A method, apparatus, and medium for calculating the energy of a target system.

Abstract

The application discloses a kind of method, device and medium for calculating the energy of target system, method includes: first determine the Hartree Fock state of fermion form of target system, then construct quantum phase estimation circuit, generate the control pulse of quantum logic gate in quantum phase estimation circuit, and the control pulse is acted on quantum bit in quantum phase estimation circuit, so that specified quantum bit is evolved from Hartree Fock state to target quantum state, finally, according to Hartree Fock state and target quantum state, the ground state energy of the target system is calculated, it is constructed by quantum phase estimation circuit that can be used for current quantum computing hardware equipment, for the realization of quantum chemistry simulation calculation target system energy provides support, improve computing speed and calculation accuracy, promote the simulation calculation of target system ground state energy.

Description

Technical Field

[0001] This invention belongs to the field of quantum computing technology, and in particular to a method, apparatus and medium for calculating the energy of a target system. Background Technology

[0002] A quantum computer is a physical device that performs high-speed mathematical and logical operations, stores and processes quantum information in accordance with the laws of quantum mechanics. When a device processes and calculates quantum information and runs quantum algorithms, it is a quantum computer. Because of its ability to process mathematical problems more efficiently than ordinary computers—for example, reducing the time to crack RSA keys from hundreds of years to hours—quantum computers have become a key technology under research.

[0003] Quantum computing simulation is a simulation program that uses numerical computation and computer science to simulate computations that follow the laws of quantum mechanics. As a simulation program, it uses the high-speed computing power of computers to characterize the spacetime evolution of quantum states based on the fundamental laws of quantum bits in quantum mechanics.

[0004] With the continuous improvement of quantum chemistry theory, computational chemistry has become an important tool for chemists to explain experimental phenomena, predict experimental results, and guide experimental design, and has wide applications in drug synthesis and catalyst preparation. Calculating the ground state energy of a target system based on quantum phase estimation algorithms requires a sufficient number of qubits. However, the number of available qubits in current quantum computers is very limited and cannot meet the computational needs of large systems. This, to some extent, restricts the development of computational chemistry, resulting in weak user applications for simulating chemical systems and hindering the further development of quantum chemical simulation applications. Summary of the Invention

[0005] The purpose of this invention is to provide a method, apparatus, and medium for calculating the energy of a target system, thereby addressing the shortcomings of existing technologies. By constructing a quantum phase estimation circuit that can be used in current quantum computing hardware devices, it provides support for the realization of quantum chemical simulation calculations of the energy of a target system, improves calculation speed and accuracy, and promotes the simulation calculation of the ground state energy of the target system.

[0006] One embodiment of this application provides a method for calculating the energy of a target system, the method comprising:

[0007] Identify the Hartree Fock states in the fermionic form of the target system;

[0008] A quantum phase estimation circuit is constructed, control pulses are generated for the quantum logic gates in the quantum phase estimation circuit, and the control pulses are applied to the qubits in the quantum phase estimation circuit to cause a specified qubit to evolve from the Hartree Fock state to a target quantum state; the quantum phase estimation circuit includes at least a controlled first quantum logic gate, and the unitary matrix of the first quantum logic gate satisfies: in, The unitary matrix representation of the first quantum logic gate. Let b be the phase, k be the iteration number (k>1), and b be the scaling factor. For the Hamiltonian of the target system;

[0009] Calculate the ground state energy of the target system based on the Hartree Fock state and the target quantum state.

[0010] Optionally, determining the Hartree Fock state in the fermionic form of the target system includes:

[0011] Based on the electronic information and electron spin orbital information of the target system, the Hartree Fock state in the fermion form of the target system is determined.

[0012] Optionally, the construction of the quantum phase estimation circuit includes:

[0013] Configure a first quantum register for storing phase information, the first quantum register comprising at least n qubits, wherein n ≥ 4;

[0014] Configure a second quantum register for storing the Hartree Fock state, wherein the number of qubits in the second quantum register is determined by the Hamiltonian of the target system;

[0015] Configure at least n direct products of second quantum logic gates acting on the first quantum register and an inverse quantum Fourier transform unit acting on the first quantum register, wherein the controlled first quantum logic gates act on the first quantum register and the second quantum register, and the qubits of the first quantum register are control bits and the qubits of the second quantum register are target bits.

[0016] Optionally, before calculating the ground state energy of the target system based on the Hartree Fock state and the target quantum state, the method further includes:

[0017] By performing an encoding operation on the Hartree Fock state using a pre-set encoding method, a quantum state in the form of a Pauli operator is obtained;

[0018] The Hartree Fock energy of the target system is calculated based on the Hamiltonian of the target system and the quantum state in the form of the Pauli operator.

[0019] Optionally, the second quantum logic gate includes a Hadamard gate.

[0020] Optionally, the pre-set encoding method includes:

[0021] Parity transform, Jordan-Wigner transform, or Bravyi-Kitaev transform.

