Quantum gate phase control method based on controllable turnover magnet and controllable turnover magnet

Abstract

The invention provides a quantum gate phase control method based on a controllable turnover magnet and the controllable turnover magnet, and mainly relates to the technical field of quantum computing. The quantum gate phase control method comprises the following steps: carrying out initialization processing on the magnetization direction of a controllable turnover magnet; the current pulse sequence is used for driving the controllable overturning magnet to overturn, so that a local magnetic field of the controllable overturning magnet is subjected to vector superposition at the quantum bit to form an equivalent rotating magnetic field; under the condition that it is determined that the equivalent rotating magnetic field rotates by one circle along the forward path and the energy level spacing of the quantum bits meets the adiabatic approximation condition, the initial quantum states of the quantum bits are driven by first microwave pulses to be overturned; based on the time symmetry principle, the current pulse sequence is used for driving the controllable overturning magnet to overturn again, so that the equivalent rotating magnetic field rotates by one circle along a reverse path, the dynamic phase of the quantum state is converted into a global phase, and the quantum state only having geometric phase information is obtained.

Description

Technical Field

[0001] The present invention relates to the field of quantum computing technology, and more specifically, to a quantum gate phase control method based on a controllable flip magnet and a controllable flip magnet. Background Art

[0002] Quantum computing provides a new way to solve complex problems that are difficult for classical computers to handle by utilizing properties such as quantum superposition and quantum entanglement. Among the many quantum bit implementation schemes, silicon-based spin qubits have become one of the ideal platforms for large-scale quantum computing because of their long coherence time, good compatibility with existing semiconductor manufacturing processes, and excellent scalability.

[0003] In order to overcome the limitations of spin quantum bit operations that rely on microwave driving technology, the existing technology has proposed a high-fidelity quantum bit operation scheme based on quantum geometric phase gates. However, the operation time of existing adiabatic geometric phase gate implementation schemes is often comparable to or even longer than the decoherence time of the bit, resulting in a significant reduction in the fidelity of gate operations, which is difficult to meet the needs of practical applications. In addition, although the operation scheme of directly rotating the magnetic field rapidly has potential in theory, there is a lack of efficient and controllable magnetic field generation and regulation methods in silicon-based platforms, making it difficult to achieve high-precision and high-speed magnetic field rotation at the nanosecond level. Summary of the invention

[0004] In view of this, the present invention provides a quantum gate phase control method based on a controllable flip magnet and a controllable flip magnet.

[0005] One aspect of the present invention provides a quantum gate phase control method based on a controllable flip magnet, wherein the quantum gate phase control method comprises: initializing the magnetization direction of the controllable flip magnet; using a current pulse sequence to drive the controllable flip magnet to flip, so that the local magnetic field of the controllable flip magnet is vector-superimposed at the quantum bit to form an equivalent rotating magnetic field; when it is determined that the equivalent rotating magnetic field rotates one circle along a forward path and the energy level spacing of the quantum bit satisfies the adiabatic approximation condition, using a first microwave pulse to drive the initial quantum state of the quantum bit to flip; based on the principle of time symmetry, using the current pulse sequence to drive the controllable flip magnet to flip again, so that the equivalent rotating magnetic field rotates one circle along a reverse path, so as to convert the dynamic phase of the quantum state into a global phase, and obtain a quantum state with only geometric phase information.

[0006] According to an embodiment of the present invention, the initialization process of the magnetization direction of the controllable flip magnet includes: applying an external magnetic field of a specific direction to the controllable flip magnet so that the initial magnetization direction of the controllable flip magnet is aligned to a preset coordinate axis direction.

[0007] According to an embodiment of the present invention, before using the current pulse sequence to drive the controllable flip magnet to flip, the quantum gate phase control method further includes: using a second microwave pulse to initialize the quantum state of the quantum bit to obtain the initial quantum state of the quantum bit.

[0008] According to an embodiment of the present invention, the controllable flip magnet comprises a plurality of magnetic units, wherein the controllable flip magnet is driven to flip by a current pulse sequence so that the local magnetic field of the controllable flip magnet is vector-superimposed at the quantum bit to form an equivalent rotating magnetic field, including: determining the flip timing and flip direction of each of the plurality of magnetic units based on the pulse amplitude, pulse interval, duration and direction of the current pulse sequence; and applying current pulses to the plurality of magnetic units in sequence based on the flip timing and flip direction of each of the plurality of magnetic units to drive the plurality of magnetic units to flip and form the equivalent rotating magnetic field.

[0009] According to an embodiment of the present invention, the above-mentioned quantum gate phase control method also includes: when the energy level spacing of the above-mentioned quantum bit does not satisfy the above-mentioned adiabatic approximation condition, applying a vertical external magnetic field to the above-mentioned quantum bit to adjust the energy level spacing of the above-mentioned quantum bit so that the energy level spacing of the above-mentioned quantum bit satisfies the above-mentioned adiabatic approximation condition.

[0010] Another aspect of the present invention provides a controllable flip magnet, which is applied to the quantum gate phase control method described in any of the above items, wherein the controllable flip magnet includes a heavy metal film layer, a plurality of magnetic units and a current channel structure, wherein: the heavy metal film layer is arranged on the surface of the substrate; the current channel structure is embedded in the heavy metal film layer, and the current channel structure is used to stimulate the contact surface between the heavy metal film layer and the plurality of magnetic units to generate a spin polarized flow under the action of a pulse current sequence; the plurality of magnetic units are symmetrically arranged around the quantum bit, each of the magnetic units is in direct contact with the heavy metal film layer, and the plurality of magnetic units are used to complete the magnetization direction flipping under the drive of the spin polarized flow.

[0011] According to an embodiment of the present invention, the plurality of magnetic units are arranged in a cross-symmetric manner with the quantum bit as the center.

[0012] According to an embodiment of the present invention, the substrate is configured as a planar silicon-germanium heterojunction.

[0013] According to an embodiment of the present invention, the heavy metal thin film layer is obtained by performing a thin film deposition operation on the substrate using a heavy metal material having a spin-orbit coupling effect.

