Quantum key distribution system based on spin LED chip

Abstract

The application discloses a quantum key distribution system based on a spin LED chip, which comprises a sending end, a receiving end, and an output end; the sending end is used for sending polarized light with different polarization states by using the spin LED chip; the receiving end is used for performing phase modulation on the polarized light sent by the sending end by using a detection base light path, detecting the modulated optical signal by using a detection circuit, and confirming whether a key is generated in this communication according to a detection result; if yes, the measurement base corresponding to the phase change is converted into 0 or 1 according to a rule agreed in advance; and the generated 01 sequence is output through the output end as a key. The application uses the spin LED integrated chip to generate a controllable polarized light signal, generates the optical signal with a specific polarization state through spin regulation, and converts the phase-modulated polarized light signal into an electrical signal by using a photoelectric detector, so that more stable and safer signal transmission can be realized in a high-speed and high-bandwidth optical communication system; and the application also provides a possibility for future optical calculation and quantum information processing.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of spintronics, and in particular to a quantum key distribution system based on a spin LED chip. BACKGROUND

[0002] With the rapid development of information technology, optical communication as a core technology for high-speed and long-distance transmission has been widely used. However, the traditional optical communication system mainly relies on intensity modulation and phase modulation, and when facing higher data transmission rate and more data information demand, it encounters a bottleneck. Polarization modulation of optical signals has gradually become a research hotspot due to its unique anti-interference and multi-dimensional information carrying capacity. The emergence of spintronics technology brings new possibilities for optical communication. As a typical representative of the combination of spintronics and semiconductor optoelectronics, spin LED can realize polarization modulation of light output by injecting polarized spin current. Compared with traditional LED, spin LED not only can adjust light intensity, but also can realize polarization control of optical signal by controlling spin polarization, and realize efficient polarized light emission by current injection, and the spin state of the photon corresponds to the state of the quantum bit.

[0003] However, the prior art in realizing phase modulation polarization state detection based on spin LED faces the following problems: accurate control of phase modulation: the current modulation technology is difficult to realize accurate control of phase in high-speed operation, which limits the running speed of the system. Noise and interference: during quantum computing, external environmental interference and noise will affect the photons emitted by the spin LED, and then affect the accuracy of detection. Lack of integrated design: current optoelectronic elements often cannot be effectively integrated in a system, resulting in low signal transmission efficiency, increasing the complexity and cost of the system. Therefore, it is difficult to apply to quantum key distribution. SUMMARY

[0004] The purpose of the present application is to solve the problems in the prior art.

[0005] The technical scheme adopted by the present application to solve its technical problems is to provide a quantum key distribution system based on a spin LED chip, comprising:

[0006] A sending end sends polarized light of different polarization states using a spin LED chip.

[0007] A receiving end modulates the polarized light sent by the sending end using a detection base light path, detects the modulated optical signal using a detection circuit, and confirms whether a key is generated this time according to the detection result; if so, converts the measurement base corresponding to the phase change to 0 or 1 according to the rules agreed in advance; and outputs a generated sequence of 01 as a key through an output end.

[0008] Preferably, the polarized light of different polarization states includes 45-degree linearly polarized light, right-handed polarized circularly polarized light, 135-degree linearly polarized light, and left-handed polarized circularly polarized light.

[0009] The phase changes include 0, π, and respectively correspond to four non-orthogonal polarization measurement bases of 45-degree linear polarization, right-handed polarized circular polarization, 135-degree linear polarization, and left-handed polarized circular polarization.

[0010] Preferably, the phase modulation of the polarized light sent by the sending end by using the detection base light path includes the following steps:

[0011] The polarized light is converged and collimated by using a focusing lens combination to obtain a focused light signal;

[0012] The focused light signal passes through a polarization beam splitter, a common beam splitter prism, a mirror, and a spatial light modulator to obtain two emergent light signals, a first emergent light signal corresponding to the polarized light sent by the sending end, and a second emergent light signal corresponding to the phase-modulated light signal; wherein the receiving party randomly generates a phase change by using the spatial light modulator to realize phase modulation.

[0013] Preferably, the receiving party randomly generates a phase change by using the spatial light modulator, specifically by controlling the input voltage to control the spatial light modulator to generate different phase changes, when the input voltage is 0, V0 / 2, V0, and 3 / 2V0, the spatial light modulator generates π, and respectively, corresponding to four non-orthogonal polarization measurement bases of 45-degree linear polarization, 135-degree linear polarization, left-handed circular polarization, and right-handed circular polarization, wherein V0 is a half-wave voltage.

