Single photon detector and method of operation

Abstract

The present invention relates to a single photon detector and an operating method, and more particularly, to a single photon detector and an operating method in which a single photon detector without a cooling system, which can be operated at room temperature and can have a reduced size, is realized by allowing a photon detection signal to be separated from dark count noise and detected in the single photon detector by means of. A single photon detector for detecting a single photon is disclosed, including a gate signal generation unit for generating a gate signal having a first pulse width (△P) with respect to a first time point (t1); and a first photon detection unit for detecting a single photon when operated in a Geiger mode by receiving the gate signal and outputting a photon detection signal at a second time point (t2), wherein the first photon detector outputs the photon detection signal at the second time point (t2) separated from the first time point (t1) by a predetermined time interval (△T).

Description

Technical Field

[0001] This disclosure relates to a single-photon detector and a method of operating the same. More specifically, this disclosure relates to a single-photon detector that detects single-photon signals by separating the signal photon signal from the dark counting noise and without requiring a cooling system, which enables the single-photon detector to operate at room temperature and has a reduced size. Background Technology

[0002] In recent years, with the widespread availability of wired and wireless communication services and increased public awareness of personal information, security issues related to communication networks have become significant concerns. In particular, security issues in communication networks connected to national, corporate, financial, and other sectors have extended beyond personal concerns, becoming societal problems and further emphasizing the importance of security.

[0003] However, with the development of hacking techniques, prior-secure communication based on existing technologies has become more vulnerable to external attacks, potentially exposing the content of communications. As a next-generation security technology, quantum cryptography communication guarantees extremely high security and is attracting increasing attention.

[0004] Here, in quantum cryptography, single photons (or quasi-single photons) ensure security by utilizing quantum properties. Single photon detectors are used to detect single photons.

[0005] Because a single photon has a very small amount of light, it is impossible to detect a single photon using a typical photodetector. Therefore, avalanche photodiodes (APDs) are commonly used to construct single-photon detectors.

[0006] like Figure 1 As shown, a periodic gating signal is applied to operate the single-photon detector, and the single-photon detector generates a response signal to the gating signal. However, the response signal is also known as background noise. This background noise can occur when the output signal of the single photon fluctuates between its minimum and maximum values, and it makes it difficult to detect single photons.

[0007] Therefore, a common method is to detect single photons by increasing the gain of the single-photon detector and separating only the single-photon detection signal generated above the background noise. However, in this case, the thermal noise inside the single-photon detector increases due to the increased gain. Furthermore, even without single-photon incident noise, noise called dark counting can occur, and it is difficult to distinguish this dark counting noise from the single-photon detection signal. In particular, since a significant amount of dark counting noise can occur when the single-photon detector operates at room temperature, it is typically cooled to -40 to -50°C using a cooling system to suppress this.

[0008] However, due to the limitations of the cooling system, the operation of single-photon detectors is easily affected by changes in the external environment, and miniaturization of single-photon detectors is difficult. On the other hand, when single-photon detectors operate at room temperature, dark counting noise increases significantly, making it even more difficult to detect single photons.

[0009] Therefore, in quantum cryptographic communication systems, there is a need for a single-photon detector that does not require a cooling system, can operate at room temperature, and has a reduced size. Summary of the Invention

[0010] Technical issues

[0011] Therefore, this disclosure has been made in view of the above-mentioned problems, and this disclosure provides a single-photon detector and a method of operating the same, which operates at room temperature, has no cooling system and has a reduced size, thereby suppressing the occurrence of errors caused by dark counting noise when operating the single-photon detector in a quantum cryptographic communication system.

[0012] Other detailed objectives of this disclosure will be clearly identified and understood by those skilled in the art or researchers through the specific details described below.

[0013] Solution to the problem

[0014] A single-photon detector for detecting a single photon according to an embodiment of the present disclosure may include a gating signal generator configured to generate a gating signal having a first pulse width ΔP relative to a first time point t1; and a first photon detector configured to detect a single photon while operating in Geiger mode by receiving the gating signal, and to output a photon detection signal at a second time point t2, wherein the first photon detector outputs the photon detection signal at a second time point t2 separated from the first time point t1 by a predetermined time interval ΔT.

[0015] In this case, the single-photon detector may further include a photon detection signal subtractor configured to subtract a noise signal, including dark counting noise, from the photon detection signal passing through the first photon detector and output a noise subtraction signal.

