CN115564051B - Method and device for acquiring eigenstates of system to be tested based on quantum gate - Google Patents
Method and device for acquiring eigenstates of system to be tested based on quantum gate Download PDFInfo
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Abstract
The embodiment of the invention provides a method and a device for acquiring the eigenstates of a system to be tested based on a quantum gate, wherein the method comprises the following steps: preparing a first quantum state; sampling to obtain a first evolution time, a second evolution time and a third evolution time based on preset probability distribution; determining the Hamiltonian amount corresponding to the system to be tested; determining first, second and third hamiltonian evolution operations according to the hamiltonian and the first, second and third evolution times; measuring a first expected value of a first operation combination applied to the first quantum state to obtain a first measurement result, wherein the first operation combination comprises a conjugation operation of a first Hamiltonian evolution operation, a system observation corresponding to the Hermiltonian operation and a second Hamiltonian evolution operation; measuring a second expected value of a third Hamiltonian evolution operation applied to the first quantum state to obtain a second measurement result, wherein the first, second and third Hamiltonian evolution operations are respectively composed of a plurality of quantum gates; and combining the first measurement result and the second measurement result to obtain the observed quantity of the system to be measured.
Description
Technical Field
The invention relates to the field of quantum computing, in particular to a method and a device for acquiring an eigenstate of a system to be tested based on a quantum gate.
Background
The efficient preparation of the eigenstates of the quantum system and the estimation of the nature of the eigenstates of the system are a long standing fundamental problem in quantum computing, and have wide application in a very large number of technical fields. For example, in differential equations in the physical and chemical fields, continuous or discrete dynamics, principal component analysis in image processing; in the preparation and synthesis of chemical molecules and materials, and in the synthesis of molecules; in the establishment of a series of functional materials such as superconducting materials, nanomaterials, ferroelectric materials, magnetic materials, topological materials, metals, organics, semiconductors, semi-metals, thermoelectric materials, polymers, catalysts, and the like, chemical reaction products are predicted for the properties of the materials. In these predictions, it is important to obtain information of the excited state (non-ground state) of the material.
In the prior art, the eigenstate |u of the system is obtained i >And obtaining information about its eigenstates, it is often necessary to consume a significant amount of time and space computing resources, e.g., with time and space complexity that scale exponentially with the problem size. Specifically, a scheme for acquiring system eigenstate information using a diagonalization matrix, which requires O (D 3 ) Time complexity of (D) and O (D) 2 ) Spatial complexity, where D isThe magnitude of the system phase space, D, for quantum systems grows exponentially with the number of qubits. Another approach may trade off some time complexity for space resource savings, but it may only be partially improved on the basis of the complexity of this polynomial, but it may not obtain the eigenstates of a real physical system (system size typically grows exponentially with particle number or physical degrees of freedom), or obtain some properties of the eigenstates of the system, such as the response function (resistance, photoconductivity, susceptibility, etc.) of the physical material. Still other solutions estimate the eigenstates of the system through a series of controlled quantum gates, which require a long quantum wire depth and a large number of qubits.
Therefore, a new scheme for acquiring the eigenstates of the system under test is needed.
Disclosure of Invention
The embodiment of the invention provides a method and a device for acquiring the eigenstates of a system to be tested based on a quantum gate. By utilizing the method, the quantum evolution line formed by the quantum gates and post-processing can be utilized to efficiently acquire the observable information of the system and equivalently acquire the eigenstate information of the system.
The invention provides a method for acquiring the eigenstates of a system to be tested based on a quantum gate, which comprises the following steps:
preparing a first quantum state;
sampling to obtain a first evolution time, a second evolution time and a third evolution time based on preset probability distribution;
determining the Hamiltonian amount corresponding to the system to be tested; determining a first hamiltonian evolution operation according to the Ha Midu amount and the first evolution time, and determining a second hamiltonian evolution operation according to the Ha Midu amount and the second evolution time; measuring a first expected value of a first operation combination applied to a first quantum state to obtain a first measurement result, wherein the first operation combination comprises a conjugation operation of a first Hamiltonian evolution operation, a Hermiltonian operation corresponding to an observed quantity of the system to be measured and a second Hamiltonian evolution operation; the first Hamiltonian evolution operation and the second Hamiltonian evolution operation are respectively composed of a plurality of quantum gates;
determining a third Hamiltonian evolution operation according to the Hamiltonian quantity and the third evolution time; measuring a second expected value of a third Hamiltonian evolution operation applied to the first quantum state to obtain a second measurement result, wherein the third Hamiltonian evolution operation is composed of a plurality of quantum gates;
and combining the first measurement result and the second measurement result to obtain the observed quantity of the system to be measured.