[0014] Preferably, the detection base light path is specifically:

[0015] The focusing lens combination receives the controllable polarized light signal emitted by the light source, and the output end of the focusing lens combination is aligned with the first port of the first polarization beam splitting prism; the second port and the third port of the first polarization beam splitting prism are respectively aligned with the first port of the first common beam splitting flat mirror and the fourth port of the second common beam splitting flat mirror; the third port of the first common beam splitting flat mirror is aligned with the spatial light modulator, and the second port is aligned with the fourth port of the second polarization beam splitting prism; the second port of the second common beam splitting flat mirror is aligned with the reflecting flat mirror, and the third port is aligned with the first port of the second polarization beam splitting prism; the second port of the second polarization beam splitting prism is aligned with the input end of the half-wave plate, and the output end of the half-wave plate is aligned with the fourth port of the third polarization beam splitting prism; the second port and the third port of the third polarization beam splitting prism respectively emit the first emergent light signal and the second emergent light signal.

[0016] Preferably, the focusing prism assembly includes a focusing lens, a plano-concave mirror, and a plano-convex mirror. The controllable polarized light signal emitted by the light source passes through the focusing lens, the plano-concave mirror, and the plano-convex mirror in sequence to obtain a focused light signal.

[0017] Preferably, the first ordinary beam-splitting plane mirror and the second ordinary beam-splitting plane mirror both have a transmission light to reflection light separation ratio of 50:50.

[0018] Preferably, the spatial light modulator requires that the polarization direction of the incident polarized light is parallel to the optical axis of the liquid crystal of the spatial light modulator.

[0019] Preferably, the detection of the modulated optical signal using the detection circuit includes the following steps:

[0020] A photodetector is used to convert the two emitted lights into two electrical signals respectively, wherein the first emitted light signal is converted into a first electrical signal and the second emitted light signal is converted into a second electrical signal.

[0021] A voltage comparator is used to convert the first electrical signal into a first high or low level signal of 0 or 1, and the second electrical signal into a second high or low level signal of 0 or 1.

[0022] If the first high / low level signal is converted to 0 and the second high / low level signal is 0, or the first high / low level signal is converted to 1 and the second high / low level signal is 1, then no key is generated in this communication; if the first high / low level signal is converted to 0 and the second high / low level signal is 1, or the first high / low level signal is converted to 1 and the second high / low level signal is 0, then a key is generated in this communication.

[0023] Preferably, the step of converting the measurement basis corresponding to the phase change into 0 or 1 according to a pre-agreed rule specifically involves: Represents binary 0, Represents binary 1.

[0024] The present invention has the following beneficial effects:

[0025] (1) This invention creatively uses a spin LED integrated chip to generate a controllable polarized light signal and uses a measurement base to detect and identify the polarized light signal output by the chip. By generating a light signal with a specific polarization state through spin modulation, the polarization direction of the light can be changed very precisely, thus providing a more flexible basis for detection accuracy. Spin LEDs have extremely fast response speed when controlling the spin state, and at the same time, they consume less energy than traditional semiconductor devices, thus effectively improving the detection speed and energy efficiency.

[0026] (2) The application utilizes photoelectric detectors to convert the phase-modulated polarized light signals into electrical signals, and utilizes the electrical signals to detect the type of polarized light emitted by the spin LED integrated chip, so that efficient and accurate polarized light signal detection is realized; the detection efficiency and accuracy can be further improved by optimizing the design of the detector and the signal processing algorithm;

[0027] (3) The application has significant technical advantages in the innovative application of the spin LED, efficient conversion of the phase-modulated polarized light signals into electrical signals, and system integration design, and has high efficiency and high accuracy when applied to quantum communication.

[0028] The application will be further described in detail below in combination with the accompanying drawings and embodiments, but the application is not limited to the embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 System schematic diagram of the embodiment of the application. DETAILED DESCRIPTION

[0030] The application proposes a quantum key distribution system based on a spin LED chip by phase-modulating the spin-injected current of the spin LED, simplifies the system structure, realizes efficient modulation of the optical signals, and meets the needs of future high-speed optical communication and quantum information processing.

[0031] Referring to Figure 1 FIG. 1 is a system schematic diagram of the embodiment of the application, which includes:

[0032] The sending end, i.e., the light-emitting light source, adopts a GaN-based spin light-emitting diode in the embodiment of the application, adopts a MgO / Fe / Pd multilayer film structure as a spin injection end, and has a large circular polarization rate.

