system pursuant to any one of Clauses 11-16, wherein the attack includes at least one of an eavesdropping attack, a jamming attack, a related jamming attack, or an interrupt-retransmission attack.

[0022] Clause 18: A system according to any one of Clauses 11-17, wherein the optical communication channel comprises a distance of at least 50 km, and wherein the transmitter is operable to determine an indication of an attack on the optical communication channel with a sensitivity of less than or equal to 0.04 dB.

[0023] Clause 19: A system according to any one of Clauses 11-18, wherein the receiver is operable to use zero-difference detection to detect third information from at least a portion of the quantum optical signal.

[0024] Clause 20: A system according to any one of Clauses 11-19, wherein the receiver is operable to use heterodyne detection to detect third information from at least a portion of the quantum optical signal. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate the teachings and, together with the description, serve to explain the principles of this disclosure.

[0026] Figure 1 This is a high-level schematic diagram of a system for detecting attacks on optical communication channels, using both quantum optics and classical optics fabrication in parallel, based on various examples.

[0027] Figure 2 This is a schematic diagram of quantum optical modulation techniques based on various examples;

[0028] Figure 3This is a high-level schematic diagram of a system for detecting attacks on optical communication channels, based on various examples of sequential use of quantum optics and classical optics fabrication.

[0029] Figure 4 A diagram depicts the superposition of quantum and classical optical signals according to various examples;

[0030] Figure 5 It is a diagram representing the superposition of quantum and classical optical signals according to various examples;

[0031] Figure 6 It is a schematic diagram illustrating systems for carrying out quantum interrupt-replay attacks based on various examples;

[0032] Figure 7 This is a schematic diagram of a system that uses multiple pairs of photodetectors to detect attacks on optical communication channels;

[0033] Figure 8 This is a schematic diagram of a system that uses a single pair of photodetectors to detect attacks on optical communication channels;

[0034] Figure 9 It is a simulated histogram depicting the correlation loss of techniques for detecting indications of attacks on optical communication channels, based on various examples, by a system using a single pair of photodetectors;

[0035] Figure 10 This is a schematic diagram of a first experimental system for detecting attacks on optical communication channels, based on various examples;

[0036] Figure 11 This is a schematic diagram of a second experimental system for detecting attacks on optical communication channels, based on various examples;

[0037] Figure 12 This is a schematic diagram of a third experimental system for detecting attacks on optical communication channels, based on various examples.

[0038] Figure 13 This is a schematic diagram of a fourth experimental system for detecting attacks on optical communication channels, based on various examples.

[0039] Figure 14 It is a description based on the fact that Figure 10 A graph showing the detected transmission loss caused by an eavesdropping attack on an example system;

[0040] Figure 15 It is a description based on the fact that Figure 10 A graph showing the detected transmission loss caused by related interference attacks on an example system;

[0041] Figure 16It is a description based on the fact that Figure 10 The graph shows the transmission loss detected due to related interference attacks on the system.

[0042] Figure 17 It is a description based on the fact that Figure 10 A graph showing the excessive noise detected caused by related interference attacks on the system;

[0043] Figure 18 These are schematic diagrams of multi-node systems for detecting attacks on optical communication channels, based on various examples; and

[0044] Figure 19 This is a flowchart illustrating methods for detecting attacks on optical communication channels based on various examples.

[0045] It should be noted that some details in the accompanying drawings have been simplified and drawn to facilitate understanding of the teachings, rather than to maintain strict structural accuracy, detail, and proportion. Detailed Implementation

[0046] Reference will now be made in detail to the disclosed examples shown in the accompanying drawings. Where possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts. In the following description, reference is made to the drawings, which form a part thereof, and specific examples are shown by way of example in the drawings. These examples are described in sufficient detail to enable those skilled in the art to practice them, and it should be understood that other examples may be utilized and changes may be made without departing from the scope of this disclosure. Therefore, the following description is merely exemplary.

[0047] I. introduction

[0048] Some examples demonstrate the use of quantum optics techniques to detect attacks on classical optical communication channels, such as in fiber optic communication networks. According to some examples, quantum techniques are used to monitor information flow and detect the presence of attackers on classical optical communication channels, such as internet communication lines.

[0049] Some examples can be implemented using existing communication hardware (e.g., existing fiber optic lines). Because some examples do not employ quantum communication to encrypt or transmit information intended to be sent over a communication channel, such examples are easy and inexpensive to implement, especially compared to quantum optical encryption techniques.

[0050] Some examples utilize quantum optical signals transmitted over the same communication channel as classical optical signals to detect attacks. Depending on the example, quantum optical signals can be interleaved, overlapped, appear simultaneously, or alternate with classical optical signals. Quantum and classical optical signals can take any of various forms and can be modulated using any of the classical and quantum optical modulation techniques. For example, quantum optical signals can be modulated using techniques different from those used to modulate classical optical communication signals.

[0051] Some examples demonstrate the detection of attacks on classical optical communication channels by detecting the correlation loss of quantum optical signals transmitted in the same channel. Correlation loss can take any of a variety of forms. For example, correlation loss can be in the form of excessive noise in the received quantum optical signal. Correlation loss can be in the form of bit loss in the received quantum optical signal. Correlation loss can be in the form of transmission loss in the received quantum optical signal. Correlation loss can be in the form of excessive average difference between modulation state values ​​in the received quantum optical signal. Correlation loss can be in any combination of the above forms. According to various examples, these and other forms of correlation loss can indicate an attack on a classical optical communication signal present in the same communication channel as the quantum optical signal against which its correlation loss is detected.

[0052] Some examples demonstrate the ability to detect various attacks on classic optical communication channels, such as, as non-limiting examples, eavesdropping attacks, jamming attacks, related jamming attacks, and interrupt-retransmission attacks. Brief descriptions of the example attacks are presented directly below.

[0053] An eavesdropping attack occurs when an attacker intercepts a small amount of signal transmitted over a communication channel (e.g., in a fiber optic communication channel). Typically, the amount of signal intercepted is very small. For example, in a fiber optic eavesdropping attack, the intercepted signal may account for less than 1% of the signal power. The attacker can analyze the intercepted signal without the knowledge of the sender or receiver to determine the data being transmitted over the communication channel.

[0054] An interference attack occurs when an attacker introduces a signal into a communication channel (e.g., a fiber optic communication channel). For example, the introduced signal can take the form of optical noise. The introduced signal can degrade the quality of service or completely block communication. For instance, the introduction of noise can reduce or completely block data transmitted in the communication channel. The introduced signal can be in-band or out-of-band relative to the signal intended to be transmitted in the communication channel.

[0055] Correlated interference attacks occur when an attacker intercepts a small amount of signal in a communication channel, such as a fiber optic communication channel (e.g., in an eavesdropping attack), but also introduces different signals into the communication channel. In interference attacks, the introduced signal can take the form of optical noise and can degrade or completely eliminate communication. In correlated interference attacks, the overall amplitude of the signal in the communication channel can remain constant. Therefore, simple detection of signal amplitude may not provide an indication of the presence of an attack in correlated interference attacks. Furthermore, correlated interference attacks in classic fiber optic communication channels can appear as if the communication channel is merely excessively noisy, potentially hindering the detection of the attack.

[0056] A break-and-retransmit attack occurs when an attacker intercepts a portion of a signal being transmitted through a communication channel (such as a fiber optic communication channel) and then retransmits some or all of the original signal back into the communication channel. Therefore, a break-and-retransmit attack combines eavesdropping with retransmission, making the signal in the communication channel appear unchanged. In optical communication channels, the overall amplitude of the signal and the information within it can remain completely unchanged through a break-and-retransmit attack. In classic fiber optic communication channels, break-and-retransmit attacks may be virtually undetectable.

[0057] II. Overview

[0058] This section provides a high-level description of the examples, especially the references. Figure 1 and Figure 3 The supplementary sections of this document disclose implementation details of the examples disclosed in this section. For example, this section discloses quantum fabricators, classical fabricators, quantum detectors, classical detectors, and multiplexers, which can be implemented as disclosed in this section and described in detail in subsequent sections.

[0059] Figure 1 This is a high-level schematic diagram of a system 100 for detecting attacks on an optical communication channel 160, based on various examples of parallel use of quantum optics and classical optics fabrication. (See diagram for details.) Figure 1 As shown, sender 150 transmits communication to receiver 152 via communication channel 160, and this communication can be compromised by an attacker. A corresponding system may be included, and this system is used to send messages from receiver 152 to sender 150 via communication channel 160 or via different communication channels. During the process of sending secure communication from sender 150 to receiver 152, multiple messages in various directions on the communication channels may be included.

[0060] like Figure 1As shown, transmitter 150 includes laser 102, which may be a continuous-wave laser. The output of laser 102 is split and directed to a quantum fabricator 104 and a classical fabricator 106 arranged in parallel. Information transmitted from transmitter 150 to receiver 152 is embodied in a classical optical signal via classical fabricator 106. For example, the classical optical signal may be a telecommunication signal, such as an internet signal. Classical fabricator 106 includes a classical optical modulator. Classical fabricator 106 may use any of a variety of modulation schemes. For example, classical fabricator 106 may include any known classical optical communication modulation technique, such as any technique used in existing optical telecommunication channels, such as for internet communication. Example modulation techniques used by classical fabricator 106 may include any of the following: phase-shift keying (PSK), amplitude-shift keying (ASK), asymmetric phase-shift keying (APSK), continuous phase modulation (CPM), frequency-shift keying (FSK), pulse position modulation (PPM), quadrature amplitude modulation (QAM), or wavelet modulation (WDM). The classical preparer 106 may also include encoding, error correction, and any other classical optical signal preparation techniques.

[0061] Quantum fabricator 104 provides a quantum optical signal for detecting whether an attack has occurred on communication channel 160. For example, the information represented by the quantum optical signal can be random or pseudo-random. Quantum fabricator 104 may include a quantum modulator implementing any of various quantum optical modulation techniques. References herein Figure 2 Example suitable quantum optical modulation techniques are shown and described. Quantum preparer 104 may include randomly selected bases for encoding each outgoing quantum optical signal information unit and / or randomly selected orthogonal bases according to their modulation information. In the example of randomly selecting such bases and / or orthogonality, classical preparer 106 may include adding representations of the randomly selected bases and / or orthogonality to the classical optical signal, as further described below with reference to classical preparer 106. Quantum preparer 104 may also include encoding, error correction, and any other quantum optical signal preparation techniques.

[0062] The classical preparer 106 may also include adding information about the transmitted quantum optical signal to the classical optical signal. This added information is used to determine whether there is a correlation loss between the quantum optical signal transmitted by sender 150 and the quantum optical signal received by receiver 152. Such a correlation loss can indicate an attack. Typically, the information in the received quantum optical signal is compared with the information in the transmitted quantum optical signal to determine such a correlation loss. The information in the received quantum optical signal can be determined based on information indicating how to detect and decode it, for example, based on an orthogonal identifier encoding the information in the received quantum optical signal. Therefore, the information about the transmitted quantum optical signal can include at least some of the information carried in the quantum optical signal prepared by quantum preparer 104, and information used to obtain the information in the received quantum optical signal. The information used to obtain the information in the received quantum optical signal can include an indication of the basis for generating the quantum optical signal, and / or an orthogonal identifier for modulating the information in the quantum optical signal. The information about the transmitted quantum optical signal may be delayed relative to the information in the quantum optical signal.

[0063] The outputs of quantum preparer 104 and classical preparer 106 are directed to the input of multiplexer 108. Multiplexer 108 combines the classical optical signal provided by classical preparer 106 and the quantum optical signal provided by quantum preparer 104 into a single combined optical signal. According to some examples, the classical optical signal and the quantum optical signal are interleaved (e.g., do not overlap). For example, the quantum optical signal and the classical optical signal can be given corresponding time slots, which can be regular intervals, random intervals, or pseudo-random intervals. Figure 1 A schematic depiction of combined classical and quantum optical signals is shown, where classical optical signal 118 and quantum optical signal 122 are interleaved, with header information 120 between them. In some examples, header information 120 may be omitted. According to some examples, multiplexer 108 may be a time-division multiplexer. The output of multiplexer 108 is transmitted to communication channel 160.

[0064] like Figure 1 As shown, the combined classical optical signal and quantum optical signal are transmitted from sender 150 to receiver 152 via communication channel 160. Communication channel 160 can be implemented as an optical fiber-based communication channel. Communication channel 160 can, for example, be part of a remote communication network (e.g., an Internet communication line). Communication channel 160 can include pre-existing hardware to which a quantum preparer 104, a multiplexer 108, a quantum detector 110, and a post-processing unit 114 are subsequently added. For example, such pre-existing hardware can include a classical preparer 106, a classical detector 112, and the optical fiber line between them.

