Quantum key distribution system based on spinning LED chip

Abstract

The invention discloses a quantum key distribution system based on a spinning LED chip, and the system comprises a transmitting end which transmits polarized light in different polarization states through the spinning LED chip; the receiving end performs phase modulation on the polarized light sent by the sending end by using a detection base light path, detects a modulated light signal by using a detection circuit, and determines whether a secret key is generated in the communication according to a detection result; if yes, converting the measurement basis corresponding to the phase change into 0 or 1 according to a pre-agreed rule; and outputting the generated 01 sequence as a secret key through the output end. The spinning LED integrated chip is used for generating a controllable polarized light signal, an optical signal in a specific polarization state is generated through spinning regulation and control, the polarized light signal after phase modulation is converted into an electric signal through the photoelectric detector, and more stable and safer signal transmission can be achieved in a high-speed and high-bandwidth optical communication system; and possibility is provided for future light calculation and quantum information processing.

Description

Technical Field

[0001] The invention relates to the field of spin electronics, and in particular to a quantum key distribution system based on a spin LED chip. Background Art

[0002] With the rapid development of information technology, optical communication has been widely used as a core technology for high-speed and long-distance transmission. However, traditional optical communication systems mainly rely on intensity modulation and phase modulation, and have encountered bottlenecks when facing higher data transmission rates and more data information requirements. Polarization modulation of optical signals has gradually become a research hotspot due to its unique anti-interference and multi-dimensional information carrying capabilities. The emergence of spintronics technology has brought new possibilities for optical communication. Spin LEDs, as a typical representative of the combination of spin electronics and semiconductor optoelectronics, can achieve polarization modulation of light output by injecting polarized spin currents. Compared with traditional LEDs, spin LEDs can not only adjust light intensity, but also achieve polarization control of optical signals by controlling spin polarization, and achieve efficient polarized light emission through current injection. The spin state of its photons corresponds to the state of the quantum bit.

[0003] However, the existing technology faces the following problems when realizing phase-modulated polarization state detection based on spin LEDs: Precise control of phase modulation: Current modulation technology is difficult to achieve precise control of phase in high-speed operation, resulting in the limitation of the system's operating speed. Noise and interference: During quantum computing, interference and noise from the external environment will affect the photons emitted by the spin LED, thereby affecting the accuracy of detection. Lack of integrated design: Current optoelectronic components often cannot be effectively integrated into a system, resulting in low signal transmission efficiency and increased system complexity and cost. Therefore, it is difficult to apply to quantum key distribution. Summary of the invention

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

[0005] The technical solution adopted by the present invention to solve the technical problem is: to provide a quantum key distribution system based on a spin LED chip, comprising:

[0006] At the transmitting end, the spin LED chip is used to transmit polarized light of different polarization states;

[0007] At the receiving end, the detection base optical path is used to phase modulate the polarized light sent by the transmitting end, and the modulated optical signal is detected by the detection circuit. According to the detection result, it is confirmed whether the communication generates a key. If so, the measurement basis corresponding to the phase change is converted into 0 or 1 according to the pre-agreed rules. The generated string of 01 sequences is output through the output end as the key.

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

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

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

[0011] A focusing lens combination is used to converge and collimate the polarized light to obtain a focused light signal;

[0012] 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, wherein the first outgoing optical signal corresponds to the polarized light sent by the transmitting end, and the second outgoing optical signal corresponds to the phase-modulated optical signal; wherein the receiving end uses the spatial light modulator to randomly generate a phase change to achieve phase modulation.

[0013] Preferably, the receiving party uses a spatial light modulator to randomly generate a phase change, 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 respectively, the spatial light modulator generates π and The phase change corresponds to four non-orthogonal polarization measurement bases, namely 45° linear polarization, 135° linear polarization, left-hand circular polarization and right-hand circular polarization, where V0 is the half-wave voltage.

[0014] Preferably, the detection base optical 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 splitter prism; the second port and the third port of the first polarization 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 splitter plane mirror is aligned with the spatial light modulator, and the second port is aligned with the fourth port of the second polarization beam splitter prism; the second port of the second ordinary beam splitter plane mirror is aligned with the reflecting plane mirror, and the third port is aligned with the first port of the second polarization beam splitter prism; the second port of the second polarization beam splitter 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 splitter prism; the second port and the third port of the third polarization beam splitter prism respectively emit the first output light signal and the second output light signal.

