Single-molecule quantum bit device based on microwave resonance regulation and preparation method thereof

Abstract

The present application relates to the technical field of microwave regulation, and particularly relates to a single-molecule quantum bit device based on microwave resonance regulation and a preparation method thereof.The quantum bit device takes a phenyl bridged copper-iron bis-porphyrin molecule or a phenyl bridged copper phthalocyanine-iron porphyrin molecule as a quantum bit functional molecule, and coordination metal ions in a main chain and a side chain of the molecule form a correlated ground state through anti-ferromagnetic coupling, the main chain metal ions play a function of stabilizing a spin environment, and the side chain metal ions serve as precise control sites, in a process of microwave-induced spin resonance, two spins are synchronously flipped to realize switching between 0 and 1; meanwhile, an entangled ground state formed by the main chain and the side chain can effectively block a tunneling electron inelastic scattering channel, inhibit spin flipping, and prolong spin lifetime, so as to maintain stability of a coherent state; the preparation method provided by the present application is simple to operate, reaction conditions are easy to control, and is helpful to scale production.

Description

Technical Field

[0001] This invention relates to the field of microwave modulation technology, and in particular to single-molecule quantum bit devices based on microwave resonance modulation and their fabrication methods. Background Technology

[0002] With the rapid development of quantum computing technology, qubits, as the core carrier of quantum information processing, are becoming a key area of ​​quantum technology research, with advancements in their fabrication processes, improved control precision, and breakthroughs in system scalability. Currently, mainstream qubit systems are mainly built based on semiconductor quantum dots or superconducting circuits. Among them, semiconductor quantum dots are considered the ideal approach for silicon-based quantum computing due to their compatibility with the existing semiconductor industry, while superconducting circuits dominate in superconducting quantum processors due to their high coherence characteristics at low temperatures. However, both types of systems face insurmountable technical bottlenecks: the quantum states of semiconductor quantum dots are susceptible to interference from nuclear spin noise and charge noise, resulting in generally limited coherence time; superconducting qubits are highly dependent on extremely low-temperature environments, and as the number of qubits increases, crosstalk between qubits and the complexity of control circuits increase exponentially, which severely restricts the integration capability of large-scale quantum chips.

[0003] Against this backdrop, single-molecule devices have attracted attention due to their atomic-level size precision and molecular-level functional designability. On the one hand, the unpaired electron spins or nuclear spins in molecules can be precisely controlled through chemical modification, thereby optimizing coherence time. On the other hand, the weak interaction between molecular spins and the environment makes their coherence time significantly better than that of traditional semiconductor quantum dots. However, the development of current molecular spin qubit systems still faces a series of challenges: First, achieving efficient and controllable spin-microwave resonant coupling at the single-molecule scale presents technical difficulties, and traditional control methods struggle to achieve precise energy exchange at microscopic interfaces. Second, reliable readout of single-molecule spin states is another bottleneck; the extraction of weak quantum signals is susceptible to noise interference, posing a challenge to improving the signal-to-noise ratio.

[0004] Therefore, there is an urgent need to develop a new type of single-molecule quantum bit device. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the related art. Therefore, the first objective of the present invention is to provide a single-molecule quantum bit device based on microwave resonance modulation; the second objective of the present invention is to provide a method for fabricating a single-molecule quantum bit device based on microwave resonance modulation.

[0006] To achieve the first objective, the technical solution adopted by this invention is as follows:

[0007] A single-molecule quantum bit device based on microwave resonance modulation includes a graphene source electrode, a quantum bit functional molecule, and a graphene drain electrode. The graphene source electrode and the graphene drain electrode form a graphene electrode pair, and the quantum bit functional molecule is covalently connected between the graphene electrode pairs.

[0008] The quantum bit functional molecules form spin-microwave resonant coupling under the action of microwave radio frequency signals. The quantum bit functional molecules are selected from phenyl-bridged copper-iron bisporphyrin molecules or phenyl-bridged copper phthalocyanine-iron porphyrin molecules.

