Single-molecule probabilistic bit device based on external circuit coupling and preparation method and application thereof

Abstract

The present application relates to the technical field of probabilistic bit device, and particularly relates to a single-molecule probabilistic bit device based on external circuit coupling, a preparation method and application, the single-molecule probabilistic bit device comprises a single-molecule junction formed by a graphene electrode pair and a probabilistic bit functional group, and a plurality of rigid benzene rings in a triphenylmethyl skeleton in the single-molecule junction realize high delocalization of unpaired electrons through a conjugated structure, effectively weakening the coupling effect between spin and molecular vibration, conformational fluctuation, inhibiting the rapid decoherence process caused by phonon scattering from the molecular structure level, so that the spin state can still maintain a limited coherence lifetime at room temperature, and the basic requirement of the device on the spin state holding time can be met.The device has randomness, controllability and scalability at the circuit level, and provides a hardware basis for constructing a brain-like probabilistic computing network.The preparation method provided by the present application is simple in process and is conducive to large-scale production.

Description

Technical Field

[0001] This invention relates to the field of probabilistic bit device technology, and in particular to a single-molecule probabilistic bit device based on external circuit coupling, its fabrication method, and its application. Background Technology

[0002] With the rapid and continuous development of artificial intelligence and quantum computing technologies, the demand for intelligent reasoning in complex scenarios such as intelligent decision-making and quantum simulation is constantly increasing. Meanwhile, low-power computing has become a core requirement for the research and development of high-end electronic devices. The shortcomings of traditional deterministic logic devices in simulating the uncertain reasoning of the human brain and achieving energy-optimal computation are becoming increasingly apparent. In this context, probabilistic bits (p-bits), as controllable random units between classical bits (0 / 1 deterministic states) and quantum bits (superposition states), have become the core hardware support for achieving efficient probabilistic computation due to their precisely controllable random response capabilities.

[0003] Currently, probabilistic bits are mainly implemented through two methods: magnetic tunnel junction (MTJ) or complementary metal-oxide-semiconductor (CMOS) pseudo-random circuits. Their randomness originates from the natural driving force of thermal fluctuations or electrical noise. These two approaches are also the most mature and widely used technologies in current laboratory research and engineering exploration. However, these implementation methods face two prominent technical challenges: First, energy consumption and integration area are strictly limited. MTJ-type devices require external magnetic fields or spin torque to adjust the internal spin state. Their special structural design makes it difficult to further miniaturize the devices to smaller sizes, failing to meet the practical application requirements of large-scale array integration. Second, the randomness quality is unstable. The macroscopic noise source itself has inherent uncontrollability, making it difficult to accurately adjust the randomness output. This prevents flexible control of the probability response characteristics according to the needs of different probability calculation scenarios, directly affecting the accuracy of probability calculations and overall operating efficiency.

[0004] Compared to the two traditional approaches mentioned above, single-molecule devices possess unique atomic-scale electron tunneling characteristics and extremely high sensitivity to environmental thermal fluctuations, naturally exhibiting tunable random switching behavior. Their atomically small size and low power consumption provide an ideal hardware foundation for developing high-density, low-power probabilistic qubits, aligning with the current trend towards miniaturization and low power consumption in electronic devices. However, the random output characteristics of single-molecule devices are significantly affected by their own electronic structure and external environmental factors such as temperature and electric field. Without a high-performance single-molecule junction and effective external circuitry for coupling and control, the random output of a single-molecule device will be in a state of disordered fluctuation, and its noise characteristics will fail to meet the basic requirements of output stability and controllability for probabilistic computation.

[0005] Therefore, developing single-molecule probabilistic bit devices based on external circuit coupling control to effectively solve existing technical problems is an urgent need to promote the development of probabilistic computing towards high density and low power consumption. Summary of the Invention

[0006] This invention aims to at least solve one of the technical problems existing in related technologies. Therefore, the first objective of this invention is to provide a single-molecule probabilistic bit device based on external circuit coupling; the second objective is to provide a method for fabricating a single-molecule probabilistic bit device based on external circuit coupling; and the third objective is to provide applications of the single-molecule probabilistic bit device based on external circuit coupling.