[0016] Furthermore, the single-photon detector may also include a second photon detector configured to output a noise signal including dark counting noise, wherein the photon detection signal subtractor can output a noise subtraction signal by receiving a photon detection signal from the first photon detector and a noise signal from the second photon detector.

[0017] Furthermore, in the second photon detector, a bias voltage higher than a predetermined reference value can be applied to the second photon detector, so that dark counting noise occurs continuously even when there is no single photon incident.

[0018] Alternatively, the first time point t1 may be the time point corresponding to the peak of the dark counting noise, and the second time point t2 may be the time point corresponding to the peak of the photon detection signal generated after the first time point t1.

[0019] Furthermore, in a single-photon detector, the first pulse width ΔP can be adjusted to include both the first time point t1 and the second time point t2.

[0020] Furthermore, since the single-photon detector does not include a cooling system for reducing the temperature of the first photon detection unit, the first photon detection unit can operate at room temperature.

[0021] A method of operating a single-photon detector according to an embodiment of the present disclosure may include: generating a gating signal having a first pulse width ΔP relative to a first time point t1; and detecting a single photon while operating in Geiger mode by receiving the gating signal, and outputting a photon detection signal at a second time point t2, wherein in the detection of the first photon, the photon detection signal may be output at a second time point t2, which is separated from the first time point t1 by a predetermined time interval ΔT.

[0022] Advantages of the invention

[0023] According to this disclosure, a single-photon detector can separate the photon detection signal from dark counting noise and detect the separated photon detection signal. Therefore, the signal photon detector according to this embodiment operates at room temperature and has a reduced size because it does not require a cooling system. Attached Figure Description

[0024] The accompanying drawings, which are included as part of the detailed description to aid in understanding the present disclosure, provide examples of the disclosure and, together with the detailed description, explain the technical ideas of the disclosure.

[0025] Figure 1 This is a schematic diagram illustrating a single-photon detector according to the prior art.

[0026] Figure 2 This is a diagram illustrating a quantum cryptographic communication system according to an embodiment of the present disclosure.

[0027] Figure 3 This is a block diagram illustrating a single-photon detector according to an embodiment of the present disclosure.

[0028] Figure 4 and 5 This is a diagram illustrating the operation of a single-photon detector according to an embodiment of the present disclosure.

[0029] Figure 6 This is a flowchart illustrating a method for operating a single-photon detector according to an embodiment of the present disclosure. Detailed Implementation

[0030] This disclosure can be modified in various ways and can have various embodiments. Specific embodiments will be described in detail below based on the accompanying drawings.

[0031] The following examples are provided to provide a full understanding of the methods, apparatus, and / or systems described in this specification. However, these are merely examples, and this disclosure is not limited thereto.

[0032] In describing exemplary embodiments of this disclosure, detailed descriptions of known technologies related to this disclosure will be omitted when it is determined that a detailed description may unnecessarily obscure the essential points of the invention. Furthermore, terms defined in consideration of the functionality in this invention and to be described below may vary depending on the intent of the user or operator or common practice. Therefore, these terms need to be defined based on the content throughout this specification. The terms used in the detailed description are only for describing exemplary embodiments of this disclosure and should not be construed as limiting in any way. Unless expressly used otherwise, singular expressions include the meaning of plural forms. In this specification, expressions such as “comprising” or “including” are intended to indicate certain features, numbers, steps, operations, elements, some or combinations thereof, and should not be construed, except as described, as excluding the presence or possibility of one or more other features, numbers, steps, operations, elements, some or combinations thereof.

[0033] Furthermore, terms such as first, second, etc. are used to describe various constituent elements, but constituent elements are not limited by these terms, and these terms are only used to distinguish one constituent element from other constituent elements.

[0034] In the following description, exemplary embodiments of a single-photon detector and its operation method according to embodiments of the present disclosure will be described in sequence with reference to the accompanying drawings.

[0035] Figure 2 A quantum cryptographic communication system 10 according to an embodiment of the present disclosure is shown. Reference Figure 2 The quantum cryptographic communication system 10 according to embodiments of the present disclosure may include a transmitter 11, a receiver 12, and a quantum channel 13. The transmitter 11 and receiver 12 generate and share a quantum cryptographic key, and simultaneously exchange optical signals through the quantum channel 13. Furthermore, the transmitter 11 and receiver 12 use the quantum cryptographic key to perform quantum communication.