Preferably, the system to be tested comprises any one of a molecular system, a superconducting material system, a metal crystal quantum system and a nano material quantum system; the observed quantity includes one or more of resistance, photoconductivity, magnetic susceptibility, absorption energy spectrum.
Preferably, preparing the first quantum state comprises:
the first quantum state is prepared based on any one of a state preparation operation and a variable component sub-intrinsic solver.
Preferably, the first expected value of the first combination of operations is applied to the first quantum state, which may be expressed as:
wherein N is a first expected value, ψ 0 In the first quantum state, U 1 、U 2 A first hamiltonian evolution operation and a second hamiltonian evolution operation respectively,
for conjugate transpose, O is the hermitian for the observation.
Preferably, the second desired value for applying the third unitary operation to the first quantum state may be expressed as:
P＝<ψ 0 |U 3 |ψ 0 >
wherein P is a second expected value, ψ 0 In the first quantum state, U 3 Is the third unitary operation.
Preferably, the plurality of quantum gates included in the first hamiltonian evolution operation is determined by:
dividing the first evolution time into a plurality of time periods in sequence;
and decomposing the first Hamiltonian evolution operation into a plurality of evolution sub-operations respectively corresponding to the time periods, wherein the evolution sub-operations are composed of a Brix rotating gate and a Brix gate.
Preferably, the rotation angle and the door category of the berliner rotation door are obtained by random sampling, respectively.
Preferably, the measuring applies a first expected value of a first combination of operations for a first quantum state, comprising:
and respectively measuring the real part and the imaginary part of the first expected value by a Hade code test method.
In a second aspect, an apparatus for obtaining an eigenstate of a system under test based on a quantum gate is provided, where the apparatus includes:
an initial state preparation unit configured to prepare a first quantum state;
the evolution time sampling unit is configured to sample and obtain a first evolution time, a second evolution time and a third evolution time based on a preset probability distribution;
the first measuring unit is configured to determine the Hamiltonian amount corresponding to the system to be measured; determining a first hamiltonian evolution operation according to the Ha Midu amount and the first evolution time, and determining a second hamiltonian evolution operation according to the Ha Midu amount and the second evolution time; measuring a first expected value of a first operation combination applied to a first quantum state to obtain a first measurement result, wherein the first operation combination comprises a conjugation operation of a first Hamiltonian evolution operation, a Hermiltonian operation corresponding to an observed quantity of the system to be measured and a second Hamiltonian evolution operation; the first Hamiltonian evolution operation and the second Hamiltonian evolution operation are respectively composed of a plurality of quantum gates;
the second measuring unit is configured to determine a third Hamiltonian evolution operation according to the Hamiltonian quantity and the third evolution time; measuring a second expected value of a third Hamiltonian evolution operation applied to the first quantum state to obtain a second measurement result, wherein the third Hamiltonian evolution operation is composed of a plurality of quantum gates;
and the observation amount determining unit is configured to acquire the observation amount of the system to be measured by combining the first measurement result and the second measurement result.
In a third aspect, there is provided a quantum computer comprising one or more quantum wires configured to implement the method of the first aspect.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for obtaining eigenstates of a system under test based on a quantum gate according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of different preparation modes of quantum states according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a measurement circuit according to an embodiment of the present invention;
fig. 4 is a block diagram of a device for obtaining an eigenstate of a system to be tested based on a quantum gate according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As described above, the existing schemes for obtaining the eigenstates of the quantum system have the disadvantage of consuming a large amount of computing resources in terms of time and space, or estimating the eigenstates of the system by means of controlled quantum gates, and have the disadvantages of long required quantum line depth and an excessive number of used quantum bits. In order to more clearly describe the advantages of the scheme for acquiring the eigenstates of the system to be tested through the quantum gate provided by the embodiment of the specification. The scheme for acquiring the eigenstates of the system and the drawbacks thereof are further outlined below.