[0007] To achieve the first objective, the technical solution adopted by this invention is as follows: A single-molecule probabilistic bit device based on external circuit coupling includes a single-molecule junction, wherein the single-molecule junction includes a graphene source electrode, a probabilistic bit functional group, and a graphene drain electrode. The graphene source electrode and the graphene drain electrode form a graphene electrode pair, and the probability bit functional group is connected between the graphene electrode pairs through amide bonds. The structural formula of the probability bit functional group is shown below: ; The probability bit functional group has a triphenylmethyl radical as its spin core, and its central sp 2 The p orbitals of hybrid carbon atoms contain stable unpaired electrons, forming a natural S=1 / 2 single-spin system that can remain stable in the ground state for a long time without external excitation. Simultaneously, its spin magnetic moment exhibits high sensitivity to applied magnetic and local electric fields, laying the physical foundation for the bistable spin variable required for probabilistic qubits. The multiple rigid benzene rings in the triphenylmethyl skeleton achieve high delocalization of unpaired electrons through conjugation, effectively weakening the coupling between spin and molecular vibrations and conformational fluctuations. This suppresses the rapid decoherence process caused by phonon scattering at the molecular structure level, allowing the spin state to maintain a finite but not completely frozen coherent lifetime at room temperature, meeting the dynamic performance requirements of probabilistic qubit operation.

[0008] Furthermore, the gap between the graphene source electrode and the graphene drain electrode is a nanometer gap.

[0009] Furthermore, it also includes an external circuit coupled to the monomolecular junction; The monomolecular junction, under the action of the external circuit, relies on thermal fluctuations to achieve spontaneous random switching between high-resistivity and low-resistivity states, providing a continuous random noise source.

[0010] Furthermore, the external circuit includes an input driving unit, a binarization amplification unit, and a probability bias adjustment unit, wherein the input driving unit, the unijunction, the binarization amplification unit, and the probability bias adjustment unit are coupled together.

[0011] Furthermore, the probability bias adjustment unit is an RC integral feedback loop formed by R and C connected in parallel, and the RC feedback loop constitutes an integral channel that can adjust the time scale of the random output; Where R is resistance and C is capacitance.

[0012] The introduction of feedback signals enables the output state to follow Markov-like stochastic transition dynamics, which can support sequence-related probabilistic computation tasks. The overall system simultaneously possesses randomness, controllability, and scalability at the circuit level, providing a hardware foundation for building large-scale neuromorphic probabilistic computation networks.

[0013] To achieve the second objective, the technical solution adopted by this invention is as follows: A method for fabricating a single-molecule probabilistic bit device based on external circuit coupling, used to fabricate any of the single-molecule probabilistic bit devices based on external circuit coupling described above, includes the following steps: S100. Using a single-layer graphene film, a graphene electrode device I comprising a graphene electrode pair is prepared. S200. The edges of the graphene electrode pair are modified with carboxyl groups using oxygen plasma technology to obtain graphene electrode device II. S300. The graphene electrode device II is immersed in a pyridine solution containing a carboxyl activator and probability bit molecules, so that the probability bit molecules are assembled between the graphene electrode pairs through an amide condensation reaction to obtain a graphene electrode device III containing a probability bit functional group precursor. The structural formula of the probability bit molecule is shown below: ; The structural formula of the probability bit functional group precursor is shown below: ; S400. The graphene electrode device III is sequentially immersed in organic solution I containing potassium tert-butoxide and organic solution II containing tetrachlorobenzoquinone to cause in-situ dehydrogenation of the probability bit functional group precursor, thereby obtaining a single-molecule probability bit device based on external circuit coupling.

[0014] Further, in step S300, the carboxyl activator is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.

[0015] Further, in step S300, the synthesis of the probability bit molecule includes the following steps: S310, with compound I and compound II Using raw materials, synthesize intermediate I ; S320, Intermediate I and Compound III The reaction synthesizes the probability bit molecule.

[0016] Furthermore, in step S400, the solvents of both organic solution I and organic solution II are tetrahydrofuran.

[0017] Furthermore, in step S400, the in-situ dehydrogenation reaction is carried out in an inert environment.

[0018] To achieve the third objective, the technical solution adopted by this invention is as follows: Applications of single-molecule probabilistic bit devices based on external circuit coupling: Constructing a brain-like probabilistic computing network using any of the above-mentioned single-molecule probabilistic bit devices based on external circuit coupling.

