A biological quantum computing device based on quadrupolar ion nuclear spins on phospholipid membranes

Abstract

The application discloses a biological quantum computing device based on quadrupole ion nuclear spins on a phospholipid membrane, comprising: a substrate; a phospholipid bilayer membrane arranged on the substrate, wherein ions with nuclear spins greater than or equal to 1 are doped; a nanowire array arranged on the other side of the substrate; and a control element arranged on the nanowire array. Nuclear spins in the phospholipid membrane are used as quantum bits, and the quantum bits are controlled by controlling an electric field gradient, so that a quantum computing function is realized. This is a brand-new quantum information processing mode, which combines a silicon-based electronic process and a complex biological molecular system, processes information through precise nuclear spin control, has obvious small-size advantages, simplifies an external control system and a preparation process, simultaneously reduces energy consumption and cost, and is convenient for integration and large-scale manufacturing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of quantum computing, and particularly relates to a method for orienting nuclear spins by using quadrupolar ion nuclear spins (nuclear spins of ions with non-zero nuclear quadrupole moments) on phospholipid membranes and a device for quantum computing by using the method. BACKGROUND

[0002] Quantum computing is a new computing model that uses quantum mechanics principles for information processing. This technology performs computing tasks by manipulating and measuring quantum states, and has potential computational advantages in solving certain complex problems. The superposition state property of quantum computing makes it exhibit performance far superior to classical computers, and has wide potential applications in the fields of cryptography, molecular simulation, optimization problems, etc. Another important feature of quantum computing is quantum entanglement, which allows non-local correlations between multiple quantum bits. This correlation enables quantum computers to process a large amount of information simultaneously, providing new possibilities for parallel computing. In addition, quantum tunneling effect is also applied in some quantum algorithms, such as quantum annealing algorithm, for solving complex optimization problems. In recent years, quantum computing research has made substantial progress, including the implementation of quantum computing prototypes and the experimental verification of quantum superiority.

[0003] Traditional quantum computing systems still face many challenges. Main quantum computing schemes, including superconducting quantum bits, ion trap systems, etc., usually require extremely low temperature environments (close to absolute zero) to ensure quantum coherence; at the same time, precise and complex control equipment is needed, which greatly limits the practical process; the scalability of the system is also a major challenge, as the number of quantum bits increases, it becomes more and more difficult to maintain the coherence of the entire system, and the difficulty of control and readout increases exponentially; in addition, many quantum computing schemes have poor compatibility with existing integrated circuit technology, making it difficult to be directly integrated into existing semiconductor processes, resulting in a large system size, which is not conducive to miniaturization and mass production. These defects are not conducive to the development of quantum computing towards practicality.

[0004] In view of these limitations of traditional quantum computing systems, the research community is actively exploring new quantum computing schemes, such as quantum computing based on solid-state systems, topological quantum computing, etc. Kane proposed an architecture for a solid-state quantum computer, which consists of a silicon wafer doped with phosphorus atoms. The spin of the phosphorus nucleus serves as a storage quantum bit, and the unpaired electron spin of the phosphorus atom acts as a control quantum bit, coupled with the phosphorus nuclear spin quantum bit and the adjacent electron spin quantum bit. The quantum computer is controlled by external magnetic and electric fields. By etching nanowires on the surface of silicon to construct circuit elements, the magnetic and electric fields can be locally varied on the scale of about 30 nanometers. These external fields move the electrons around and control the wave function overlap of the electrons with the nuclear spin and with the neighboring electrons. In this way, they control the exchange of quantum information between the nuclear storage quantum bits and the electronic control quantum bits.

[0005] Quantum effects in biological systems are also attracting increasing attention. Some studies have shown that quantum coherence can be maintained for a considerable period of time within the environment of biological systems, and certain biological processes may utilize quantum effects, such as energy transfer in photosynthesis, quantum sensing in bird navigation, etc. These findings have inspired scientists to consider whether biological molecules or biologically inspired systems can be used to construct new quantum computing platforms. This approach can work at room temperature and has the advantages of biological systems such as self-assembly and self-repair. SUMMARY

[0006] The present application aims to provide a quantum computing device based on quadrupole ion nuclear spins on a phospholipid membrane based on the quantum computing architecture proposed by Kane, using ion nuclear spins with nuclear spins greater than or equal to 1 in the phospholipid membrane as quantum bits, and controlling the quantum bits through control of the electric field gradient to achieve quantum computing functionality, thereby solving the problems of harsh working environment, complex system, poor scalability, etc. in existing quantum computing technologies.