[0016] Preferably, the focusing prism combination includes a focusing lens, a plano-concave mirror and a plano-convex mirror, and 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 separation ratio of the transmitted light and the reflected light of the first ordinary beam splitting plane mirror and the second ordinary beam splitting plane mirror is 50:50.

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

[0019] Preferably, the detecting the modulated optical signal by using a detection circuit comprises the following steps:

[0020] A photoelectric detector is used to convert two outgoing lights into two electrical signals respectively, wherein the first outgoing light signal is converted into a first electrical signal, and the second outgoing light signal is converted into a second electrical signal;

[0021] Using a voltage comparator to convert the first electrical signal into a first high-low level signal of 0 or 1, and convert the second electrical signal into a second high-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, 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, a key is generated in this communication.

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

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

[0025] (1) The present 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 spin LED integrated chip. By generating a light signal with a specific polarization state through spin regulation, the polarization direction of the light can be changed very accurately, thereby providing a more flexible basis for detection accuracy. The spin LED has an extremely fast response speed when controlling the spin state, and compared with traditional semiconductor devices, it has lower energy consumption, so it can effectively improve the detection speed and energy efficiency.

[0026] (2) The present invention uses a photodetector to convert the phase-modulated polarized light signal into an electrical signal, and uses these electrical signals to detect the type of polarized light emitted by the spin LED integrated chip, thereby achieving efficient and accurate polarized light signal detection. The detection efficiency and accuracy can be further improved by optimizing the design of the detector and the signal processing algorithm.

[0027] (3) The present invention has significant technical advantages in the innovative application of spin LEDs, the phase modulation of polarized light signals and the efficient conversion of electrical signals, and system integration design, and has high efficiency and high precision when applied to quantum communication.

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of a system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The present invention proposes a quantum key distribution system based on a spin LED chip by phase modulating the spin injection current of a spin LED. While simplifying the system structure, it achieves efficient modulation of optical signals to meet the needs of future high-speed optical communications and quantum information processing.

[0031] See also Figure 1 FIG. 1 is a schematic diagram of a system according to an embodiment of the present invention, comprising:

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

[0033] The receiving end includes a detection base optical path part, a detection circuit and an output end. The detection base optical path part includes a focusing lens C1, a plano-concave mirror C2, a plano-convex mirror C3, a first polarization beam splitter PBS1, a second polarization beam splitter PBS2, a third polarization beam splitter PBS3, a first ordinary beam splitter BS1, a second ordinary beam splitter BS2, a reflector R1, a spatial light modulator SLM and a half-wave plate P1; the detection circuit includes a first photodetector D1, a second photodetector 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 polarization beam splitter prism PBS1, the second and third ports of the polarization beam splitter prism PBS1 are aligned with the first port and the fourth port of the ordinary beam splitter plane mirror BS1 and BS2 respectively, the third port of BS1 is aligned with the spatial light modulator SLM, and the second port of BS2 is aligned with the reflective plane mirror R1. The second port of BS1 and the third port of BS2 are aligned with the fourth port and the first port of the second polarization beam splitter prism PBS2 respectively. The second port of the second polarization 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 polarization beam splitter prism PBS3, and the second port and the third port of the third polarization beam splitter prism are aligned with the first photodetector D1 and the second photodetector D2 respectively. The first photodetector D1 and the second photodetector D2 are connected to the input ends of the voltage amplifiers F1 and F2 respectively, and the output ends of the voltage amplifiers F1 and F2 are connected to the voltage comparators B1 and B2 respectively. Finally, the voltage amplifiers F1 and F2 and the voltage comparators B1 and B2 are respectively connected to the input end of the data acquisition card, and finally the output end of the data acquisition card is connected to the back-end computer.