[0022] Optionally, calculating the ground state energy of the target system based on the Hartree Fock state and the target quantum state includes:

[0023] The ground state energy of the target system is calculated using the following formula:

[0024]

[0025] Where E represents the ground state energy of the target system, E HF This represents the Hartree Fock energy of the target system. This represents the phase after superposition.

[0026] Another embodiment of this application provides an apparatus for calculating the energy of a target system, the apparatus comprising:

[0027] The determination module is used to determine the Hartree Fock states in the fermionic form of the target system;

[0028] A construction module is used to construct a quantum phase estimation circuit, generate control pulses for the quantum logic gates in the quantum phase estimation circuit, and apply the control pulses to the qubits in the quantum phase estimation circuit to cause a specified qubit to evolve from the Hartree Fock state to a target quantum state; the quantum phase estimation circuit includes at least a controlled first quantum logic gate, and the unitary matrix of the first quantum logic gate satisfies: in, The unitary matrix representation of the first quantum logic gate. Let b be the phase, k be the iteration number (k>1), and b be the scaling factor. For the Hamiltonian of the target system;

[0029] The calculation module is used to calculate the ground state energy of the target system based on the Hartree Fock state and the target quantum state.

[0030] Optionally, the determining module includes:

[0031] The determining unit is used to determine the Hartree Fock state in the fermion form of the target system based on the electronic information and electron spin orbital information of the target system.

[0032] Optionally, the building module includes:

[0033] A first configuration unit is configured to configure a first quantum register for storing phase information, the first quantum register comprising at least n qubits, wherein n ≥ 4;

[0034] The second configuration unit is used to configure a second quantum register for storing the Hartree Fock state, wherein the number of qubits in the second quantum register is determined by the Hamiltonian of the target system;

[0035] The third configuration unit is used to configure at least n direct products of second quantum logic gates acting on the first quantum register and an inverse quantum Fourier transform unit acting on the first quantum register. The controlled first quantum logic gates act on the first quantum register and the second quantum register, and the qubits of the first quantum register are control bits, and the qubits of the second quantum register are target bits.

[0036] Optionally, the device further includes:

[0037] The execution module is used to perform encoding operations on the Hartree Fock state through a pre-set encoding method to obtain a quantum state in the form of a Pauli operator;

[0038] An energy calculation module is used to calculate the Hartree Fock energy of the target system based on the Hamiltonian of the target system and the quantum state in the form of the Pauli operator.

[0039] One embodiment of this application provides a storage medium storing a computer program, wherein the computer program is configured to execute the method described in any of the above descriptions when it is run.

[0040] One embodiment of this application provides an electronic device including a memory and a processor, wherein the memory stores a computer program and the processor is configured to run the computer program to perform the method described in any of the above-described embodiments.

[0041] Compared with existing technologies, this invention first determines the Hartree Fock state in fermionic form of the target system, then constructs a quantum phase estimation circuit, generates control pulses for the quantum logic gates in the quantum phase estimation circuit, and applies the control pulses to the qubits in the quantum phase estimation circuit to cause the specified qubits to evolve from the Hartree Fock state to the target quantum state. Finally, based on the Hartree Fock state and the target quantum state, the ground state energy of the target system is calculated. By constructing a quantum phase estimation circuit that can be used in current quantum computing hardware devices, it provides support for the realization of quantum chemical simulation calculation of the target system energy, improves the calculation speed and accuracy, and promotes the simulation calculation of the ground state energy of the target system. Attached Figure Description

[0042] Figure 1 This is a system network block diagram for calculating the energy of a target system provided in an embodiment of the present invention;

[0043] Figure 2 This is a flowchart illustrating a method for calculating the energy of a target system according to an embodiment of the present invention;

[0044] Figure 3 This is a schematic diagram of a quantum circuit for generating a Hartree Fock state provided in an embodiment of the present invention;

[0045] Figure 4 This is a schematic diagram of the structure of a quantum phase estimation circuit provided in an embodiment of the present invention;

[0046] Figure 5 This is a schematic diagram of the structure of a device for calculating the energy of a target system provided in an embodiment of the present invention. Detailed Implementation

[0047] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0048] This invention first provides a method for calculating the energy of a target system. This method can be applied to electronic devices, such as computer terminals, specifically ordinary computers, quantum computers, etc.

[0049] The following detailed explanation uses a computer terminal as an example. Figure 1 This is a system network block diagram for calculating the energy of a target system according to an embodiment of the present invention. The system applied to calculating the energy of the target system may include a network 110, a server 120, a wireless device 130, a client 140, a storage unit 150, a classical processing system 160, a quantum processing system 170, and may also include additional memory, classical processor, quantum processor and other devices not shown.

[0050] Network 110 is a medium that provides communication links between various devices and computers connected together within a system network for methods of calculating the energy of a target system. This includes, but is not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof. The connection method can be wired, wireless communication links, or fiber optic cables.

[0051] Server 120 and client 140 are conventional data processing systems that may contain data and applications or software tools that perform conventional computational processes. Client 140 may be a personal computer or a network computer, so the data may also be provided by server 120. Wireless device 130 may be a smartphone, tablet, laptop, smart wearable device, etc. Storage unit 150 may include database 151, which can be configured to store data such as qubit parameters, quantum logic gate parameters, quantum circuits, and quantum programs.