[0007] To achieve the above technical purposes, the present application adopts the following technical solutions:

[0008] A biological quantum computing device based on quadrupole ion nuclear spins on a phospholipid membrane, comprising: a substrate; a phospholipid bilayer membrane disposed on the substrate, wherein the phospholipid bilayer membrane is doped with ions having nuclear spins greater than or equal to 1; a nanowire array disposed on the other side of the substrate; and a control element disposed on the nanowire array.

[0009] In the biological quantum computing device based on quadrupole ion nuclear spins on a phospholipid membrane:

[0010] The substrate can be a silicon oxide, high-resistance silicon, aluminum oxide, etc. substrate, serving as a support structure to provide a flat and stable surface;

[0011] The phospholipid bilayer membrane is arranged on the substrate, and is formed by self-assembly of phospholipid molecules into a bilayer structure; the phospholipid molecules that constitute the phospholipid bilayer membrane include, but are not limited to, phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), etc., and the proportions of the phospholipid molecules can be changed at will;

[0012] The ions with nuclear spin greater than or equal to 1, such as sodium ions, copper ions, manganese ions, etc., are injected into the phospholipid bilayer membrane and are fixed in the membrane structure by forming coordination bonds with the phospholipid molecules; the nuclear spins of the ions are oriented in the direction perpendicular to the membrane by the anisotropic motion of the phospholipid molecules, thereby providing a reference for the direction of the phosphorus nuclear spin and the proton nuclear spin used for quantum information storage.

[0013] The nanowire array is arranged on the other side of the substrate and is used to construct a control element, which can be composed of silicon, metal or semiconductor materials, etc.

[0014] The control element is used to adjust the local electric field and / or magnetic field, so as to realize the manipulation of the single phosphorus nuclear spin, the proton nuclear spin and the ion nuclear spin, and then perform quantum computation. For example, a micro electrode is arranged on the nanowire array, and the functions of the micro electrode include controlling the direction of the single phosphorus nuclear spin or the proton nuclear spin (for example, a metal electrode A gate is arranged near a phosphorus atom, and by adjusting the voltage on the A gate, the wave function of the electron around the phosphorus nucleus can be affected, thereby controlling the coupling between the electron spin and the phosphorus nuclear spin), or adjusting the interaction between adjacent spins (for example, a metal electrode J gate is arranged between two adjacent phosphorus atoms, and by adjusting the voltage on the J gate, the size of the electron cloud overlap between the two atoms can be affected, thereby controlling the coupling between the two nuclear spins).

[0015] The rotational motion of the phospholipid molecules in the phospholipid bilayer membrane around the normal direction of the membrane and the diffusion motion of the phospholipid molecules in the plane of the membrane generate a time-averaged electric field gradient for the nuclear spin of the coordinated ions, and the direction of the maximum component of the electric field gradient is consistent with the normal direction of the phospholipid bilayer membrane, thereby orienting the nuclear spin of the ions and making the direction of the nuclear spin of the ions consistent with the normal direction of the phospholipid bilayer membrane.

[0016] In a specific implementation, the phospholipid bilayer membrane can be sandwiched between two substrates, and nanowire arrays are arranged on the other sides of the two substrates, respectively. Alternatively, only one substrate is used, and the phospholipid bilayer membrane is formed on one side of the substrate, and the nanowire array is arranged on the other side of the substrate. In an embodiment of the present application, a set of parallel nanowires is arranged on each of the upper and lower substrates, and the two sets of nanowires are perpendicular to each other in the plane projection, thereby forming an orthogonal control grid.

[0017] Preferably, a microelectrode is arranged on the nanowire array to generate a local magnetic field to control the state of a single phosphorus nuclear spin or proton nuclear spin.

[0018] Preferably, by applying a suitable voltage through the microelectrode, electrolysis of water or other oxygen-containing compounds generates oxygen radicals, thereby injecting oxygen radicals with unpaired electrons into the phospholipid bilayer membrane, and controlling the concentration and distribution of the generated oxygen radicals by controlling the voltage of the microelectrode. Two unpaired electrons of one oxygen radical interact with two proton nuclear spins, respectively, which can entangle the two nuclear spins with each other, for adjusting the coupling between the two nuclear spins.