[0033] The receiving end includes a detection base light path part, a detection circuit, and an output end. The detection base light path part includes a focusing lens C1, a plane-concave mirror C2, a plane-convex mirror C3, a first polarized beam splitter PBS1, a second polarized beam splitter PBS2, a third polarized beam splitter PBS3, a first ordinary beam splitter BS1, a second ordinary beam splitter BS2, a reflecting mirror R1, a spatial light modulator SLM, and a half-wave plate P1; the detection circuit includes a first photoelectric detector D1, a second photoelectric detector D2, a first voltage amplifier F1, a second voltage amplifier F2, a first voltage comparator B1, and a second voltage comparator B2. The output end includes a data acquisition card S1 and a computer.

[0034] Specifically, the input end of the focusing lens is the input end of the light wave, the output end of the focusing lens is aligned with the input end of the plano-concave mirror, the output end of the plano-concave mirror is aligned with the input end of the plano-convex mirror, the output end of the plano-convex mirror is aligned with the first port of the polarizing beam splitter prism PBS1, the second and third ports of the polarizing beam splitter prism PBS1 are respectively aligned with the first port and the fourth port of the ordinary beam splitter plane mirror BS1 and BS2, the third port of BS1 is aligned with the spatial light modulator SLM, and the second port of BS2 is aligned with the reflecting plane mirror R1. The second port of BS1 and the third port of BS2 are respectively aligned with the fourth port and the first port of the second polarizing beam splitter prism PBS2. The second port of the second polarizing beam splitter prism PBS2 is aligned with the input end of the half-wave plate P1, the output end of the half-wave plate is aligned with the fourth port of the third polarizing beam splitter prism PBS3, and the second port and the third port of the third polarizing beam splitter prism are respectively aligned with the first photodetector D1 and the second photodetector D2. The first photodetector D1 and the second photodetector D2 are respectively connected to the input ends of the voltage amplifiers F1 and F2, and the output ends of the voltage amplifiers F1 and F2 are respectively connected to the voltage comparators B1 and B2. Finally, the voltage amplifiers F1 and F2 and the voltage comparators B1 and B2 are respectively connected to the input ends of the data acquisition card, and finally the output end of the data acquisition card is connected to the computer at the back end.

[0035] Specifically, the light wave output by the spin LED needs to be converged and collimated after passing through focusing lens C1, flat concave mirror C2 and flat convex mirror C3 due to its large divergence. After passing through first polarization beam splitter PBS1, the polarized light is divided into two components, vertical component and horizontal component, wherein the vertical component and the horizontal component are reflected and transmitted respectively. The horizontal component transmitted through the first polarization beam splitter PBS1 passes through common beam splitter BS1, and the component is further divided into transmitted component and reflected component. The transmitted component after passing through the common beam splitter BS1 is reflected by the reflecting surface of the spatial light modulator SLM, and the transmitted component after being reflected by the spatial light modulator SLM passes through the common beam splitter BS1 again, and is divided into transmitted component and reflected component. The reflected component after passing through the common beam splitter BS1 enters the second polarization beam splitter PBS2. The vertical component reflected by the first polarization beam splitter PBS1 passes through the common beam splitter BS2, and the component is further divided into transmitted component and reflected component. The transmitted component after passing through the common beam splitter BS2 is reflected by the reflecting surface of the mirror R1, and the transmitted component after being reflected by the mirror R1 passes through the common beam splitter BS1 again, and is divided into transmitted component and reflected component. The reflected component after passing through the common beam splitter BS1 enters the second polarization beam splitter PBS2. The two components are combined after passing through the second polarization beam splitter PBS2. The measurement bases of the phase modulation polarized light path are controlled by the loaded gray scale of the spatial light modulator, that is, when the SLM inputs four different voltage values, 0, V0 / 2, V0, 3V0 / 2 (V0 is half-wave voltage), four non-orthogonal polarization measurement bases of 45° linear polarization, 135° linear polarization, left-handed circular polarization and right-handed circular polarization are provided. The combined light wave passes through half-wave plate P1, and finally passes through third polarization beam splitter PBS3. The exit direction of the light wave is affected by the measurement base, that is, the exit light signal can be controlled by the measurement base.

[0036] The reflected and transmitted light signals after passing through the third polarization beam splitter PBS3 are finally received by photodetectors D1 and D2. Due to the modulation of the SLM, the measurement bases are also different, so different respective electrical signals are converted. According to the different conditions of the electrical signals of the two photodetectors, the type of the polarized light emitted by the LED chip can be determined. After passing through the voltage amplifier, the signal is further amplified, and then passes through the voltage comparator (with a specific threshold voltage). If the voltage is less than and greater than the threshold voltage, it will become 0 and 1 high and low level respectively. According to the source of the high and low level of the detector, the polarization state of the polarized light input by the spin LED integrated chip can be determined.