[0065] Receiver 152 receives and separates the combined classical and quantum optical signals from communication channel 160 to detect them separately. Each of the classical detector 312 and quantum detector 310 can be executed for a corresponding portion of the combined optical signal. For example, the receiver can utilize a demultiplexer or can time which of the quantum detector 310 or classical detector 312 is active for each corresponding time slot. Along the classical optical signal path, classical detector 112 can include any detection technique suitable for the classical optical signal portion. For example, classical detector 112 can include demodulation. Classical detector 112 can also include decoding and error correction. Classical detector 112 provides a signal representing classical data 116, which can be in the form of an electrical signal, such as a binary signal encoded from communication sent from sender 150 to receiver 152. At least a portion of the retrieved classical data 116 is passed to post-processing 114. For example, information about the transmitted quantum optical signal (e.g., the information carried in the quantum optical signal, possibly along with information used by the receiver to obtain the quantum optical signal) can be transmitted to post-processing 114. Alternatively, for example, classical data 116 can be transmitted to another communication channel or sent to its final destination.

[0066] Along the quantum optical signal path, quantum detector 110 may include signal attenuation, followed by demodulation of the quantum optical signal portion. Quantum detector 110 may include randomly selected bases and / or orthogonality used to detect each incoming quantum optical signal increment. Quantum detector 110 may also include the use of fixed bases and / or fixed orthogonality used to detect the incoming quantum optical signal. Quantum detector 110 provides the retrieved information encoded in the quantum optical signal to post-processing 114.

[0067] Post-processing 114 uses information from both the quantum optical signal and the classical optical signal to detect a loss of correlation between the transmitted and received quantum optical signals in order to detect whether an attack has occurred. Post-processing 114 can be executed by an electronic processor configured to perform the post-processing techniques disclosed herein. For example, post-processing 114 can compare a portion of the information transmitted in the quantum optical signal with a portion of the information carried in the classical optical signal representing the information transmitted in the quantum optical signal. Post-processing 114 can use the basis and / or orthogonality identifiers included in the classical optical signal to select the portion to be compared. For example, post-processing can select a portion of the information in the received quantum optical signal detected by receiver 152 using the correct basis and / or orthogonality for comparison.

[0068] Correlation loss (e.g., above or below a predetermined threshold) can indicate that an attack has occurred on communication channel 160. The threshold can be set by the user and based on the maximum amount of information allowed to be leaked before triggering an alarm, the system's sensitivity (e.g., how quickly it can detect an attack), and its tolerance for false positives. Furthermore, the threshold can be set after a calibration phase, during which the corresponding form of correlation loss is measured in the absence of an attack. For example, for a 10dB communication channel, a possible threshold for detecting an eavesdropping attack is 10% transmission, where an attack is indicated if transmission drops below the threshold. Considering practical implementation factors such as temperature and weather, false alarms (e.g., in eavesdropping or interrupt-repeat attacks) can be reduced by forcing the attacker to acquire a larger amount of information. This can be achieved, for example, by adding additional noise to the classical optical signal or using classical encryption techniques on the classical optical signal.

[0069] Correlation loss can be detected in various forms. For example, correlation loss can take the form of transmission loss, indicating, for instance, the absence of a portion of the quantum optical signal. As another example, correlation loss can take the form of bit loss, indicating, for instance, that a portion of the quantum optical signal received by receiver 152 differs from the quantum optical signal initially transmitted by transmitter 150. As another example, correlation loss can take the form of excess noise in the quantum optical signal. As another example, correlation loss can take the form of fluctuations (e.g., standard deviation or variance) of any of the above forms, such as fluctuations in transmission loss, fluctuations in bit loss, or fluctuations in excess noise. As another example, correlation loss can take the form of excessive average difference between modulation state values ​​in the received quantum optical signal, referencing... Figure 9 Further discussion. Based on sufficient correlation loss, System 100 can detect any of a variety of attacks, including eavesdropping attacks, jamming attacks, correlated jamming attacks, and interrupt-retransmission attacks.

[0070] like Figure 1As shown, post-processing 114 is performed by receiver 152. However, in other examples, post-processing may be performed by sender 150. In such examples, receiver 152 may transmit to sender 150 the information detected by receiver 152 in the quantum optical signal, along with the basis and / or orthogonality identifiers used by receiver 152 to detect the information in the quantum optical signal. Sender 150 may detect correlation loss based on a comparison of the information detected by receiver 152 in the quantum optical signal on one hand with the information initially transmitted by sender 150 in the quantum optical signal on the other hand. Sender 150 may perform such comparisons for receiver 152 for the portion of the information used to detect the quantum optical signal with the correct basis and / or orthogonality. According to the example in which sender 150 performs post-processing, sender 150 may omit the representation of the information in the quantum optical signal from classical preparer 106. The determination of correlation loss, and whether it indicates an attack, may otherwise be as described above with reference to post-processing 114 performed by receiver.

[0071] System 100 can take various actions in response to the detection of an attack. According to some examples, system 100 provides alerts, for example, in the form of messages displayed on a computer monitor, sent in emails, or sent in text messages. According to some examples, system 100 can reroute communication by bypassing different parts of the network through communication channel 160 in response to the detection of an attack.

[0072] Figure 2 This is a schematic diagram of a quantum optical modulation technique 200 based on various examples. The quantum optical signal generated by the transmitter can have various positions on a P / X orthogonal plane (where P and X represent the orthogonality of coherent states), where these positions indicate information. For example... Figure 2 As shown, there are four possible positions: 202, 204, 206, and 208 (other suitable modulation examples may have more or fewer positions, such as 2, 8, 16, 32, etc.). In operation, the sender generates 2N random numbers X. i＝1,…,N P i＝1,…,N X i＝1,…,N and P i＝1,…,N Each N random number in the data is based on a variance V. A The coherent state is prepared using a central normal Gaussian distribution. The transmitter uses one or more modulators to prepare the coherent state |X+iP>, where the coordinates of orthogonal X and P in phase space are (X+iP>). i ,P i ) i＝1,…,N .exist Figure 2 In the diagram, each circle at positions 202, 204, 206, and 208 represents a vacuum fluctuation or shot noise with a variance of N0.

[0073] Figure 1The orthogonal X and P in the diagram can be implemented with various optical properties. According to some examples, orthogonal X and P can be implemented as amplitude and phase. According to some examples, orthogonal X and P can be implemented as wavelength and phase. According to some examples, orthogonal X and P can be implemented as wavelength and amplitude. According to some examples, orthogonal X and P can be implemented as polarization and amplitude. According to some examples, orthogonal X and P can be implemented as polarization and phase. According to some examples, orthogonal X and P can be implemented as polarization and wavelength. As non-limiting examples, unless otherwise stated, this disclosure presents examples with respect to amplitude and phase; however, any orthogonality described herein can be used by making appropriate modifications or substitutions to the disclosed hardware elements.

[0074] The receiver can use one or more pairs of photodetectors to capture the X portion and / or P portion of orthogonal signals. An example could be using one pair of photodetectors for one orthogonal signal, or two pairs of photodetectors for simultaneously measuring two orthogonal signals. An example could also use two additional pairs of photodetectors for polarization diversity.

[0075] Attacks are detected by post-processing the quantum states measured by the receiver. This can be performed by comparing the information transmitted by the sender with the information received by the receiver to determine the correlation loss, for example, indicated by the presence of transmission loss, bit loss, and / or excessive noise in the quantum optical signal. The comparison can be limited to the portion of the information correctly detected by the receiver, for example, using the same basis and / or orthogonality as used by the sender in transmitting the information. The comparison can be performed at the sender's location or the receiver's location.

[0076] Figure 3 This is a high-level schematic diagram of a system 300 for detecting attacks on an optical communication channel 360, fabricated using both quantum optics and classical optics in sequence, based on various examples. (See diagram for details.) Figure 3 As shown, sender 350 sends communication to receiver 352 via communication channel 360, and this communication can be attacked. A corresponding system may be included, and this system is used to send messages from receiver 352 to sender 350 via communication channel 360 or via a different communication channel.

[0077] The transmitter 350 includes a laser 302, which may be a continuous-wave laser. The output of the laser 102 is directed to a quantum fabricator 304 and a classical fabricator 306 arranged in series. Figure 2 The classical preparer 306 is depicted following the quantum preparer; however, according to some examples, this order can be reversed, with the quantum preparer 304 following the classical preparer 306.

[0078] The information transmitted from sender 350 to receiver 352 is embodied in a classical optical signal via classical preparer 306, for example, according to amplitude shift keying (ASK) modulation. The classical optical signal can be a long-distance communication signal, such as an internet signal. Classical preparer 306 can use any of a variety of modulation schemes, for example, as referenced above. Figure 1 As described, the classical preparer 306 may also include encoding, error correction, and any other classical optical signal preparation techniques. The classical preparer 306 may also include adding information about the transmitted quantum optical signal, used to determine whether there is a correlation loss indicating an attack, as referenced above. Figure 1 As stated above.

[0079] The quantum fabricator 304 provides a quantum optical signal for detecting whether an attack has occurred on the communication channel 360. The information represented by the quantum optical signal can be random or pseudo-random. The quantum fabricator 304 may include, as referenced above. Figure 1 The quantum fabricator 304 may include any of the techniques shown and described herein. The quantum fabricator 304 may comprise any of a variety of quantum optical modulation techniques. References herein are... Figure 2 Examples of suitable quantum optical modulation techniques are shown and described.

[0080] After processing by both quantum fabricator 304 and classical fabricator 306, the resulting laser beam comprises both a classical optical signal provided by classical fabricator 106 and a quantum optical signal provided by quantum fabricator 104. According to some examples, the classical optical signal and the quantum optical signal occur simultaneously (e.g., overlap). According to some examples, the quantum optical signal and the classical optical signal completely overlap, for example, permanently or within a time interval. Further description of such complete overlap is referenced below. Figure 4 Given. According to some examples, quantum optical signals overlap with classical optical signals (e.g., only when the classical optical signal is at its lowest power state, i.e., amplitude). Further description of such partial overlap is referenced below. Figure 5 Given. According to some examples, such as when the classical optical signal uses amplitude modulation, the quantum optical signal overlaps with the classical optical signal at the zero-value position represented by the classical optical signal.

[0081] The combined classical and quantum optical signals are transmitted from sender 350 to receiver 352 via communication channel 360. Communication channel 360 can be referenced as described above. Figure 1 Implement as shown and described. Figure 3 The combined classical and quantum optical signals in the optical communication channel 360 are schematically depicted, wherein the combined optical signal 324 includes classical and quantum optical signals that coextensively expand within a time interval. Figure 3 A block depicting such a combined optical signal 324 is shown, with header information 320 interspersed within it. In some examples, header information 320 may be omitted.

[0082] Receiver 352 is similar to Figure 1 The receiver 352 differs from receiver 152 in that, relative to receiver 152, receiver 352 may have an adjusted threshold for determining whether the detected correlation loss indicates an attack, and receiver 352 may use different techniques to determine when either quantum detector 310 or classical detector 312 should be used to process the combined optical signal. For example, because the combined optical signal of system 300 may simultaneously include information from both the quantum optical signal portion and the classical optical signal portion, the activity of quantum detector 310 may overlap with the activity of classical detector 312. Therefore, receiver 352 receives the combined classical and quantum optical signals from communication channel 360 and separates them to detect the classical and quantum optical signals separately. Along the classical optical signal path, classical detector 312 may include any detection technique suitable for the classical optical signal portion, as referenced above. Figure 1 The classic detector 112 is shown and described.

[0083] Along the quantum optical signal path, the quantum detector 310 may include attenuation, followed by demodulation of the quantum optical signal portion. The quantum detector 310 may also include other features as described above. Figure 1 The quantum detector 110 is shown and described.

[0084] Post-processing 314 can be as shown and described above with reference to post-processing 114 of system 100. For example, in order to detect an attack, post-processing 314 of system 300 can be performed by receiver 352 or sender 350, for example, as described above with reference to post-processing 114 of system 100. System 300 can take various actions in response to the detection of an attack, for example, as described above with reference to... Figure 1 The system 100 described.

[0085] System 300 can detect any of various attacks, including eavesdropping attacks, jamming attacks, related jamming attacks, and interrupt-retransmission attacks. See below for reference. Figure 6 A detailed description of using System 300 to detect interrupt-retransmission attacks is provided.