[0019] The present application also provides a preparation method of the above-mentioned biological quantum computing device, comprising the following steps:

[0020] 1) Preparing a nanowire array on a substrate (such as a silicon wafer) by deposition and etching;

[0021] 2) Forming a phospholipid bilayer membrane on the other side of the substrate;

[0022] 3) Injecting ions with nuclear spin greater than or equal to 1 into the phospholipid bilayer membrane, so that the ions form coordination bonds with the phospholipid molecules.

[0023] The present application further provides a method for quantum computing using the above-mentioned biological quantum computing device, comprising:

[0024] The rotational motion of the phospholipid molecules around the normal of the phospholipid bilayer membrane and the diffusion motion in the plane of the phospholipid bilayer membrane generate a time-averaged electric field gradient that orients the ion nuclear spin to the normal direction of the phospholipid bilayer membrane, initializes the ion nuclear spin, and the oriented ion nuclear spin transmits this direction information to the phosphorus nuclear spin and the proton nuclear spin by interacting with the surrounding phosphorus nuclear spin and proton nuclear spin;

[0025] By manipulating the control elements on the nanowire array, the coupling strength between the nuclear spins is adjusted. The specific methods include but are not limited to: adjusting the concentration and distribution of the oxygen radicals generated by electrolysis in the phospholipid bilayer membrane through the control elements, thereby adjusting the coupling strength between the nuclear spins; or, by applying a local electric field through the control elements such as electrodes, the head position of a charged phospholipid molecule at a certain position is rotated towards the direction of the electric field to adjust the relative position of the charged phospholipid molecule and other phospholipid molecules, thereby changing the relative distance between two phosphorus nuclear spins, and thereby adjusting the coupling strength between the nuclear spins.

[0026] By measuring the nuclear magnetic resonance signal, the state of the phosphorus nuclear spin and the proton nuclear spin, i.e. the calculation result, is read out.

[0027] The present application has the following beneficial effects:

[0028] 1. The electric field gradient generated by the phospholipid molecule motion is used to simplify the external control system;

[0029] 2. The biomolecule self-assembly characteristics are used to simplify the preparation process of the quantum computing system;

[0030] 3. The device can be integrated on a silicon-based chip, facilitating large-scale manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0031] The device structure and the above advantages, features of the present application will become more apparent through the following description in conjunction with the accompanying drawings.

[0032] Figure 1 is a schematic diagram of the direction of the time-averaged electric field gradient generated by the phospholipid molecule motion in the present application.

[0033] Figure 2 is a schematic diagram of the cross-sectional structure of the biological quantum computing device in an embodiment of the present application.

[0034] Figure 3 is a schematic diagram of the upper surface structure of the biological quantum computing device in an embodiment of the present application.

[0035] Figure 4 is a schematic diagram of the lower surface structure of the biological quantum computing device in an embodiment of the present application. DETAILED DESCRIPTION

[0036] The specific embodiments of the present application will be further described below in conjunction with the accompanying drawings.

[0037] Figure 2 is a schematic diagram of the cross-sectional structure of the biological quantum computing device in an embodiment of the present application. The biological quantum computing device of the present embodiment includes a substrate 2, a phospholipid bilayer membrane 3 is stacked in the middle of the two substrates 2, and ions 4 with nuclear spin greater than or equal to 1 are distributed in the phospholipid bilayer membrane 3; a plurality of parallel upper nanowires 1 and lower nanowires 5 are respectively arranged on the other side of the two substrates 2.

[0038] 1. Substrate 2: as the basic support structure of the entire device. In a preferred embodiment, the substrate 2 is made of high-resistance silicon material, and the resistivity thereof is preferably above 10,000 Ω·cm. The thickness of the substrate 2 can be between 100 μm and 1000 μm, and is preferably 500 μm. The surface of the substrate 2 is subjected to precision polishing treatment, and the surface roughness thereof is controlled to be below 1 nm, so as to ensure the uniformity and stability of the subsequent structure.

[0039] 2. Upper nanowires 1, lower nanowires 5: multiple parallel nanowires arranged on the surface of the substrate 2. These nanowires can be made of metallic materials (such as gold, silver, platinum, etc.) or doped semiconductor materials. The material and size of the upper nanowires 1 can be the same as the lower nanowires 5, or can be adjusted as needed. The upper nanowires 1 and the lower nanowires 5 are perpendicular to each other in the planar projection, forming an orthogonal control grid. In this embodiment, the upper nanowires 1 and the lower nanowires 5 are made of gold material, with a width of 50-200 nm and a height of 20-100 nm. The spacing between adjacent nanowires can be adjusted to 100 nm-1 μm. These nanowires are used to form control elements to regulate the state of phosphorus nuclear spins or proton nuclear spins.