[0036] For example, transmitter 11 and receiver 12 can be 1) a server, 2) a client or terminal device connected to the server, 3) a communication device such as a gateway and router, or 4) a portable device with mobility. Furthermore, transmitter 11 and receiver 12 can be configured with various devices capable of generating and sharing quantum cryptographic keys to perform communication.

[0037] Furthermore, a quantum channel 13 is provided between the transmitter 11 and the receiver 12 to transmit optical signals. According to an embodiment, the quantum channel 13 may be configured with an optical fiber. However, this disclosure is not limited thereto. For example, the quantum channel 13 may be any medium capable of transmitting optical signals.

[0038] Therefore, transmitter 11 and receiver 12 can use various protocols such as BB84 to exchange information necessary for generating quantum cryptographic keys using the phase, polarization, etc., of optical signals, and can generate and share quantum cryptographic keys. This can effectively prevent attacker 14 from attempting to steal quantum cryptographic keys and launch hacking attacks.

[0039] According to an embodiment, transmitter 11 and receiver 12 may include a quantum key distribution device and a quantum key management device. The quantum key distribution device (QKD) generates a quantum key stream and provides it to the quantum key management device (QKM). The quantum key management device (QKM) generates quantum cryptographic keys according to the relevant standard specifications of the service device performing quantum cryptographic communication and provides the generated quantum cryptographic keys to the service device. Therefore, the service device can perform quantum cryptographic communication by encrypting and transmitting or decrypting plaintext using the provided quantum cryptographic keys, thereby enhancing the security of the communication system.

[0040] Figure 3 This is a block diagram illustrating a single-photon detector 100 according to an embodiment of the present disclosure. Here, the single-photon detector 100 can detect single photons (or corresponding quasi-single photons) from the receiver 12, etc.

[0041] Single photons contain a very small amount of light, making it impossible to detect them using typical photodetectors. According to embodiments of this disclosure, a single-photon detector 100 includes an avalanche photodiode (APD) that operates in Geiger mode to detect single photons.

[0042] More specifically, such as Figure 3 As shown, a single-photon detector 100 according to an embodiment of this disclosure may include a gating signal generator 110 configured to generate a gating signal having a first pulse width ΔP relative to a first time point t1; and a first photon detector 120 configured to detect single photons when operating in Geiger mode by receiving the gating signal, and to output a photon detection signal at a second time point t2. The first photon detector 120 outputs the photon detection signal at a second time point t2, which is separated from the first time point t1 by a predetermined time interval ΔT.

[0043] More specifically, the gating signal generator 110 can generate a gating signal with a first pulse width ΔP relative to the first time point t1, and provide the generated gating signal to the first photon detector 120.

[0044] Therefore, the first photon detector 120 can receive a gating signal, detect a single photon from the received gating signal, and output a photon detection signal.

[0045] Here, according to an embodiment, the first photon detector 120 may be configured with an avalanche photodiode (APD). However, this disclosure is not limited thereto.

[0046] Therefore, when a periodic gating signal is applied to the APD, the APD can generate an output signal while operating in Geiger mode.

[0047] Here, when the first photon detector 120 receives a single photon (or its corresponding quasi-single photon), the first photon detector 120 can output a photon detection signal through the single photon.

[0048] The first photon detector 120 can output a photon detection signal at a second time point t2, which is separated from the first time point t1 by a predetermined time interval ΔT. This allows the output of a photon detection signal caused by a single photon to be separated from noise signals caused by dark counting noise. Therefore, even if noise such as dark counting noise occurs, a single photon can be detected by identifying the photon detection signal.

[0049] In addition, such as Figure 3 As shown, the single-photon detector 100 according to an embodiment of the present disclosure may further include a second photon detector 130 configured to output a noise signal including dark count noise, and a photon detection signal subtractor 140 configured to output a noise subtraction signal by subtracting the noise signal including dark count noise from the photon detection signal caused by the first photon detector 120.

[0050] like Figure 4 As shown, the single-photon detector 100 according to an embodiment of the present disclosure separates and detects a noise signal including dark counting noise from the photon detection signal output from the first single-photon detector 120. Therefore, the single-photon detector 100 can detect single photons without a cooling system, thereby operating at room temperature and having a reduced size.