[0052] The classical processing system 160 (quantum processing system 170) may include a classical processor 161 (quantum processor 171) for processing classical data (quantum data) and a memory 163 (memory 172) for storing classical data (quantum data). The classical data (quantum data) may be a boot file, an operating system image, and an application program 162 (application program 173). The application program 162 (application program 173) may be used to implement a quantum algorithm compiled by the method for calculating the energy of a target system provided in the embodiments of the present invention.

[0053] Any data or information stored or generated in the classical processing system 160 (quantum processing system 170) can also be configured to be stored or generated in another classical (quantum) processing system in a similar manner, and any application executed therein can also be configured to be executed in another classical (quantum) processing system in a similar manner.

[0054] It should be noted that a true quantum computer has a hybrid structure, which includes at least... Figure 1 The system consists of two main parts: the classical processing system 160, which is responsible for performing classical calculations and control; and the quantum processing system 170, which is responsible for running quantum programs and thus realizing quantum computing.

[0055] The aforementioned classical processing system 160 and quantum processing system 170 can be integrated into a single device or distributed across two different devices. For example, the first device, including the classical processing system 160, runs a classical computer operating system that provides quantum application development tools and services, as well as the storage and network services required for quantum applications. Users develop quantum applications using the quantum application development tools and services on the second device and send the quantum program to the second device, including the quantum processing system 170, via the network services. The second device runs a quantum computer operating system, which parses the code of the quantum program and compiles it into instructions that can be recognized and executed by the quantum computer control system. The quantum processor 170 then implements the quantum algorithm corresponding to the quantum program based on these instructions.

[0056] In the classic silicon-based processing system 160, the units of the classic processor 161 are CMOS transistors. These computing units are not limited by time or coherence; that is, they are available at any time without time constraints. Furthermore, the number of these computing units in a silicon chip is sufficient; currently, a classic processor contains tens of thousands of computing units. The sufficient number of computing units and the fixed selectable computing logic of the CMOS transistors, such as AND logic, allow for computational efficiency through a combination of numerous CMOS transistors and limited logic functions.

[0057] Unlike the logic units in the classical processing system 160, the basic computational unit of the quantum processor 171 in the quantum processing system 170 is the qubit. The input of a qubit is limited by coherence and coherence time; that is, a qubit is limited by its available usage time and is not always readily available. Making full use of qubits within their available usage time is a key challenge in quantum computing. Furthermore, the number of qubits in a quantum computer is one of the representative indicators of its performance. Each qubit performs computational functions through on-demand configured logic functions. Given the limited number of qubits and the diverse logic functions available in quantum computing, such as Hadamard gates (H gates), Pauli-X gates (X gates), Pauli-Y gates (Y gates), Pauli-Z gates (Z gates), X gates, RY gates, RZ gates, CNOT gates, CR gates, iSWAP gates, Tofoli gates, etc., quantum computing requires combining a limited number of qubits with diverse combinations of logic functions to achieve computational effects.

[0058] Based on these differences, the design of logical functions for qubits (including the design of whether qubits are used and the design of the efficiency of each qubit) is crucial to improving the computational performance of quantum computers and requires special design. The aforementioned design of qubits is a technical problem that ordinary computing devices do not need to consider or address. In this application, with the continuous improvement of quantum chemistry theory, computational chemistry has become an important tool for chemists to explain experimental phenomena, predict experimental results, and guide experimental design, with wide applications in drug synthesis and catalyst preparation. Calculating the ground state energy of a target system based on quantum phase estimation algorithms requires a sufficient number of qubits, but the number of available qubits in current quantum computers is very limited and cannot meet the computational needs of large systems. This, to some extent, restricts the development of computational chemistry, resulting in weak application of simulation calculations of chemical systems and hindering the further development of quantum chemical simulation applications. This application addresses the shortcomings of existing technologies by providing a method, apparatus, and medium for calculating the energy of a target system. It constructs a quantum phase estimation circuit that can be used in current quantum computing hardware devices, providing support for the realization of quantum chemical simulation calculations of the target system's energy, improving computational speed and accuracy, and promoting the simulation calculation of the target system's ground state energy.

[0059] See Figure 2 , Figure 2 This is a flowchart illustrating a method for calculating the energy of a target system according to an embodiment of the present invention.

[0060] This embodiment provides an example of a method for calculating the energy of a target system, the method of calculating the energy of the target system may include:

[0061] S201: Determine the Hartree Fock state in the fermionic form of the target system.

[0062] Specifically, to determine the Hartree Fock state in the fermionic form of the target system, we can first determine the information of the target system, including the Hamiltonian, electronic information, and electron spin orbital information.

[0063] Specifically, the target system can be considered as the molecular structure model that the user wants to simulate the ground state energy of, including, for example, the number of electrons that make up the molecule, the type of electrons, and the spin orbital information of the electrons.