The prior technical scheme mainly comprises a variable component sub-intrinsic solver, a derivative scheme thereof and a quantum phase estimation (quantum phase estimation) scheme.
The general procedure of the variable component sub-eigenvector is as follows: preparing a quantum state in the parameterized quantum circuit; measuring the average value of Hamiltonian quantity of the quantum system to be measured in a parameterized quantum state; optimizing parameters by using a classical computer; repeating the measurement and optimization processes to minimize the energy average value, namely optimizing to a final result, wherein the corresponding quantum state is the ground state prepared in production; quantum measurement is performed on the ground state to obtain an average value of observables on the ground state<u i |O|u i >Wherein O represents an observable. For example in the special case of o=h,<u i |O|u i >gives the intrinsic energy E of the system i . However, the variable component sub-eigenvector and its derivative scheme have the following problems: first, variable component quantum eigensolver algorithms and their derivatives are generally focused on parameter optimization and quantum gate forms of quantum circuits using classical computers. Therefore, the quantum entanglement characteristics that can be actually expressed are limited by the limitations of the existing quantum chip resources. For more complex, entangled deeper systems, the accuracy and resources of the prior art are limited, which is currently not addressed by the current structural technology. Parameters of the second, optimized variable component sub-eigenvector require classical computational assistance. For a real problem, the variable component sub-eigenvalue solver cannot guarantee that a real ground state can be obtained. In particular, the complexity of the process of classical optimization may likewise be exponentially increasing. Third, the variable component sub-eigenvaluer typically focuses on the ground state of the solution system, which findsThe resolution of any excited state is extremely difficult, whereas the preparation of an excited state is particularly important for the resolution of many practical problems.
Quantum phase estimation schemes can then estimate the eigenstates of the system through a series of controlled quantum gates. But it has the following problems: first, because of the long line depth required, more qubits are required and it is difficult to run on existing or near-term quantum devices. Furthermore, it is generally very resistant to noise and therefore needs to rely on fault tolerant quantum computing. Second, the number of qubits depends on the precision
Epsilon is the accuracy of the target. However, it requires a controlled multi-bit coherent operation Ctrl-U, where the operation is a coherent operation. In practice, therefore, a relatively large number of single-double bit gates are required to achieve this operation. Third, the coherence time is long. Since the depth of the line is proportional to pi/∈for applications with high accuracy requirements, such as chemical molecules (∈=10) -3 ) The line depth is long.
In order to solve the above technical problems. The embodiment of the specification provides a scheme for acquiring the eigenstates of a system to be tested based on a quantum gate. The method is characterized in that Hamiltonian evolution U=expiht is obtained through sampling, a projection operator which cannot be directly realized on a quantum computer is realized, and the evolution time t is obtained through probability sampling. Then, hamiltonian evolution is realized by utilizing a quantum circuit formed by quantum gates. Further, by measuring the result of the quantum system after operation and post-processing the measuring result, an observable of the system is obtained.
The method has the following advantages: in the first aspect, since the existing unitary evolution operation based on the segment evolution (tr method) brings about an evolution error, the existing unitary evolution operation cannot achieve the technical effect of high-precision evolution of the scheme. And no additional auxiliary qubits need to be introduced in the evolution. The existing quantum signal processing scheme and the like cannot achieve the technical effect because more complex operation is introduced. Compared with a Hamiltonian amount evolution scheme based on quantum simulation, the method only needs single-bit quantum gates and double-bit quantum gates, and does not need to realize a simulated quantum device for Hamiltonian amount evolution. And, the method can be applied to more general fault tolerant quantum computers (universal fault-tolerant quantum computer) and noise containing quantum computers (noisy quantumcomputer, noisy quantum processor, or NISQ device). In the third aspect, the method can be conveniently expanded to process the Hamiltonian H which is a more general problem, and is not limited to the quantum simulation evolution U=expiht, namely the encoding of the target problem is more flexible, and the problem which can be processed is more extensive.