[0014] According to an embodiment of the present invention, the plurality of magnetic units are formed by performing micro-nano processing on the heavy metal film layer to form magnetic materials.

[0015] The embodiment of the present invention drives the controllable flip magnet to generate a fast rotating magnetic field through a current pulse sequence, providing a controllable parameter space path for quantum state evolution. In addition, by combining the quantum state flip of microwave π pulses with the time symmetry operation of the reverse path, the operation time of the adiabatic geometric phase gate is shortened, and the random phase accumulation caused by environmental noise is eliminated, solving the problem of long operation time in traditional microwave driving schemes, thereby improving the fidelity and practicality of the adiabatic geometric phase gate operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings.

[0017] Figure 1 A schematic diagram of a quantum gate phase control method based on a controllable flip magnet according to an embodiment of the present invention is shown.

[0018] Figure 2a A schematic diagram showing how to change the geometric phase of spin quantum bit accumulation by applying an external magnetic field in the z direction according to a specific embodiment of the present invention.

[0019] Figure 2b A schematic diagram showing the changes of adiabatic parameters during quantum state evolution according to a specific embodiment of the present invention is shown.

[0020] Figure 3a A top view of a single-bit device for realizing an adiabatic geometric phase gate in strained silicon according to a specific embodiment of the present invention is shown.

[0021] Figure 3b A cross-sectional view of a single-bit device for realizing an adiabatic geometric phase gate in strained silicon according to a specific embodiment of the present invention is shown.

[0022] Figure 4 A schematic diagram showing the configuration of magnetization directions of multiple magnets according to a specific embodiment of the present invention is shown.

[0023] Figure 5 A schematic diagram showing the configuration changes of the magnetization directions of multiple magnets according to a specific embodiment of the present invention is shown.

[0024] Figure 6 A schematic diagram of a magnetic field path according to a specific embodiment of the present invention is shown.

[0025] Figure 7a A schematic diagram of the spatial magnetic field distribution generated by the x-direction magnetic field component of configuration 402 according to a specific embodiment of the present invention in the area near the quantum dots is shown.

[0026] Figure 7b A schematic diagram of the spatial magnetic field distribution generated by the y-direction magnetic field component of configuration 402 according to a specific embodiment of the present invention in the area near the quantum dots is shown.

[0027] Figure 7c A schematic diagram of the spatial magnetic field distribution generated by the z-direction magnetic field component of configuration 402 according to a specific embodiment of the present invention in the area near the quantum dots is shown.

[0028] Figure 8a A schematic diagram of the spatial magnetic field distribution generated by the x-direction magnetic field component of configuration 404 according to a specific embodiment of the present invention in the area near the quantum dots is shown.

[0029] Figure 8b A schematic diagram of the spatial magnetic field distribution generated by the y-direction magnetic field component of configuration 404 according to a specific embodiment of the present invention in the area near the quantum dots is shown.

[0030] Figure 8c A schematic diagram of the spatial magnetic field distribution generated by the z-direction magnetic field component of configuration 404 according to a specific embodiment of the present invention in the area near the quantum dots is shown.

[0031] Fig. 9 A block diagram of a quantum gate phase control device based on a controllable flip magnet according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0032] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0033] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0034] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0035] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.)

[0036] As a cutting-edge technology that has developed rapidly in recent years, quantum computing provides a new way to solve complex problems that are difficult for classical computers to handle by utilizing properties such as quantum superposition and quantum entanglement. Among the many quantum bit implementation schemes, silicon-based spin qubits have become one of the ideal platforms for large-scale quantum computing due to their long coherence time, good compatibility with existing semiconductor manufacturing processes, and excellent scalability. However, to achieve universal quantum computing, quantum bit gate operations must reach the fault-tolerant quantum computing threshold and maximize the fidelity of operations, which places extremely high demands on operation accuracy.

[0037] At present, the operation of spin quantum bits mainly relies on microwave driving technology, but this technology has certain limitations: microwave-driven quantum gates are easily affected by environmental noise and driving field drift, resulting in reduced operation accuracy; at the same time, in large-scale bit expansion, microwave driving also faces problems such as crosstalk and frequency crowding, further reducing the fidelity of bit operations.

[0038] To overcome the above problems, the prior art proposes a high-fidelity quantum bit operation scheme based on quantum geometric phase gates. Quantum geometric phase refers to the phase that is independent of dynamics accumulated when a quantum state undergoes a closed path evolution in parameter space. Its characteristic is that it only depends on the geometric properties of the evolution path and is independent of the specific time information of the evolution process. This characteristic makes the geometric phase gate naturally robust to certain types of noise, making it one of the preferred solutions for building high-fidelity quantum gates.

[0039] Depending on whether the system evolution satisfies the adiabatic approximation, the geometric phase gate can be divided into two types: non-adiabatic geometric phase gate and adiabatic geometric phase gate. Among them, the non-adiabatic geometric phase gate has high requirements on the accuracy of microwave pulses and is easily affected by waveform distortion in actual operation, resulting in reduced operational reliability. In contrast, the adiabatic geometric phase gate only depends on the ratio between the parameters, is insensitive to changes in the absolute value of the parameters, and exhibits stronger parameter robustness. This feature makes it a more stable and anti-interference quantum operation scheme, especially suitable for the needs of high-fidelity operations in fault-tolerant quantum computing.

[0040] However, existing adiabatic geometric phase gate implementation schemes usually rely on microwave drive and have the problem of long operation time. Its operation time is often equivalent to or even longer than the decoherence time of the bit, resulting in a significant reduction in the fidelity of gate operation, making it difficult to meet the needs of practical applications. In addition, although the operation scheme of directly rotating the magnetic field rapidly has potential in theory, there is a lack of efficient and controllable magnetic field generation and regulation methods in silicon-based platforms, making it difficult to achieve high-precision and high-speed magnetic field rotation at the nanosecond level.