[0064] The Hamiltonian is a physical concept in classical mechanics. In quantum mechanics, classical physical quantities are transformed into corresponding operators, and the Hamiltonian corresponds to the Hamiltonian operator. The Hamiltonian can be understood as the sum of the kinetic energies of all particles in a target system plus the potential energy of particles associated with the target system. The Hamiltonian differs for different situations or numbers of particles because it includes the sum of the kinetic energies of the particles and the potential energy function corresponding to that situation, generally denoted by H.

[0065] In quantum mechanics, all measurable mechanical quantities can be described by a Hermitian matrix. A Hermitian matrix is ​​defined as the matrix itself, where its transpose and conjugate are equal.

[0066]

[0067] Such matrices are usually called measurement operators. Non-zero operators will have at least one non-zero eigenvalue λ and a corresponding eigenstate |ψ>.

[0068] H|ψ>=λ|ψ>

[0069] If the eigenvalues ​​of the operator H correspond to the energy level distribution of a certain system, then such an operator can also be called a Hamiltonian.

[0070] An electron is a fundamental particle, generally referring to the number of electrons outside the nucleus of a target system; electron spin orbital information is a mathematical description of the probability of finding an electron in a specific space outside the atomic nucleus of a target system, and indicates the possible position of the electron in three-dimensional space.

[0071] In one alternative implementation, determining the Hartree Fock state of the fermion form of the target system may include: determining the Hartree Fock state of the fermion form of the target system based on the electronic information and electron spin orbital information of the target system.

[0072] It should be noted that in quantum computing, determining the Hartree Fock state can be understood as selecting a wavefunction, which requires a ground state wavefunction as a basis vector. For example, in quantum chemistry, the Hartree Fock state vector is usually used as the ground state wavefunction to satisfy:

[0073] ψ(θ)=U(θ)|ψ> Hartree-Fock

[0074] Where ψ(θ) represents the wavefunction corresponding to a set of parameters θ, U(θ) represents the matrix operator corresponding to a set of parameters θ, and the ground state wavefunction |ψ> Hartree-FockIn chemistry, this corresponds to the Hartree Fock ground state, which means that all the electrons in the molecule are in their lowest orbitals.

[0075] In one alternative implementation, see [link to implementation details]. Figure 3 , Figure 3 This is a schematic diagram of a quantum circuit for generating a HartreeFock state provided by an embodiment of the present invention. For example, for a hydrogen molecule target system, it is only necessary to add a NOT gate to each of the two qubits to initialize |0000> to |0101> in the quantum circuit.

[0076] Taking the target system as a hydrogen molecule as an example, it contains four single-electron spin molecular orbitals and two electrons. Based on the number of electrons and electron spin orbital information of the hydrogen molecule, if one quantum bit represents one electron spin orbital, that is, 0 represents an empty orbital and 1 represents an occupied orbital, the Hartree Fock state of the hydrogen molecule target system can be represented by the quantum state |0101>.

[0077] S202: Construct a quantum phase estimation circuit, generate control pulses for the quantum logic gates in the quantum phase estimation circuit, and apply the control pulses to the qubits in the quantum phase estimation circuit to cause the specified qubits to evolve from the Hartree Fock state to the target quantum state; the quantum phase estimation circuit includes at least a controlled first quantum logic gate, and the unitary matrix of the first quantum logic gate satisfies: in, The unitary matrix representation of the first quantum logic gate. Let b be the phase, k be the iteration number (k>1), and b be the scaling factor. The Hamiltonian of the target system.

[0078] Specifically, the construction of the quantum phase estimation circuit may include:

[0079] Configure a first quantum register for storing phase information, the first quantum register comprising at least n qubits, wherein n ≥ 4;

[0080] Configure a second quantum register for storing the Hartree Fock state, wherein the number of qubits in the second quantum register is determined by the Hamiltonian of the target system;

[0081] Configure at least n direct products of second quantum logic gates acting on the first quantum register and an inverse quantum Fourier transform unit acting on the first quantum register, wherein the controlled first quantum logic gates act on the first quantum register and the second quantum register, and the qubits of the first quantum register are control bits and the qubits of the second quantum register are target bits.

[0082] The second quantum logic gate may include a Hadamard gate.

[0083] For example, see Figure 4 , Figure 4 This is a schematic diagram of a quantum phase estimation circuit provided in an embodiment of the present invention. The first quantum register includes 4 qubits, and each qubit in the first quantum register is connected to an H-gate with a direct product. The second quantum register includes m qubits, and is in the form of a Hartree Fock state |ψ> in the fermion form of the target system. Hartree-Fock The initial state of the second quantum register is stored thereon. The diagram shows the controlled first quantum logic gate. Composed of quantum functional modules The inverse quantum Fourier transform unit is applied to the first quantum register, and finally a measurement operation is performed on the first quantum register to obtain the target quantum state.

[0084] It should be noted that the control pulses of quantum logic gates are an important part of quantum simulation computation. They involve designing control pulses to achieve the desired target quantum operation based on the target problem. The goal of control pulse design is to enable the system to realize the desired quantum logic gate operation within a certain time frame, while exhibiting robustness and fault tolerance to noise and system errors. Specifically, control pulse design requires clearly defining the target quantum operation to be generated, and this target quantum operation is typically composed of some basic quantum logic gate operations, such as the H-gate in this application.