Fig. 1 is a flowchart of a method for obtaining an eigenstate of a system to be tested based on a quantum gate according to an embodiment of the present invention. As shown in fig. 1, the method at least comprises the following steps:
and step 15, combining the first measurement result and the second measurement result to obtain the observed quantity of the system to be measured.
First, in step 11, a first quantum state is prepared.
In different embodiments, the system under test may characterize quantum systems of different specific problems. In one embodiment, the system to be tested comprises any one of a molecular system, a superconducting material system, a metal crystal system, and a nanomaterial system.
In different embodiments, the first quantum state may be prepared in different specific ways, which are not limited in this specification. For example, in one embodiment, the first quantum state |ψ may be prepared based on any one of a state preparation operation, a variable component sub-eigensolver 0 >. For example, in one embodiment, the first quantum state may be prepared in an initial state, which may be, for example, a simple straight-product state, such as a chemical problem, which may be obtained using an average field scheme, also known as the Hartree-Fock method. In various embodiments, the initial state may be any experimentally realizable state, such as a micro-direct product state
Fig. 2 is a schematic diagram of different preparation modes of quantum states according to an embodiment of the present invention. As shown in FIG. 2, in one example, the initial straight product state +.>
The operation allowed on an analog quantum device is applied to produce an initial state. In one example, the state resulting from the variation optimization may be used as an initial state using a variation component sub-eigensolver. In one example, the initial state method may be prepared using a unitary operation, as shown in fig. 2 (a 1). In one example, the early state may also be prepared using an hermitian operation, as shown in fig. 2 (a 2). In other examples, a multi-body perturbation (many-body perturbation theory) scheme for use in chemical problems, a unitary coupling cluster scheme (unitary coupled cluster), and the like may also be used.
Then, in step 12, based on a preset probability distribution, the first evolution time, the second evolution time and the third evolution time are obtained by sampling.
In different embodiments, the first evolution time, the second evolution time and the third evolution time may be obtained based on different probability distributions and in different specific manners. In one embodiment, the evolution time t=yτ can be obtained, where y can be sampled according to the probability distribution p (y), τ being a preset parameter. In a specific example, the probability distribution may be embodied as
In one embodiment, multiple samplings can be performed according to the probability distribution to obtain the first evolution time t respectively m ＝y m τ, second evolution time t n ＝y n τ, third evolution time t k ＝y k τ, m, n, k are sample identifiers.
In one embodiment, this operation may be implemented by a classical computing unit. In various embodiments, this operation may also be achieved by analog quantum devices, such as ion traps, semiconductor chips, silicon-based quantum devices, quantum dots, superconducting chips (superconducting quantum wires, superconducting cavities, josephson junctions), optical lattices, reed-burg atoms, optical waveguides, etc.
Next, in step 13, determining the hamiltonian amount corresponding to the system to be tested; determining a first hamiltonian evolution operation according to the Ha Midu amount and the first evolution time, and determining a second hamiltonian evolution operation according to the Ha Midu amount and the second evolution time; measuring a first expected value of a first operation combination applied to a first quantum state to obtain a first measurement result, wherein the first operation combination comprises a conjugation operation of a first Hamiltonian evolution operation, a Hermiltonian operation corresponding to an observed quantity of the system to be measured and a second Hamiltonian evolution operation; the first Hamiltonian evolution operation and the second Hamiltonian evolution operation are respectively composed of a plurality of quantum gates.
In this step, the first and second evolution times obtained in step 12 and the system under test can be usedCorresponding hamiltonian H, respectively determining a first hamiltonian evolution operation and a second hamiltonian evolution operation, which may be respectively expressed as
It should be noted that the first and second hamiltonian evolution operations are not implemented by analog quantum devices, but are each formed by a plurality of quantum gates (note that, unlike analog quantum devices that can independently simulate hamiltonian evolution, individual quantum gates themselves, such as for example, a beret, a controlled not gate, etc., cannot independently simulate hamiltonian evolution).