[0019] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: The present invention provides a single-molecule probabilistic bit device based on external circuit coupling, comprising a single-molecule junction, wherein the single-molecule junction includes a graphene source electrode, a probabilistic bit functional group, and a graphene drain electrode. The probabilistic bit functional group is connected between the graphene source electrode and the graphene drain electrode pair formed by the graphene source electrode and the graphene drain electrode through amide bonds. This technical solution has at least the following beneficial effects: Firstly, the probabilistic bit functional group has a triphenylmethyl radical as its spin core, and its central sp 2 The p orbitals of hybrid carbon atoms contain stable unpaired electrons, forming a natural S=1 / 2 single-spin system that can remain stable in the ground state for a long time without external excitation. Simultaneously, its spin magnetic moment exhibits high sensitivity to applied magnetic and local electric fields, laying the physical foundation for the bistable spin variable required for probabilistic qubits. The multiple rigid benzene rings in the triphenylmethyl skeleton achieve high delocalization of unpaired electrons through conjugation, effectively weakening the coupling between spin and molecular vibrations and conformational fluctuations. This suppresses the rapid decoherence process caused by phonon scattering at the molecular structure level, allowing the spin state to maintain a finite but not completely frozen coherent lifetime at room temperature, meeting the basic requirements of device spin state retention time.

[0020] Secondly, the probabilistic bit functional groups are anchored to the electrodes through covalent amide bonds, forming a stable molecular junction interface, which effectively reduces the contact resistance and ensures the reliability of the probabilistic bit device under long-term operation driven by thermal fluctuations.

[0021] Thirdly, using single molecules as carriers of probability bits can further increase the integration density of probability bit chips, better meeting the needs of probability computing and the miniaturization of devices.

[0022] The present invention provides a method for fabricating a single-molecule probabilistic qubit device based on external circuit coupling. This method employs monolayer graphene to prepare graphene electrode pairs, a simple process that balances high conductivity with atomic-level interface characteristics. Oxygen plasma technology is used to modify the carboxyl groups of the graphene electrodes, a gentle, controllable, and uniform modification that does not damage the intrinsic structure and electrical properties of graphene. Amide condensation reaction is used to achieve directional and ordered assembly of probabilistic qubit molecules, resulting in stable bonding and high single-molecule positioning accuracy. The liquid-phase immersion and in-situ dehydrogenation reaction processes are simple, require low-requirement equipment, and have good repeatability, making them suitable for large-scale fabrication. The in-situ dehydrogenation reaction avoids interface contamination, preserves the intrinsic quantum properties of the probabilistic qubit molecules, and results in outstanding charge transport efficiency and reliability of the device.

[0023] The single-molecule probabilistic bit device based on external circuit coupling provided by this invention has randomness, controllability and scalability at the circuit level, providing a hardware foundation for building large-scale brain-like probabilistic computing networks.

[0024] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0025] Figure 1 This is a current-time response characteristic curve of the single-molecule probabilistic bit device based on external circuit coupling provided in Embodiment 2 of the present invention at a voltage of 0.15V and different temperatures.

[0026] Figure 2 This is a current-time response characteristic curve of the single-molecule probabilistic bit device based on external circuit coupling provided in Embodiment 2 of the present invention, under the condition of temperature 200K, within a time range of 0 to 70s, at different voltages.

[0027] Figure 3 The figure provided in Embodiment 2 of the present invention shows the current-time response characteristic curves and the distribution statistics of the corresponding current values ​​of the single-molecule probabilistic bit device based on external circuit coupling under the condition of 200K and within a time range of 5s at voltages of 0.1V, 0.15V, 0.2V, 0.25V and 0.3V.

[0028] Figure 4 The figure provided in Embodiment 2 of the present invention shows the current-time response characteristic curves and the distribution statistics of the corresponding current values ​​of the single-molecule probabilistic bit device based on external circuit coupling under different voltages of 0.35V, 0.4V, 0.45V, 0.5V and 0.55V within a time range of 5s under the condition of 200K temperature.

[0029] Figure 5 This is a schematic diagram of the external circuit structure of the single-molecule probability bit (p-bit) device based on external circuit coupling to regulate the molecular state flipping probability, provided in Embodiment 3 of the present invention.

[0030] Figure 6 This is a schematic diagram of a brain-like probabilistic computing network constructed based on a single-molecule probabilistic bit device coupled with external circuitry, provided in Embodiment 3 of the present invention.

[0031] Figure Labels 1. Input drive unit; 2. Single-molecule random unit; 3. Binarization amplification unit; 4. Probability bias adjustment unit; 5. Observation module; 6. Feedback control unit. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention, but cannot be used to limit the scope of this invention.

[0033] In the following embodiments, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available, unless otherwise specified, and are carried out in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions.

[0034] A single-molecule probabilistic bit device based on external circuit coupling includes a single-molecule junction, wherein the single-molecule junction includes a graphene source electrode, a probabilistic bit functional group, and a graphene drain electrode. The graphene source electrode and the graphene drain electrode form a graphene electrode pair, and the probability bit functional group is connected between the graphene electrode pairs through amide bonds. The structural formula of the probability bit functional group is shown below: .