[0051] Figure 4 Figure (a) illustrates the relevant techniques for applying gating pulses to operate the APD. For example... Figure 4 As shown in (a), when the gating pulse is applied to the APD, the incident timing of the single photon is controlled to be positioned at as many points as possible where single-photon detection signals are generated. Furthermore, in order to maximize the stability of single-photon detection even if the timing of single-photon incident varies slightly due to temperature changes in the quantum channel 13, the single photon is also adjusted to be incident at a first time point t1 corresponding to the center point of the gating signal having a first pulse width ΔP.

[0052] Therefore, in related technologies, it is necessary to suppress the occurrence of dark counting noise as much as possible in the APD. Consequently, a cooling system is necessary for the APD, thus cooling its internal temperature to -40 to -50°C to suppress dark counting noise.

[0053] exist Figure 4 Figure (b) illustrates the operation of a single-photon detector 100 according to an embodiment of the present disclosure. A first photon detector 120 can detect single photons when operating in Geiger mode by receiving a gating signal and outputs a photon detection signal at a second time point t2. The first photon detector 120 can output the photon detection signal at a second time point t2, separated from the first time point t1 by a predetermined time interval ΔT, such that the photon detection signal caused by the single photon can be output at a distance from noise signals caused by dark counting noise. Therefore, even if noise such as dark counting noise occurs, single photons can be detected by identifying the photon detection signal.

[0054] like Figure 4 As shown, the single-photon detector 100 according to an embodiment of this disclosure can adjust the second time point t2 to a time interval ΔT delayed from the first time point t1.

[0055] Furthermore, considering the time point at which dark counting noise is generated in the first photon detector 120, the single-photon detector 100 according to the embodiments of this disclosure can be spaced out at the second time point t2 of the output photon detection signal.

[0056] More specifically, the first time point t1 may be the time point corresponding to the peak of the dark counting noise, and the second time point t2 may be the time point corresponding to the peak of the photon detection signal generated after the first time point t1.

[0057] Furthermore, the single-photon detector 100 according to embodiments of this disclosure can adjust the first pulse width ΔP to include both a first time point t1 and a second time point t2.

[0058] More specifically, such as Figure 4 As shown, when the interval between the first time point t1, corresponding to the peak of the dark counting noise, and the second time point t2, corresponding to the peak of the photon detection signal, is insufficient, the single-photon detector 100 according to the embodiment may have difficulty effectively detecting single photons. Therefore, according to the embodiment, the second time point t2 can be adjusted to be appropriately spaced from the first time point t1. Thus, the detection efficiency of single photons can be improved by adjusting the first pulse width ΔP to include both the first time point t1 and the second time point t2.

[0059] Therefore, the single-photon detector 100 according to the embodiments of this disclosure can delay the output of the photon detection signal from the first single-photon detector 120 to a second time point t2 from the first time point t1, and adjust the first pulse width ΔP of the gating signal. Thus, the single-photon detection efficiency in the single-photon detector 100 can be improved.

[0060] like Figure 5 As shown, a single-photon detector 100 according to an embodiment of the present disclosure may include i) a second photon detector 130 configured to output a noise signal including dark count noise and ii) a photon detection signal subtractor 140 configured to subtract the noise signal including dark count noise from the photon detection signal caused by the first photon detector 120 and output a noise subtraction signal.

[0061] Therefore, the photon detection signal subtractor 140 can output a noise subtraction signal by receiving a photon detection signal from the first photon detector 120 and a noise signal from the second photon detector 130.

[0062] At this time, the second photon detector 130 may have a structure provided with a bias voltage higher than a predetermined reference value so as to continuously generate dark counting noise while blocking the incidence of single photons.

[0063] Therefore, as Figure 5 As shown, the photon detection signal subtractor 140 can receive a photon detection signal from the first photon detector 120, receive a noise signal from the second photon detector 130, and output a noise subtraction signal obtained by subtracting the noise signal from the photon detection signal.

[0064] like Figure 5 As shown, the noise subtraction signal output from the photon detection signal subtractor 140 can remove not only dark count noise but also background signal noise. Furthermore, it may even detect weak photon detection signals that are otherwise impossible to detect. Therefore, according to the embodiment, detection efficiency can be improved.

[0065] Furthermore, according to the embodiments of the present disclosure, the first photon detector 120 of the single-photon detector 100 can operate at room temperature without requiring a cooling system to reduce the temperature of the first photon detector 120, thus enabling efficient detection of single photons even when dark counting noise is generated. Therefore, the single-photon detector can have a reduced size.