In one embodiment, applying a first desired value of a first combination of operations for a first quantum state may be expressed as:
wherein N is a first expected value, ψ 0 In the first quantum state, U 1 、U 2 A first hamiltonian evolution operation and a second hamiltonian evolution operation respectively,
for conjugate transpose, O is the hermitian for the observation.
In different embodiments, the plurality of quantum gates that make up the first hamiltonian evolution operation may be determined in different specific ways. In one embodiment, the plurality of quantum gates comprised by the first hamiltonian evolution operation may be determined by: dividing the first evolution time into a plurality of time periods in sequence; and decomposing the first Hamiltonian evolution operation into a plurality of evolution sub-operations respectively corresponding to the time periods, wherein the evolution sub-operations are composed of a Brix rotating gate and a Brix gate. In another embodiment, the rotation angle and the door class of the berliner rotation door can be obtained by random sampling, respectively. For example, the error compensation operation may be based on compensating for an algorithm error of the hamiltonian evolution operation. And according to the operation form and probability distribution of the error compensation operation, randomly sampling to obtain the rotation angle and the door class.
In this step, measurement can be performed
Wherein O represents an hermitian operation. U (U) 1 、U 2 The first hamiltonian evolution operation and the second hamiltonian evolution operation, respectively, and may be denoted as +.>
Wherein t is m ＝y m τ，t n ＝y n τ. y is sampled (step 12) from the probability distribution p (y). In particular, the quantum circuit formed by quantum gates can be realized for +.>
Is a measurement of (a). In different embodiments, the measurement may be performed in different specific ways. In one embodiment, the real and imaginary parts of the first expected value may be measured separately by hadamard testing. In a specific embodiment, for example, the quantum pair +.can be used as shown in FIG. 3 (a), (b)>
The real and imaginary parts of the first expected value are measured separately. Here due to U 1 ，U 2 Are Hamiltonian evolution operations, which are collectively denoted below by U for simplicity of description. This quantum wire constituting U can be determined by the following procedure: first, the evolution time of U is segmented. And according to the time ends obtained after segmentation, U=e iHt Dividing into a plurality of evolutionary sub-operations respectively corresponding to a plurality of time periods, wherein the evolutionary sub-operations can be expressed as +.>
Furthermore, the original Hamiltonian evolution operation can be expressed as +.>
See fig. 3 (c). Secondly, realize U r . In one example, U r This can be achieved by the line shown in fig. 3 (d). I.e. each U r Through a Brix revolving door and a Brix door. Wherein, the Brix door can be expressed as +.>
Which consists of only one layer of single-bit gates (P 1 、P 2 、...P n ) Constitution (S)>
Representing a direct product. In one embodiment, the brix gate P may be obtained by classical computer sampling. Wherein the form of the Brix revolving door is expiV theta, and V is the Brix door of the set category. In one embodiment, the angle θ of the Brix and the class of Brix V can be sampled by classical computer post-processing. The brix turnstile can be implemented by being broken down into a basic CNOT gate (controlled-NOT-gate, a 2-qubit control gate) and a single-bit brix gate. It should be noted that U r May be randomly determined, and the specific manner of determination may be different in different specific embodiments, which is not limited in this specification. For example, in a specific example, for each time segment r, only one sample may be used, resulting in a U r Sequence of (i.e.)>
) Realizing U. In another example, the sampling may be repeated several times to obtain several sets of U r To realize U.
In step 14, determining a third hamiltonian evolution operation according to the hamiltonian amount and the third evolution time; and measuring a second expected value of a third Hamiltonian evolution operation applied to the first quantum state, and obtaining a second measurement result, wherein the third Hamiltonian evolution operation is composed of a plurality of quantum gates.
In one embodiment, the second desired value for the application of the third hamiltonian evolution operation for the first quantum state may be expressed as:
P k ＝<ψ 0 |U 3 |ψ 0 >
wherein P is a second expected value, ψ 0 In the first quantum state, U 3 And (5) performing evolution operation for the third hamiltonian.
t k ＝y k τ. Wherein τ is a preset parameter, t k Is the third evolution time.