[0035] According to a specific embodiment of the present invention, the gap between the graphene source electrode and the graphene drain electrode is a nanometer gap.

[0036] According to a specific embodiment of the present invention, an external circuit coupled to the monomolecular junction is further included. The external circuit includes an input driving unit, a binarization amplification unit, and a probability bias adjustment unit, wherein the input driving unit, the monomolecular junction, the binarization amplification unit, and the probability bias adjustment unit are coupled.

[0037] According to a specific embodiment of the present invention, the probability bias adjustment unit is an RC integral feedback loop formed by R and C connected in parallel; Where R is resistance and C is capacitance.

[0038] A method for fabricating a single-molecule probabilistic bit device based on external circuit coupling, used to fabricate any of the aforementioned single-molecule probabilistic bit devices based on external circuit coupling, includes the following steps: S100. Using a single-layer graphene film, a graphene electrode device I comprising a graphene electrode pair is prepared. S200. The edges of the graphene electrode pair are modified with carboxyl groups using oxygen plasma technology to obtain graphene electrode device II. S300. The graphene electrode device II is immersed in a pyridine solution containing a carboxyl activator and probability bit molecules, so that the probability bit molecules are assembled between the graphene electrode pairs through an amide condensation reaction to obtain a graphene electrode device III containing a probability bit functional group precursor. The structural formula of the probability bit molecule is shown below: ; The structural formula of the probability bit functional group precursor is shown below: S400. The graphene electrode device III is sequentially immersed in organic solution I containing potassium tert-butoxide and organic solution II containing tetrachlorobenzoquinone to cause in-situ dehydrogenation of the probability bit functional group precursor, thereby obtaining a single-molecule probability bit device based on external circuit coupling.

[0039] According to a specific embodiment of the present invention, in step S300, the carboxyl activator is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.

[0040] According to a specific embodiment of the present invention, in step S300, the synthesis of the probability bit molecule includes the following steps: S310, with compound I and compound II Using raw materials, synthesize intermediate I ; S320, Intermediate I and Compound III The reaction synthesizes the probability bit molecule.

[0041] According to a specific embodiment of the present invention, in step S400, the solvents of both organic solution I and organic solution II are tetrahydrofuran.

[0042] According to a specific embodiment of the present invention, in step S400, the in-situ dehydrogenation reaction is carried out in an inert environment.

[0043] Applications of single-molecule probabilistic bit devices based on external circuit coupling: Constructing a brain-like probabilistic computing network using any of the above-mentioned single-molecule probabilistic bit devices based on external circuit coupling.

[0044] Example 1 The target probability bit molecule is prepared, and its structural formula is shown below: ; The synthetic route is shown below: ; Its synthesis process is as follows: A toluene solution (60 mL) containing compound I (3.2 mmol), compound II (3.2 mmol), tris(dibenzylacetone)dipalladium (0.1 mmol), tri-tert-butylphosphine tetrafluoroborate (0.2 mmol), and sodium tert-butoxide (9.6 mmol) was refluxed under nitrogen for 16 h. After the reaction was completed and the mixture was allowed to cool to room temperature, it was extracted with ethyl acetate. The organic phases were combined, dried, and concentrated to obtain the crude product. The crude product was then purified by column chromatography to obtain intermediate I. The characterization data are shown below: 1 H NMR (400MHz, CDCl3): δ =7.51(s, 2H), 7.42(d, J =8.4Hz, 2H), 7.30-7.40(m, 5H), 7.23(t, J =8.0Hz, 2H), 7.11(s, 2H), 6.93(d, J =7.4Hz, 2H), 6.24(s, 1H), 6.10(s, 1H).

[0045] 13 C NMR (100MHz, CDCl3): δ=144.82, 142.02, 138.39, 137.82, 135.59, 135.56, 135.52, 134.93, 134.86, 134.82, 132.73, 132.68, 132.50, 130.08, 128.79, 128.55, 128.52, 128.46, 128.41, 128.08, 128.06, 126.03, 126.00, 122.66, 122.64, 121.75, 121.71, 58.37, 43.96.