[0035] Specifically, the light waves output by the spin LED have a large divergence and need to be converged and collimated after passing through the focusing lens C1, the plano-concave mirror C2, and the plano-convex mirror C3 respectively. After passing through the first polarization beam splitter prism PBS1, the polarized light will be divided into two components, namely the vertical component and the horizontal component, wherein the vertical component and the horizontal component will be reflected and reflected respectively. The horizontal component transmitted through the first polarization beam splitter prism PBS1 passes through the ordinary beam splitter prism BS1, and the component is further divided into two components, transmitted and reflected respectively, wherein the component transmitted after passing through the ordinary beam splitter prism BS1 reaches the reflective surface of the spatial light modulator and is reflected, and the component transmitted through the ordinary beam splitter prism BS1 after being reflected by the spatial light modulator SLM passes through the ordinary beam splitter prism BS1 again and is divided into a transmission component and a reflection component, wherein the component reflected by the ordinary beam splitter prism BS1 enters the second polarization beam splitter prism PBS2. The vertical component reflected by the first polarization beam splitter prism PBS1 passes through the ordinary beam splitter prism BS2, and the component is further divided into two halves, transmitted and reflected respectively. The component transmitted after passing through the ordinary beam splitter prism BS2 reaches the reflective surface of the reflector R1 and is reflected. The component transmitted by the ordinary beam splitter prism BS2 after being reflected by the reflector R1 passes through the ordinary beam splitter prism BS1 again and is divided into a transmission component and a reflection component. The component reflected by the ordinary beam splitter prism BS1 enters the second polarization beam splitter prism PBS2. These two components are combined after reaching the second polarization beam splitter prism PBS2. The measurement basis of the phase modulation polarization optical path is controlled by the loaded grayscale of the spatial light modulator, that is, when the SLM inputs four different voltage values, 0, V0 / 2, V0, 3V0 / 2 (V0 is a half-wave voltage), four non-orthogonal polarization measurement bases such as 45° linear polarization, 135° linear polarization, left-handed circular polarization and right-handed circular polarization are provided. The combined light wave passes through the half-wave plate P1 and finally passes through the third polarization beam splitter prism PBS3. Finally, the emission direction of the light wave will be affected by the measurement basis, that is, the emission light signal can be controlled by the measurement basis.

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

[0037] When using the embodiment of the present invention to distribute quantum keys, first, the transmitting end Alice uses a high-frequency signal generator and a random generator to randomly send light in four polarization states: 45-degree linear polarization, right-handed circular polarization, 135-degree linear polarization, and left-handed circular polarization. At the same time, the receiving end Bob uses a random number generator and a driving voltage to apply a voltage with the same frequency as the high-frequency signal generator at the transmitting end, thereby randomly generating 0, π, The phase change of π generates four non-orthogonal polarization measurement bases: 45-degree linear polarization, right-handed circular polarization, 135-degree linear polarization, and left-handed circular polarization. The 45-degree linear polarization and 135-degree linear polarization measurement bases generated by 0 and π are a pair of conjugate measurement bases. and The right-handed circular polarization and left-handed circular polarization generated are a pair of conjugate measurement bases, which detect the polarization state of the high-frequency pulse light sent by the transmitter; finally, according to the agreement between the transmitter Alice and the receiver Bob, 45-degree linear polarization and right-handed circular polarization represent binary 0, 135-degree linear polarization and left-handed circular polarization represent binary 1, and Bob randomly modulates the phase, that is, randomly selects the measurement basis to measure the polarized light sent by Alice. For example, the transmitter Alice sends linearly polarized light, and the receiver Bob performs phase modulation of 0 and π to generate a linear polarization measurement basis. After comparing the bases, it can be considered that Bob has selected the correct measurement basis, and the result of this communication can be used as part of the key. And Bob performs or Phase modulation is used to generate circular polarization measurement basis to detect it. After comparing the basis, it can be considered that the measurement basis is not selected correctly. In this case, both parties will abandon the measurement. Finally, after all the comparisons, the sender and the receiver can jointly form a string of keys.

[0038] Specifically, the photodetectors D1 and D2 convert the optical signals transmitted and reflected from the second polarization beam splitter prism PBS2 into electrical signals, and then the voltage amplifier amplifies the gain of the electrical signals F1 and F2. The voltage comparators B1 and B2 can further convert the signals with electrical signals greater than or less than the threshold into high and low level signals of 0 or 1 respectively by setting appropriate thresholds, and output the data acquisition results through the data acquisition device. For example, if Bob applies Phase change, that is, providing a right-hand circular polarization measurement basis, detects the right-hand chiral circular polarized light (more right-hand circular polarized light than left-hand circular polarized light) emitted by the spin LED. According to the previous agreement, it represents the key of binary 0. The light intensity detected by detector 2 is stronger than that detected by detector 1. After comparison by the voltage comparator and the threshold, it can be further converted into high and low level signals of 0 and 1 that are greater than and less than the threshold. That is to say, the final voltage signal output by detector 1 is 0, and the final voltage signal output by detector 2 is 1. Therefore, according to the final output voltage signal, it can be known that when the polarization state of the measurement basis and the transmitting end are the same, then the final output is an accurate signal, and we can keep the key 0 carried by this detection. Next, if Bob applies a phase change of 0, that is, providing a linear polarization light measurement basis, if the right-hand chiral polarized light (more right-hand circular polarized light than left-hand circular polarized light) emitted by the spin LED is still detected, according to the previous agreement, it represents the key of binary 0. However, because the measurement basis and polarization state are different, the detection results are random, and the high-level signals presented in the subsequent voltage signals are all 1. Therefore, according to the final output voltage signal, we can know that when the measurement basis is different from the polarization state of the transmitter, the final output is an inaccurate signal, so we can discard the key 0 carried by this detection according to the result. Therefore, after the transmitter continuously emits polarized light at a certain frequency, and the receiver generates a measurement basis at the same frequency to measure it, after a series of tests, according to the specific level of the back-end voltage signal, the key of each measurement is discarded or retained, and finally an ideal key string can be formed, completing the distribution of a key string.