[0066] [Modes for Implementing the Invention]

[0067] also, Figure 6A flowchart of a method for operating a single-photon detector according to an embodiment of the present disclosure is shown. The method for operating a single-photon detector according to an embodiment of the present disclosure may include generating (S110) a gating signal having a first pulse width ΔP relative to a first time point t1; and detecting (S120) a single photon in Geiger mode operation by receiving the gating signal and outputting a photon detection signal at a second time point t2, wherein, in the detection of the first photon (S12), the photon detection signal is output at a second time point t2, which is separated from the first time point t1 by a predetermined time interval ΔT.

[0068] In this case, due to the description of the single-photon detector 100 and Figures 2 to 5 Methods for operating a single-photon detector according to embodiments of this disclosure can be referenced, and therefore a detailed description thereof will be omitted herein.

[0069] Furthermore, the computer program according to another embodiment of this disclosure is characterized in that it is a computer program stored in a computer-readable medium to perform each step of the method for operating a single-photon detector described above on a computer. The computer program can be a computer program including machine language code generated by a compiler, or a computer program including high-level language code that can be executed on a computer using an interpreter or the like. In this case, the computer is not limited to a personal computer (PC) or a laptop computer, and is equipped with a central processing unit (CPU) such as a server, communication device, smartphone, tablet computer, PDA, mobile phone, etc., to execute the computer program of the information processing device. Furthermore, the computer-readable medium includes electronic recording media (e.g., ROM, flash memory, etc.), magnetic storage media (e.g., floppy disk, hard disk, etc.), optical reading media (e.g., CD-ROM, DVD, etc.), and carrier waves (e.g., transmission via the Internet), encompassing all storage media that a computer can read.

[0070] Therefore, in the single-photon detector and its operation method according to the embodiments of the present disclosure, the photon detection signal can be separated from and detected by dark counting noise, so that the single-photon detector can be realized without a cooling system, thereby enabling the single-photon detector to operate at room temperature and having a reduced size.

[0071] The above description is merely an example of the technical concept of the present invention, and various modifications and variations can be made by those skilled in the art without departing from the concept of the present invention. Therefore, the above embodiments are not intended to limit the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by the embodiments. The scope of protection of the present invention should be interpreted according to the claims, and all technical concepts equivalent to them should be interpreted as being included within the scope of this disclosure.

Claims

1. A single-photon detector for detecting single photons, comprising: A gating signal generator is configured to generate a gating signal having a first pulse width ΔP relative to a first time point t1; The first photon detector is configured to receive the gating signal, operate in Geiger mode, detect single photons, and output a photon detection signal at a second time point t2. as well as A photon detection signal subtractor is configured to subtract a noise signal, including dark count noise, from the photon detection signal generated by the first photon detector, and output a noise subtraction signal. The first photon detector outputs a photon detection signal at a second time point t2, which is separated from the first time point t1 by a predetermined time interval ΔT.

2. The single-photon detector according to claim 1, further comprising: The second photon detector is configured to output a noise signal that includes dark counting noise. The photon detection signal subtractor receives a photon detection signal from the first photon detector, receives a noise signal from the second photon detector, and outputs a noise subtraction signal.

3. The single-photon detector according to claim 2, wherein the second photon detector receives a bias voltage higher than a predetermined reference value to generate dark counting noise in the absence of single-photon incident.

4. The single-photon detector according to claim 2, wherein: The first time point t1 is the time point corresponding to the peak value of the dark counting noise; and The second time point t2 is the time point corresponding to the peak value of the photon detection signal generated after the first time point t1.

5. The single-photon detector according to claim 1, wherein the single-photon detector adjusts the first pulse width ΔP to include both the first time point t1 and the second time point t2.

6. The single-photon detector of claim 1, wherein the first photon detector operates at room temperature without a cooling system for reducing the temperature of the first photon detector.

7. A method for operating a single-photon detector, the single-photon detector comprising a gating signal generator, a first photon detector, and a photon detection signal subtractor, the method comprising: The gating signal generator generates a gating signal with a first pulse width ΔP relative to the first time point t1; The first photon detector receives the gating signal, operates in Geiger mode, detects single photons, and outputs a photon detection signal at a second time point t2; and The photon detection signal subtractor subtracts noise, including dark count noise, from the photon detection signal and outputs a noise subtraction signal. Specifically, in the output of the photon detection signal, the first photon detector outputs the photon detection signal at a second time point t2, which is separated from the first time point t1 by a predetermined time interval ΔT.

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