[0041] In view of this, the quantum gate phase control method based on controllable flip magnets proposed in the implementation of the present invention drives the controllable flip magnets to generate a fast rotating magnetic field through a current pulse sequence, providing a controllable parameter space path for quantum state evolution. In addition, by combining the quantum state flip of microwave π pulses with the time symmetry operation of the reverse path, the operation time of the adiabatic geometric phase gate is shortened, and the random phase accumulation caused by environmental noise is eliminated, solving the problem of long operation time in traditional microwave driving schemes, thereby improving the fidelity and practicality of the adiabatic geometric phase gate operation.

[0042] Specifically, an embodiment of the present invention provides a quantum gate phase control method based on a controllable flip magnet, wherein the quantum gate phase control method includes: initializing the magnetization direction of the controllable flip magnet; using a current pulse sequence to drive the controllable flip magnet to flip, so that the local magnetic field of the controllable flip magnet is vector-superimposed at the quantum bit to form an equivalent rotating magnetic field; when it is determined that the equivalent rotating magnetic field rotates one circle along a forward path and the energy level spacing of the quantum bit satisfies the adiabatic approximation condition, using a first microwave pulse to drive the initial quantum state of the quantum bit to flip; based on the principle of time symmetry, using a current pulse sequence to drive the controllable flip magnet to flip again, so that the equivalent rotating magnetic field rotates one circle along a reverse path, so as to convert the dynamic phase of the quantum state into a global phase, and obtain a quantum state with only geometric phase information.

[0043] It should be noted that the quantum gate phase control method based on controllable flip magnets and the controllable flip magnets determined in the embodiments of the present invention can be used in the field of quantum computing technology. The quantum gate phase control method based on controllable flip magnets and the controllable flip magnets determined in the embodiments of the present invention can also be used in any field other than the field of quantum computing technology, such as quantum information processing, the field of spin electronics technology, etc. The application field of the quantum gate phase control method based on controllable flip magnets and the controllable flip magnets determined in the embodiments of the present invention is not limited.

[0044] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0045] Figure 1A schematic diagram of a quantum gate phase control method based on a controllable flip magnet according to an embodiment of the present invention is shown.

[0046] like Figure 1 As shown, the quantum gate phase control method includes operations S110 to S140.

[0047] In operation S110, the magnetization direction of the controllable flip magnet is initialized.

[0048] In operation S120, the controllable flipping magnet is driven to flip using a current pulse sequence, so that the local magnetic field of the controllable flipping magnet is vector-superimposed at the quantum bit to form an equivalent rotating magnetic field.

[0049] In operation S130, when it is determined that the equivalent rotating magnetic field rotates one circle along the forward path and the rotation rate of the equivalent rotating magnetic field satisfies the adiabatic approximation condition, the initial quantum state of the quantum bit is driven to flip using the first microwave pulse.

[0050] In operation S140, based on the principle of time symmetry, the controllable flipping magnet is driven again to flip using a current pulse sequence, so that the local magnetic field rotates one circle along the reverse path to convert the dynamic phase of the quantum state into a global phase, thereby obtaining a quantum state with only geometric phase information.

[0051] According to an embodiment of the present invention, the magnetization direction of the controllable flip magnet is adjusted to a preset initial direction, for example, along the coordinate axes x, y, -x, -y, to provide consistent initial conditions for subsequent magnetic field rotation operations and avoid operational errors caused by magnetization direction deviations.

[0052] According to an embodiment of the present invention, a timed current pulse is applied to a controllable flip magnet, and multiple magnets included in the controllable flip magnet are driven to flip in sequence, so that the direction of the local magnetic field around the quantum bit changes continuously along a predetermined path (such as rotating around the z-axis) and vector superposition is performed at the quantum bit to form a closed evolution path as an equivalent rotating magnetic field. The current pulse can be configured as a square wave pulse current.

[0053] Among them, the equivalent rotating magnetic field can be used to represent the rotating magnetic field around the quantum bit formed after the magnetic field is superimposed.

[0054] According to an embodiment of the present invention, when the equivalent rotating magnetic field rotates one circle along the forward path and satisfies the adiabatic condition, a first microwave pulse resonating with the quantum bit energy level is applied to the quantum bit to drive the initial quantum state to flip, for example, to change the quantum state from Flip to , and then rotate one circle in the reverse path at the same time. The two rotations convert the dynamic phase accumulated in the quantum state during the evolution process into a global phase, and then its influence is eliminated. The first microwave pulse may include a microwave π pulse, the frequency of which matches the quantum bit energy level difference and resonates.

[0055] According to an embodiment of the present invention, a current pulse with a reverse timing is applied to the controllable flip magnet again to drive multiple magnets included in the controllable flip magnet to flip in sequence, keeping the magnetic field rotation rate consistent with the forward path, so that the local magnetic field rotates one circle in the opposite direction along the original path.

[0056] For example, in the actual evolution process, the system accumulates both the geometric phase and the dynamic phase. In order to eliminate the influence of the dynamic phase, the echo method can be used. The evolution process is as follows:

[0057] (1);

[0058] (2);

[0059] In the formula, and Represents the initial two quantum states of the quantum bit, one of which is the ground state and the other is the excited state; and Respectively The dynamic and geometric phases of accumulation. and Respectively The dynamic and geometric phases of accumulation; represents the forward path, Indicates the reverse path.

[0060] In this specific embodiment, first follow the forward path After one cycle of adiabatic evolution, a microwave pulse is applied to flip the quantum state, and then the quantum state is reversed. Reverse evolution and apply a second microwave pulse to restore the initial state. The phase changes during the overall evolution process are shown in the above formulas (1) and (2). After the overall operation is completed, both the ground state and the excited state will accumulate The dynamical phase is converted into a global phase factor to eliminate it, leaving only Accumulated geometric phase and Accumulated geometric phase .

[0061] Based on this, the embodiment of the present invention drives the controllable flip magnet to generate a fast rotating magnetic field through a current pulse sequence, providing a controllable parameter space path for quantum state evolution. In addition, by combining the quantum state flip of the microwave π pulse with the time symmetry operation of the reverse path, the operation time of the adiabatic geometric phase gate is shortened, and the random phase accumulation caused by environmental noise is eliminated, solving the problem of long operation time in the traditional microwave driving scheme, thereby improving the fidelity and practicality of the adiabatic geometric phase gate operation.