[0046] A solution (20 mL, in a mixture of tetrahydrofuran and water at a volume ratio of 10:1) containing intermediate I (2.0 mmol), compound III (2 mmol), 1,1'-bis(diphenylphosphino)ferrocene palladium dichloride (0.01 mmol), and potassium carbonate (20 mmol) was refluxed under nitrogen for 16 h. After the reaction was completed and the mixture was allowed to cool to room temperature, it was extracted with ethyl acetate. The organic phases were combined, dried, and concentrated to obtain the crude product, which was then purified by column chromatography to obtain the target probability bit molecule. The characterization data are shown below: 1 H NMR (400MHz, CDCl3): δ =7.68(s, 2H), 7.53(d, J =8.2Hz, 2H), 7.42 (d, J =8.5Hz, 2H), 7.31-7.40(m, 3H), 7.07-7.19(m, 8H), 6.98(d, J =7.4Hz, 2H), 6.69 (d, J =8.2Hz, 2H), 6.64 (d, J =7.8Hz, 2H), 6.29(s, 1H), 5.49(s, 1H), 4.20(s, 2H), 4.12(s, 2H).

[0047] 13 C NMR (100MHz, CDCl3): δ=148.29, 146.20, 145.09, 144.41, 144.38, 140.60, 139.06, 138.10, 136.34, 135.59, 135.56, 134.86, 134.82, 134.67, 132.57, 131.07, 131.05, 130.88, 130.08 , 128.79, 128.39, 128.36, 128.16, 128.12, 128.06, 128.03, 127.90, 124.35, 124.31, 122.35, 121.75, 121.71, 116.22, 116.20, 115.25, 115.21, 48.10, 47.30.

[0048] Example 2 Fabrication of a single-molecule probabilistic bit device based on external circuit coupling includes the following steps: I. Preparation of monolayer graphene.

[0049] In a fume hood, cut copper foil is soaked in acetic acid for 15–20 minutes; then, the copper foil is rinsed with ultrapure water and anhydrous ethanol in sequence, and dried with a nitrogen gun for later use; next, monolayer graphene is grown on the clean copper foil by chemical vapor deposition (CVD) to obtain graphene-copper foil.

[0050] II. Preparation of poly(methyl methacrylate, PMMA) support layer.

[0051] PMMA was spin-coated onto the aforementioned prepared monolayer graphene (rotation speed 3000-4000 r / min, time 40 s). After spin-coating, it was baked on a hot plate at 180℃ for 2 min to obtain a PMMA-graphene-copper foil composite structure. Subsequently, it was placed in a reactive ion etching (RIE) machine and etched with oxygen plasma for 45 s to remove impurities and avoid contamination.

[0052] III. Etching of the copper substrate.

[0053] The PMMA-graphene-copper foil was immersed in a ferric chloride solution (1 mol / L) to etch and remove the copper substrate. After etching, the floating PMMA-graphene film was transferred sequentially to the following solutions for soaking and rinsing: hydrochloric acid solution (1 mol / L), hydrochloric acid solution (0.1 mol / L), ultrapure water, potassium hydroxide aqueous solution (0.1 mol / L), ultrapure water, hydrochloric acid solution (0.1 mol / L). After soaking in ultrapure water, the graphene with PMMA was detached from the copper foil, thus obtaining PMMA-graphene.

[0054] IV. Remove the PMMA layer.

[0055] Prepare a lightly doped silicon substrate (covered with a 300nm thick silicon dioxide insulating layer), and cut the silicon substrate into 1×1cm pieces. 2 After reaching the specified specifications, place the sample in a piranha solution (concentrated sulfuric acid and 30% hydrogen peroxide aqueous solution in a volume ratio of 7:3) and heat at 110°C for 2-3 hours until no more bubbles emerge from the solution. Then, remove the piranha solution, add ultrapure water, and clean the sample three times in an ultrasonic cleaner for about 15 minutes each time. After drying with nitrogen, examine the sample under a microscope. If the surface is smooth and free of impurities, the cleaning effect is good. PMMA-graphene was transferred and bonded to a silicon substrate, and heated to 80°C to ensure a firm bond. The sample (PMMA-graphene-silicon substrate) was then immersed in fresh acetone and heated to a slight boiling state for 10 minutes to dissolve and remove the PMMA layer, resulting in a clean graphene-silicon substrate.

[0056] V. Fabrication of graphene electrode devices I.

[0057] The process for preparing gold markers on a single-layer graphene film is as follows: A graphene-silicon substrate is placed on a spin coater, and photoresist (AR-P 5350) is dropped onto the graphene surface. The substrate is then spin-coated at 4000 r / min for 40 s. After spin-coating, the substrate is placed on a heating plate at 105 °C and heated for 3 min. Subsequently, positioning markers are prepared on the graphene film using photolithography. The film is developed for 15–20 s and fixed for 30 s. The substrate is then placed in a magnetron sputtering machine for sputtering, where chromium (8 nm) and gold (60 nm) are deposited sequentially. Finally, the substrate is immersed in acetone and peeled off to obtain the gold marker-graphene-silicon substrate.