[0085] S203: Calculate the ground state energy of the target system based on the Hartree Fock state and the target quantum state.

[0086] Specifically, before calculating the ground state energy of the target system based on the Hartree Fock state and the target quantum state, the method further includes:

[0087] Step 1: By using a pre-set encoding method, perform the encoding operation on the Hartree Fock state to obtain the quantum state in the form of the Pauli operator.

[0088] Specifically, we can first determine N preset qubits, and then use a pre-set encoding method to transform the Hartree Fock state in fermion form into the Hilbert space in Pauli operator form, so that each fermion state can be represented by a quantum state.

[0089] The electronic information of the target system can include α electrons and β electrons, and the quantum state in the form of the Pauli operator can be represented in the following form:

[0090]

[0091] p is the spin orbital number of the α or β electron, and M is the number of spin orbitals of the α or β electron.

[0092] In one alternative implementation, the pre-set encoding method can be one of the Parity transform, Jordan-Wigner transform, or Bravyi-Kitaev transform. The Jordan-Wigner mapping to the Parity transform or Bravyi-Kitaev mapping is possible because the number of electrons and spin electrons in the target system are conserved, as is the case for any Slater determinant that preserves the number of α electrons. Therefore, the ground state is simply a linear combination of Slater determinants, and since calculating the ground state energy can essentially be viewed as a problem of electron distribution among orbitals, this information can be used to simplify the calculation. Specifically, if the expected occupancy of an orbital is close to 0 or 1, it can be removed from the calculation. Thus, the calculation is simplified to include only the most important orbitals; this is referred to as performing the calculation of the target system energy in a reduced active space.

[0093] For example, the Slater determinant of the Jordan-Wigner transform can be expressed as:

[0094]

[0095]

[0096] Step 2: Calculate the Hartree Fock energy of the target system based on the Hamiltonian of the target system and the quantum state in the form of the Pauli operator.

[0097] Specifically, based on the Hamiltonian of the target system, the expected value corresponding to the Hamiltonian can be measured. In the second-order quantization method, the Hamiltonian of the target system can be mapped to a linear combination of local Pauli operator products through a pre-defined transformation. The expected value of the second-order quantization operator must be equivalent to the expected value of the corresponding first-order quantization operator. Since the first-order quantization operator maintains the same number of electrons, the second-order quantization operator must contain an equal number of production and annihilation operators. Thus, the second-order quantization form of the electron Hamiltonian can be obtained using these requirements:

[0098]

[0099] In one alternative implementation, calculating the Hartree Fock energy of the target system based on the Hamiltonian of the target system and the quantum state in the form of the Pauli operator may include:

[0100] Step a: Obtain the fermion Hamiltonian corresponding to the target system, and transform the fermion Hamiltonian corresponding to the target system into the Pauli Hamiltonian of the target system.

[0101] Specifically, based on the mechanical analysis of the target system, the Hamiltonian of this system can be obtained. Obtaining the fermionic Hamiltonian corresponding to the target system requires the use of the creation operator. and annihilation operator a q To achieve this, they satisfy the opposition to easy relations.

[0102] For example, for the hydrogen molecule system, the corresponding fermion Hamiltonian is:

[0103]

[0104] It's important to note that in quantum computing, the fermionic form of the Hamiltonian cannot be directly derived on the circuit. Therefore, a process is needed to convert the integral expectation value into a quantum circuit-readable form; this process is called mapping. It's crucial to understand that mapping merely changes the form of the Hamiltonian; the system energy information represented by different types of Hamiltonians is equivalent. Furthermore, for a quantum simulation circuit or a real quantum chip, Pauli operators are easier to manipulate and generate. Therefore, the fermionic Hamiltonian corresponding to the target system can be transformed into the Pauli Hamiltonian of the target system, facilitating subsequent simulation operations.

[0105] Following the example above, for the hydrogen molecule system, its corresponding fermion Hamiltonian is transformed into the Pauli Hamiltonian as follows:

[0106]

[0107] Step b: Based on the sub-terms of the Pauli Hamiltonian decomposition of the target system, construct the quantum circuits corresponding to each sub-term of the Pauli Hamiltonian of the target system.

[0108] Specifically, we can first obtain the experimental state |ψ of the target system. n Then, the quantum expectation estimation algorithm is used to calculate the experimental state |ψ n >Expectation over the molecular Hamiltonian. The so-called quantum expectation estimate refers to the fact that the Hamiltonian H of multi-electron systems, Heisenberg models, quantum Ising models, etc., can be expanded into a sum of multiple sub-terms, i.e.:

[0109]

[0110] Where h is a real number, σ is the Pauli operator, α, β and γ∈(X,Y,Z,I), and i, j and k represent the subspaces in which the Hamiltonian quantum terms operate.