[0040] 3. Phospholipid bilayer membrane 3: a biological membrane structure sandwiched between two substrates 2. The phospholipid bilayer membrane 3 can be composed of various phospholipid molecules, such as phosphatidylcholine (PC), phosphatidylethanolamine (PE), etc. The thickness of the phospholipid bilayer membrane 3 is usually between 4 nm and 6 nm, preferably 5 nm. This membrane structure provides a medium similar to a biological environment for accommodating and orienting ions with nuclear spin greater than or equal to 1 (preferably sodium ions).

[0041] 4. Ions with nuclear spin greater than or equal to 1 4: functional ions distributed in the phospholipid bilayer membrane 3. These ions form coordinate bonds with the phospholipid molecules of the phospholipid bilayer membrane 3, and their concentration can be adjusted to 10-100 mM.

[0042] The nuclear spin of the ion 4 as a directional quantum bit is a key element for realizing quantum computing.

[0043] In some embodiments, the device can further include:

[0044] 5. Protective layer (not shown in the figure, optional): a thin layer covering the surface of the phospholipid bilayer membrane 3. It can be made of hydrophilic polymers such as polyethylene glycol (PEG), with a thickness of 1-10 nm. The protective layer can increase the stability of the phospholipid membrane and prolong the service life of the device.

[0045] Figure 1 The schematic diagram of the direction of the time-averaged electric field gradient generated by the motion of the phospholipid molecules in the present application is shown, and the three principal axis components of the time-averaged electric field gradient are and According to the principle of nuclear magnetic resonance, electric field gradients (EFG) can be used to control the nuclear spins of nuclei with spin greater than 1 / 2. Inside an atom, the charge distribution of the nucleus is influenced by the nuclear spin, which forms a rotating ellipsoid along the direction of the nuclear spin. The deviation of the nucleus from a sphere creates a nuclear electric quadrupole moment, which interacts with the electric field generated by the electrons, known as the nuclear electric quadrupole interaction. Therefore, for nuclei with spin greater than 1 / 2 (and thus with a non-zero electric quadrupole moment), a local EFG will interact with its electric quadrupole moment, causing these nuclear spins to produce energy level splitting. The size of the energy level gap is related to the value of the EFG. Under the EFG, the nuclear quadrupole moment precesses around an axis, and the nuclear spin also precesses around the axis, the direction of which depends on the EFG, generally tending to align with the direction of the principal axis of the maximum component of the EFG.

[0046] The EFG experienced by the nuclei of ions 4 with spin greater than or equal to 1 in the phospholipid bilayer membrane 3 is influenced by the distribution of valence electrons or bonds from nearby atoms. Differences in the surrounding electronic environment, including differences in coordination number and the shape of the coordination sphere, can cause changes in the EFG of the nucleus. Phospholipid molecules can move within the membrane plane, possibly rotating around the membrane normal direction (referred to as the z-axis), or diffusing laterally within the membrane plane. Therefore, the direction of the coordination bond between the ion 4 nucleus and the phospholipid molecule also changes in an anisotropic manner.

[0047] On a longer time scale, due to the rapid rotational and diffusive motion of phospholipid molecules within the membrane plane, the EFG of the position of ion 4 coordinated with the phospholipid molecule experiences rapid fluctuations in the tangential components, resulting in the time-averaged EFG of these tangential components being canceled out. In contrast, in the normal direction perpendicular to the plane, the dynamics of the phospholipid molecules are less, exhibiting a relatively more consistent and significant EFG. This different behavior results in an anisotropic equivalent EFG, which has a smaller component in the tangential direction of the membrane and a more significant component in the normal direction. The unification of the EFG axis direction will provide a unified quantization axis for the nuclear spin of sodium ions on the phospholipid membrane.

[0048] Figure 3 The upper surface structure of the biomass quantum computing device in the embodiment of the present application is shown. On the upper surface of the device, there are a plurality of upper layer nanowires 1 arranged in parallel. These nanowires are used to form a high-density control element array to generate a local electric field or magnetic field to regulate the process of quantum computing. The number of nanowires depends on the required control accuracy and the overall size of the device.

[0049] Figure 4 ​The lower surface structure of the biological quantum computing device in the embodiment of the present application is shown. On the lower surface of the device, there are also a plurality of parallel arranged lower nanowires 5, which generate local electric or magnetic field to regulate the process of quantum computing. The nanowires 5 are perpendicular to the nanowires 1 on the upper surface in space, and the nanowires on the two surfaces together constitute a two-dimensional control grid.