[0086] Figure 4 Graphs depicting the superposition of quantum and classical optical signals according to various examples are presented. Figure 4As shown, the quantum optical signal completely overlaps with the described classical optical signal. The combined optical signal has a classical optical signal data rate of 5 Gb / s above the quantum optical signal with a pulse width of 10 ns. The repetition frequency is 25 MHz. Figures 402, 404, and 406 illustrate the combined optical signal and its ability to be functionally separated while still being able to apply the techniques disclosed herein to detect attacks. According to a specific example, Figure 402 shows the quantum and classical combined voltage signal over time before the variable optical attenuator 1062, Figure 404 shows the quantum and classical combined signal over time after the variable optical attenuator 1062, and Figure 406 shows the quantum and classical combined voltage signal at the quantum detector 1040.

[0087] Figure 5 This is a graph representing the superposition of quantum and classical optical signals 500 according to various examples. See the reference above. Figure 3 As described in system 300, some examples allow for the superposition of quantum optical signals onto classical optical signals at the portion of the classical optical signal having a minimum power level (e.g., amplitude). According to some examples, and by way of non-limiting example, such a minimum amplitude portion of the classical optical signal may correspond to a bit having a zero value. Optical signal 500 depicts a classical high-power signal 502 and classical low-power signals 504, 506. For example, according to... Figure 3 In the example of system 300, the quantum optical signal can be superimposed on the classical low-power signals 504, 506. Embodiments that superimpose the quantum optical signal onto the portion of the classical optical signal with the lowest power level can avoid the potential difficulty in detecting the quantum signal when the classical signal is relatively large.

[0088] The systems disclosed in this article (including) Figure 1 System 100 and Figure 3 System 300 can be used to detect various attacks, including interrupt-retransmission attacks. Interruption-retransmission attacks can include classical interrupt-retransmission attacks that only interrupt and retransmit classical optical signals, and quantum interrupt-retransmission attacks that interrupt and retransmit both classical and quantum optical signals. The system disclosed herein can detect classical intercept-retransmission attacks by detecting correlation loss in the form of a drop in quantum transmission to zero and / or a sharp increase in excessive noise in the quantum optical signal, where the attacker only retransmits the classical optical signal. The system disclosed herein can also detect quantum intercept-retransmission attacks, where the attacker attempts to retransmit both the quantum and classical optical signals. References are provided below. Figure 6 Presentation Figure 3 A description of how System 300 detects quantum interruption-retransmission attacks.

[0089] Figure 6This is a schematic diagram illustrating a system 600 for conducting a quantum interrupt-retransmission attack, according to various examples. An attacker 602 eavesdrops on an optical communication line to obtain a portion of a signal 604. With respect to classical optical signals, the attacker 602 can use known techniques (not shown) that typically successfully evade detection to measure and retransmit the classical optical signal. However, with respect to quantum optical signals, the attacker 602 can attempt to detect the quantum optical signal using a measuring device 608 and retransmit a copy 606 of the attempt to retransmit the quantum optical signal using a retransmission device 610. The attacker 602 redirects the attempted copy 606 back onto the same optical communication line, in the same direction it was originally transmitted in. However, due to the properties of quantum mechanics, the attacker 602 cannot perfectly replicate the sender's state, and the receiver will detect the increase of two shot noise units through its quantum excess noise monitoring, as described in detail hereafter.

[0090] As a non-restrictive example, an attacker attempts to... Figure 3 The system 300's communication channel 360 was used to launch a quantum interrupt-retransmission attack, in which the sender used Figure 2 Quantum optical modulation technology 200. Information in quantum optical signals is modulated with orthogonal information (X, P) and transmitted by the sender, where (X... A ,P A ) Follows the variance V A The Gaussian distribution of the shot noise is denoted as N0. Encoding information into coherent states results in:

[0091] (1) X = X A +X0

[0092] (2) P = P A +P0

[0093] In equations (1) and (2), X0 and P0 represent noise caused by vacuum fluctuations. The intermediate attacker 602 cuts off the quantum channel and intercepts all pulses transmitted from the sender. The attacker 602's actions consist of two steps: orthogonal measurement via measurement device 608 and orthogonal re-creation via retransmission device 610. To measure X... A and P A Orthogonal to both, attacker 602 uses two pairs of light detectors (e.g., as referenced herein). Figure 7 (As shown and described), it can generate the following results:

[0094] (3)

[0095] (4)

[0096] In equations (3) and (4), X0' and P0' are noise terms caused by the 50:50 beam splitter preceding the measuring device 608. This represents random noise caused by the transmitter's modulation and measurement noise caused by the attacker caused by the measuring device 608.

[0097] The retransmission device 610 then transmits the signal based on the measurement result (X) from the measuring device 608. M ,P M ) will (X E ,P E The quantum state is retransmitted by encoding it into a new coherent state. The retransmission device 610 can also retransmit the retransmitted data X. M This leads to amplification (G). The results of X-orthogonality are described below; the analysis is the same for P-orthogonality. Therefore, the X-orthogonality of the coherent state retransmitted by the retransmission device 610 can be expressed as:

[0098] (5)

[0099] In equation (5), X”0 is a noise term added by the repeater 610 due to modulation. It should be noted that X0, X'0, and X”0 all follow a shot noise distribution, for example, N ~ (0, N0).

[0100] On the receiver side, the receiver uses two pairs of photodetectors to perform detection on the coherent state retransmitted by the attacker 602. The measured orthogonal X... B It can be written as:

[0101] (6)

[0102] After transmission through the lossy channel 360, the received state will have three noise items, such as noise added by the attacker (602). Vacuum noise caused by the channel and the receiver's detection noise X ele Added to the status retransmitted by the attacker with a 602 error. Here Where T is the channel loss between the attacker (602) and the receiver, and η is the detector efficiency of the receiver. The correlation between the sender and receiver using a Gaussian linear model can be described as:

[0103] (7)

[0104] (8)

[0105] In equations (7) and (8), the channel transmission estimate is To compensate for the loss from the receiver detection using two pairs of photodetectors, the amplification factor can be selected as follows: This allows the overall loss to be maintained. The excess noise estimate on the transmitter side can be written as... Therefore, even if ξ sys =0, for example, even if attacker 602 has a perfect system 600 that does not introduce noise, after an intercept-retransmission attack, at least two shot noise units will be added to the signal received by the receiver. Therefore, the additional noise will be easily detected in the post-processing step. In other words, it is impossible to retransmit a perfect copy of the sender's quantum state.

[0106] III. Example hardware

[0107] This chapter describes in detail various hardware systems, including specific systems used for sending and receiving information and for detecting attacks on optical communication channels. Figure 1 System 100 and Figure 3 System 300 can be implemented using the hardware and techniques described in this section. Some examples shown and described in this section depict how the quantum fabricator 104 and quantum detector 110 of system 100, and the quantum fabricator 304 and quantum detector 310 of system 300, can be implemented. Therefore, the examples shown and described in this section can be compared with those in reference to... Figure 1 and Figure 3 The examples shown and described are in combination with existing or known embodiments of the classical preparer 106, multiplexer 108, classical detector 112, classical preparer 306, and classical detector 312. The examples in this section can be disclosed as detecting attacks on communications sent from a sender to a receiver; however, it should be understood that the examples may include corresponding systems for detecting attacks on communications sent from a receiver to a sender on the same or different communication channels.

[0108] Figure 7 This is a schematic diagram of a system 700 that uses multiple pairs of photodetectors to detect attacks on optical communication channels. System 700 can be used in conjunction with a reference... Figure 1 System 100 or Figure 3 The system 300 shown and described is combined with the classical optical communication system to detect attacks on classical optical communication channels. In system 700, as referenced above... Figure 2 Quantum optical signals are prepared as shown and described. System 700 can be used to transmit information from sender 712 to receiver 734 while detecting attacks on communication channel 716, which may include attacker 718. A corresponding system can be used to detect attacks on information transmitted from receiver 734 to sender 712 in the same or different communication channels.

[0109] The transmitter 712 includes a 1550nm pulsed laser 702, which generates a laser beam that is guided to a beam splitter 704, such as a 50:50 half-silvered mirror beam splitter. One path leaving the beam splitter 704 is guided to an amplitude modulator 706 and a phase modulator 708 channel, as well as a Faraday mirror 710, which protects against back-propagating light and forms a polarization-maintaining delay line. This path carries a quantum optical signal. Another path leaving the beam splitter 704 carries a local oscillator signal. One of the paths (i.e., the quantum beam or the local oscillator beam) can be polarized 90° relative to the other path. A polarization beam splitter 714 recombines the quantum optical signal with the local oscillator, and the combined beam propagates through a communication channel 716. Note that the communication channel 716 contains both the quantum optical signal and the local oscillator (LO), each polarized 90° relative to each other to allow for later separation, for example, via a polarization beam splitter. The local oscillator beam allows receiver 734 to efficiently and more accurately detect information in the quantum optical signal. According to some examples, the local oscillator beam is not combined with the quantum optical signal beam; instead, according to such examples, the local oscillator beam is transmitted in a separate optical communication channel, such as on a separate optical fiber. According to some examples, the local oscillator beam is not generated by transmitter 712. According to such examples, receiver 734 can generate the local oscillator beam, for example, using a laser included in the system of receiver 734.

[0110] Receiver 734 receives the combined beam, which is passed to polarization controller 748 and then to polarization beamsplitter 720. Polarization beamsplitter 720 generates a quantum optical signal path (solid line) and a local oscillator path (dashed line). The quantum optical signal path from polarization beamsplitter 720 is passed to Faraday mirror 722 and then to beamsplitter 738, which provides a portion (e.g., 50% each) of the quantum optical signal path to beamsplitter 724 and phase shifter 740. The Faraday mirror protects against backpropagating light and forms a portion of the polarization-maintaining delay line. From phase shifter 740, the beam is directed to beamsplitter 742. The local oscillator path from polarization beamsplitter 720 is passed to beamsplitter 736, which provides a portion (e.g., 50% each) of the local oscillator path to beamsplitter 724 and beamsplitter 742. (Alternatively, according to some examples, receiver 734 generates a local oscillator beam locally.) The output from beamsplitter 724 is coupled to photodetector pairs 726 and 730. The output from beamsplitter 742 is coupled to photodetector pairs 744 and 746. According to some examples, receiver 734 can utilize heterodyne detection techniques that measure multiple orthogonal components. Photodetector pairs 726, 730 and 744, 746 detect information modulated to be orthogonal in their respective aspects (e.g., amplitude X and phase P). Specifically, the electrical outputs of photodetector pairs 726, 730 are directed to comparator 728, which provides an electrical signal representing orthogonality in X, and the electrical outputs of photodetector pairs 744, 746 are directed to comparator 732, which provides an electrical signal representing orthogonality in P. Each photodetector pair 726, 730 and 744, 746 can detect information in its respective orthogonality by detecting the consistency and difference between the quantum optical signal and the local oscillator. Random phase changes caused by propagation, for example, in a communication channel, can be canceled out by using multiple photodetectors.

[0111] Information detected in orthogonality can be represented by one or more electrical signals. These signals are used for post-processing to detect attacks. For example, information from the quantum optical signal, along with information about the transmitted quantum optical signal, can be sent to an electronic processor to determine the correlation loss, as referenced above. Figure 1 and Figure 3 The electronic processor can be configured to perform post-processing, for example, as described above. Figure 1 The post-processing 114 shown and described, and / or as referenced above Figure 3 Post-processing 314 is shown and described. Additional techniques for post-processing are now described.

[0112] Ideally, the sender and receiver communicate through a lossless and noise-free channel, so that any increase in excessive noise or loss is due to eavesdropping. However, in practice, the instantaneous fluctuations and long-term drift of loss and excessive channel noise should be considered to avoid false alarms. Statistical techniques such as change point detection, Bayesian change point detection, supervised learning, or Cumulative Summation (CUSUM) can be used to distinguish false alarms from actual eavesdropping events. An example CUSUM algorithm is given in Table 1 below. The algorithm is able to identify small changes in large datasets. The algorithm can be tuned by setting shorter block lengths for faster response times but with greater estimation uncertainty, or by setting longer block lengths for less estimation uncertainty but with longer response times.

[0113] Algorithm 1: CUSUM Algorithm for Security Monitoring

[0114]

[0115]

[0116] Table 1

[0117] Figure 8 This is a schematic diagram of a system 800 that uses a single pair of photodetectors to detect attacks on optical communication channels. For some applications, the cheaper hardware using a pair of photodetectors is an acceptable trade-off for lower bit rates. System 800 can be compared with reference... Figure 1 System 100 or Figure 3 System 300, shown and described, is combined with the classical optical communication system to detect attacks on classical optical communication channels. System 800 may include a sender (as a non-limiting example, sender 712, as referenced) Figure 7 (System 700 is shown and described). System 800 can be combined with classical optical fabrication, for example, as referenced herein. Figure 1 and Figure 3 The system shown and described is used to send information from sender 712 to receiver 801 when an attack on the communication channel is detected. The corresponding system can be used to detect attacks on communications sent from receiver 801 to sender 712 in the same or different communication channels.