[0062] In addition, the embodiments of the present invention utilize square wave current pulses to drive the magnet flipping, thus avoiding the crosstalk and frequency crowding problems existing in the conventional microwave driving scheme. In addition, since the magnet flipping is insensitive to waveform distortion, the reliability and accuracy of the operation are further improved.

[0063] According to an embodiment of the present invention, initializing the magnetization direction of the controllable flip magnet includes: applying an external magnetic field in a specific direction to the controllable flip magnet so that a preset initial magnetization direction of the controllable flip magnet is aligned to a preset coordinate axis direction.

[0064] According to an embodiment of the present invention, rapid initialization can be achieved by applying an external magnetic field in a specific direction to the controllable flip magnet, or by applying a current pulse to the controllable flip magnet to drive it to generate a spin polarized current. The external magnetic field can be generated by a permanent magnet array or an electromagnetic coil.

[0065] According to an embodiment of the present invention, before using a current pulse sequence to drive the controllable flipping magnet to flip, the quantum gate phase control method further includes: using a second microwave pulse to initialize the quantum state of the quantum bit to obtain an initial quantum state of the quantum bit.

[0066] According to an embodiment of the present invention, a second microwave pulse is applied to the quantum bit to drive it from an excited state (such as state) to the ground state (such as state) to provide a clean initial quantum state (such as ), reducing the background noise in subsequent phase operations and ensuring the accuracy of dynamic phase conversion.

[0067] According to an embodiment of the present invention, a current pulse sequence is used to drive a controllable flip magnet to flip, so that the local magnetic field of the controllable flip magnet is vector-superimposed at the quantum bit to form an equivalent rotating magnetic field, including: determining the flipping timing and flipping direction of each of the multiple magnetic units based on the pulse amplitude, pulse interval, duration and direction of the current pulse sequence; and driving the multiple magnetic units to flip based on the flipping timing and flipping direction of each of the multiple magnetic units to form an equivalent rotating magnetic field.

[0068] According to an embodiment of the present invention, by adjusting the pulse amplitude, duration (pulse width) and direction of the current pulse sequence, the flipping timing and flipping direction of multiple magnets in the controllable flipping magnet can be accurately controlled, thereby generating a fast and stable equivalent rotating magnetic field.

[0069] According to a specific embodiment of the present invention, the flipping speed of the controllable flipping magnet can be controlled by the pulse amplitude of the current pulse. For example, the initial pulse amplitude range can be determined based on the flipping characteristics of the magnetic material of the controllable flipping magnet, and then adjusted by a high-precision current source to achieve control of the current pulse amplitude. The larger the pulse amplitude, the stronger the spin-orbit torque (SOT), and the faster the magnet flips.

[0070] According to an embodiment of the present invention, the pulse width of the current pulse sequence can be controlled to ensure that the magnet is completely flipped. Specifically, the initial pulse width can be set according to the magnet flipping time, a fast switching circuit (such as MOSFET or GaN device) can be used to generate a narrow pulse, and the magnet flipping state can be monitored in real time by a magnetoresistive sensor to dynamically adjust the pulse width.

[0071] Based on this, the embodiments of the present invention optimize the magnetic field rotation path and parameters by controlling the amplitude, duration and direction of the pulse current, thereby achieving precise control of the flipping moment and order of each magnet, ensuring that the magnets flip in sequence according to a predetermined order, and utilizing the generated spin polarization flow to drive the magnets to flip quickly, so as to complete the magnetic field rotation within tens of nanoseconds, which is far longer than the magnetic field rotation time of traditional adiabatic methods (microseconds), so as to achieve fast adiabatic geometric phase gate operation, while maintaining high parameter robustness, being insensitive to parameter changes, and significantly improving the stability and anti-interference ability of the operation.

[0072] According to an embodiment of the present invention, the phase control method also includes: when the rotation rate of the equivalent rotating magnetic field does not satisfy the adiabatic approximation condition, applying a vertical external magnetic field to the quantum bit to adjust the energy level spacing of the quantum bit so that the rotation rate of the equivalent rotating magnetic field satisfies the adiabatic approximation condition.

[0073] According to an embodiment of the present invention, the adiabatic approximation condition is used to characterize that the adiabatic parameter is much less than 1, that is, Among them, the adiabatic parameter is used to characterize the relative relationship between the system evolution rate and the energy level spacing of the quantum bit. When , the system evolution rate is much smaller than the rate of change of the energy level spacing, and the quantum state always remains in the instantaneous eigenstate, satisfying the adiabatic approximation condition. The adiabatic parameter is expressed as follows:

[0074] (3);

[0075] In the formula, represents the adiabatic parameter, represents the first instantaneous eigenenergy of the qubit, represents the second instantaneous eigenenergy of the qubit, represents the energy level spacing of the quantum bit, represents the Hamiltonian, Represents the Hamiltonian The rate of change over time, represents the reduced Planck constant, where the larger the energy level spacing of the quantum bit, the easier it is to satisfy the adiabatic parameter.

[0076] According to an embodiment of the present invention, when the energy level spacing of a qubit does not satisfy the adiabatic approximation condition, the energy level spacing of the qubit can be adjusted by applying a vertical external magnetic field to the qubit.

[0077] For example, the energy level spacing , Hamiltonian change rate In the case of, the adiabatic parameter is calculated by the above formula (3) By applying a 0.5T vertical external magnetic field to the quantum bit, the energy level spacing Upgrade to , recalculated by the above formula (3) , thus satisfying the adiabatic approximation condition .

[0078] Figure 2a A schematic diagram showing how to change the geometric phase of spin quantum bit accumulation by applying an external magnetic field in the z direction according to a specific embodiment of the present invention.

[0079] Figure 2b A schematic diagram showing the changes of adiabatic parameters during quantum state evolution according to a specific embodiment of the present invention is shown.