[0058] The fabrication process of graphene strips and electrode pairs is as follows: Photoresist is spin-coated again on a gold-labeled graphene-silicon substrate, followed by photolithographic exposure, development, and fixing of the strip and electrode patterns (exposure parameters are the same as the previous steps); Subsequently, a chromium thin film (8nm) and a gold electrode layer (60nm) are sequentially deposited using a thermal evaporation machine. The same electrode pattern is exposed 190 times on the gold-labeled graphene-silicon substrate using photolithography to form a regularly arranged gold electrode-graphene strip-silicon substrate. This device integrates 190 pairs of adjacent electrode pairs, with each pair of electrodes having a graphene channel size of 40μm wide and 12μm long, using SiO2 as the insulating layer and Au as the conductive layer.

[0059] Ten pairs of electrodes were randomly selected to test their conductivity (current value was measured under a bias voltage of 50mV). Then, PMMA 950 electron beam resist was spin-coated at a speed of 4000r / min for 40s. After that, the resist was baked at 180℃ for 2min. Alignment marks were prepared by mechanically puncturing both ends of the strip using a probe station (for subsequent electron beam focusing).

[0060] Design of the nano-gap exposure pattern: A 5nm wide, equally spaced dashed line etch window (40nm imaginary, 150nm real) running through the graphene strip. Electron beam direct writing exposure technology is used to expose the graphene region between each pair of electrodes. After development for 15-20 seconds, it is fixed in isopropanol for 3 seconds, forming a nanoscale graphene electrode array on the protective PMMA layer, denoted as graphene electrode device I. Observation of the development effect under an optical microscope: The dashed line pattern is clearly discernible under a 50x lens and faintly visible under a 20x lens, indicating good development.

[0061] VI. Preparation of graphene electrode devices II.

[0062] Graphene electrode device I was placed in a reactive ion etching machine, and the graphene point electrodes exposed in the dashed window were etched using oxygen plasma to obtain carboxyl-modified graphene point electrode pairs. As etching proceeded, the window gradually expanded, and the expanded etched areas intersected to form closely spaced triangular point contact electrodes. Based on real-time conductivity monitoring, etching was immediately stopped when the resistance between the electrodes approached infinity (resistance > 1 GΩ).

[0063] Nanoscale gaps were further prepared by electro-sintering of incompletely etched RIE strips: a stepped voltage increase (starting voltage 2V, step size 0.1V) was applied to both ends of the graphene strip, and the graphene was locally oxidized and cleaved by the thermal effect of the current. Repeated experiments showed that a low voltage (2-3V) with a step-like slow decrease in voltage could obtain nanoscale gaps that matched the molecular size (1-2nm); while high voltage (voltage >4V) or current drop-type sintering would result in gaps that were too large, which was not conducive to molecular bonding.

[0064] After oxygen plasma etching and electrical burn-off treatment, a graphene point contact electrode array with edge carboxyl (–COOH) modification is obtained, denoted as graphene electrode device II.

[0065] VII. Preparation of graphene electrode devices III.

[0066] After being broken and burned, the edges of the graphene gaps between each pair of electrodes on the device were modified with carboxyl groups (-COOH). Probability bit molecules with amino (-NH2) ends (prepared in Example 1) reacted with the carboxyl groups at both ends of the graphene electrode pair to form amide bonds, thereby assembling individual probability bit molecules between the graphene electrode pairs to form monomolecular junctions. The specific process is as follows: Under positive pressure of argon, probability bit molecules (1 mg), EDCI (2.0 mg), and anhydrous pyridine (10 mL) were added to a three-necked flask and allowed to stand for 48 h to allow the monomolecular probability bit molecules to self-assemble between the graphene electrode pairs, obtaining graphene electrode device III containing probability bit functional group precursors.

[0067] 8. A single-molecule probabilistic bit device based on external circuit coupling was prepared by in-situ oxidation of free radical molecules. The synthetic route is shown below: .

[0068] Under a nitrogen atmosphere, graphene electrode device III was immersed in a 0.1 mol / L solution of potassium tert-butoxide (t-BuOK) in tetrahydrofuran (THF) for 30 min, and then transferred to a 0.1 mol / L solution of tetrachlorobenzoquinone (TCQ) in tetrahydrofuran (THF) for 15 min. After drying under nitrogen, a single-molecule probabilistic bit device based on external circuit coupling was obtained. Electrical testing of the device showed that it had a current response, indicating that the probabilistic bit groups were chemically bonded between the graphene electrode pairs.