[0118] In System 800, the quantum optical signal can be prepared by the sender, as referenced above. Figure 2 As shown and described, for example, amplitude modulation can be used to prepare the signal, or it can be prepared in a different manner. As a non-limiting example, the transmitter 712 of system 800 can transmit information represented by two states, alpha (α) and beta (β). For the use of reference... Figure 2Some examples of modulation shown and described, these states can be represented in any orthogonal manner. For those using reference... Figure 2 Some examples of modulation shown and described illustrate that these states can be represented in two orthogonals, for example, by randomly selecting orthogonals for measurement for each information unit. Information obtained by the receiver from an erroneous orthogonal measurement can be removed in post-processing. For an example using amplitude modulation, these states can be represented by two amplitude levels.

[0119] At receiver 801, a beam splitter can be used to divide the received signal into portions for classical optical processing. Figure 8 (Not shown in the diagram) and the portion for quantum optical signal processing. Quantum optical signal processing can be performed as follows. The combined quantum optical signal and the quantum optical signal portion of the local oscillator transmitted from the transmitter are passed to polarization beamsplitter 802. (In some examples, the transmitter omits the local oscillator, and the receiver 801 generates a local oscillator as part of its system.) The signal path from polarization beamsplitter 802 is directed to photodetector 804, and the local oscillator path from polarization beamsplitter 802 is directed to the input of phase modulator 806. The output of phase modulator 806 is directed to Faraday mirror 808 and then to photodetector 810. The Faraday mirror protects against backpropagating light and forms part of the polarization-maintaining delay line. The outputs of photodetectors 804 and 810 are provided to comparator 814, which outputs the received information in the quantum optical signal, for example, as an electrical signal. The difference in the measured intensity, as determined by comparator 814, is proportional to the quadrature amplitudes (e.g., α and β). The Kalman filter 812 is used to predict and interpret phase fluctuations in quantum optical signals, for example, those caused by propagation in optical communication channels.

[0120] The choice of measurement orthogonality between receiver 801 and X or P can be determined by the phase of the local oscillator relative to the quantum optical signal. The local oscillator, as a strongly coherent state, has an amplitude... At the output of the beam splitter, the number of photons in the two arms can be described by the following operator:

[0121] (9)

[0122] (10)

[0123] And the difference can be expressed as:

[0124] (11)

[0125] Because the local oscillator has high intensity, it can be modeled as classical light. Therefore, equation (11) becomes:

[0126] (12)

[0127] Therefore, values ​​orthogonally represented by X or P can be measured by changing the phase of the local oscillator relative to the quantum optical signal. This can be achieved using a phase modulator 806, which... Figure 8 The phase modulator is shown as being located in the local oscillator branch. In other examples, the phase modulator may be located in the quantum optical signal branch. Receiver 801 can choose any orthogonal branch for measurement, or can randomly select which orthogonal branch to measure for each information unit.

[0128] For an example of measuring an orthogonal signal, post-processing can remove information transmitted using another orthogonal signal. An orthogonal example of measuring an orthogonal signal can be achieved using zero-difference detection. Typically, the effects of phase variations in the communication channel can be removed during post-processing. Furthermore, the output may vary over time due to the possibility of random phase (due to propagation in the communication channel, for example), but this can be mitigated by using a grand classical optical signal as a reference for estimating the random phase (e.g., using a Kalman filter). Alternatively or additionally, for the purpose of classical phase recovery, this can be addressed by including an additional header with a quantum optical signal.

[0129] Figure 9 This is a simulated histogram 900 depicting techniques for detecting correlation loss indicating an attack on an optical communication channel, based on various examples, by a system using a single pair of photodetectors. Current Reference Figure 9 The described technology can be related to Figure 8 The system 800 is used in conjunction with it to detect relevance loss indicating an attack. However, the detection techniques described herein are not limited to use with the system 800.

[0130] The received quantum optical signal can be expressed by the following equation:

[0131] (13)X=Acosθ+N.

[0132] In equation (13), A is the amplitude of the quantum state, θ is the angle between the state in quantum space and the local oscillator signal, and N is the noise term, which includes vacuum noise and system noise. According to some examples, the local oscillator can be considered to be freely running, so the angle θ follows a uniform distribution, which can be expressed as:

[0133] (14)

[0134] Therefore, examples can determine the presence of a correlation loss indicating an attack by analyzing the received distribution (e.g., as represented by histogram 900). For example, for quantum modulation of two states (α and β), the correlation loss can be determined as the average difference between the two levels. Histogram 900 depicts orthogonal values ​​measured for each of the two states according to the square root of the shot noise level. If such an average difference exceeds a threshold, an attack can be indicated. Typically, the correlation loss can be determined as an excessive average difference between the modulation state values. This type of correlation loss detection can be repeated for incoming data, for example, by calculating the difference between the average levels over a sliding window of values.

[0135] IV. Experimental System and Results

[0136] This section describes various experimental systems and results. In some cases, the experimental systems presented represent proof of a concept study. Some experimental systems have been implemented, and in such cases, the test results are given herein. However, some of the experimental systems presented herein are not intended for use with unmodified deployed systems. For example, some experimental systems shown and described in this section use an oscilloscope to determine correlation loss; in deployed systems, the oscilloscope would be replaced by specialized electronics, for example, to determine whether the correlation loss is sufficient to indicate an attack. As another example, some experimental systems shown and described in this section include out-of-band communication between the sender and receiver for coordinating the sender and receiver systems and analyzing the results; in deployed systems, such out-of-band communication may be unnecessary and can be omitted. As yet another example, the experimental systems disclosed in this section are not integrated with classical optical communication systems; in deployed systems, such integration would allow the detection of attacks on classical optical communication systems, such as remote communication networks, for example, on Internet communication lines.

[0137] Figure 1 System 100 and Figure 3 Parts of System 300 can be implemented using the hardware and techniques described in this section. Some examples shown and described in this section depict experimental implementations of the quantum fabricator 104 and quantum detector 110 of System 100, and the quantum fabricator 304 and quantum detector 310 of System 300. Therefore, the examples shown and described in this section can be modified for deployment and, as referenced... Figure 1 and Figure 3The examples shown and described are in combination with existing or known embodiments of the classical preparer 106, multiplexer 108, classical detector 112, classical preparer 306, and classical detector 312. The examples in this section can be disclosed as detecting attacks on communications sent from a sender to a receiver; however, it should be understood that the examples may include corresponding systems for detecting attacks on communications sent from a receiver to a sender on the same or different communication channels.

[0138] Figure 10 This is a schematic diagram of a first experimental system 1000 for detecting attacks on optical communication channels, based on various examples. System 1000 represents a simulated sender (e.g., including but not limited to elements 1002, 1016), a simulated receiver (e.g., including but not limited to elements 1066, 1068), a simulated optical communication channel (e.g., including but not limited to elements 1062, 1064), and a simulated attacker (e.g., including but not limited to elements 1050, 1052).

[0139] System 1000 includes a laser 1002, which may be a continuous-wave laser. Laser 1002 may also be a coherent source carrier providing a stable beam. The output of laser 1002 is coupled to a 50:50 beam splitter 1004, which may be implemented as a half-silvered mirror. The output of 50:50 beam splitter 1004 provides a beam 1006 that initiates a quantum optical signal path 1008 and a beam 1010 that initiates a reference beam path 1012. Quantum optical signal path 1008 carries information for detecting attacks. Reference beam path 1012 provides a local oscillator and a reference for timing between the simulated transmitter and receiver in experimental system 1000. Along quantum optical signal path 1008, beam 1006 is directed to the first input of 1:99 beam splitter 1014.

[0140] The second input of the 1:99 beam splitter 1014 is configured to receive input from the noise source 1050. The 99% side of the output of the 1:99 beam splitter 1014 is directed to the input of the quantum amplitude (QA) modulator 1020. The 1% side of the output of the 1:99 beam splitter 1014 is tapped to the eavesdropper 1052. The eavesdropper 1052 can be implemented as an oscilloscope in the experimental system 1000. For example, an erbium-doped fiber amplifier can be used to implement the noise source. The noise source 1050 can be used to simulate an interference attack, the eavesdropper 1052 can be used to simulate an eavesdropping attack, and both the noise source 1050 and the eavesdropper 1052 can be used to simulate a related interference attack. The elements simulating an attacker (i.e., the noise source 1050 and the eavesdropper 1052) appear before the modulator 1020 in the quantum optical signal path. This arrangement allows the test system 1000 to detect, for example, interference attacks and related interference attacks. However, more generally, an attacker could appear just before, during, or after the emulated channel 1028. In such an arrangement, system 1000 can be used to detect any type of attack described herein.

[0141] QA modulator 1020 includes amplitude modulator 1016 and 1:99 beam splitter 1018. The input of QA modulator 1020 is passed to the input of amplitude modulator 1016. QA modulator 1020 is configured to receive control signal 1022 from arbitrary wave generator 1060. Arbitrary wave generator 1060 also provides control signal 1024 to amplitude modulator 1030 and trigger signal 1046 to oscilloscope 1048. Amplitude modulator 1016 applies information from control signal 1022 to its input optical signal to generate an amplitude-modulated quantum optical signal. The amplitude-modulated quantum optical signal is directed to the input of 1:99 beam splitter 1018. 1% of the output of the 1:99 beam splitter 1018 is fed to the input of the PIN diode 1042, and the corresponding electrical output of the PIN diode 1042 is fed to the oscilloscope 1048 as a power reference signal 1044. 99% of the output of the 1:99 beam splitter 1018 is fed as the output of the QA modulator 1020, which is fed to the input of the emulation channel 1028.

[0142] The simulated channel 1028 transforms the input amplitude-modulated quantum optical signal based on the characteristics of a typical optical communication channel. The simulated channel 1028 includes a variable optical attenuator (VOA) 1062 and a non-variable attenuator 1064. The input of the simulated channel 1028 is fed to the input of the VOA 1062, and the output of the VOA 1062 is fed to the input of the attenuator 1064. The output of the attenuator 1064 is fed as the output of the simulated channel 1028, which is then passed to the input of the detector 1040. Together, the VOA 1062 and the attenuator 1064 provide a simulation of the optical loss of a deployed fiber optic communication channel.

[0143] Detector 1040 is implemented using two pairs of photodetectors, for example, as referenced above. Figure 7 As shown and described. The input of detector 1040 receives an amplitude-modulated quantum optical signal from the emulated channel 1028 and directs it to a 90° mixer 1066. The output of the 90° mixer 1066 is passed to two pairs of photodetectors 1068, which can be referenced above. Figure 7 As shown and described, this is implemented. The two pairs of photodetectors 1068 also receive a local oscillator from the 1:99 beam splitter 1036 in the reference beam path 1012, which is used to amplify the input by mixing it with a higher-power local oscillator. The two pairs of photodetectors 1068 generate electrical signals representing information in the amplitude-modulated quantum optical signal, and these electrical signals are transmitted to an oscilloscope 1048 for analysis.

[0144] Along the reference beam path 1012, beam 1010 is directed to the input of amplitude modulator 1030. Amplitude modulator 1030 also receives control signal 1024 from arbitrary wave generator 1060 and applies the information from control signal 1024 to beam 1010 using amplitude modulation to generate an amplitude-modulated local oscillator. The amplitude-modulated local oscillator is directed to the input of polarization controller 1032, which adjusts the polarization of the modulated reference beam. The modulated and polarized reference signal is then directed to delay element 1034, such as a delay line, where the delay corresponds to the delay of the signal through quantum optical signal path 1008. The modulated, polarized, and delayed reference signal output from delay element 1034 is directed to the input of 1:99 beam splitter 1036. The 99% side of the output of the 1:99 beam splitter 1036 is directed to the input of a PIN diode 1038, and the electrical output of the PIN diode 1038 is directed to an oscilloscope 1048 to represent a local oscillator power monitor providing timing information. The 1% side of the output of the 1:99 beam splitter 1036 is directed to two pairs of photodetectors 1068, thereby recombining the quantum optical signal path 1008 and the reference beam path 1012.