In different embodiments, the second desired value may be measured in different specific ways. In a manner similar to the measurement of the first desired value in step 13 (e.g., the corresponding operation of the first desired value may be changed to the corresponding operation of the first desired value in the quantum wire diagram shown in fig. 2, e.g., the corresponding operation of the U 1 And O is an identity operation, i.e. the latter two operations are not performed, so that the real part and the imaginary step of the second desired value are measured in the same way, e.g. by hadamard testing), see the description of step 13 for details, which are not repeated here.
It should be noted that step 13 and step 14 are not limited to be performed sequentially. In one embodiment, steps 13 and 14 may be performed in parallel. In another embodiment, steps 13 and 14 may be performed in any order.
Thereafter, in step 15, the first measurement result and the second measurement result are combined to obtain an observed quantity of the system to be tested.
In different embodiments, the observed quantity may be determined in different specific ways. In one embodiment, steps 13 and 14 may be performed multiple times (e.g., M times) to obtain multiple different results, respectively, for example, based on the results of the multiple times of step 12
And P k ＝<ψ 0 |U 3 |ψ 0 >In one embodiment, steps 13 and 14 performed multiple times may be performed in parallel over multiple quantum wires,the results do not interfere with each other. Then, according to the measurement results, an estimated value of the observable quantity on the eigenstates is obtained through classical calculation post-processing, and then the eigenstate information of the system is equivalently obtained.
In different embodiments, the observables may be different specific observables. For example, in one embodiment, the observed quantity may include one or more of resistance, photoconductivity, magnetic susceptibility, absorption spectrum.
According to an embodiment of another aspect, a device for acquiring eigenstates of a system under test based on a quantum gate is provided. Fig. 4 is a block diagram of a device for obtaining an eigenstate of a system to be tested based on a quantum gate according to an embodiment of the present invention, as shown in fig. 4, the device 400 includes:
an initial state preparation unit 41 configured to prepare a first quantum state;
the evolution time sampling unit 42 is configured to sample to obtain a first evolution time, a second evolution time and a third evolution time based on a preset probability distribution;
a first measurement unit 43 configured to determine a hamiltonian amount corresponding to the system to be measured; determining a first hamiltonian evolution operation according to the Ha Midu amount and the first evolution time, and determining a second hamiltonian evolution operation according to the Ha Midu amount and the second evolution time; measuring a first expected value of a first operation combination applied to a first quantum state to obtain a first measurement result, wherein the first operation combination comprises a conjugation operation of a first Hamiltonian evolution operation, a Hermiltonian operation corresponding to an observed quantity of the system to be measured and a second Hamiltonian evolution operation; the first Hamiltonian evolution operation and the second Hamiltonian evolution operation are respectively composed of a plurality of quantum gates;
a second measurement unit 44 configured to determine a third hamiltonian evolution operation based on the hamiltonian and the third evolution time; measuring a second expected value of a third Hamiltonian evolution operation applied to the first quantum state to obtain a second measurement result, wherein the third Hamiltonian evolution operation is composed of a plurality of quantum gates;
and an observation amount determining unit 45 configured to acquire an observation amount of the system under test in combination with the first measurement result and the second measurement result.
According to an embodiment of a further aspect, there is also provided a computer readable medium comprising a computer program stored thereon, which computer, when run, performs the method described above.
According to an embodiment of a further aspect, there is also provided a quantum computer comprising one or more quantum wires configured to implement the above-described method.