[0009] The structural formula of the phenyl-bridged copper-iron bisporphyrin molecule is shown below:

[0010] ;

[0011] The structural formula of the phenyl-bridged copper phthalocyanine-iron porphyrin molecule is shown below:

[0012] .

[0013] Cu coordinated in the functional molecule of the quantum bit 2+ Fe 2+ The d orbitals contain unpaired electrons, and their spin magnetic moments are easily modulated by an external magnetic field in their natural state. Simultaneously, the rigid benzene ring bridging significantly reduces the probability of central decoherence due to molecular vibrational and conformational disorder, thereby extending the coherence time of the spin state. Coordinating metal ions in the molecular backbone and side chains form a correlated ground state through antiferromagnetic coupling. The backbone metal ions function to stabilize the spin environment, while the side chain metal ions act as precise manipulation sites. During microwave-induced spin resonance, the two spins synchronously flip, switching between 0 and 1. Furthermore, the entangled ground state formed by backbone-side chain coupling effectively blocks the inelastic scattering channel of tunneling electrons, suppresses spin flipping, and extends spin lifetime, thus maintaining the stability of the coherent state.

[0014] Preferably, the microwave radio frequency signal is 5GHz to 15GHz.

[0015] Preferably, the single-molecule quantum bit device based on microwave resonance modulation further includes a silicon substrate, and the graphene electrode pair is disposed on the top layer of the silicon substrate.

[0016] Preferably, the single-molecule quantum bit device based on microwave resonance modulation further includes a microstrip patch antenna, which is disposed on the top layer of the silicon substrate and is used to output microwave radio frequency signals to the quantum bit functional molecules.

[0017] Preferably, the microstrip patch antenna includes an insulating layer, a nickel film, and a gold conductive layer disposed sequentially from bottom to top.

[0018] Preferably, the thickness of the nickel film is 70–90 nm, and the thickness of the gold conductive layer is 450–550 nm.

[0019] Preferably, the graphene electrode pair is a nano-gap array electrode.

[0020] Preferably, a single quantum bit functional molecule is connected between the graphene electrode pairs.

[0021] To achieve the second objective, the technical solution adopted by this invention is as follows:

[0022] A method for fabricating a single-molecule quantum bit device based on microwave resonance modulation, used to fabricate any of the single-molecule quantum bit devices based on microwave resonance modulation described above, includes the following steps:

[0023] S100. Graphene electrode pairs are prepared using monolayer graphene.

[0024] S200. Using a dehydration condensation reaction, quantum bit functional molecules are covalently linked between the graphene electrode pairs.

[0025] Preferably, in step S200, the reaction solvent for the dehydration condensation reaction is selected from pyridine.

[0026] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0027] Microwave resonance-controlled single-molecule quantum bit devices use phenyl-bridged copper-iron bisporphyrin molecules or phenyl-bridged copper phthalocyanine-iron porphyrin molecules as the functional molecules for the quantum bits. The Cu atoms coordinated in the structural formula of these functional molecules... 2+ Fe 2 + The d orbitals contain unpaired electrons, and their spin magnetic moments are easily modulated by external magnetic fields in their natural state. Simultaneously, the rigid benzene ring bridging significantly reduces the probability of central decoherence due to molecular vibrational and conformational disorder, thereby extending the coherence time of the spin state. Coordinating metal ions in the molecular backbone and side chains form a correlated ground state through antiferromagnetic coupling. The backbone metal ions function to stabilize the spin environment, while the side chain metal ions act as precise manipulation sites. During microwave-induced spin resonance, the two spins synchronously flip, switching between 0 and 1. Furthermore, the entangled ground state formed by backbone-side chain coupling effectively blocks the inelastic scattering channels of tunneling electrons, suppresses spin flipping, and extends spin lifetime, thus maintaining the stability of the coherent state.

[0028] In addition, the functional molecules of qubits are covalently connected between graphene electrode pairs, which can ensure the stability of device operation; using functional molecules as qubit carriers can further improve the integration density of quantum chips, better meet the needs of quantum computing and the miniaturization of devices.

[0029] The method for fabricating single molecular quantum bit devices based on microwave resonance modulation provided by this invention is simple to operate and the reaction conditions are easy to control, which is conducive to large-scale production.