[0145] Experimental system 1000 can be converted into a deployable system by implementing several modifications. For example, system 1000 can be combined with a classical optical communication system and used to detect attacks on the classical optical communication system. Such classical optical communication systems can also encode information in classical optical signals for determining correlation loss, such as information carried in quantum optical signals or information for obtaining information carried in quantum optical signals, as referenced above. Figure 1 Detailed description. As another example, the oscilloscope 1048 can be replaced by dedicated logic circuitry for determining whether the output from the detector 1040, along with information about the transmitted quantum optical signal, indicates a loss of correlation indicative of an attack. As another example, tolerances can be tightened to omit the trigger signal 1046 and the local oscillator power monitor generated by the PIN diode 1038.

[0146] Figure 11 This is a schematic diagram of a second experimental system 1100 for detecting attacks on optical communication channels, based on various examples. System 1100 is identical to system 1000, except that it uses card 1102 to control amplitude modulators 1016 and 1030 and analyze whether an attack has occurred. Card 1102 can be implemented as an FPGA, such as the VIRTEX-6 provided by Xilinx Corporation of San Jose, California, USA. Card 1102 may include one or more analog-to-digital converters (ADCs) and / or digital-to-analog converters (DACs). One or more DACs of card 1102 can be used to control the modulation of amplitude modulators 1016 and 1030 on the analog transmitter side. For example, according to the experimental use of system 1100, the gain of one such DAC can be set to 0.18 and its offset can be set to 1500, and the gain of another DAC can be set to 0.35 and its offset can be set to 2000. One or more ADCs of card 1102 can be used to record and analyze data detected by the analog receiver.

[0147] Experimental system 1100 can be converted into a deployable system by implementing several modifications. For example, system 1100 can be combined with a classical optical communication system and used to detect attacks on the classical optical communication system. Such classical optical communication systems can also encode information in classical optical signals for determining correlation loss, such as information carried in quantum optical signals or information for obtaining information carried in quantum optical signals, as referenced above. Figure 1Detailed description. As another example, card 1102 can be replaced by dedicated logic circuitry for determining whether the output from detector 1040, along with information about the transmitted quantum optical signal, indicates a loss of correlation indicative of an attack. As another example, tolerances can be tightened to omit the power reference signal 1044 generated by PID diode 1042 and the local oscillator power monitor generated by PIN diode 1038.

[0148] Figure 12 This is a schematic diagram of a third experimental system 1200 for detecting attacks on optical communication channels, based on various examples. System 1200 includes a simulated transmitter 1232, a simulated receiver 1234, and a communication channel 1204. In operation, the simulated transmitter 1232 and the simulated receiver 1234 are co-located, with the communication channel 1204 forming a 10-kilometer-long fiber optic loop that begins and ends in the same room.

[0149] System 1200 is similar to System 1100 in that it utilizes Card 1202 to perform post-processing and control the quantum optical signal path and amplitude modulation of the local oscillator. Card 1202 can be referenced as above. Figure 11 Implemented as shown and described in card 1102.

[0150] Sender 1232 includes the above reference. Figure 10 The laser 1002 and the 50:50 beam splitter 1004 are described. One path from the 50:50 beam splitter is used for the quantum optical signal, and another path is used for the local oscillator. The quantum optical signal path is directed to the amplitude modulator 1208 and then to the variable optical attenuator 1210. The amplitude modulator 1208 generates pulses with two amplitude levels, and the variable optical attenuator attenuates the optical signal, resulting in a difference between the two amplitudes at the quantum level. The output of the variable optical attenuator is directed to the input of the 50:50 beam splitter 1214. A first output from the 50:50 beam splitter 1214 is passed to a PIN diode 1212, which generates an electrical signal corresponding to the input optical signal, which is passed to the card 1202 as an input power reference. A second output from the 50:50 beam splitter is coupled to a communication channel 1204 and passes the quantum optical signal to this communication channel. The local oscillator path from the 50:50 beam splitter 1004 is coupled to the input of the amplitude modulator 1216, the output of which is coupled to the receiver 1234. Both the amplitude modulator 1208 and the amplitude modulator 1216 are controlled by control signals sent from the card 1202.

[0151] Communication channel 1204 carries quantum optical signals from sender 1232 to receiver 1234. The communication channel is implemented using a 10-kilometer optical fiber under real-world conditions.

[0152] Receiver 1234 receives the quantum optical signal from communication channel 1204 and transmits it to the input of dynamic polarization controller 1218. Dynamic polarization controller 1218 can be used to interpret polarization fluctuations caused by propagation through communication channel 1204 and / or select the orthogonality used for measurement, for example, when using a device such as those referenced herein. Figure 2 In the modulation example shown and described, the output of the dynamic polarization controller is coupled to the input of the 50:50 beamsplitter 1220. System 1200 can be configured such that transmitter 1232 provides a combined quantum optical signal and a classical optical signal, and the classical optical signal may include information about the transmitted quantum optical signal for determining correlation loss. For such an example, the first output of the 50:50 beamsplitter 1220 can be directed to classical detection via a PIN diode 1236, for example... Figure 1 The classic detector 112 or Figure 3 The classical detector 312. PIN diode 1236 generates an electrical signal corresponding to the classical optical signal, which can be included in the quantum optical signal by transmitter 1232. The second output of 50:50 beam splitter 1220 is directed to the input of variable optical attenuator 1222, which reduces the intensity to avoid detector saturation. The output of variable optical attenuator 1222 is coupled to the first input of 90° mixer 1228. Receiver 1234 receives the local oscillator from amplitude modulator 1216 and passes it to the input of delay line 1224. In this way, delay line 1224 forms an fiber stretcher. The output of delay line 1224 is coupled to the input of 50:50 beam splitter 1226. The first output of 50:50 beam splitter 1226 can be coupled to card 1202 via PIN diode 1238 to provide a timing signal. PIN diode 1238 generates an electrical signal corresponding to the local oscillator, which can be used for local oscillator power monitoring and clock generation. The second output of 50:50 beam splitter 1226 is coupled to the second input of 90° mixer 1228. The output of 90° mixer 1228 is coupled to a single pair of photodetectors 1230, which can be referenced herein. Figure 8 Implemented as shown and described. Alternatively, the single pair of photodetectors 1230 can be replaced by two pairs of photodetectors, for example, as referenced herein. Figure 7 As shown and described herein, a single pair of photodetectors 1230 provides card 1202 with an electrical signal corresponding to a quantum optical signal. Card 1202 uses the information disclosed herein (e.g., references to...). Figure 9 The technology is used to perform post-processing to detect attacks.

[0153] Experimental system 1200 can be converted into a deployable system by implementing several modifications. For example, system 1200 can be combined with a classical optical communication system and used to detect attacks on the classical optical communication system. Such classical optical communication systems can encode information in classical optical signals for determining correlation loss, such as information carried in quantum optical signals or information for obtaining information carried in quantum optical signals, as referenced above. Figure 1 The classical processing of such classical optical signals can be used to obtain information about the transmitted quantum optical signal, and this information can be used in conjunction with information in the quantum optical signal detected by a single pair of photodetectors 1230 to detect a correlation loss indicating an attack using the techniques disclosed herein. As another example, card 1202 can be replaced by dedicated logic circuitry for determining whether the output from detector 1230 (representing the received quantum optical signal) along with information about the transmitted quantum optical signal reveals a correlation loss indicating an attack. As another example, a local oscillator can be combined with the quantum optical signal and transmitted via communication channel 1204, for example, as referenced herein. Figure 7 As shown and described, or transmitted via different communication channels. As another example, card 1202 can be omitted, and different controllers can be used to control amplitude modulators 1208 and 1216.

[0154] Figure 13 This is a schematic diagram of a fourth experimental system 1300 for detecting attacks on optical communication channels, based on various examples. System 1300 includes a simulated transmitter 1332, a simulated receiver 1334, and a communication channel 1204 (connected to...). Figure 12 (The same communication channel in system 1200). In operation, the analog transmitter 1332 and the analog receiver 1334 are located in the same room, where the communication channel 1204 forms a 10-kilometer-long fiber optic loop.

[0155] System 1300 is similar to Figure 12 The system 1200 has similar or identical components including: laser 1002, communication channel 1204, amplitude modulator 1208, variable optical attenuator 1210, PIN diode 1212, 50:50 beam splitter 1214, dynamic polarization controller 1218, 50:50 beam splitter 1220, variable optical attenuator 1222, delay line 1224, 50:50 beam splitter 1226, and 90° optical mixer 1228.

[0156] System 1300 differs from others in several aspects. Figure 12 System 1200. First, Figure 13The electrical signal from PIN diode 1212 is processed by power meter 1302 before being passed to card 1202. Second, system 1300 uses two pairs of photodetectors 1304 to detect the quantum optical signal. For an example using amplitude modulation for the quantum optical signal, the effects of phase noise can be eliminated by measuring that X and P are orthogonal and removing phase information (e.g., at post-processing). Third, system 1300 includes a local oscillator path with laser 1306 at receiver 1334, instead of obtaining the local oscillator from transmitter 1332. For an example using a local oscillator close to the receiver (e.g., included in the receiver system or in the same room as the receiver system), the receiver can utilize precise phase locking between the transmitter and receiver lasers.

[0157] Figure 14 It is a description due to the Figure 10 Graph 1400 shows the detected transmission loss caused by an eavesdropping attack on System 1000. Graph 1400 depicts the change in transmission loss relative to time over a three-hour time span, where the y-axis represents transmission rate loss and the x-axis represents time. In the eavesdropping attack, 1% of the quantum optical signal was intercepted by eavesdropper 1052 of System 1000 for approximately one hour. Figure 10 The transmission loss detected by the example system 1000 during time interval 1402 is in the form of correlation loss indicating an eavesdropping attack. Specifically, the transmission loss in time interval 1402 corresponds to an eavesdropping attack on system 1000. As shown in the figure, there is a large amount of shot noise in the system that makes the difference in signal amplitude undetectable by normal classical detection. However, the detector 1040 of system 1000 is able to detect the presence of the eavesdropping attack, as shown in Figure 1400.

[0158] Figure 15 It is a description due to the Figure 10 The example system 1000 is shown in Figure 1500, which illustrates the detected transmission loss caused by a related interference attack. Figure 1500 depicts the change in transmission loss relative to time over a three-hour time span, where the y-axis represents transmission rate loss and the x-axis represents time. Figure 15 Considering no channel loss, e.g., transmission equals one. In a correlated interference attack, 1% of the quantum optical signal is intercepted by eavesdropper 1052 of system 1000 and replaced by the equivalent energy in optical noise from noise source 1050 for approximately one hour. Therefore, during the attack, there is no change in the energy of the entire quantum optical signal. Figure 10The loss detected in time interval 1502 by the example system 1000 is in the form of correlation loss indicating a related interference attack. Specifically, the loss during time interval 1402 corresponds to a related interference attack on system 1000. As shown in Table 1500, there is a large amount of shot noise in the system, so much so that classical detection techniques of the prior art cannot detect the difference in signal amplitude. However, the detector 1040 of system 1000 is able to detect the presence of a related interference attack.

[0159] Figure 16 It is a description due to the Figure 1 The example of system 1000 is illustrated in graph 1600, which shows the detected transmission loss caused by a correlation interference attack. In graph 1600, the x-axis represents time and the y-axis represents the transmission rate. The detected transmission loss is presented in the form of correlation loss indicating the attack. In the example of system 1000 used to generate graph 1600, the sender uses time-division multiplexing to prepare a combination of classical and quantum optical signals, for example, as referenced herein. Figure 1 As shown and described, the multiplexer randomly switches between transmitting classical optical signals and quantum optical signals on the same channel using the same time slot duration, for example, as referenced. Figure 4 As shown and described. Classical optical signals to include random data are prepared using on / off keyed modulation schemes. Quantum optical signals are prepared using a two-state modulation scheme that randomly sends one of two quantum states, for example, as referenced. Figure 2 and Figure 8 As shown and described, the signal amplitude is shifted to match the zero level of a classical optical signal. Therefore, a typical (e.g., classical optical) attacker would be unable to distinguish the quantum optical signal from the zero level of a classical optical signal.

[0160] To prepare the combined optical signal, system 1000 uses a single amplitude modulator (amplitude modulator 1016) to modulate both the quantum optical signal and the classical optical signal. A 50 / 50 splitter is inserted between attenuator 1064 and detector 1040, and half of the received signal is passed to a PIN diode for classical optical signal detection, while the other half is passed to detector 1040, which measures the X and P phases of the signal as orthogonal. Although phase orthogonality does not encode information in system 1000, it is measured and used to eliminate phase noise. The measurements of both the quantum optical signal and the classical optical signal are recorded by a personal computer for post-processing. In the test shown in graph 1600, the system time slot repetition rate was set to 25 MHz, with the classical data rate set to 1 Gbps.