[0111] Since the observables are linear, the average energy of the system can be calculated using the following formula:

[0112] E HF =<ψ * |H|ψ>

[0113] Where, ψ * Since ψ is orthogonal and uniform, the right side of the equation can also be expanded into this form:

[0114]

[0115] Therefore, we can obtain the average energy E of the system by first calculating the expectation of each sub-term and then summing the expectations. It should be noted that the measurement of the expectation of each sub-term can be performed on a quantum processor, while a classical processor can handle the summation of the expectations.

[0116] For example, suppose the Hamiltonian of a system is H, it can ultimately be expanded into this form:

[0117]

[0118] In this formula, all sub-term coefficients h are 1, and it is assumed that the obtained experimental state is of the following form:

[0119] |ψ n >=a|00>+b|01>+c|10>+d|11>

[0120] Among them, a 2 b 2 c 2 d 2 These refer to the probabilities P of collapsing to |00>, |01>, |10>, and |11> when measuring the experimental state. S By applying the Hamiltonian's sub-terms H1, H2, and H3 to the experimental state, we can obtain the expected values ​​E1, E2, and E3 in sequence, specifically:

[0121] E1=<ψ * |H1|ψ>

[0122] E2=<ψ * |H2|ψ〉

[0123] E3 = <ψ * |H3|ψ〉

[0124] Taking E1, E2, and E3 as examples, for the expected value E1, the coefficient h is the expected value, and there is no need to construct a line measurement. For the expected value E2, its Hamiltonian is Because the measurement operation is in σ Z Above (with σ) Z The measurement is performed on the eigenvectors of the qubits (which are subspaces formed by the basis vectors), so it is only necessary to add a measurement gate to the qubits and then pass the measurement results to a classical processor for summation.

[0125] Step c: Measure the Hartree Fock energy of the experimental state using the quantum circuits corresponding to each subterm of the Pauli Hamiltonian of the target system.

[0126] Specifically, by expanding the expected measurement circuits of each sub-term of the Pauli Hamiltonian of the target system, the measurement circuits of the expected E(i) of each sub-term can be obtained. Then, the quantum processor transmits E(i) to the classical processor in sequence for summation, thus obtaining the Hartree Fock energy of the target system in the experimental state.

[0127] It should be noted that, since the measurement operation is performed at σ Z The above is performed, for those containing σ x σ y The Hamiltonian cannot be directly measured at this point; it requires the determination of σ. x and σ y Performing a basis change operation, that is, letting the experimental state evolve again, due to σ x =H×σ Z ×H, That is, for σ x and σ y Before measurement, Hadamard gates and gates need to be added to the corresponding qubits respectively. The gate is then used to sum the measurement results, which are then passed to a classical processor.

[0128] It should be emphasized that the above-mentioned design methods, mapping methods and optimization methods are merely examples and do not constitute a limitation on the present invention. For example, design methods also include HE (Hardware Efficient) and SP (Symmetry Preserved) methods.

[0129] In one optional implementation, calculating the ground state energy of the target system based on the Hartree Fock state and the target quantum state may include:

[0130] The ground state energy of the target system is calculated using the following formula:

[0131]

[0132] Where E represents the ground state energy of the target system, E HF This represents the Hartree Fock energy of the target system. This represents the phase after superposition.

[0133] For example, using such Figure 4 The quantum phase estimation circuit shown, which performs the evolution and measurement operations on the Hartree Fock state, can be represented as follows:

[0134] U|ψ>=e (i*2πθ) |ψ>

[0135] Right now:

[0136] e (-ibH) |ψ>=e (-ibE) |ψ>=e (i*2πθ) |ψ>

[0137] It can be known that:

[0138]

[0139] Where θ is the phase and θ∈[0,1).

[0140] It should be noted that, due to e (i*2πθ) Since it is a periodic function, to ensure that θ∈[0,1), a reasonable scaling factor b needs to be set. For example, the scaling factor b can be determined based on the Hartree Fock energy of the target system, and the phase θ=0.5 is preset to this point, resulting in:

[0141]

[0142] because

[0143] When k=1 Assuming the target quantum state obtained by the measurement of the first quantum register is |ψ1>, then the corresponding phase

[0144] When k=2 Assuming the target quantum state obtained by the measurement of the first quantum register is |ψ2>, then the corresponding phase

[0145] When k=3 Assuming the target quantum state obtained by the measurement of the first quantum register is |ψ3>, then the corresponding phase

[0146] And so on, when it reaches the k-th iteration, Suppose that the target quantum state obtained by the measurement of the first quantum register is |ψ k >, then the corresponding phase

[0147] Furthermore, due to:

[0148]

[0149] Right now:

[0150]

[0151] according to:

[0152]

[0153] get:

[0154]

[0155] Therefore, we can deduce that the phase θ is:

[0156]

[0157] The ground state energy of the target system is calculated using the following formula:

[0158]

[0159] As can be seen from the above formula, the more iterations there are, the higher the accuracy of obtaining the ground state energy of the target system.