[0080] like Figure 2a As shown, by applying a perpendicular external magnetic field, such as an external magnetic field B in the z direction ext (T), to change the geometric phase of the accumulated spin qubit , and then realize different adiabatic geometric gate operations. For example, B ext The geometric phase of the spin qubit accumulation in a single closed path at (T) = 19 mT .like Figure 2b As shown, based on the calculation formula (3) of the adiabatic parameter, the adiabatic parameter calculated in the specific embodiment of the present invention is , which satisfies the adiabatic approximation condition.

[0081] Based on this, the adiabatic geometric phase quantum gate control method proposed in the embodiment of the present invention adjusts the energy level spacing of the quantum bit by applying a vertical external magnetic field. Adiabatic Parameter , ensuring that the adiabatic approximation conditions hold, thereby ensuring that the quantum bit still meets the adiabatic evolution conditions under rapid magnetic field rotation, avoiding errors caused by non-adiabatic transitions, and supporting long-term quantum state evolution. In addition, by adjusting the external magnetic field strength to control the geometric phase of quantum bit accumulation, different adiabatic geometric gate operations (such as Pauli-Z gate, phase gate) can be realized to support flexible switching of multiple quantum gate operations and meet the needs of complex quantum algorithms.

[0082] On the other hand, the present invention provides a controllable flip magnet, wherein the controllable flip magnet includes a heavy metal film layer, a plurality of magnetic units and a current channel structure, wherein the heavy metal film layer is arranged on the surface of a substrate; the current channel structure is embedded in the heavy metal film layer, and the current channel is used to stimulate the contact surface between the heavy metal film layer and the plurality of magnetic units to generate a spin polarized flow under the action of a pulse current sequence; the plurality of magnetic units are symmetrically arranged around the quantum bit, each magnetic unit is in direct contact with the heavy metal film layer, and the plurality of magnetic units are used to complete the magnetization direction flipping under the drive of the spin polarized flow.

[0083] According to an embodiment of the present invention, a heavy metal film layer is arranged on the surface of a substrate, and a heavy metal material with a strong spin-orbit coupling effect (such as Pt, Ta or W, etc.) can be selected. Magnetron sputtering, electron beam evaporation or other thin film deposition techniques are used to prepare a heavy metal film with nanometer thickness on a suitable substrate, thereby ensuring sufficient spin-orbit coupling effect while ensuring the uniformity and consistency of the film.

[0084] According to an embodiment of the present invention, on the heavy metal film layer, a plurality of flippable magnetic units are symmetrically arranged around the quantum bit through micro-nano processing technology, and each magnetic unit is in direct contact with the heavy metal film layer. Each magnetic unit can be made of a magnetic material with high magnetic susceptibility (such as CoFeB, NiFe, etc.) so that high-speed and stable flipping can be achieved after the spin polarization current is applied.

[0085] Among them, multiple magnetic units are arranged in a cross-symmetric pattern with the quantum bit as the center. The cross-symmetric layout makes the magnetic field components of each magnet superimposed orthogonally at the quantum dot, forming a continuously rotating synthetic magnetic field. This arrangement can gradually rotate the direction of the magnetic field when the magnets are flipped in sequence (such as clockwise or counterclockwise). , which facilitates timing control.

[0086] In a specific embodiment of the present invention, the micro-nano processing technology includes any one or more combinations of the following: laser direct writing, electron beam exposure, reactive ion etching, ion implantation, rapid thermal processing, atomic layer deposition, electron beam evaporation, wet etching, and magnetron sputtering. The micro-nano processing technology is not limited in the embodiment of the present invention.

[0087] According to an embodiment of the present invention, a current channel structure is constructed on the surface of the heavy metal film layer, so that a spin polarization flow is generated on the surface where the heavy metal film contacts the magnetic unit by applying a pulse current, so that the magnetic unit completes the magnetization direction flipping under the drive of the spin polarization flow. The spin polarization flow is used to represent an electron flow with a certain spin polarization direction.

[0088] According to a specific embodiment of the present invention, the substrate can be configured as a planar germanium-silicon heterojunction, which is compatible with silicon-based quantum dot processes and is easy to integrate into existing semiconductor quantum computing platforms. In addition, the high thermal conductivity of germanium helps to dissipate heat in a low temperature (millikelvin) environment and reduce the interference of Joule heat on quantum bits. During the preparation process, the surface roughness can be less than or equal to 0.5nm by chemical mechanical polishing (CMP) to ensure uniform deposition of heavy metal films.

[0089] Figure 3a A top view of a single-bit device for realizing an adiabatic geometric phase gate in strained silicon according to a specific embodiment of the present invention is shown.

[0090] like Figure 3a As shown, in the single-bit device of this specific embodiment, the quantum dot is located at the center of the single-bit device for trapping the electron spin bit. The heavy metal film layer 103 covers the area between the magnetic unit and the quantum dot to generate a spin polarized current through the spin Hall effect.

[0091] In the single-bit device of this specific embodiment, the controllable flip magnet includes four magnetic units 104, which are symmetrically distributed around the quantum dot and directly contact the heavy metal film layer 103, so as to complete the magnetization direction flipping under the drive of the spin polarization flow and generate an equivalent rotating magnetic field.

[0092] In a specific embodiment of the present invention, the four magnetic units 104 can all be rectangular parallelepiped magnets with a magnet size of The four magnetic units 104 are arranged in a cross shape with the central quantum dot as the symmetric point. The distance between each magnetic unit and the quantum dot plane projection is 50nm, and the horizontal spacing between the magnetic units is 160nm. The magnetic material uses CoFe with a larger saturation magnetization to obtain a larger magnetic field. Its saturation magnetization is .

[0093] like Figure 3a As shown, the gate structure of the single-bit device includes a shielding gate 101, a side top gate 102 and a top gate 105, which are used to control the potential and electronic state of the quantum dot.

[0094] like Figure 3a As shown, the single-bit device further includes a planar silicon substrate 106 to serve as a supporting substrate of the single-bit device.

[0095] like Figure 3a As shown, the single-bit device also includes an electrode lead 107, wherein the electrode lead 107 can be configured to provide electron injection for the quantum dots.