[0030] 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

[0031] Figure 1 This is a schematic diagram of the structure of a single molecular quantum bit device based on microwave resonance modulation provided in an embodiment of the present invention.

[0032] Figure 2 This is the current-voltage curve of the single molecular quantum bit device based on microwave resonance modulation provided in Embodiment 3 of the present invention under the condition of no microwave signal.

[0033] Figure 3 This is the current-voltage curve of a single molecular quantum bit device based on microwave resonance modulation provided in Embodiment 3 of the present invention under the condition of adding a microwave signal.

[0034] Figure 4 This is a graph showing the measurement results of the dynamic process time-resolved characteristics of the single molecular quantum bit device based on microwave resonance modulation provided in Embodiment 3 of the present invention.

[0035] Figure label:

[0036] 1. Graphene source electrode; 2. Quantum bit functional molecule; 3. Graphene drain electrode; 4. Silicon substrate; 5. Microstrip patch antenna. Detailed Implementation

[0037] 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.

[0038] like Figure 1As shown, a single-molecule quantum bit device based on microwave resonance modulation includes a graphene source electrode 1, a quantum bit functional molecule 2, and a graphene drain electrode 3. The graphene source electrode 1 and the graphene drain electrode 3 form a graphene electrode pair, and the quantum bit functional molecule 2 is covalently connected between the graphene electrode pairs.

[0039] Among them, the quantum bit functional molecules form spin-microwave resonant coupling under the action of microwave radio frequency signals. The quantum bit functional molecules are selected from phenyl-bridged copper-iron bisporphyrin molecules or phenyl-bridged copper phthalocyanine-iron porphyrin molecules.

[0040] The structural formula of the phenyl-bridged copper-iron bisporphyrin molecule is shown below:

[0041] ;

[0042] The structural formula of the phenyl-bridged copper phthalocyanine-iron porphyrin molecule is shown below:

[0043] ;

[0044] According to a specific embodiment of the invention, the single molecular quantum bit device based on microwave resonance modulation further includes a silicon substrate 4, and the graphene electrode pair is disposed on the top layer of the silicon substrate 4.

[0045] According to a specific embodiment of the present invention, the single-molecule quantum bit device based on microwave resonance modulation further includes a microstrip patch antenna 5, which is disposed on the top layer of the silicon substrate 4 and is used to output microwave radio frequency signals to the quantum bit functional molecules.

[0046] 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.

[0047] Example 1

[0048] Preparation of functional molecules of quantum bits The process is as follows:

[0049] I. Synthesis of Compound 1 .

[0050] Anhydrous CH2Cl2 (80 mL) was added to a dry Schlenk reaction flask and nitrogen gas was introduced. Benzaldehyde (3.0 mmol), 4-bromobenzaldehyde (1.0 mmol), and pyrrole (4.0 mmol) were added sequentially using a syringe. After stirring for 5 min, the catalyst borofluorotriethyl ether (BF3·OEt2) (0.5 mL) was added using a syringe. Under a nitrogen atmosphere, at room temperature and in the dark, the reaction was stirred for 3 h. Then, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (1.0 mmol) was added, and the reaction was stirred for another 1 h. The reaction was then quenched with methanol (5 mL), concentrated by rotary evaporation, and the concentrate was purified by column chromatography (using a 1:1 volume ratio of dichloromethane and petroleum ether mixture as eluent). The product was then collected.

[0051] Add 100 mg of CuSO4·2H2O to a 50 ml round-bottom flask, then add the previously collected product. Reflux at 120 °C in the dark for 12 h, then cool to room temperature. Pour the mixture into ice water to precipitate the precipitate, filter, and obtain the filter cake. Wash with water to obtain compound 1, whose characterization data are as follows:

[0052] 1 ¹H NMR (500 MHz, deuterated chloroform): δ = 8.75 (d, J = 7.0, 1H), 8.61 (d, J = 7.1, 1H), 7.78–7.64 (m, 3H), 7.63–7.57 (m, 1H), 7.50–7.37 (m, 5H), 6.94 (s, 1H), 3.91 (s, 1H);

[0053] 13 C NMR (125MHz, deuterated chloroform): δ=158.31, 158.30, 157.94, 141.95, 140.70, 140.57, 137.51, 136.35, 135.88, 132.82, 130.83, 130.55, 129.98, 129.79, 129.11, 128.65, 128.45, 126.83, 126.39, 125.68, 125.63, 125.62, 123.39, 115.88, 113.11, 29.96;

[0054] TOF-ESI (+) (m / z): C 45 H 30 BrCuN4 768.0950.