[0160] As can be seen, this invention first determines the Hartree Fock state in fermionic form of the target system, then constructs a quantum phase estimation circuit, generates control pulses for the quantum logic gates in the quantum phase estimation circuit, and applies the control pulses to the qubits in the quantum phase estimation circuit to cause the specified qubits to evolve from the Hartree Fock state to the target quantum state. Finally, based on the Hartree Fock state and the target quantum state, the ground state energy of the target system is calculated. By constructing a quantum phase estimation circuit that can be used in current quantum computing hardware devices, it provides support for the realization of quantum chemical simulation calculation of the target system energy, improves the calculation speed and accuracy, and promotes the simulation calculation of the ground state energy of the target system.

[0161] See Figure 5 , Figure 5 This is a schematic diagram of the structure of a device for calculating the energy of a target system provided in an embodiment of the present invention. Figure 2 Corresponding to the process shown, the apparatus includes:

[0162] Module 501 is used to determine the Hartree Fock state in the fermionic form of the target system;

[0163] Construction module 502 is used to construct a quantum phase estimation circuit, generate control pulses for the quantum logic gates in the quantum phase estimation circuit, and apply the control pulses to the qubits in the quantum phase estimation circuit to cause a specified qubit to evolve from the Hartree Fock state to a target quantum state; the quantum phase estimation circuit includes at least a controlled first quantum logic gate, and the unitary matrix of the first quantum logic gate satisfies: in, The unitary matrix representation of the first quantum logic gate. Let b be the phase, k be the iteration number (k>1), and b be the scaling factor. For the Hamiltonian of the target system;

[0164] The calculation module 503 is used to calculate the ground state energy of the target system based on the Hartree Fock state and the target quantum state.

[0165] Specifically, the determining module includes:

[0166] The determining unit is used to determine the Hartree Fock state in the fermion form of the target system based on the electronic information and electron spin orbital information of the target system.

[0167] Specifically, the building module includes:

[0168] A first configuration unit is configured to configure a first quantum register for storing phase information, the first quantum register comprising at least n qubits, wherein n ≥ 4;

[0169] The second configuration unit is used to configure a second quantum register for storing the Hartree Fock state, wherein the number of qubits in the second quantum register is determined by the Hamiltonian of the target system;

[0170] The third configuration unit is used to configure at least n direct products of second quantum logic gates acting on the first quantum register and an inverse quantum Fourier transform unit acting on the first quantum register. The controlled first quantum logic gates act on the first quantum register and the second quantum register, and the qubits of the first quantum register are control bits, and the qubits of the second quantum register are target bits.

[0171] Specifically, the device further includes:

[0172] The execution module is used to perform encoding operations on the Hartree Fock state through a pre-set encoding method to obtain a quantum state in the form of a Pauli operator;

[0173] An energy calculation module is used to calculate the Hartree Fock energy of the target system based on the Hamiltonian of the target system and the quantum state in the form of the Pauli operator.

[0174] Compared with existing technologies, this invention first determines the Hartree Fock state in fermionic form of the target system, then constructs a quantum phase estimation circuit, generates control pulses for the quantum logic gates in the quantum phase estimation circuit, and applies the control pulses to the qubits in the quantum phase estimation circuit to cause the specified qubits to evolve from the Hartree Fock state to the target quantum state. Finally, based on the Hartree Fock state and the target quantum state, the ground state energy of the target system is calculated. By constructing a quantum phase estimation circuit that can be used in current quantum computing hardware devices, it provides support for the realization of quantum chemical simulation calculation of the target system energy, improves the calculation speed and accuracy, and promotes the simulation calculation of the ground state energy of the target system.

[0175] This invention also provides a storage medium storing a computer program, wherein the computer program is configured to execute the steps in any of the above method embodiments when running.

[0176] Specifically, in this embodiment, the storage medium can be configured to store a computer program for performing the following steps:

[0177] S201: Determine the Hartree Fock state in the fermionic form of the target system;

[0178] S202: Construct a quantum phase estimation circuit, generate control pulses for the quantum logic gates in the quantum phase estimation circuit, and apply the control pulses to the qubits in the quantum phase estimation circuit to cause the specified qubits to evolve from the Hartree Fock state to the target quantum state; the quantum phase estimation circuit includes at least a controlled first quantum logic gate, and the unitary matrix of the first quantum logic gate satisfies: in, The unitary matrix representation of the first quantum logic gate. Let b be the phase, k be the iteration number (k>1), and b be the scaling factor. For the Hamiltonian of the target system;

[0179] S203: Calculate the ground state energy of the target system based on the Hartree Fock state and the target quantum state.

[0180] Specifically, in this embodiment, the storage medium may include, but is not limited to, USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks, and other media capable of storing computer programs.

[0181] This invention also provides an electronic device, including a memory and a processor, characterized in that the memory stores a computer program, and the processor is configured to run the computer program to perform the steps in any of the above method embodiments.

[0182] Specifically, the aforementioned electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the aforementioned processor, and the input / output device is connected to the aforementioned processor.