[0096] Among them, the current injection point included in the current channel structure is located at the contact interface between the four magnetic units 104 and the heavy metal film layer 103, and the embedded low-impedance wire included in the current channel structure can be configured to be arranged along the symmetrical distribution direction of the four magnetic units 104 to ensure that a spin-polarized current is generated at the current injection point.

[0097] Figure 3b A cross-sectional view of a single-bit device for realizing an adiabatic geometric phase gate in strained silicon according to a specific embodiment of the present invention is shown.

[0098] Figure 3b for Figure 3a The cross-section along the dotted line in Figure 2 is shown in Figure 2. Figure 3b As shown, the single-bit device also includes an insulating layer 201, a germanium silicon substrate 202, a germanium silicon barrier layer 203, and a strained silicon layer 204, wherein the insulating layer 201 covers between the gates to prevent overlapping contact leakage of different gates. The germanium silicon substrate 202 serves as the bottom support of the device. The germanium silicon barrier layer 203 is located above the germanium silicon substrate 202 and is used to limit the electron wave function. The strained silicon layer 204 is located on the germanium silicon barrier layer 203, and quantum dots are formed at the interface between it and the germanium silicon barrier layer 203.

[0099] like Figure 3b As shown, the current channel structure is embedded in the heavy metal film layer 103, located near the contact surface between the four magnetic units 104 and the heavy metal film layer 103, directly in contact with the four magnetic units 104, and isolated from the top gate 105 above by the insulating layer 201. The electron spin bit is formed directly below the top gate 105, at the junction of the strained silicon layer 204 and the germanium silicon barrier layer 203.

[0100] In the single-bit device of this specific embodiment, a pulse current is directly passed through the heavy metal film layer 103. Due to its strong spin-orbit coupling effect, spin polarization flow is accumulated at the upper and lower interfaces. The spin polarization flow is injected into the contact surface between the four magnetic units 104 and the heavy metal film layer 103, and the four magnetic units 104 are driven to flip according to the magnetization direction through the spin-orbit moment (SOT) of the spin polarization flow. By sequentially triggering the current channels corresponding to the four magnetic units 104, the pulse current flows through each magnetic region in sequence to drive the magnetic field direction to rotate step by step (for example, the magnetic field direction of the magnets is driven to rotate in a clockwise direction), thereby generating an equivalent rotating magnetic field at the quantum dot.

[0101] Based on this, the embodiments of the present invention use germanium silicon substrates as substrates, which are compatible with silicon-based quantum dot processes and are easy to integrate into existing semiconductor quantum computing platforms. In addition, the high thermal conductivity of germanium helps to dissipate heat in low-temperature environments and reduce the interference of Joule heat on quantum bits. In addition, since the embodiments of the present invention only rely on the spin Hall effect of heavy metal films (Pt, Ta, W) rather than specific substrate materials, it is not only suitable for planar silicon-based systems, but can also be extended to other planar electron spin quantum bit systems, such as graphene, transition metal sulfides (such as MoS2) and other two-dimensional materials. Electron spin quantum bits, showing good versatility and scalability.

[0102] Figure 4 A schematic diagram showing the configuration of magnetization directions of multiple magnets according to a specific embodiment of the present invention is shown.

[0103] like Figure 4 As shown in the figure, the four magnetic units of the controllable flip magnet are symmetrically distributed with the quantum dot as the center, and the arrows indicate the magnetization direction of each magnetic unit. By independently controlling the flip state of each magnetic unit, the system can achieve a total of 2 4 = 16 different magnetization direction configurations, specifically, can include Figure 4 Configurations 401 to 416 are shown.

[0104] Figure 5 A schematic diagram showing the configuration changes of the magnetization directions of multiple magnets according to a specific embodiment of the present invention is shown.

[0105] like Figure 5 As shown, 8 of the above 16 configurations (e.g., configuration 403, configuration 409, configuration 405, configuration 402, configuration 411, configuration 413, configuration 406, configuration 404) can be selected to construct a magnetic field path, and these configurations are related by rotational symmetry. Each time a magnetic unit is flipped, the configuration of the magnetization direction will change, and eventually return to the initial state, completing a closed evolution path. For example, the initial state is configuration 405, and the right magnetic unit is flipped to change to configuration 406. By flipping each magnetic unit in turn, a closed evolution path such as configuration 402 → configuration 404 → configuration 403 → configuration 411 → configuration 409 → configuration 413 → configuration 405 → configuration 406 → configuration 402 is finally formed.

[0106] Figure 6 A schematic diagram of a magnetic field path according to a specific embodiment of the present invention is shown.

[0107] like Figure 6 As shown, based on the flipping process of the above multiple magnetic units, it can be obtained Figure 6The evolution trajectory of the quantum state on the Bloch sphere shown is a closed evolution path. When the magnetization direction configuration of the magnet changes in sequence from configuration 402 → configuration 404 → configuration 403 → configuration 411 → configuration 409 → configuration 413 → configuration 405 → configuration 406 → configuration 402, the trajectory of the quantum state on the Bloch sphere is A evolving to H and finally returning to A.

[0108] Figure 7a A schematic diagram of the spatial magnetic field distribution generated by the x-direction magnetic field component of configuration 402 according to a specific embodiment of the present invention in the area near the quantum dots is shown.

[0109] Figure 7b A schematic diagram of the spatial magnetic field distribution generated by the y-direction magnetic field component of configuration 402 according to a specific embodiment of the present invention in the area near the quantum dots is shown.

[0110] Figure 7c A schematic diagram of the spatial magnetic field distribution generated by the z-direction magnetic field component of configuration 402 according to a specific embodiment of the present invention in the area near the quantum dots is shown.

[0111] like Figure 7a~Figure 7c As shown, the magnetic field distribution of the configuration 402 is used to determine the micromagnetism at the central quantum dot. Specifically, Figure 7a As shown, Bx = 12.2mT, such as Figure 7b As shown, By = 0mT, such as Figure 7c As shown, Bz=-8.37mT. Among them, By≈0 indicates that the symmetry of the magnet layout effectively suppresses the magnetic field component in the non-target direction, and the negative sign of Bz indicates that the direction is downward. Since configurations 403, 409, and 405 are similar to configuration 402, they are formed by rotating configuration 402 by a certain angle, and the magnetic field distributions formed are also similar, so the magnetic field distributions are not given separately.