[0161] In a related interference attack, 1% of the quantum optical signal is intercepted by the eavesdropper 1052, and the optical power at another wavelength is injected by the optical noise source 1050 to maintain the total optical power of the signal.

[0162] Graph 1600 depicts the transmission rate of the quantum optical signal 1602, along with a smoothed thirty-point moving average 1604. The correlated interference attack occurs between points 100 and 300 on the x-axis. Although the average optical power remains constant, there is a significant decrease in the transmission rate of the quantum optical signal during the attack. The measured transmission rate is still reduced because the injected laser noise from noise source 1050 cannot compensate for the eavesdropped quantum optical signal. The transmission rate fluctuates much more significantly during the correlated interference attack, as the standard deviation of the measured transmission rate is approximately 0.009 during the attack, for example, 0.4 dB, while the standard deviation of the secure channel is less than 0.0015, for example, 0.04 dB. Without the attack, the transmission rate is 0.10, as seen in the moving average 1604 outside the interval between 100 and 300. During the attack, for example, within the interval between 100 and 300, the moving average of the transmission rate drops to less than 0.99 of the transmission rate outside the attack, or 1% lower than the transmission rate outside the attack. To avoid false alarms, an alarm is triggered when the moving average (whose fluctuation is only 0.05% outside of an attack) crosses below the 1% threshold 1606 at point 110 on the x-axis. The 1% threshold 1606 indicates 99% of the transmission rate of 0.10 in the absence of an attack. Generally, and based on secure channel fluctuations, the probability that the moving average falling below the 1% threshold is caused by an attack is 99.99%. Experimental results confirm that the loss sensitivity within 50 km is better than 0.04 dB compared to 0.4 dB of classical optical techniques.

[0163] Figure 17 It is a description due to the Figure 10 Graph 1700 illustrates the excessive noise detected as a result of a related interference attack on an example of System 1000. Specifically, Graph 1700 depicts the same related interference attack on the same example of System 1000 (as referenced above). Figure 16Excess noise in the quantum optical signal detected during (shown and described). Quantum excess noise is calculated by removing believable noise from the measured variance of the quantum optical signal. Figure 1700 depicts the measured noise 1702 in the quantum optical signal, and the moving average of the measured noise 1704. As shown in Figure 1700, the moving average 1704 increases from 0.14 shot noise units (SNU) to 0.64 SNU during a correlated interference attack. This corresponds to a 1.5 dB reduction in the optical signal-to-noise ratio (OSNR). In the experiment, an alarm threshold of 0.5 SNU for excess noise was set, which was triggered at approximately 117 points on the x-axis, where the moving average 1704 crossed the 0.5 shot noise threshold. In practice, due to the sporadic nature of such attacks, it is difficult to detect this additional noise and temporary drop in bit error rate using classical existing techniques. Nevertheless, the example using System 1000 easily detects excess noise in the quantum optical signal, as it increases to nearly five times its original value.

[0164] V. Multi-node implementation for remote communication

[0165] This section describes an implementation involving multiple senders and receivers among nodes deployed in a communication network. In practice, the sender / receiver pair can have a limited range within which communication and attack detection are performed. The examples in this section extend the range of the examples indefinitely by using relay communication. Furthermore, the examples in this section allow communication and attack detection to be sent in either direction. The examples can be implemented using any type of sender and receiver disclosed herein.

[0166] Figure 18 This is a schematic diagram of a multi-node system 1800 for detecting attacks on optical communication channels, based on various examples. System 1800 depicts three nodes: a first node 1802, a second node 1812, and a third node 1822. Each node 1802, 1812, and 1822 may have the same architecture. Each node may be located in a different geographical location. Each node may be located in a building or other structure. The first node 1802 is communicatively coupled to the second node 1812 via an optical communication channel 1830, and the second node 1812 is communicatively coupled to the third node 1822 via an optical communication channel 1832. The optical communication channels 1830 and 1832 may be implemented as fiber optic lines, for example, in a remote communication network. Figure 18Nodes 1802, 1812, and 1822 arranged as lines are depicted; however, examples of system 1800 may have any number of nodes arranged in any communication mode (e.g., in a communication network). Each node 1802, 1812, and 1822 includes a corresponding sender and receiver. Each sender includes a classical fabricator and a quantum fabricator, and each receiver includes a classical optical detector and a quantum detector. Thus, the first node 1802 includes: a sender 1803, which includes a classical fabricator 1804 and a quantum fabricator 1805; and a receiver 1806, which includes a classical detector 1807 and a quantum detector 1808. The second node 1812 includes: a sender 1813, which includes a classical fabricator 1814 and a quantum fabricator 1815; and a receiver 1816, which includes a classical detector 1817 and a quantum detector 1818. The third node 1822 includes: a sender 1823, which includes a classical preparer 1824 and a quantum preparer 1825; and a receiver 1826, which includes a classical detector 1827 and a quantum detector 1828.

[0167] Each classical preparer 1804, 1814, 1824 can be implemented as any classical preparer disclosed herein, such as classical preparer 106 or 306 or variations thereof disclosed herein. Each quantum preparer 1805, 1815, 1825 can be implemented as any quantum preparer disclosed herein, such as quantum preparer 104 or 304 or variations thereof disclosed herein. For example, each quantum preparer 1805, 1815, 1825 may include a quantum optical modulator. Each classical detector 1807, 1817, 1827 can be implemented as any classical detector disclosed herein, such as classical detector 112 or 312 or variations thereof disclosed herein. Each quantum detector 1808, 1818, 1828 can be implemented as any quantum detector disclosed herein, such as quantum detector 110 or 310 or variations thereof disclosed herein.

[0168] In operation, each node uses the techniques disclosed herein to communicate with any communicatively coupled node in any direction.

[0169] A non-limiting example of communication in one direction between nodes is presented. A first node 1802 may be implemented to include at least a sender 150 (or sender 350); a second node 1812 may be implemented to include at least a receiver 152 (or receiver 352) and a sender 150 (or sender 350); and a third node 1822 may be implemented to include at least a receiver 152 (or receiver 352). The first node 1802 may send a classical optical signal (e.g., a telecommunication signal) to the second node 1812, which may then send the signal to the third node 1822. The classical optical signal may remain unchanged, except perhaps for the possible addition of information for detecting correlation loss. According to this example, the first node 1802 may send information from the classical optical signal portion of a combined classical and quantum optical signal to the second node 1812. The first node may use a classical preparer 1804 to prepare the classical optical signal portion and a quantum preparer 1805 to prepare the quantum optical signal portion. The second node 1812 can receive combined optical signals and direct a portion to the classical detector 1817 and a portion to the quantum detector 1818.

[0170] Continuing with this example, post-processing of information transmitted from the first node 1802 to the second node 1812 for detecting attacks in communication channel 1830 can be performed at either node. In the embodiment where post-processing occurs at the second node 1812, the first node 1802 can transmit information about the transmitted quantum optical signal, which the second node 1812 can use to determine whether there is a correlation loss between the quantum optical signal transmitted by the first node 1802 and the quantum optical signal detected by the second node 1812. The information about the transmitted quantum optical signal may include at least some of the following: information encoded in the quantum optical signal by the first node 1802, and information for obtaining information in the quantum optical signal received by the second node 1812.

[0171] Continuing with this example, in an implementation where post-processing of information sent from first node 1802 to second node 1812 is performed at first node 1802, once second node 1812 receives and detects a quantum optical signal, for example, using a randomly selected basis and / or orthogonality, second node 1812 can transmit back to first node 1802 the information it detected in the quantum optical signal portion, along with information indicating how it detected the information in the quantum optical signal portion (e.g., the basis and / or orthogonality it detected for each information unit) (e.g., in a classical optical signal). First node 1802 can discard incorrectly detected information and, for the remaining correctly detected information, continue to compare it with the information it sent to determine if there is a loss of relevance indicating an attack.

[0172] Continuing with the example, the second node 1812 can transmit a classical optical signal to the third node 1822, possibly adding information for detecting correlation loss, for example, using a classical preparer 1814. Besides potentially adding such information, the classical optical signal sent from the second node 1812 to the third node 1822 can be the same as or contain the same information as the classical optical signal sent from the first node 1802 to the second node 1812. The second node 1812 can generate a new quantum optical signal independent of the quantum optical signal sent by the first node 1802. The second node 1812 can combine the quantum optical signal with the classical optical signal and send it to the third node 1822. The third node 1822 and / or the second node 1812 can perform post-processing to determine whether an attack has occurred in the communication channel 1832.

[0173] The example above outlines how the first node 1802 can send information to the third node 1822 via the second node 1812 in a manner that can detect attacks. However, the techniques described in this example can be applied to any two communicatively coupled nodes for information sent in either direction, such as information sent from the second node 1812 to the first node 1802, or information sent between the second node 1812 and the third node 1822 in either direction.

[0174] Note that in the implementation of system 1800, the classical transmitters 1804, 1814, and 1824 can be implemented as existing classical optical transmitters in an optical communication network, modified to perform the actions disclosed herein for detecting attacks. Similarly, the classical detectors 1807, 1817, and 1827 can be implemented as existing classical detectors in such optical communication networks, modified to perform the actions disclosed herein for detecting attacks.

[0175] VI. in conclusion

[0176] Figure 19 This is a flowchart of method 1900 for detecting attacks on optical communication channels, based on various examples. Method 1900 can be implemented by any system disclosed herein.

[0177] At 1902, method 1900 includes preparing a quantum optical signal. As a non-limiting example, referring to quantum preparer 104 or quantum preparer 304, the action at 1902 can include any quantum optical signal preparation action disclosed herein. The action at 1902 can be performed by any sender as disclosed herein.

[0178] At 1904, method 1900 includes preparing a classical optical signal. As a non-limiting example, referring to classical preparer 106 or classical preparer 306, the action at 1904 may include any classical optical signal preparation action disclosed herein. The action at 1904 may include receiving a pre-existing signal (electrical signal or classical optical signal), and adding any information and / or modulating the classical optical signal as disclosed herein. The action at 1904 may be performed by any sender as disclosed herein.

[0179] At 1906, method 1900 includes combining quantum optical signals and classical optical signals. Any signal combining technique as disclosed herein can be used, such as the one described in the reference document. Figure 1 Public multiplexing or reference Figures 3-5 Public overlay. The action of 1906 can be performed by any sender as disclosed herein.

[0180] At 1908, method 1900 includes transmitting combined optical signals. Action at 1908 may include transmission via an optical communication line (e.g., as part of a remote communication network). Action at 1908 may be performed by any sender as disclosed herein.

[0181] At 1910, method 1900 includes receiving combined optical signals. Action 1919 may include receiving from an optical communication line (e.g., as part of a remote communication network). Action 1910 may be performed by any receiver as disclosed herein.

[0182] At 1912, method 1900 includes obtaining information detected in a quantum optical signal. As a non-limiting example, referring to quantum detector 110 or quantum detector 310, the action at 1912 can include any quantum optical signal detection action disclosed herein. The detection action at 1912 can be performed by any receiver as disclosed herein. For an example where post-processing is performed by the sender, the action at 1912 can also include the receiver sending information about the detected quantum information (e.g., the value of such information) and information about how the detected quantum information was detected.

[0183] At 1914, method 1900 includes obtaining information transmitted in a quantum optical signal. For an example where post-processing is performed by the receiver, the action at 1914 may include detecting information about the transmitted quantum optical signal (e.g., obtained as from a classical optical signal) and discarding any incorrectly detected information. For an example where post-processing is performed by the sender, the operation of this block may include retrieving such information from a memory or storage device.

[0184] At 1916, method 1900 includes determining a correlation loss that indicates an attack. The correlation loss may lie between the information detected in the quantum optical signal and the information initially transmitted in the quantum optical signal, and may exclude any falsely detected information. Any of the various forms of correlation loss disclosed herein can be determined. If any such form exceeds (or falls below) a predetermined threshold, it can indicate an attack.

[0185] At 1918, method 1900 includes taking action in response to a detected attack. Any of a variety of actions can be taken, such as rerouting communications, sending a message, or triggering an alarm.

[0186] This disclosure provides examples under the following terms.