The foregoing describes specific embodiments of the present disclosure. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims can be performed in a different order than in the embodiments and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative elements and steps are described above generally in terms of function in order to clearly illustrate the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied in hardware, in a software module executed by a processor, or in a combination of the two. The software modules may be disposed in Random Access Memory (RAM), memory, read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the scope of the invention, but to limit the invention to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (9)
1. A method for obtaining an eigenstate of a system to be detected based on a quantum gate, wherein the system to be detected comprises any one of a molecular system, a superconducting material system, a metal crystal system and a nano material system, and the method comprises the following steps:
preparing a first quantum state;
sampling to obtain a first evolution time, a second evolution time and a third evolution time based on preset probability distribution;
determining the Hamiltonian amount corresponding to the system to be tested; determining a first hamiltonian evolution operation according to the Ha Midu amount and the first evolution time, and determining a second hamiltonian evolution operation according to the Ha Midu amount and the second evolution time; measuring a first expected value of a first operation combination applied to a first quantum state to obtain a first measurement result, wherein the first operation combination comprises a conjugation operation of a first Hamiltonian evolution operation, a Hermiltonian operation corresponding to an observed quantity of the system to be measured and a second Hamiltonian evolution operation; the first Hamiltonian evolution operation and the second Hamiltonian evolution operation are respectively composed of a plurality of quantum gates;
determining a third Hamiltonian evolution operation according to the Hamiltonian quantity and the third evolution time; measuring a second expected value of a third Hamiltonian evolution operation applied to the first quantum state to obtain a second measurement result, wherein the third Hamiltonian evolution operation is composed of a plurality of quantum gates;
and combining the first measurement result and the second measurement result to obtain an observed quantity of the system to be measured, wherein the observed quantity comprises one or more of resistance, photoconduction, magnetic susceptibility and absorption energy spectrum.
2. The method of claim 1, wherein preparing the first quantum state comprises:
the first quantum state is prepared based on any one of a state preparation operation and a variable component sub-intrinsic solver.
3. The method of claim 1, wherein applying a first expected value of a first combination of operations for a first quantum state may be expressed as:
wherein N is a first expected value, ψ 0 In the first quantum state, U 1 、U 2 A first hamiltonian evolution operation and a second hamiltonian evolution operation respectively,
for conjugate transpose, O is the hermitian for the observation.
4. The method of claim 1, wherein applying a second desired value of a third hamiltonian evolution operation for the first quantum state may be expressed as:
P＝<ψ 0 |U 3 |ψ 0 >
wherein P is a second expected value, ψ 0 In the first quantum state, U 3 And (5) performing evolution operation for the third hamiltonian.
5. The method of claim 1, wherein the first hamiltonian evolution operation comprises a plurality of quantum gates determined by:
dividing the first evolution time into a plurality of time periods in sequence;
and decomposing the first Hamiltonian evolution operation into a plurality of evolution sub-operations respectively corresponding to the time periods, wherein the evolution sub-operations are composed of a Brix rotating gate and a Brix gate.
6. The method of claim 5, wherein the rotation angle and the door class of the berlin turnstile are obtained by random sampling, respectively.
7. The method of claim 1, wherein the measuring applies a first expected value of a first combination of operations for a first quantum state, comprising:
and respectively measuring the real part and the imaginary part of the first expected value by a Hade code test method.
8. A device for obtaining an eigenstate of a system to be measured based on a quantum simulator, wherein the system to be measured comprises any one of a molecular system, a superconducting material system, a metal crystal system and a nano material system, and the device comprises:
an initial state preparation unit configured to prepare a first quantum state;
the evolution time sampling unit is configured to sample and obtain a first evolution time, a second evolution time and a third evolution time based on a preset probability distribution;
the first measuring unit is configured to determine the Hamiltonian amount corresponding to the system to be measured; determining a first hamiltonian evolution operation according to the Ha Midu amount and the first evolution time, and determining a second hamiltonian evolution operation according to the Ha Midu amount and the second evolution time; measuring a first expected value of a first operation combination applied to a first quantum state to obtain a first measurement result, wherein the first operation combination comprises a conjugation operation of a first Hamiltonian evolution operation, a Hermiltonian operation corresponding to an observed quantity of the system to be measured and a second Hamiltonian evolution operation; the first Hamiltonian evolution operation and the second Hamiltonian evolution operation are respectively composed of a plurality of quantum gates;
the second measuring unit is configured to determine a third Hamiltonian evolution operation according to the Hamiltonian quantity and the third evolution time; measuring a second expected value of a third Hamiltonian evolution operation applied to the first quantum state to obtain a second measurement result, wherein the third Hamiltonian evolution operation is composed of a plurality of quantum gates;
and the observation quantity determining unit is configured to acquire an observation quantity of the system to be measured by combining the first measurement result and the second measurement result, wherein the observation quantity comprises one or more of resistance, photoconduction, magnetic susceptibility and absorption energy spectrum.
9. A quantum computer comprising one or more quantum wires configured to implement the method of any of claims 1-7.
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