[0112] Figure 8a A schematic diagram of the spatial magnetic field distribution generated by the x-direction magnetic field component of configuration 404 according to a specific embodiment of the present invention in the area near the quantum dots is shown.

[0113] Figure 8b A schematic diagram of the spatial magnetic field distribution generated by the y-direction magnetic field component of configuration 404 according to a specific embodiment of the present invention in the area near the quantum dots is shown.

[0114] Figure 8c A schematic diagram of the spatial magnetic field distribution generated by the z-direction magnetic field component of configuration 404 according to a specific embodiment of the present invention in the area near the quantum dots is shown.

[0115] like Figure 8a~Figure 8c As shown, the magnetic field distribution of the configuration 404 is used to determine the micromagnetism at the central quantum dot. Specifically, Figure 8aAs shown, Bx = 12.10mT, such as Figure 8b As shown, By = 12.10mT, such as Figure 8c As shown, Bz=0.2mT. Based on Figure 7b to Figure 8b As shown in the magnetic field change, the direction of the magnetic field rotates synchronously during the change from configuration 402 to configuration 404, thereby verifying the feasibility of realizing continuous rotation of the magnetic field by magnet flipping. Since configurations 411, 413, and 406 are similar to configuration 404, they are formed by rotating configuration 404 by a certain angle, and the magnetic field distributions formed are also similar, so the magnetic field distributions are not given separately.

[0116] Based on this, the embodiment of the present invention converts the pulse current into a spin-polarized current through the spin Hall effect of the heavy metal film layer to drive the magnet to flip, thereby realizing low-power, high-speed magnet flipping operation and meeting the requirements of quantum computing for operation speed. Multiple magnetic units are symmetrically distributed (such as cross-symmetrical arrangement) to generate a uniform controllable rotating magnetic field at the quantum bit, ensuring that the quantum bit evolves in a uniform magnetic field and improving the fidelity of the phase gate operation. In addition, driven by the spin-polarized current, multiple magnetic units can complete the magnetization direction flipping in sub-nanosecond time to support high-speed magnetic field rotation (such as shortening the magnetic field rotation period to 80ns / turn), and the operation speed matches the quantum bit decoherence time, significantly improving the practicality of the system.

[0117] Fig. 9 A block diagram of a quantum gate phase control device based on a controllable flip magnet according to an embodiment of the present invention is shown.

[0118] like Fig. 9 As shown, the quantum gate phase control device based on the controllable flip magnet includes an initialization module 910 , a first driving module 920 , a second driving module 930 , and a third driving module 940 .

[0119] The initialization module 910 is used to initialize the magnetization direction of the controllable flip magnet.

[0120] The first driving module 920 is used to drive the controllable flipping magnet to flip using a current pulse sequence, so that the local magnetic field of the controllable flipping magnet is vector-superimposed at the quantum bit to form an equivalent rotating magnetic field.

[0121] The second driving module 930 is used to drive the initial quantum state of the quantum bit to flip by using the first microwave pulse when it is determined that the equivalent rotating magnetic field rotates one circle along the forward path and the energy level spacing of the quantum bit meets the adiabatic approximation condition.

[0122] The third driving module 940 is used to drive the controllable flip magnet to flip again based on the principle of time symmetry using a current pulse sequence, so that the equivalent rotating magnetic field rotates one circle along the reverse path to convert the dynamic phase of the quantum state into a global phase, and obtain a quantum state with only geometric phase information.

[0123] According to an embodiment of the present invention, the initialization module 910 includes an initialization unit.

[0124] The magnetization direction initialization unit is used to apply an external magnetic field of a specific direction to the controllable flip magnet so that the initial magnetization direction of the controllable flip magnet is aligned to a preset coordinate axis direction.

[0125] According to an embodiment of the present invention, the quantum gate phase control device based on a controllable flip magnet further includes a quantum state initialization module.

[0126] The quantum state initialization module is used to initialize the quantum state of the quantum bit using the second microwave pulse to obtain the initial quantum state of the quantum bit.

[0127] According to an embodiment of the present invention, the first driving module 920 includes a timing determination unit and a magnet driving unit.

[0128] The timing determination unit is used to determine the flipping timing and flipping direction of each of the plurality of magnetic units based on the pulse amplitude, pulse interval, duration and direction of the current pulse sequence.

[0129] The magnet driving unit is used to apply current pulses to the multiple magnetic units in sequence based on the flipping timing and flipping direction of each of the multiple magnetic units, so as to drive the multiple magnetic units to flip and form an equivalent rotating magnetic field.

[0130] According to an embodiment of the present invention, the quantum gate phase control device based on the controllable flip magnet further includes an energy level spacing adjustment module.

[0131] The energy level spacing adjustment module is used to apply a vertical external magnetic field to the quantum bit when the energy level spacing of the quantum bit does not meet the adiabatic approximation condition, so as to adjust the energy level spacing of the quantum bit so that the energy level spacing of the quantum bit meets the adiabatic approximation condition.

[0132] According to the embodiments of the present invention, any one or more of the modules, submodules, units, and subunits, or at least part of the functions of any one of them can be implemented in one module. According to the embodiments of the present invention, any one or more of the modules, submodules, units, and subunits can be split into multiple modules for implementation. According to the embodiments of the present invention, any one or more of the modules, submodules, units, and subunits can be at least partially implemented as hardware circuits, such as field programmable gate arrays (FPGAs), programmable logic arrays (PLAs), systems on chips, systems on substrates, systems on packages, application specific integrated circuits (ASICs), or can be implemented by hardware or firmware in any other reasonable way of integrating or packaging the circuit, or by any one of the three implementation methods of software, hardware, and firmware, or by a proper combination of any of them. Alternatively, according to the embodiments of the present invention, one or more of the modules, submodules, units, and subunits can be at least partially implemented as computer program modules, and when the computer program modules are run, the corresponding functions can be executed.