[0187] Clause 1: A system for detecting attacks on an optical communication channel, the system comprising: a first beam splitter operable to split a first optical signal into a second optical signal and a third optical signal, wherein the first optical signal is obtained from the optical communication channel and wherein the first optical signal comprises a classical optical signal and a quantum optical signal; a classical detector operable to detect the classical optical signal in the second optical signal; a second beam splitter operable to receive the third optical signal and a fourth optical signal including a local oscillator and generate a fifth optical signal and a sixth optical signal; a pair of photodetectors operable to receive the fifth optical signal and the sixth optical signal and generate an electrical signal; and an electronic processor configured to determine an indication of an attack on the optical communication channel based on the electrical signal and a representation of information encoded in the quantum optical signal.

[0188] Clause 2: The system according to Clause 1 further includes a phase modulator operable to receive one of the third optical signal or the fourth optical signal.

[0189] Clause 3: A system according to any one of Clauses 1 or 2, wherein the quantum optical signal includes information encoded in at least one of phase or amplitude, and wherein the phase modulator selects a measurement of one of the phase or amplitude of the quantum optical signal.

[0190] Clause 4: A system according to any one of Clauses 1, 2 or 3, wherein the second beam splitter includes a polarization beam splitter.

[0191] Clause 5: The system according to any one of Clauses 1-4 further includes a local oscillator located near the pair of photodetectors and operable to generate the fourth optical signal.

[0192] Clause 6: A system according to any one of Clauses 1-5, wherein the first optical signal comprises the classical optical signal time-division multiplexed with the quantum optical signal.

[0193] Clause 7: A system according to any one of Clauses 1-6, wherein the indication of said attack comprises an average difference in the distribution of a plurality of states encoded in the quantum optical signal that is higher than a predetermined threshold.

[0194] Clause 8: A system according to any one of Clauses 1-7, wherein the indication of the attack includes the transmission loss of the quantum optical signal.

[0195] Clause 9: The system pursuant to any one of Clauses 1-8, wherein the indication of the attack includes the presence of excessive noise.

[0196] Clause 10: A system pursuant to any one of Clauses 1-9, wherein the attack includes at least one of an eavesdropping attack, a jamming attack, a related jamming attack, or an interrupt-retransmission attack.

[0197] Clause 11: A method for detecting an attack on an optical communication channel, the method comprising: splitting a first optical signal obtained from the communication channel into a second optical signal and a third optical signal, wherein the first optical signal includes a classical optical signal and a quantum optical signal; detecting the classical optical signal in the second optical signal; directing the third optical signal and a fourth optical signal including a local oscillator to a beam splitter to generate a fifth optical signal and a sixth optical signal; directing the fifth optical signal and the sixth optical signal to a pair of photodetectors to generate an electrical signal; and determining an indication of an attack on the optical communication channel by an electronic processor and based on the electrical signal and a representation of information encoded in the quantum optical signal.

[0198] Clause 12: The method according to Clause 11 further includes directing one of the third optical signal or the fourth optical signal to the phase modulator.

[0199] Clause 13: The method according to any one of Clauses 11 or 12, wherein the quantum optical signal includes information encoded in at least one of phase or amplitude, and wherein the phase modulator selects a measurement of one of the phase or amplitude of the quantum optical signal.

[0200] Clause 14: The method according to any one of Clauses 11-13, wherein the beam splitter includes a polarization beam splitter.

[0201] Clause 15: The method according to any one of Clauses 11-14, wherein the local oscillator is generated near the pair of photodetectors.

[0202] Clause 16: The method according to any one of Clauses 11-15, wherein the first optical signal comprises the classical optical signal time-division multiplexed with the quantum optical signal.

[0203] Clause 17: The method according to any one of Clauses 11-16, wherein the indication of the attack comprises an average difference in the distribution of a plurality of states encoded in the quantum optical signal that is higher than a predetermined threshold.

[0204] Clause 18: The method according to any one of Clauses 11-17, wherein the indication of the attack includes the transmission loss of the quantum optical signal.

[0205] Clause 19: The method according to any one of Clauses 11-18, wherein the indication of the attack includes the presence of excessive noise.

[0206] Clause 20: The method according to any one of Clauses 11-19, wherein the attack includes at least one of eavesdropping attack, jamming attack, related jamming attack, or interrupt-retransmission attack.

[0207] Clause 21: A system for detecting attacks on an optical communication channel, the system comprising: a beam splitter operable to split a first optical signal into a second optical signal and a third optical signal, wherein the first optical signal is obtained from the optical communication channel, and wherein the first optical signal comprises a classical optical signal and a quantum optical signal; a classical optical demodulator operable to demodulate the classical optical signal in the second optical signal; a first pair of photodetectors operable to detect a first characteristic of the quantum optical signal in the third optical signal; a second pair of photodetectors operable to detect a second characteristic of the quantum optical signal in the third optical signal; and an electronic processor communicatively coupled to the first pair of photodetectors and the second pair of photodetectors and configured to detect attacks on the optical communication channel based on information encoded by at least one of the first characteristic of the quantum optical signal or the second characteristic of the quantum optical signal.

[0208] Clause 22: The system according to Clause 21, wherein the first characteristic includes phase, and wherein the second characteristic includes amplitude.

[0209] Clause 23: A system according to any one of Clauses 21 or 22, wherein the first characteristic includes wavelength, and wherein the second characteristic includes amplitude.

[0210] Clause 24: A system according to any one of Clauses 21-23, wherein the first characteristic includes phase, and wherein the second characteristic includes wavelength.

[0211] Clause 25: A system according to any one of Clauses 21-24, wherein the first characteristic includes polarization, and wherein the second characteristic includes phase.

[0212] Clause 26: A system according to any one of Clauses 21-25, wherein the first characteristic includes polarization, and wherein the second characteristic includes amplitude.

[0213] Clause 27: A system according to any one of Clauses 21-26, wherein the first characteristic includes polarization, and wherein the second characteristic includes wavelength.

[0214] Clause 28: The system according to any one of Clauses 21-27 further includes a polarization beamsplitter disposed in the path of the third optical signal before the first pair of photodetectors and the second pair of photodetectors and operable to separate the third optical signal based on polarization.

[0215] Clause 29: A system according to any one of Clauses 21-28, wherein the electronic processor is configured to detect an attack on the optical communication channel by detecting at least one of transmission loss or excessive noise.

[0216] Clause 30: A system pursuant to any one of Clauses 21-29, wherein the attack on the optical communication channel includes at least one of an eavesdropping attack, a jamming attack, a related jamming attack, or an interrupt-retransmission attack.

[0217] Clause 31: A method for detecting an attack on an optical communication channel, the method comprising: splitting a first optical signal obtained from the optical communication channel into a second optical signal and a third optical signal, wherein the first optical signal includes a classical optical signal and a quantum optical signal; detecting the classical optical signal in the second optical signal; directing a portion of the third optical signal and a portion of the fourth optical signal including a local oscillator to a first pair of photodetectors, the first pair of photodetectors being operable to detect a first characteristic of the quantum optical signal; directing a portion of the third optical signal and a portion of the fourth optical signal to a second pair of photodetectors, the second pair of photodetectors being operable to detect a second characteristic of the quantum optical signal; and determining an indication of an attack on the optical communication channel based on an electronic processor communicatively coupled to the first pair of photodetectors and the second pair of photodetectors, and based on a representation of information in the quantum optical signal and information detected in at least one of the first characteristic or the second characteristic of the quantum optical signal.

[0218] Clause 32: The system according to Clause 31, wherein the first characteristic includes phase, and wherein the second characteristic includes amplitude.

[0219] Clause 33: A system according to any one of Clauses 31 or 32, wherein the first characteristic includes wavelength, and wherein the second characteristic includes amplitude.

[0220] Clause 34: A system according to any one of Clauses 31-33, wherein the first characteristic includes phase, and wherein the second characteristic includes wavelength.

[0221] Clause 35: A system according to any one of Clauses 31-34, wherein the first characteristic includes polarization, and wherein the second characteristic includes phase.

[0222] Clause 36: A system according to any one of Clauses 31-35, wherein the first characteristic includes polarization, and wherein the second characteristic includes amplitude.

[0223] Clause 37: A system according to any one of Clauses 31-36, wherein the first characteristic includes polarization, and wherein the second characteristic includes wavelength.

[0224] Clause 38: The system according to any one of Clauses 31-37 further includes polarization-based separation of the third optical signal.

[0225] Clause 39: A system according to any one of Clauses 31-38, wherein the indication of the attack on the optical communication channel includes at least one of transmission loss or excessive noise.

[0226] Clause 40: A system pursuant to any one of Clauses 31-39, wherein the attack on the optical communication channel includes at least one of an eavesdropping attack, a jamming attack, a related jamming attack, or an interrupt-retransmission attack.

[0227] Clause 41: An optical communication system operable to detect attacks, the system comprising: a first node including a first node optical transmitter, wherein the first node optical transmitter includes a first node classical optical modulator and a first node quantum optical modulator; a second node including a second node optical transmitter and a second node optical receiver, wherein the second node optical transmitter includes a second node classical optical modulator and a second node quantum optical modulator; and a third node including a third node optical receiver; wherein the first node is coupled to the second node via a first optical communication channel, wherein the second node is coupled to the third node via a second optical communication channel, wherein the second node is operable to transmit information in a first classical optical signal in the first optical communication channel to a second classical optical signal in the second optical communication channel; wherein the system is operable to detect a first attack on the first optical communication channel by detecting a correlation loss in the first quantum optical signal in the first optical communication channel; and wherein the system is operable to detect a second attack on the second optical communication channel by detecting a correlation loss in the second quantum optical signal in the second optical communication channel.

[0228] Clause 42: The system according to Clause 41, wherein the first optical communication channel includes a first remote communication fiber optic cable, and wherein the second optical communication channel includes a second remote communication fiber optic cable.

[0229] Clause 43: The system according to any one of Clauses 41 or 42, wherein the first node, the second node and the third node are installed after the first remote communication fiber optic cable and after the second remote communication fiber optic cable.

[0230] Clause 44: The system according to any one of Clauses 41-43, wherein the first classical optical signal includes a first remote communication signal, and wherein the second classical optical signal includes a second remote communication signal.

[0231] Clause 45: A system according to any one of Clauses 41-44, wherein the system is operable to detect the correlation loss of the first quantum optical signal in the first optical communication channel at least by transmitting a representation of information modulated into the first quantum optical signal by the quantum optical modulator of the first node from the first node to the second node, and wherein the system is operable to detect the correlation loss of the second quantum optical signal in the second optical communication channel at least by transmitting a representation of information modulated into the second quantum optical signal by the quantum optical modulator of the second node from the second node to the third node.

[0232] Clause 46: A system according to any one of Clauses 41-45, wherein the first node includes a first node optical receiver, and wherein the third node includes a third node optical transmitter.

[0233] Clause 47: A system according to any one of Clauses 41-46, wherein the system is operable to detect the correlation loss of the first quantum optical signal in the first optical communication channel at least by transmitting a representation of information detected by the optical receiver of the second node from the second node to the first node, and wherein the system is operable to detect the correlation loss of the second quantum optical signal in the second optical communication channel at least by transmitting a representation of information detected by the optical receiver of the third node from the third node to the second node.

[0234] Clause 48: A system pursuant to any one of Clauses 41-47, wherein the first node, the second node, and the third node have the same architecture.

[0235] Clause 49: The system pursuant to any one of Clauses 41-48, wherein the first attack includes at least one of an eavesdropping attack, a jamming attack, a related jamming attack, or an interrupt-retransmission attack, and wherein the second attack includes at least one of an eavesdropping attack, a jamming attack, a related jamming attack, or an interrupt-retransmission attack.

[0236] Clause 50: The system according to any one of Clauses 41-49, wherein the correlation loss of the first quantum optical signal includes at least one of transmission loss or the presence of excessive noise, and wherein the correlation loss of the second quantum optical signal includes at least one of transmission loss or the presence of excessive noise.

[0237] Clause 51: A method for detecting an attack on an optical communication system, the method comprising: providing a first node, the first node including a first node optical transmitter, wherein the first node optical transmitter includes a first node classical optical modulator and a first node quantum optical modulator; providing a second node, the second node including a second node optical transmitter and a second node optical receiver, wherein the second node optical transmitter includes a second node classical optical modulator and a second node quantum optical modulator, and wherein the first node is coupled to the second node via a first optical communication channel; providing a third node, the third node including a third node optical receiver, wherein the second node is coupled to the third node via a second optical communication channel; transmitting information in a first classical optical signal in the first optical communication channel to a second classical optical signal in the second optical communication channel; and detecting at least one of a first attack on the first optical communication channel by detecting a correlation loss in the first quantum optical signal in the first optical communication channel, or a second attack on the second optical communication channel by detecting a correlation loss in the second quantum optical signal in the second optical communication channel.