[0069] 9. Testing the electrical performance of single-molecule probabilistic bit devices based on external circuit coupling.

[0070] The fabricated single-molecule probabilistic bit device based on external circuit coupling was tested using a cryogenic probe station system (TTPX). Under a voltage of 0.15V, the single-molecule probabilistic bit device was subjected to temperatures ranging from 100K to 260K with a temperature gradient of 20K. The current-time response characteristics of the device at different temperatures were measured, and the test results are shown below. Figure 1 As shown in the figure, it can be seen that the single-molecule probabilistic bit device based on external circuit coupling provided by the present invention has temperature dependence and is highly sensitive to external temperature stimuli. At a temperature of 200K, voltages ranging from 0.1V to 0.55V were applied to the device with a voltage gradient of 0.05V. The current-time response of the device under different voltages was tested, and the test results are as follows. Figure 2 , Figure 3 and Figure 4As shown in the figures, it can be seen that the distribution of the high and low conductivity states of the probability bit functional group changes regularly with voltage. As the voltage increases, the high conductivity state gradually jumps to the low conductivity state, which reflects the controlled binary output characteristics of the probability bit. The test results confirm that the external circuit can effectively control the flipping process of the probability bit.

[0071] Example 3 like Figure 5 As shown, the external circuit of a single-molecule probability bit (p-bit) device based on external circuit coupling to regulate the molecular state flipping probability is designed, including an input driving unit 1, a single-molecule random unit 2 (including a single-molecule probability bit device based on external circuit coupling), a binarization amplification unit 3, a probability bias adjustment unit 4, an observation module 5, and a feedback control unit 6. The input driving unit 1, the single-molecule random unit 2, the binarization amplification unit 3, the probability bias adjustment unit 4, the observation module 5, and the feedback control unit 6 are coupled together to form a feedback circuit.

[0072] Specifically, the input drive unit includes an input terminal and a multiplier A2. The input terminal provides an external drive signal for adjusting the output probability bias. The function of the multiplier A2 is to couple the input signal with the random source signal; its output amplitude determines the strength of the influence of the external signal on the behavior of the probability bits. When the input signal is zero, the p-bit output randomly switches between +1 and -1 with similar probabilities. When the input signal is positive or negative, the multi-stage amplifier circuit converts the input signal into a probability bias, making the output more inclined towards a certain state, but still maintaining randomness.

[0073] The single-molecule random unit comprises a single-molecule probabilistic bit device, voltage divider resistors R1 / R4 / R5, and operational amplifiers U1 / U4. This invention selects a molecular structure with two-state switchable conductivity characteristics for the probabilistic bit functional group; specifically, it is a single-molecule junction with a bistable spin configuration and a thermally excited tunneling channel. Under constant bias, the resistance of this device spontaneously jumps due to thermal fluctuations, exhibiting random switching between high-resistance and low-resistance states. Utilizing the random transition characteristics of the single-molecule probabilistic bit device, a raw electrical signal with random fluctuations is generated, and preliminary comparison and amplification are performed by the operational amplifiers. The binarization amplification unit consists of a multiplier comparator A3, which converts the continuous voltage noise signal from the unimolecule probabilistic bit device into a binarized output. Specifically, when the unimolecule probabilistic bit device is in a low-impedance state, it generates a higher voltage, and the comparator outputs "+1"; while the high-impedance state corresponds to a lower voltage, and the comparator outputs "-1".

[0074] The probability bias adjustment unit consists of an RC integral feedback loop composed of R2, R3, and C1, providing both timing control and probability bias adjustment functions. The probability bias adjustment unit linearly combines the binarized output signal with the random noise of the single-molecule junction, ensuring that the average bias of the final output signal is determined by the external input, while the instantaneous fluctuations are dominated by the probability bit molecule noise, thus satisfying the following formula: P(output = +1) = sigmoid(input × gain); Where P is the probability, sigmoid is the S-type saturation activation function, input refers to the amplitude of the external driving signal voltage (or current) received by the input driving unit, and gain is determined by the amplification factor of the multiplier A2 in the input driving unit and the comparator threshold in the binarization amplification unit.

[0075] The observation module includes an oscilloscope, which is used to monitor the circuit output waveform in real time and intuitively verify the generation, amplification and feedback adjustment effects of random signals. It is a key observation window for debugging and performance analysis.