[0133] For example, any of the initialization module 910, the first driver module 920, the second driver module 930, and the third driver module 940 can be combined in one module / unit / sub-unit for implementation, or any of the modules / units / sub-units can be split into multiple modules / units / sub-units. Alternatively, at least part of the functions of one or more of these modules / units / sub-units can be combined with at least part of the functions of other modules / units / sub-units and implemented in one module / unit / sub-unit. According to an embodiment of the present invention, at least one of the initialization module 910, the first driver module 920, the second driver module 930, and the third driver module 940 can be at least partially implemented as a hardware circuit, such as a field programmable gate array (FPGA), a programmable logic array (PLA), a system on a chip, a system on a substrate, a system on a package, an application specific integrated circuit (ASIC), or can be implemented by hardware or firmware such as any other reasonable way of integrating or packaging the circuit, or by any one of the three implementation methods of software, hardware, and firmware, or by a suitable combination of any of them. Alternatively, at least one of the initialization module 910 , the first driving module 920 , the second driving module 930 , and the third driving module 940 may be at least partially implemented as a computer program module, and when the computer program module is executed, a corresponding function may be executed.

[0134] It should be noted that the part of the quantum gate phase control device based on controllable flip magnets in the embodiment of the present invention corresponds to the part of the quantum gate phase control method based on controllable flip magnets in the embodiment of the present invention. The description of the part of the quantum gate phase control device based on controllable flip magnets specifically refers to the part of the quantum gate phase control method based on controllable flip magnets, which will not be repeated here.

[0135] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present invention. In this regard, each box in the flowchart or block diagram may represent a module, a program segment, or a part of a code, and the above-mentioned module, program segment, or a part of the code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box may also occur in an order different from the order marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flowchart, and the combination of boxes in the block diagram or flowchart, can be implemented with a dedicated hardware-based system that performs the specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions. It can be understood by those skilled in the art that the features recorded in the various embodiments of the present invention can be combined and / or combined in various ways, even if such a combination or combination is not explicitly recorded in the present invention. In particular, without departing from the spirit and teachings of the present invention, the features recorded in the various embodiments of the present invention can be combined and / or combined in various ways. All these combinations and / or combinations fall within the scope of the present invention.

[0136] The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination advantageously. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A quantum gate phase control method based on a controllable flip magnet, characterized in that: The quantum gate phase control method comprises: Initializing the magnetization direction of the controllable flip magnet; Using a current pulse sequence to drive the controllable flipping magnet to flip, so that the local magnetic field of the controllable flipping magnet is vector-superimposed at the quantum bit to form an equivalent rotating magnetic field; When it is determined that the equivalent rotating magnetic field rotates one circle along the forward path and the energy level spacing of the quantum bit satisfies the adiabatic approximation condition, a first microwave pulse is used to drive the initial quantum state of the quantum bit to flip, wherein the frequency of the first microwave pulse resonates with the energy level of the quantum bit; Based on the principle of time symmetry, the current pulse sequence is used to drive the controllable flip magnet to flip again, so that the equivalent rotating magnetic field rotates one circle along the reverse path to convert the dynamic phase of the quantum state into a global phase, thereby obtaining a quantum state with only geometric phase information.

2. The quantum gate phase control method according to claim 1, characterized in that: The initialization process of the magnetization direction of the controllable flip magnet includes: An external magnetic field in a specific direction is applied to the controllable flip magnet so that the initial magnetization direction of the controllable flip magnet is aligned to the preset coordinate axis direction.

3. The quantum gate phase control method according to claim 2, characterized in that: Before using the current pulse sequence to drive the controllable flip magnet to flip, the quantum gate phase control method further includes: The quantum state of the quantum bit is initialized using a second microwave pulse to obtain an initial quantum state of the quantum bit.

4. The quantum gate phase control method according to claim 1, characterized in that: The controllable flip magnet includes a plurality of magnetic units, wherein the current pulse sequence is used to drive the controllable flip magnet to flip, so that the local magnetic field of the controllable flip magnet is vector-superimposed at the quantum bit to form an equivalent rotating magnetic field, including: Determining the flipping timing and flipping direction of each of the plurality of magnetic units based on the pulse amplitude, pulse interval, duration and direction of the current pulse sequence; Based on the respective flipping timings and flipping directions of the plurality of magnetic units, current pulses are sequentially applied to the plurality of magnetic units to drive the plurality of magnetic units to flip and form the equivalent rotating magnetic field.

5. The quantum gate phase control method according to claim 1, characterized in that: The quantum gate phase control method further comprises: When the energy level spacing of the quantum bit does not satisfy the adiabatic approximation condition, a vertical external magnetic field is applied to the quantum bit to adjust the energy level spacing of the quantum bit so that the energy level spacing of the quantum bit satisfies the adiabatic approximation condition.

6. A controllable flip magnet, applied to the quantum gate phase control method according to any one of claims 1 to 5, characterized in that: The controllable flip magnet includes a heavy metal film layer, a plurality of magnetic units and a current channel structure, wherein: The heavy metal film layer is arranged on the surface of the substrate; The current channel structure is embedded in the heavy metal film layer, and the current channel structure is used to stimulate the contact surface between the heavy metal film layer and the plurality of magnetic units to generate spin polarized current under the action of a pulse current sequence; The multiple magnetic units are symmetrically arranged around the quantum bit, each of the magnetic units is in direct contact with the heavy metal film layer, and the multiple magnetic units are used to complete the magnetization direction reversal under the drive of the spin polarization flow.

7. The controllable flip magnet according to claim 6, characterized in that: The plurality of magnetic units are arranged in a cross-symmetrical manner with the quantum bit as the center.

8. The controllable flip magnet according to claim 6 or claim 7, characterized in that: The substrate is configured as a planar silicon-germanium heterojunction.

9. The controllable flip magnet according to claim 8, characterized in that: The heavy metal thin film layer is obtained by performing a thin film deposition operation on the substrate using a heavy metal material having a spin-orbit coupling effect.

10. The controllable flip magnet according to claim 6, characterized in that: The plurality of magnetic units are formed by performing micro-nano processing on the heavy metal film layer to form magnetic materials.

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