[0037] When performing quantum key distribution using this embodiment of the invention, the transmitting end, Alice, first uses a high-frequency signal generator and a random number generator to randomly transmit light in four polarization states: 45-degree linear polarization, right-handed circular polarization, 135-degree linear polarization, and left-handed circular polarization via a spin LED chip. Simultaneously, the receiving end, Bob, applies a voltage of the same frequency as the high-frequency signal generator at the transmitting end using a random number generator and a driving voltage, thereby randomly generating 0. π The phase changes of these phases generate measurement bases for four non-orthogonal polarization states: 45-degree linear polarization, right-handed circular polarization, 135-degree linear polarization, and left-handed circular polarization. Among these, the 45-degree and 135-degree linear polarization measurement bases generated by 0 and π are a pair of conjugate measurement bases. and The generated right-handed and left-handed circularly polarized beams form a pair of conjugate measurement bases, which are used to detect the polarization state of the high-frequency pulsed light transmitted from the transmitter. Finally, according to the agreement between Alice (transmitter) and Bob (receiver), 45-degree linearly polarized light and right-handed circularly polarized light represent binary 0, and 135-degree linearly polarized light and left-handed circularly polarized light represent binary 1. Bob randomly modulates the phase, that is, randomly selects the measurement base to measure the polarized light transmitted by Alice. For example, if Alice transmits linearly polarized light, Bob modulates the phase between 0 and π to generate a linearly polarized measurement base. After comparing the bases, it can be considered that Bob has selected the correct measurement base, and the result of this communication can be used as part of the key. Bob then performs... or The phase modulation generates a circular polarization measurement base for detection. If the base is not selected correctly, the two communicating parties will discard the measurement. Finally, after all comparisons, the sending and receiving ends can jointly form a key.

[0038] Specifically, photodetectors D1 and D2 convert the light signals transmitted and reflected from the second polarizing beam splitter PBS2 into electrical signals, respectively. These electrical signals F1 and F2 are then amplified by voltage amplifiers. Voltage comparators B1 and B2 can further convert signals greater than or less than a threshold into high or low level signals (0 or 1), respectively, by setting appropriate thresholds. The data acquisition results are then output through a data acquisition device. For example, if Bob is subjected to... Phase change, that is, the right-handed circularly polarized measurement base is provided, the right-handed chiral circularly polarized light (the right-handed circularly polarized light is more than the left-handed circularly polarized light) emitted by the spin LED is detected, according to the previous agreement, it represents the key of binary 0, the light intensity detected by the detector 2 is greater than the light intensity detected by the detector 1, then after comparison by the voltage comparator and the threshold, it can be further converted into the high and low level signals of 0,1 of the signal greater than and less than the threshold, that is, the voltage signal finally output by the detector 1 is 0, and the voltage signal finally output by the detector 2 is 1, so according to the voltage signal finally output, it can be known that when the measurement base and the polarization state of the emission end are the same, the finally output is the accurate signal, we can keep the key 0 brought by this detection. Then, if the Bob end applies 0 phase change, that is, the linearly polarized light measurement base is provided, if the right-handed chiral polarized light (the right-handed circularly polarized light is more than the left-handed circularly polarized light) emitted by the spin LED is still detected, according to the previous agreement, it represents the key of binary 0. But because the measurement base and the polarization state are different, the detection result is random, and the high level signal of 1 is presented on the voltage signal finally output, so according to the voltage signal finally output, it can be known that when the measurement base and the polarization state of the emission end are different, the finally output is the inaccurate signal, then we can remove the key 0 brought by this detection according to the result. Therefore, after the emission end continuously emits polarized light at a certain frequency, and the receiving end generates the measurement base to measure it at the same frequency, after a series of detections, according to the specific level of the voltage signal at the back end, the key of each measurement is removed or kept, finally a series of ideal keys can be formed, and the distribution of a series of keys is completed.