[0055] II. Synthetic Compound 2 .

[0056] Anhydrous CH2Cl2 (80 mL) was added to a dry Schlenk reaction flask and nitrogen gas was introduced. Formaldehyde (1.0 mmol), 4'-amino-[1,1'-biphenyl]-4-carboxaldehyde (2.0 mmol), 4-boron ester benzaldehyde (1.0 mmol), and pyrrole (4.0 mmol) were added sequentially using a syringe. After stirring for 5 min, catalyst BF3·OEt2 (0.5 mL) was added using a syringe. The reaction was carried out under nitrogen atmosphere, at room temperature and in the dark, and stirred for 3 h. Then, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (1.0 mmol) was added, and the reaction was stirred for another 1 h. The reaction was quenched with methanol (5 mL), concentrated by rotary evaporation, and the concentrate was purified by column chromatography (eluent was a 1:1 mixture of dichloromethane and petroleum ether). The product was then collected.

[0057] 100 mg of ferric chloride dihydrate was added to a 50 ml round-bottom flask, followed by the previously collected product. The mixture was refluxed at 120 °C in the dark for 12 h, then cooled to room temperature. The precipitate was precipitated by pouring it into ice water, filtered, and the filter cake was washed with water to obtain compound 2. Its characterization data are as follows:

[0058] 1 ¹H NMR (500 MHz, deuterated chloroform): δ = 8.71 (d, J = 9.2, OH), 8.60 (d, J = 9.3, OH), 8.05 (d, J = 9.3, OH), 7.86–7.79 (m, 2H), 7.75–7.55 (m, 5H), 7.47 (d, J = 6.6, OH), 7.40 (d, J = 1.5, OH), 7.18–7.11 (m, 1H), 7.04 (s, 1H), 6.80–6.74 (m, 2H), 4.48 (s, 1H);

[0059] 13 C NMR (125MHz, deuterated chloroform): δ=160.23, 155.31, 149.46, 149.04, 148.69, 140.74, 138.16, 138.04, 135.42, 133.95, 133.89, 133.76, 132.22, 132.06, 131.92, 1 30.31, 130.26, 128.12, 127.98, 127.82, 125.07, 122.94, 122.44, 120.75, 119.54, 118.06, 117.87, 116.76, 113.61, 111.52, 111.44, 110.08, 106.68;

[0060] TOF-ESI (+) (m / z): C 50 H 35 BFeN6O3 834.2213.

[0061] III. Preparation of functional molecules for target qubits.

[0062] Compound 1 (50.0 mg), compound 2 (50.0 mg), and catalyst tetra(triphenylphosphine)palladium (7.7 mg) were added sequentially to a dry Schlenk reaction tube. Under a nitrogen atmosphere, anhydrous toluene (8 mL) and a 2M sodium carbonate aqueous solution (2 mL) were added to the reaction tube. The reaction tube was placed in an oil bath at 85 °C and refluxed with stirring for 12 h in the dark. After cooling to room temperature, the reaction mixture was transferred to a separatory funnel, and extracted with distilled water (20 mL) and dichloromethane (20 mL). The organic phase was collected and concentrated by rotary evaporation. The concentrate was purified by column chromatography (using a 2:1 mixture of dichloromethane and petroleum ether as eluent) to obtain the target quantum bit functional molecule, the structure of which is as follows:

[0063] .