[0050] The present application proposes a brand new quantum information processing method, which combines silicon-based electronic technology and complex biological molecular system to process information through precise nuclear spin control. The present application uses phospholipid membrane and ions with nuclear spin greater than or equal to 1 as the material basis of nuclear spin, which has obvious small size advantage, which means higher integration and smaller device size. In terms of computing speed and capacity, the present application uses nuclear spin on the phospholipid membrane as quantum bits for computing, which has a large number of quantum bits, similar to the physical architecture of modern computers. In addition, phospholipid membrane and ions with nuclear spin greater than or equal to 1 such as sodium ions are relatively common and low in cost. The present application uses electric field gradient control system to control the quantization axis direction, without the need for an external magnetic field, which simplifies the experimental equipment and operation, while reducing energy consumption and cost.

[0051] Although the present application has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various modifications and changes can be made without departing from the spirit and scope of the application as defined in the claims.

Claims

1. A biological quantum computing device based on quadrupolar ion nuclear spins on phospholipid membranes, comprising: a substrate; a phospholipid bilayer membrane doped with ions with nuclear spin larger than or equal to 1 disposed on the substrate; a nanowire array disposed on the other side of the substrate; a control element disposed on the nanowire array; the biological quantum computing device comprises two substrates, the phospholipid bilayer membrane is sandwiched between the two substrates, and a nanowire array is disposed on the other side of each of the two substrates; or the biological quantum computing device comprises one substrate, a phospholipid bilayer membrane is formed on one side of the substrate, and a nanowire array is disposed on the other side of the substrate; wherein: the phospholipid bilayer membrane is a bilayer structure formed by self-assembly of phospholipid molecules on the substrate, and the ions with nuclear spin larger than or equal to 1 are fixed in the membrane structure by forming coordination bonds with the phospholipid molecules, and the nuclear spins of the ions are oriented in the direction perpendicular to the membrane by the anisotropic motion of the phospholipid molecules; the phospholipid molecules are selected from phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine; and the ions with nuclear spin larger than or equal to 1 are selected from sodium ions, copper ions, and manganese ions; the control element is a microelectrode.

2. The biological quantum computing device of claim 1, wherein, the substrate is a silicon oxide, high-resistance silicon, or aluminum oxide substrate; and the nanowire array is composed of silicon, metal, or semiconductor materials.

3. The biological quantum computing device of claim 1, wherein, the biological quantum computing device comprises two substrates, a set of parallel nanowires is disposed on the upper surface of the upper substrate and the lower surface of the lower substrate, and the two sets of nanowires are perpendicular to each other in the planar projection, forming an orthogonal control grid.

4. A preparation method of the biological quantum computing device according to any one of claims 1 to 3, comprising the following steps: 1) preparing a nanowire array on a substrate by deposition and etching; 2) forming a phospholipid bilayer membrane on the other side of the substrate; 3) injecting ions with nuclear spin larger than or equal to 1 into the phospholipid bilayer membrane to form coordination bonds between the ions and the phospholipid molecules.

5. A method for quantum computing using the biological quantum computing device according to any one of claims 1 to 3, comprising: using the rotational motion of the phospholipid molecules around the normal of the phospholipid bilayer membrane and the diffusion motion in the plane of the phospholipid bilayer membrane to generate a time-averaged electric field gradient that orients the nuclear spins of the ions in the direction of the normal of the phospholipid bilayer membrane, initializing the nuclear spins of the ions, and the direction information is transmitted to the phosphorus nuclear spins and proton nuclear spins by the interaction between the oriented nuclear spins of the ions and the surrounding phosphorus nuclear spins and proton nuclear spins; adjusting the coupling strength between the nuclear spins by manipulating the control element; reading out the states of the phosphorus nuclear spins and the proton nuclear spins by measuring the nuclear magnetic resonance signals to obtain the computing results.

6. The method of claim 5, wherein, adjusting the coupling strength between the nuclear spins by adjusting the concentration and distribution of the oxygen radicals generated by electrolysis in the phospholipid bilayer membrane through the control element; or adjusting the coupling strength between the nuclear spins by applying a local electric field through the control element to rotate the head of a charged phospholipid molecule in a certain position toward the direction of the electric field to adjust the relative position of the charged phospholipid molecule and other phospholipid molecules, thereby changing the relative distance between two phosphorus nuclear spins.

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