[0183] Specifically, in this embodiment, the processor can be configured to perform the following steps via a computer program:

[0184] S201: Determine the Hartree Fock state in the fermionic form of the target system;

[0185] S202: Construct a quantum phase estimation circuit, generate control pulses for the quantum logic gates in the quantum phase estimation circuit, and apply the control pulses to the qubits in the quantum phase estimation circuit to cause the specified qubits to evolve from the Hartree Fock state to the target quantum state; the quantum phase estimation circuit includes at least a controlled first quantum logic gate, and the unitary matrix of the first quantum logic gate satisfies: in, The unitary matrix representation of the first quantum logic gate. Let b be the phase, k be the iteration number (k>1), and b be the scaling factor. For the Hamiltonian of the target system;

[0186] S203: Calculate the ground state energy of the target system based on the Hartree Fock state and the target quantum state.

[0187] This invention can also provide a quantum computer operating system, which implements a method for calculating the energy of a target system according to any of the above-described method embodiments provided in this invention.

[0188] Embodiments of this application may also provide a quantum computer, which includes the aforementioned quantum computer operating system.

[0189] The above description, based on the embodiments shown in the figures, details the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A method of calculating the energy of a target system, characterized by, The method comprises: determining the fermionic form of the target system states; A quantum phase estimation circuit is constructed, control pulses are generated for the quantum logic gates in the quantum phase estimation circuit, and the control pulses are applied to the qubits in the quantum phase estimation circuit so that a specified qubit is controlled by the quantum logic gates. The state evolves to the target quantum state; the quantum phase estimation circuit includes at least a controlled first quantum logic gate, and the unitary matrix of the first quantum logic gate satisfies: ,in, The unitary matrix representation of the first quantum logic gate. For phase, The number of iterations and , Scaling factor The Hamiltonian of the target system; the construction of the quantum phase estimation circuit includes: configuring a first quantum register for storing phase information, the first quantum register including at least 100 qubits, and the stated ;Configuration for storing the A second quantum register of the state, the number of qubits in the second quantum register being determined by the Hamiltonian of the target system; configuring at least... A second quantum logic gate consisting of a direct product and an inverse quantum Fourier transform unit acting on the first quantum register, wherein the controlled first quantum logic gate acts on the first quantum register and the second quantum register, and the qubits of the first quantum register are control bits and the qubits of the second quantum register are target bits; According to the above The target quantum state and the ground state energy of the target system are calculated.

2. The method of claim 1, wherein, The determining the fermionic form of the target system state, comprising: determining a fermionic form of a target system state based on electronic information of the target system and electronic spin-orbit information of the target system state.

3. The method of claim 2, wherein, The method according to the Before calculating the ground state energy of the target system according to the target quantum state, the method further comprises: By pre-setting the encoding mode, the encoding operation on the quantum state is performed to obtain a quantum state in the form of a Pauli operator. the encoding operation on the quantum state, to obtain a quantum state in the form of a Pauli operator. calculating the energy of the target system based on the quantum state of the Pauli operator form, according to the Hamiltonian of the target system. energy.

4. The method of claim 3, wherein, The second quantum logic gate comprises a Hadamard gate.

5. The method of claim 4, wherein, The pre-set encoding mode comprises: A parity transformation, a Jordan-Wigner transformation, or a Bravyi-Kitaev transformation.

6. The method according to any one of claims 3 to 5, characterized in that, The method according to the The method according to the The method according to the The ground state energy of the target system is calculated by the following formula: wherein, represents the ground state energy of the target system, represents the ground state energy of the target system, energy, is the phase after superposition.

7. An apparatus for calculating the energy of a target system, characterized by The device comprises: determining module configured to determine a target system fermionic form of states; The constructing module is configured to construct a quantum phase estimation circuit, generate a control pulse of a quantum logic gate in the quantum phase estimation circuit, and apply the control pulse to a quantum bit in the quantum phase estimation circuit, so that a specified quantum bit evolves from an initial quantum state to a target quantum state by the quantum phase estimation circuit; the quantum phase estimation circuit comprises at least a controlled first quantum logic gate, and a unitary matrix of the first quantum logic gate satisfies: wherein, is a unitary matrix representation of the first quantum logic gate, is a phase, is a number of iterations, and , , is a scaling factor, is a Hamiltonian of a target system; the constructing quantum phase estimation circuit comprises: configuring a first quantum register for storing phase information, the first quantum register comprising at least quantum bits, and the ; configuring a second quantum register for storing the state, a number of quantum bits of the second quantum register being determined by the Hamiltonian of the target system; configuring at least second quantum logic gates acting on a direct product of the first quantum register and an inverse quantum Fourier transform unit acting on the first quantum register, the controlled first quantum logic gate acting on the first quantum register and the second quantum register, and quantum bits of the first quantum register being control bits and quantum bits of the second quantum register being target bits. a computing module configured to calculate a ground state energy of the target system according to the target quantum state and the target Hamiltonian. a computing module configured to calculate a ground state energy of the target system according to the target quantum state and the target Hamiltonian.

8. A storage medium, characterized by The storage medium stores a computer program, wherein the computer program is configured to execute the method of any one of claims 1 to 6 when running. 9.An electronic device comprising a memory and a processor, the electronic device characterized by, The memory stores a computer program, and the processor is configured to execute the computer program to execute the method of any one of claims 1 to 6.

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