[0039] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A quantum key distribution system based on spin LED chip, characterized in that: include: At the transmitting end, the spin LED chip is used to transmit polarized light of different polarization states; At the receiving end, the detection base optical path is used to phase modulate the polarized light sent by the transmitting end, and the modulated optical signal is detected by the detection circuit. According to the detection result, it is confirmed whether the communication generates a key. If so, the measurement basis corresponding to the phase change is converted into 0 or 1 according to the pre-agreed rules. The generated string of 01 sequences is output through the output end as the key.

2. The quantum key distribution system based on spin LED chip according to claim 1 is characterized in that: The polarized light of different polarization states includes 45-degree linear polarized light, right-handed circular polarized light, 135-degree linear polarized light and left-handed circular polarized light; The phase changes include 0, π and The measurement bases of four non-orthogonal polarization states, namely, 45-degree linear polarization, right-handed circular polarization, 135-degree linear polarization and left-handed circular polarization, are generated respectively.

3. The quantum key distribution system based on spin LED chip according to claim 1, characterized in that: The method of using the detection base optical path to phase modulate the polarized light sent by the transmitting end comprises the following steps: A focusing lens combination is used to converge and collimate the 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, wherein the first outgoing optical signal corresponds to the polarized light sent by the transmitting end, and the second outgoing optical signal corresponds to the phase-modulated optical signal; wherein the receiving end uses the spatial light modulator to randomly generate a phase change to achieve phase modulation.

4. The quantum key distribution system based on spin LED chip according to claim 3 is characterized in that: The receiving side uses the spatial light modulator to randomly generate a phase change, 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 respectively, the spatial light modulator generates π and The phase change corresponds to four non-orthogonal polarization measurement bases, namely 45° linear polarization, 135° linear polarization, left-hand circular polarization and right-hand circular polarization, where V0 is the half-wave voltage.

5. The quantum key distribution system based on spin LED chip according to claim 3 is characterized in that: The detection base optical path is specifically: 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 polarization beam splitter prism; the second port and the third port of the first polarization beam splitter prism are aligned with the first port of the first common beam splitter plane mirror and the fourth port of the second common beam splitter plane mirror respectively; 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 polarization 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 polarization beam splitting prism; The second port of the second polarization beam splitter 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 splitter prism; the second port and the third port of the third polarization beam splitter prism emit the first outgoing light signal and the second outgoing light signal respectively.

6. The quantum key distribution system based on spin LED chip according to claim 5, characterized in that: The focusing prism assembly comprises 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.

7. The quantum key distribution system based on spin LED chip according to claim 6, characterized in that: The separation ratio of the transmitted light and the reflected light of the first ordinary beam splitting plane mirror and the second ordinary beam splitting plane mirror is 50:

50.

8. The quantum key distribution system based on spin LED chip according to claim 7, characterized in that: The spatial light modulator requires that the polarization direction of the incident polarized light is parallel to the liquid crystal optical axis of the spatial light modulator.

9. The quantum key distribution system based on spin LED chip according to claim 3, characterized in that: The method of detecting the modulated optical signal by using a detection circuit comprises the following steps: A photoelectric detector is used to convert two outgoing lights into two electrical signals respectively, wherein the first outgoing light signal is converted into a first electrical signal, and the second outgoing light signal is converted into a second electrical signal; Using a voltage comparator to convert the first electrical signal into a first high-low level signal of 0 or 1, and convert the second electrical signal into a second high-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, 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, a key is generated in this communication.

10. The quantum key distribution system based on spin LED chip according to claim 1, characterized in that: The measurement basis corresponding to the phase change is converted to 0 or 1 according to the pre-agreed rule, specifically: Represents binary 0, Represents binary 1.

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