[0076] The feedback control unit consists of a multiplier A1 forming a closed-loop feedback path. It receives the feedback signal output by the system, performs coupled calculations with the input signal, and realizes dynamic control of the entire circuit's operating state to maintain the system's stable timing and operating point.

[0077] The aforementioned external circuit realizes the controllable random signal generation based on single-molecule devices, which combines randomness, probabilistic adjustability, and system stability.

[0078] In practical applications, the neuromorphic probabilistic computing network constructed based on a single-molecule probabilistic bit device coupled by external circuitry provided by this invention, such as... Figure 6 As shown, the entire architecture realizes a complete link from the underlying single-molecule random phenomenon to the top-level probabilistic computing hardware: the inherent randomness of the single-molecule probabilistic bit device is transformed into a controllable probabilistic bit stream, which is then processed by the closed-loop control of neuromorphic circuits and the parallel processing of physical neural networks to form a low-power, highly adaptable probabilistic computing system, providing a feasible brain-like computing solution to break through the bottleneck of the traditional von Neumann architecture.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A single-molecule probabilistic bit device based on external circuit coupling, characterized in that, It includes a monomolecular junction, wherein the monomolecular junction comprises a graphene source electrode, a probability qubit functional group, and a graphene drain electrode; The graphene source electrode and the graphene drain electrode form a graphene electrode pair, and the probability bit functional group is connected between the graphene electrode pairs through amide bonds. The structural formula of the probability bit functional group is shown below: 。 2. The single-molecule probabilistic bit device based on external circuit coupling as described in claim 1, characterized in that, The gap between the graphene source electrode and the graphene drain electrode is a nanometer gap.

3. The single-molecule probabilistic bit device based on external circuit coupling as described in claim 2, characterized in that, It also includes an external circuit coupled to the monomolecular junction, the external circuit including an input driving unit, a binarization amplification unit and a probability bias adjustment unit, the input driving unit, the monomolecular junction, the binarization amplification unit and the probability bias adjustment unit being coupled.

4. The single-molecule probabilistic bit device based on external circuit coupling as described in claim 3, characterized in that, The probability bias adjustment unit is an RC integral feedback loop formed by R and C connected in parallel. Where R is resistance and C is capacitance.

5. A method for fabricating a single-molecule probabilistic bit device based on external circuit coupling, characterized in that, The method for fabricating a single-molecule probabilistic bit device based on external circuit coupling as described in any one of claims 1 to 4 comprises the following steps: S100. Using a single-layer graphene film, a graphene electrode device I comprising a graphene electrode pair is prepared. S200. The edges of the graphene electrode pair are modified with carboxyl groups using oxygen plasma technology to obtain graphene electrode device II. S300. The graphene electrode device II is immersed in a pyridine solution containing a carboxyl activator and probability bit molecules, so that the probability bit molecules are assembled between the graphene electrode pairs through an amide condensation reaction to obtain a graphene electrode device III containing a probability bit functional group precursor. The structural formula of the probability bit molecule is shown below: ； The structural formula of the probability bit functional group precursor is shown below: ； S400. The graphene electrode device III is sequentially immersed in organic solution I containing potassium tert-butoxide and organic solution II containing tetrachlorobenzoquinone to cause in-situ dehydrogenation of the probability bit functional group precursor, thereby obtaining a single-molecule probability bit device based on external circuit coupling.

6. The method for fabricating a single-molecule probabilistic bit device based on external circuit coupling as described in claim 5, characterized in that, In step S300, the carboxyl activator is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.

7. The method for fabricating a single-molecule probabilistic bit device based on external circuit coupling as described in claim 5, characterized in that, In step S300, the synthesis of the probability bit molecule includes the following steps: S310, with compound I and compound II Using raw materials, synthesize intermediate I ; S320, Intermediate I and Compound III The reaction synthesizes the probability bit molecule.

8. The method for fabricating a single-molecule probabilistic bit device based on external circuit coupling as described in claim 5, characterized in that, In step S400, the solvents of both organic solution I and organic solution II are tetrahydrofuran.

9. The method for fabricating a single-molecule probabilistic bit device based on external circuit coupling as described in claim 5, characterized in that, In step S400, the in-situ dehydrogenation reaction is carried out in an inert environment.

10. The application of a single-molecule probabilistic bit device based on external circuit coupling, characterized in that, A brain-like probabilistic computing network is constructed using a single-molecule probabilistic bit device based on external circuit coupling as described in any one of claims 1 to 4.

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