[0039] The above is only the preferred embodiment of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A quantum key distribution system based on a spin LED chip, characterized in that, include: At the transmitting end, a spin LED chip is used to transmit polarized light with different polarization states; At the receiving end, the polarized light transmitted by the transmitting end is phase-modulated using the detection base optical path, and the modulated optical signal is detected using the detection circuit. Based on the detection result, it is confirmed whether a key has been generated in this communication. If so, the measurement base corresponding to the phase change is converted to 0 or 1 according to the pre-agreed rules. A string of 01 sequences generated is output as the key through the output end. The step of using a detection base optical path to perform phase modulation on the polarized light transmitted from the transmitting end includes the following steps: A combination of focusing lenses is used to converge and collimate polarized light to obtain a focused light signal; The focused optical signal passes through a polarization beam splitter, a beam splitter prism, a reflector, and a spatial light modulator to obtain two outgoing optical signals. The first outgoing optical signal corresponds to the polarized light transmitted by the transmitting end, and the second outgoing optical signal corresponds to the phase-modulated optical signal. The receiving end uses the spatial light modulator to randomly generate a phase change to achieve phase modulation. The receiver uses a spatial light modulator to randomly generate a phase change. Specifically, the input voltage is controlled to control the spatial light modulator to generate different phase changes. When the input voltage is 0, V0 / 2, V0, and 3 / 2V0, the spatial light modulator generates different phase changes. The phase change corresponds to four non-orthogonal polarization measurement bases: 45° linear polarization, 135° linear polarization, left-hand circular polarization, and right-hand circular polarization, where V0 is the half-wave voltage.

2. The quantum key distribution system based on a spin LED chip according to claim 1, characterized in that, The polarized light with different polarization states includes 45-degree linearly polarized light, right-handed polarized circularly polarized light, 135-degree linearly polarized light, and left-handed polarized circularly polarized light; The phase change includes 0, , and These correspond to measurement bases that generate four non-orthogonal polarization states: 45-degree linear polarization, right-handed polarized circular polarization, 135-degree linear polarization, and left-handed polarized circular polarization.

3. The quantum key distribution system based on a spin LED chip according to claim 1, characterized in that, The detection optical path is specifically as follows: The focusing lens assembly receives the controllable polarized light signal emitted by the light source, and the output end of the focusing lens assembly is aligned with the first port of the first polarizing beam splitter prism; the second and third ports of the first polarizing beam splitter prism are respectively aligned with the first port of the first ordinary beam splitter plane mirror and the fourth port of the second ordinary beam splitter plane mirror. The third port of the first ordinary beam-splitting plane mirror is aligned with the spatial light modulator, and the second port is aligned with the fourth port of the second polarizing beam-splitting prism. The second port of the second ordinary beam-splitting plane mirror is aligned with the reflecting plane mirror, and the third port is aligned with the first port of the second polarizing beam-splitting prism. The second port of the second polarizing beam splitter is aligned with the input end of the half-wave plate, and the output end of the half-wave plate is aligned with the fourth port of the third polarizing beam splitter; the second port and the third port of the third polarizing beam splitter emit the first outgoing light signal and the second outgoing light signal, respectively.

4. The quantum key distribution system based on a spin LED chip according to claim 3, characterized in that, The focusing lens assembly includes a focusing lens, a plano-concave mirror, and a plano-convex mirror. The controllable polarized light signal emitted by the light source passes through the focusing lens, the plano-concave mirror, and the plano-convex mirror in sequence to obtain a focused light signal.

5. The quantum key distribution system based on a spin LED chip according to claim 4, characterized in that, The first and second ordinary beam-splitting plane mirrors both have a transmission light to reflection light separation ratio of 50:

50.

6. The quantum key distribution system based on a spin LED chip according to claim 5, characterized in that, The spatial light modulator requires that the polarization direction of the incident polarized light be parallel to the optical axis of the liquid crystal of the spatial light modulator.

7. The quantum key distribution system based on a spin LED chip according to claim 1, characterized in that, The detection of the modulated optical signal using a detection circuit includes the following steps: A photodetector is used to convert the two emitted lights into two electrical signals respectively, wherein the first emitted light signal is converted into a first electrical signal and the second emitted light signal is converted into a second electrical signal. A voltage comparator is used to convert the first electrical signal into a first high or low level signal of 0 or 1, and the second electrical signal into a second high or low level signal of 0 or 1. If the first high / low level signal is converted to 0 and the second high / low level signal is 0, or the first high / low level signal is converted to 1 and the second high / low level signal is 1, then no key is generated in this communication; if the first high / low level signal is converted to 0 and the second high / low level signal is 1, or the first high / low level signal is converted to 1 and the second high / low level signal is 0, then a key is generated in this communication.

8. The quantum key distribution system based on a spin LED chip according to claim 1, characterized in that, The step of converting the measurement basis corresponding to the phase change into 0 or 1 according to a pre-agreed rule is specifically as follows: (0, ) represents binary 0, ( , ) represents binary 1.

Images