[0238] Clause 52: The method according to Clause 51, wherein the first optical communication channel comprises a first remote communication fiber optic cable, and wherein the second optical communication channel comprises a second remote communication fiber optic cable.

[0239] Clause 53: The method according to any one of Clauses 51 or 52, wherein the provision of the first node, the provision of the second node, and the provision of the third node occur after the installation of the first remote communication fiber optic cable and the second remote communication fiber optic cable.

[0240] Clause 54: The method according to any one of Clauses 51-53, wherein the first classical optical signal includes a first remote communication signal, and wherein the second classical optical signal includes a second remote communication signal.

[0241] Clause 55: The method according to any one of Clauses 51-54, wherein detecting the correlation loss of the first quantum optical signal in the first optical communication channel includes a representation of information modulated into the first quantum optical signal by the quantum optical modulator of the first node being transmitted from the first node to the second node, and wherein detecting the correlation loss of the second quantum optical signal in the second optical communication channel includes a representation of information modulated into the second quantum optical signal by the quantum optical modulator of the second node being transmitted from the second node to the third node.

[0242] Clause 56: The method according to any one of Clauses 51-55, wherein the first node includes a first node optical receiver, and wherein the third node includes a third node optical transmitter.

[0243] Clause 57: The method according to any one of Clauses 51-56, wherein detecting the correlation loss of the first quantum optical signal in the first optical communication channel includes transmitting a representation of information detected by the optical receiver of the second node from the second node to the first node, and wherein detecting the correlation loss of the second quantum optical signal in the second optical communication channel includes transmitting a representation of information detected by the optical receiver of the third node from the third node to the second node.

[0244] Clause 58: The method according to any one of Clauses 51-57, wherein the first node, the second node and the third node have the same architecture.

[0245] Clause 59: The method according to any one of Clauses 51-58, wherein the first attack includes at least one of an eavesdropping attack, a jamming attack, a related jamming attack, or an interrupt-retransmission attack, and wherein the second attack includes at least one of an eavesdropping attack, a jamming attack, a related jamming attack, or an interrupt-retransmission attack.

[0246] Clause 60: The method according to any one of Clauses 51-59, wherein the correlation loss of the first quantum optical signal includes at least one of transmission loss or the presence of excessive noise, and wherein the correlation loss of the second quantum optical signal includes at least one of transmission loss or the presence of excessive noise.

[0247] Clause 61: A method for detecting an attack on an optical communication channel, the method comprising: generating a laser beam by a transmitter; directing the laser beam to a first optical modulator to obtain a first modulated laser beam, wherein the first optical modulator is one of a quantum optical modulator or a classical optical modulator; directing the first modulated laser beam to a second optical modulator to generate a second modulated laser beam, wherein the second optical modulator is the other of the quantum optical modulator or the classical optical modulator, and wherein the second modulated laser beam comprises a classical optical signal and a quantum optical signal; transmitting the second modulated laser beam to a receiver via the optical communication channel; detecting an attack on the classical optical signal in the optical communication channel based on detecting a correlation loss of the quantum optical signal; and providing an indication of the attack.

[0248] Clause 62: The method according to Clause 61, wherein the first optical modulator is a quantum optical modulator, and wherein the second optical modulator is a classical optical modulator.

[0249] Clause 63: The method according to any one of Clauses 61 or 62, wherein the quantum optical signal overlaps with the classical optical signal.

[0250] Clause 64: The method according to any one of Clauses 61-63, wherein the quantum optical signal overlaps with the classical optical signal only on a portion of the classical optical signal having a minimum amplitude.

[0251] Clause 65: The method according to any one of Clauses 61-64, wherein the correlation loss includes the transmission loss of the quantum optical signal.

[0252] Clause 66: The method according to any one of Clauses 61-65, wherein the correlation loss includes the presence of excessive noise.

[0253] Clause 67: The method according to any one of Clauses 61-66, wherein the presence of said excessive noise comprises at least two shot noise units.

[0254] Clause 68: The method according to any one of Clauses 61-67, wherein the attack includes at least one of eavesdropping attack, interference attack, related interference attack, or interrupt-retransmission attack.

[0255] Clause 69: The method according to any one of Clauses 61-68, wherein the detection includes measuring using at least two pairs of photodetectors.

[0256] Clause 70: The method according to any one of Clauses 61-69, wherein the detection includes sharing information encoded in the quantum optical signal between the sender and the receiver.

[0257] Clause 71: A system for detecting an attack on an optical communication channel, the system comprising: a laser; a first optical modulator coupled to the laser and operable to provide a first modulated laser beam, wherein the first optical modulator is one of a quantum optical modulator or a classical optical modulator; a second optical modulator coupled to the first optical modulator and operable to receive the first modulated laser beam and generate a second modulated laser beam, wherein the second optical modulator is the other of the quantum optical modulator or the classical optical modulator, and wherein the second modulated laser beam comprises a classical optical signal and a quantum optical signal; and an electronic processor configured to detect a correlation loss of the quantum optical signal indicating an attack on a classical optical signal in the optical communication channel.

[0258] Clause 72: The system according to Clause 71, wherein the first optical modulator is a quantum optical modulator and wherein the second optical modulator is a classical optical modulator.

[0259] Clause 73: A system according to any one of Clauses 71 or 72, wherein the quantum optical signal overlaps with the classical optical signal.

[0260] Clause 74: A system according to any one of Clauses 71-73, wherein the quantum optical signal overlaps with the classical optical signal only on a portion of the classical optical signal having a minimum amplitude.

[0261] Clause 75: A system according to any one of Clauses 71-74, wherein the correlation loss includes the transmission loss of the quantum optical signal.

[0262] Clause 76: The system pursuant to any one of Clauses 71-75, wherein the correlation loss includes the presence of excessive noise.

[0263] Clause 77: A system according to any one of Clauses 71-76, wherein the presence of said excessive noise comprises at least two shot noise units.

[0264] Clause 78: A system pursuant to any one of Clauses 71-77, wherein the attack includes at least one of an eavesdropping attack, a jamming attack, a related jamming attack, or an interrupt-retransmission attack.

[0265] Clause 79: The system according to any one of Clauses 71-78 further includes a receiver, wherein the receiver includes at least two pairs of photodetectors operable to detect the quantum optical signal.

[0266] Clause 80: A system according to any one of Clauses 71-79, wherein the electronic processor is further configured to acquire information encoded in the quantum optical signal.

[0267] Typically, portions of the examples disclosed herein can be combined with portions of any other examples disclosed herein. For example, any disclosed modulation, detection, preparation, transmission, reception, and / or post-processing techniques from any example can be used (e.g., replaced) in any other disclosed example.

[0268] The subject matter disclosure is not limited to the specific examples described herein, which are intended to illustrate various aspects. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and apparatus within the scope of this disclosure, other than those listed herein, will be apparent to those skilled in the art based on the foregoing description. It should also be understood that the terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting.

[0269] Regarding the use of virtually any plural and / or singular terms in this document, those skilled in the art can translate from plural to singular and / or from singular to plural depending on the context and / or application. For clarity, various singular / plural permutations may be explicitly described herein.

Claims

1. A method (1900) for detecting attacks on optical communication channels (160, 360, 716, 1204, 1830, 1832), the method comprising: A laser beam is directed to a classical optical modulator to obtain a first modulated laser beam, the first modulated laser beam including a classical optical signal representing first information; The first modulated laser beam is directed to a quantum optical modulator to generate a second modulated laser beam, the second modulated laser beam including a quantum optical signal representing second information, wherein the quantum optical signal includes the second information modulated with two quantum states, wherein the two quantum states include amplitude and phase; Optical signals (324, 500) are transmitted from the sender (150, 350, 712, 1232, 1332, 1803, 1813, 1823) to the receiver (152, 352, 734, 801, 1234, 1334, 1806, 1816, 1826) via the optical communication channel (1908), wherein the optical signals include classical optical signals (118, 502, 504, 506) representing the first information and quantum optical signals (122, 604, 1602) representing the second information. The receiver detects (1912) at least a portion of the third information from the quantum optical signal; An indication of an attack on the optical communication channel is determined (1916) at least based on the third information, wherein the determination is based on determining a correlation loss in the third information, and wherein the correlation loss includes an excess difference between the distribution means of the two quantum states in the third information; as well as The alarm is triggered based on the determination (1918).

2. The method of claim 1, wherein the indication for determining the attack further includes determining an increase in noise (1702).

3. The method of claim 1, further comprising using statistical techniques to distinguish false alarms from actual attacks, wherein the statistical techniques include one of the following: change point detection, Bayesian change point detection, supervised learning, or cumulative sum (CUSUM).

4. The method of claim 1, further comprising using a Kalman filter at the receiver to predict and interpret phase fluctuations in the quantum optical signal.

5. The method of claim 1, wherein determining the correlation loss in the third information comprises using a sliding window of values ​​to calculate the excess difference between the distribution means of the two quantum states in the third information for the sliding window of values.

6. The method according to claim 1, wherein the classical optical signal and the quantum optical signal are interleaved.

7. The method of claim 1, wherein the attack includes at least one of an eavesdropping attack, a jamming attack, a related jamming attack, or an interrupt-retransmission attack.

8. The method of claim 1, wherein the optical communication channel comprises a distance of at least 50 km, and wherein the method has a sensitivity of less than or equal to 0.04 dB.

9. The method of claim 1, wherein the detection includes using zero-difference detection for measurement.

10. The method of claim 1, wherein the detection includes using heterodyne detection for measurement.

11. The method of claim 2, wherein determining the indication of the attack further comprises determining transmission loss, and wherein determining the indication of the attack further comprises determining bit loss.

12. A system (100, 300, 600, 700, 800, 1000, 1100, 1200, 1300, 1800) for detecting attacks on optical communication channels (160, 360, 716, 1204, 1830, 1832), said system comprising: Transmitters (150, 350, 712, 1232, 1332, 1803, 1813, 1823), each transmitter comprising a laser, a hardware classical optical modulator, and a hardware quantum optical modulator, wherein the transmitter is configured to guide a laser beam generated by the laser to the hardware classical optical modulator to obtain a first modulated laser beam, the first modulated laser beam comprising a classical optical signal representing first information, wherein the transmitter is further configured to guide the first modulated laser beam to the hardware quantum optical modulator to generate a second modulated laser beam. The laser beam, the second modulated laser beam including a quantum optical signal representing second information, wherein the quantum optical signal includes the second information modulated by two quantum states, wherein the two quantum states include amplitude and phase, and wherein the transmitter is operable to transmit (1908) optical signals (324, 500) to the receiver via the optical communication channel, the optical signals including the classical optical signals (118, 502, 504, 506) representing the first information and the quantum optical signals (122, 604, 1602) representing the second information. Receivers (152, 352, 734, 801, 1234, 1334, 1806, 1816, 1826), the receivers comprising a hardware quantum optical detector and an electronic processor, and operable to detect (1912) a third information from at least a portion of the quantum optical signal; The receiver is operable to determine (1916) an indication of an attack on the optical communication channel based at least on the third information and on determining a correlation loss in the third information, wherein the correlation loss includes an excess difference between the distribution means of the two quantum states in the third information; and The receiver is operable to trigger an alarm indicating the attack.

13. The system of claim 12, wherein the indication of the attack further includes noise increase (1702).

14. The system of claim 12, wherein the sender is operable to use statistical techniques to distinguish false alarms from actual attacks, wherein the statistical techniques include one of: change point detection, Bayesian change point detection, supervised learning, or cumulative sum (CUSUM).

15. The system of claim 12, wherein the receiver further comprises a Kalman filter operable to predict and interpret phase fluctuations in the quantum optical signal.

16. The system of claim 12, wherein the receiver is operable to determine the correlation loss in the third information using a sliding window of values, and to calculate the excess difference between the distribution means of the two quantum states in the third information with respect to the sliding window of values.

17. The system of claim 12, wherein the classical optical signal and the quantum optical signal are interleaved.

18. The system of claim 12, wherein the attack includes at least one of an eavesdropping attack, a jamming attack, a related jamming attack, or an interrupt-retransmission attack.

19. The system of claim 12, wherein the optical communication channel comprises a distance of at least 50 km, and wherein the transmitter is operable to determine the indication of an attack on the optical communication channel with a sensitivity of less than or equal to 0.04 dB.

20. The system of claim 12, wherein the receiver is operable to use zero-difference detection to detect the third information from at least a portion of the quantum optical signal.

21. The system of claim 12, wherein the receiver is operable to use heterodyne detection to detect the third information from at least a portion of the quantum optical signal.

22. The system of claim 13, wherein the indication of the attack further includes transmission loss, and wherein the indication of the attack further includes bit value loss.

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