[0064] Its characterization data are shown below:

[0065] 1 ¹H NMR (500 MHz, deuterated chloroform): δ = 8.77–8.69 (m, 1H), 8.63–8.57 (m, 1H), 7.93–7.85 (m, 1H), 7.88–7.82 (m, 1H), 7.85–7.79 (m, 1H), 7.78–7.69 (m, 1H), 7.73–7.65 (m, 2H), 7.68–7.61 (m, 1H), 7.61–7.55 (m, 1H), 7.50–7.37 (m, 4H), 7.11 (s, 1H), 6.94 (s, 1H), 6.80–6.74 (m, 1H), 4.48 (s, 1H), 3.91 (s, 1H);

[0066] 13C NMR (125MHz, deuterated chloroform): δ=158.32, 158.30, 157.94, 155.31, 149.46, 149.04, 148.72, 141.95, 141.46, 141.05, 140.74, 140.61, 140.57, 138.16, 138.04, 137.51, 137.25, 135.88, 135.42, 134.17, 133.95, 133.92, 133.76, 132.06, 131.92, 130.83, 130. 55, 130.31, 130.26, 129.98, 129.11, 128.83, 128.65, 128.45, 128.12, 128.00, 127.98, 126.83, 126.58, 125.68, 125.62, 125.07, 122.92, 120.75, 119.54, 118.06, 117.87, 116.76, 115.88, 113.61, 113.11, 111.52, 110.53, 110.08, 106.68, 29.96;

[0067] TOF-ESI (+) (m / z): C 95 H 63 CuFeN 10 1462.3882.

[0068] Example 2

[0069] Preparation of functional molecules of quantum bits The process is as follows:

[0070] I. Synthesis of Compound 3 .

[0071] In a round-bottom flask, phthalonitrile (3.0 mmol), 4-bromophthalonitrile (1.0 mmol), and Zn(OAc)₂ (1.0 mmol) were dissolved in n-pentanol (20 mL). Under a nitrogen atmosphere, the reaction mixture was refluxed at 140 °C for 8 h. After cooling to room temperature, methanol (20 mL) was added to precipitate the precipitate. The precipitate was separated and washed with methanol to obtain a crude product. The crude product was purified by column chromatography (using a 2:1 mixture of dichloromethane and petroleum ether as eluent) and the product was collected.

[0072] Add 100 mg of CuSO4·2H2O to a 50 ml round-bottom flask, then add the previously collected product. Reflux at 120 °C in the dark for 12 h, cool to room temperature, pour into ice water to precipitate the precipitate, filter, obtain filter cake, wash with water to obtain compound 3.

[0073] 1 ¹H NMR (500 MHz, deuterated chloroform): δ = 8.48 (dd, J = 6.2, 1.2, 1H), 8.26–8.19 (m, 1H), 8.18–8.08 (m, 1H), 7.66 (dd, J = 7.8, 2.5, 0H), 7.50 (ddd, J = 7.0, 3.8, 1.6, 1H), 7.44–7.36 (m, 2H);

[0074] 13 C NMR (125MHz, deuterated chloroform): δ=158.77, 157.87, 157.36, 156.95, 147.19, 147.17, 145.78, 145.27, 139.32, 139.04, 138.14, 137.53, 134.19, 130.95, 130.93, 129.27, 129.20, 129.15, 128.17, 128.03, 126.20, 126.10, 126.05, 125.78, 122.28, 120.53, 120.11;

[0075] TOF-ESI (+) (m / z): C 32 H 17 BrCuN8 655.0556.

[0076] II. Synthesis of functional molecules for target qubits.

[0077] Compound 3 (50.0 mg), Compound 2 prepared in Example 1 (50.0 mg), and catalyst tetra(triphenylphosphine)palladium (7.7 mg) were added sequentially to a dry reaction tube. Under a nitrogen atmosphere, anhydrous toluene (8 mL) and a 2M sodium carbonate aqueous solution (2 mL) were added to the reaction tube. The reaction tube was placed in an oil bath at 85°C, protected from light, and refluxed with stirring for 12 h. After cooling to room temperature, the reaction mixture was transferred to a separatory funnel, and extracted with distilled water (20 mL) and dichloromethane (20 mL). The organic phase was collected and concentrated by rotary evaporation. The concentrate was purified by column chromatography (using a 2:1 volume ratio of dichloromethane and petroleum ether mixture as eluent) to obtain the target quantum bit functional molecule, the structure of which is as follows:

[0078] ;

[0079] Its characterization data are shown below:

[0080] 1¹H NMR (500 MHz, deuterated chloroform): δ = 8.48 (dd, J = 6.2, 1.2, 1H), 8.25–8.17 (m, 1H), 8.17–8.09 (m, 2H), 8.01–7.95 (m, 1H), 7.85–7.79 (m, 2H), 7.75–7.64 (m, 2H), 7.61–7.55 (m, 2H), 7.53–7.44 (m, 2H), 7.44–7.36 (m, 2H), 7.11 (d, J = 17.0, 1H), 6.80–6.74 (m, 2H), 4.48 (s, 1H);

[0081] 13 C NMR (125MHz, deuterated chloroform): δ=158.80, 158.77, 157.98, 157.48, 155.31, 149.46, 149.04, 148.72, 147.19, 147.17, 145.78, 145.27, 140.91, 140.74, 140.58, 139.04, 138.16, 138.14, 138.04, 137.72, 137.42, 135.42, 134.17, 133.95, 133.92, 133.76, 132.06, 132.04, 1 31.92, 130.95, 130.93, 130.31, 130.26, 129.27, 129.15, 128.59, 128.12, 128.07, 128.03, 127.98, 126.20, 126.18, 126.05, 125.78, 125.07, 124.83, 122.92, 120.75, 120.53, 120.11, 119.54, 118.06, 117.87, 116.76, 113.61, 111.52, 110.53, 110.08, 106.68;

[0082] TOF-ESI (+) (m / z): C 82 H 50 CuFeN 14 1349.2998.

[0083] Example 3

[0084] The fabrication process of single-molecule quantum bit devices based on microwave resonance modulation is as follows:

[0085] I. Preparation of monolayer graphene.

[0086] The copper foil was ultrasonically cleaned with acetone and isopropanol for 10 minutes each, then soaked in 5wt% dilute hydrochloric acid for 5 minutes, rinsed with deionized water and dried with nitrogen.

[0087] The dried copper foil was placed in a chemical vapor deposition reaction chamber and heated to 1000℃. H2 (flow rate 200 sccm) and Ar (flow rate 200 sccm) were introduced, and the annealing time was 60 min. Methane (flow rate 20 sccm) and hydrogen (flow rate 200 sccm) were introduced, and the temperature was maintained at 1000℃ for 20 min. Then the heating was turned off, and the temperature was cooled to room temperature at a rate of 50℃ / min under the H2 / Ar atmosphere to obtain monolayer graphene.

[0088] II. Preparation of graphene-silicon wafer structure.

[0089] The monolayer graphene was adhered to a clean quartz sheet using transparent tape. Polymethyl methacrylate (PMMA) was then spin-coated onto the monolayer graphene (4000 rpm, 40 s). The quartz sheet was then placed on a heating stage at 180°C for 2 minutes to bake the adhesive. Excess PMMA and graphene on the back of the copper foil were then etched using oxygen plasma to obtain a PMMA-monolayer graphene-copper foil structure.

[0090] The PMMA-monolayer graphene-copper foil structure was cut into 1cm×1cm pieces and placed in a 1M ferric chloride aqueous solution to dissolve the copper foil on the back. It was then soaked in a 0.1M HCl aqueous solution for 10 minutes and rinsed three times with deionized water to obtain a monolayer graphene coated with PMMA. This monolayer graphene was then transferred onto a silicon wafer and soaked in a 0.1M HCl aqueous solution for 5 minutes, rinsed with deionized water, soaked in a 0.01M KOH aqueous solution for 2 minutes, rinsed with deionized water, allowed to stand, dried, and the adhesive removed to obtain the graphene-silicon wafer structure.

[0091] III. Preparation of magnetic electrode-graphene strip-silicon wafer structure.

[0092] Using an ultraviolet lithography machine to etch strips on a graphene layer, and then placing it in an oxygen plasma etching machine to etch the graphene outside the strips, a graphene strip-silicon wafer structure is obtained.

[0093] Electrode patterns were etched onto the graphene strip-silicon wafer structure using an ultraviolet lithography machine. Then, an aluminum oxide film with a thickness of about 1.5 nm was first sputtered using a magnetron sputtering coating machine, followed by a nickel film with a thickness of 80 nm. Finally, the photoresist was removed with acetone to form magnetic electrodes on the strip. A total of 169 pairs of magnetic electrodes constituted a magnetic electrode array, resulting in a magnetic electrode-graphene strip-silicon wafer structure.

[0094] IV. Fabrication of microstrip patch antenna.

[0095] A microstrip antenna pattern was etched onto a magnetic electrode-graphene strip-silicon wafer structure using an ultraviolet lithography machine. First, an 80nm thick nickel film was sputtered using a magnetron sputtering coating machine, and then a 500nm thick gold film was deposited using a thermal resistance evaporation coating machine. After removing the photoresist with acetone, the magnetic electrode antenna-graphene strip-silicon wafer structure was obtained.

[0096] The microstrip patch antenna is located at the end of the graphene strip, with silicon dioxide as the insulating layer and gold as the conductive layer. The nickel thin film utilizes its magnetic anisotropy to enhance the localization of the microwave field and improve the coupling efficiency with molecular spin. The antenna size is 5mm×3.2mm, and it can transmit microwave radio frequency signals from 5GHz to 15GHz well.

[0097] V. Preparation of graphene point electrode array.

[0098] After spin-coating PMMA (4000 rpm, 40 s) onto a magnetic electrode antenna-graphene strip-silicon wafer, dashed lines were etched between each pair of magnetic electrodes using an electron beam lithography machine (total length of dashed lines is 60 μm: each dashed line segment is 150 nm long and spaced 40 nm apart). Then, the array was etched in an oxygen plasma etching machine to form 315 conductive channels between each pair of magnetic electrodes, resulting in a carboxylic acid-modified graphene point electrode array.

[0099] The conductivity of graphene dot array electrodes was tested under a voltage of 50mV, and graphene dot electrode arrays with conductivity in the range of 10μA were screened for use in subsequent preparation processes.

[0100] VI. Connecting quantum bit functional molecules to graphene electrode pairs:

[0101] The graphene point electrode array prepared above was cleaned with acetone and then dried in a 60°C oven for 30 min. Subsequently, the dried graphene point electrode array and quantum bit functional molecules were... (1mg) or 1 mg, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.1 g), and anhydrous pyridine (10 mL) were added sequentially to the reaction vessel. The reaction was allowed to stand for 48 h under a nitrogen atmosphere to obtain a single molecular quantum bit device based on microwave resonance modulation.

[0102] Signal detection was performed using a comprehensive physical property measurement system and a lock-in amplifier, and the results are as follows: Figure 2 As shown in the figure, the curve shows that the current gradually increases with increasing voltage, which indicates that single-molecule quantum bits have been successfully connected between graphene point electrode pairs.

[0103] During the initialization of qubits, a static magnetic field of 0.3T is first applied perpendicularly to the single-molecule qubit device, pointing upwards. Based on the Zeeman effect, the intramolecular spin magnetic moments interact with this magnetic field, inducing energy level splitting. This results in a significantly larger number of particles in the lower energy states than in the higher energy states, thus forming a spin-polarized initial state.

[0104] Furthermore, a microwave signal with an intensity of 10 dBm and a frequency of 15 GHz is generated using a radio frequency and microwave signal generator (SMB100A type). This microwave signal is introduced to the microstrip patch antenna electrodes on the device surface via a low-temperature microstrip line. The microstrip patch antenna converts the microwave electrical signal into a directional electromagnetic field and radiates it between the graphene point electrode pair (i.e., the graphene source electrode and the graphene drain electrode) where the qubit functional molecules are located. This causes the qubit functional molecules to resonate and absorb microwave energy, driving the spin state to transition between high and low energy levels. The electron spin flip caused by microwave resonance manifests as a change in the magnitude of the spin transport current. By measuring the current of the qubit device using a high-sensitivity lock-in amplifier, the spin state of the qubit can be detected, thereby enabling the readout operation of the qubit system.

[0105] To The results of measuring the current-time (It) fluctuation curves and dynamic process time-resolved characteristics of single-molecule quantum bit devices based on microwave resonance modulation, prepared from functional quantum bit molecules, are as follows: Figure 3 and Figure 4 As shown.

[0106] from Figure 3 It can be seen that under the condition that the bias voltage is kept constant at 0.1V, the microwave response current of the single molecular qubit device based on microwave resonance modulation provided by the present invention will change with the introduction of microwave signal. The jump of the current signal reflects the transition between different electronic spin states of the qubit functional molecule.

[0107] Figure 4 The study demonstrated the Rabi oscillation characteristic generated by electron spin, which persisted throughout the measurement process. This result further proves the successful manipulation of qubit functional molecules by microwaves.

[0108] Where the horizontal axis τ is the time constant and the vertical axis P is the probability, representing the probability of Rabi oscillations generated by electron spin occurring under the corresponding time constant.

[0109] 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 quantum bit device based on microwave resonance modulation, characterized in that, It includes a graphene source electrode, a quantum bit functional molecule, and a graphene drain electrode, wherein the graphene source electrode and the graphene drain electrode form a graphene electrode pair, and the quantum bit functional molecule is connected between the graphene electrode pairs by covalent bonds. The quantum bit functional molecules form spin-microwave resonant coupling under the action of microwave radio frequency signals. The quantum bit functional molecules are selected from phenyl-bridged copper-iron bisporphyrin molecules or phenyl-bridged copper phthalocyanine-iron porphyrin molecules. The structural formula of the phenyl-bridged copper-iron bisporphyrin molecule is shown below: ； The structural formula of the phenyl-bridged copper phthalocyanine-iron porphyrin molecule is shown below: 。 2. The single-molecule quantum bit device based on microwave resonance modulation as described in claim 1, characterized in that, The microwave radio frequency signal is 5GHz to 15GHz.

3. The single-molecule quantum bit device based on microwave resonance modulation as described in claim 1, characterized in that, The single-molecule quantum bit device based on microwave resonance modulation also includes a silicon substrate, and the graphene electrode pair is disposed on the top layer of the silicon substrate.

4. The single-molecule quantum bit device based on microwave resonance modulation as described in claim 3, characterized in that, The single-molecule quantum bit device based on microwave resonance modulation also includes a microstrip patch antenna, which is disposed on the top layer of the silicon substrate and is used to output microwave radio frequency signals to the quantum bit functional molecules.

5. The single-molecule quantum bit device based on microwave resonance modulation as described in claim 4, characterized in that, The microstrip patch antenna comprises, from bottom to top, an insulating layer, a nickel film, and a gold conductive layer.

6. The single-molecule quantum bit device based on microwave resonance modulation as described in claim 5, characterized in that, The thickness of the nickel film is 70–90 nm, and the thickness of the gold conductive layer is 450–550 nm.

7. The single-molecule quantum bit device based on microwave resonance modulation as described in claim 1, characterized in that, The graphene electrode pair is a nano-gap array electrode.

8. The single-molecule quantum bit device based on microwave resonance modulation as described in claim 4, characterized in that, The graphene electrode pairs are connected to individual qubit functional molecules.

9. A method for fabricating a single-molecule quantum bit device based on microwave resonance modulation, characterized in that, The method for fabricating a single-molecule quantum bit device based on microwave resonance modulation as described in any one of claims 1 to 8 comprises the following steps: S100. Graphene electrode pairs are prepared using monolayer graphene. S200. Using a dehydration condensation reaction, quantum bit functional molecules are covalently linked between the graphene electrode pairs.

10. The method for fabricating a single-molecule quantum bit device based on microwave resonance modulation as described in claim 9, characterized in that, In step S200, the reaction solvent for the dehydration condensation reaction is selected from pyridine.

Images