Method for solving quantum computer problems and quantum computer with configurable quantum circuit

Abstract

In the case of a method for solving a quantum computer problem, a configurable quantum circuit (QC) with a qubit arrangement is used, and a quantum computer problem (QCPROB) is accepted, in which a solution algorithm is determined from the accepted quantum computer problem, and determining a configuration of the quantum circuit according to the solution algorithm and the error-susceptibility of the solution algorithm, that is, the configuration has qubits for error correction according to the error-susceptibility of the solution algorithm, and wherein the configurable quantum circuit (QC) is configured with the determined configuration, and solving (SOL) quantum computer problems by means of the configured quantum circuit (QC).

Description

Technical Field

[0001] The invention relates to a method for solving a quantum computer problem using a quantum circuit with a qubit arrangement and a quantum computer having a configurable quantum circuit with a qubit arrangement. Background Art

[0002] During every process in electronic data processing, there is the possibility of errors in the form of unintentional changes of bits. In the case of classical computers, the causes for this are, for example, external influences such as cosmic radiation or radioactivity or solar flares or noise effects during computing operations or during data transmission. However, since the states "0" and "1" or "low" and "high" cover a sufficiently large voltage range and small voltage deviations in the signal compared to this voltage range therefore have little influence on the read value of the classical bit, in the case of classical computers, the classical bit is error-tolerant.

[0003] In the case of a quantum computer, also referred to as a quantum computer, quantum computing operations are performed on qubits in a manner known per se instead of computing operations on classical bits. Such quantum computing operations are, in particular, gate operations such as NOT or CNOT and, as is currently the case, are very error-prone, since the energy levels for the different quantum states of a qubit hardly differ from one another. Effects from the outside (e.g. caused by temperature due to electrical signals) or internal influences, such as undesired coupling between adjacent qubits or faulty quantum gates, can cause bit flips or phase flips, i.e. changes in the phase shift or combinations thereof. For this reason, current quantum computers must be strongly shielded and operated at low temperatures of a few millikelvin.

[0004] Successfully furthering calculations using faulty qubits in quantum circuits is difficult or even impossible, depending on the fault tolerance of the algorithm used.

[0005] Classical error correction and error detection algorithms mostly use redundancy in the data, such as parity bits or the multiplication of bits, so that the majority of these multiplied bits are likely to indicate the set value of the corresponding multiplied bit. However, such error correction and error detection algorithms are not possible in the case of quantum computers, since due to the no-cloning theorem, the multiplication of the state of a quantum bit is not possible.

[0006] Nevertheless, error correction is possible even in quantum computers. However, for this purpose, up to 1000 physical qubits are required for each logical qubit in order to be able to realize the logical qubit for practical applications.

[0007] Even in the case of particularly efficient quantum algorithms, error correction requires a certain number of qubits that are additionally provided, which number significantly exceeds the number of logical qubits.

[0008] Current quantum computers have a very limited number of qubits. Because only a small number of logical qubits are available on such quantum computers, current quantum computer problems cannot be properly solved on such quantum computers. Summary of the invention

[0009] It is therefore an object of the present invention to specify a method for solving a quantum computer problem using a quantum circuit and a quantum computer having a quantum circuit.

[0010] This object of the invention is achieved by a method for solving a quantum computer problem using a quantum circuit having the features specified in claim 1 and by a quantum computer having a quantum circuit having the features specified in claim 8. Preferred developments of the invention are described in the associated dependent claims, the following description and the drawings.

[0011] In the case of the method according to the invention for solving a quantum computer problem, a configurable quantum circuit with a qubit arrangement is used and a quantum computer problem is received, wherein a solution algorithm is determined as a function of the received quantum computer problem and a configuration of the qubits is determined as a function of the solution algorithm and the error susceptibility of the solution algorithm, i.e., the configuration has a number of qubits for error correction that is dependent on the error susceptibility of the solution algorithm. In the case of the method according to the invention, the configurable quantum circuit is configured with the determined configuration and the quantum computer problem is solved with the aid of the configured quantum circuit.

[0012] In the case of the method according to the invention, such a configuration of qubits is advantageously determined according to the solution algorithm and according to the error-proneness of the solution algorithm, that is, the configuration has a number of qubits for error correction related to the error-proneness of the solution algorithm. With the help of this dependence on the error-proneness of the solution algorithm, the number of qubits required for error correction can be set for the determined solution algorithm of the corresponding quantum computer problem. The set number of qubits for error correction is therefore related to the solution algorithm and thus to the corresponding quantum computer problem. Therefore, according to the quantum computer problem, the number of qubits required for error correction can be set. Therefore, only as many qubits as required for the error-proneness of the solution algorithm must be set for error correction. Therefore, it is not necessary to set a number of qubits that are specified in advance and are independent of the specific quantum computer problem for error correction. Therefore, the method according to the invention allows the selection of the number of qubits required for error correction as small as possible for the implementation of the solution algorithm. Therefore, with the help of the method according to the invention using a quantum circuit with a predetermined number of qubits, more complex quantum computer problems than those known so far can be solved. Therefore, a particularly large number of qubits in the qubits of the quantum circuit can be used as logical qubits, because the qubits do not necessarily have to be used for error correction.

[0013] In the case of the method according to the invention, the error susceptibility of the solution algorithm relative to the errors of the individual steps of the solution algorithm is preferably determined, and the configuration of the qubits is determined according to the error susceptibility of the solution algorithm relative to the errors of the individual steps. Thus, the number of qubits used for error correction, which is related to the error susceptibility of the solution algorithm, can be specifically adapted to the error susceptibility of the solution algorithm relative to the errors of the individual steps of the solution algorithm. Preferably, the number of qubits used for error correction is weighted differently for the individual steps of the solution algorithm and is adapted to the error susceptibility of the solution algorithm relative to the errors of these individual steps. In particular, a different number of qubits is provided for error correction for specific individual steps of the solution algorithm than for other individual steps.

[0014] In a further development of the method according to the invention, it is preferably provided that different numbers of physical qubits are provided for different logical qubits for carrying out the solution algorithm. In this further development, the physical qubits are advantageously arranged for the individual logical qubits in a manner adapted to the requirements, depending on the correlation of the errors that occur. Thus, in the case of individual logical qubits, error correction is essential for solving the quantum computer problem, while in the case of other logical qubits, error correction is not necessary. This situation is advantageously taken into account in this further development.

[0015] In the case of the method according to the invention, such a configuration is expediently determined that fully utilizes the available amount of qubits of the quantum circuit. In this way, a configuration can be selected so that as many logical qubits as possible can be realized with the quantum circuit. Thus, the quantum circuit can be configured so that as complex a quantum computer problem as possible can be solved with the quantum circuit.

[0016] Advantageously, in the case of the method according to the invention, a measure of the error-freeness of the solution determined by the solution algorithm is predefined, and such a configuration is determined that takes into account or satisfies the measure of the error-freeness of the solution. In this refinement of the invention, the measure of the error-freeness of the solution to the quantum computer problem can be used to determine the number of qubits used for error correction. In particular, if only a low error-freeness of the solution determined by the solution algorithm is predefined, the number of qubits used for error correction can be expected to be lower than if a higher error-freeness is predefined.

[0017] In an advantageous development of the method according to the invention, a measure of the complexity of the quantum computer problem is predetermined and the configuration is determined as a function of the measure of the complexity. In this development of the invention, the complexity of the quantum computer problem required for the real problem can be predetermined as a boundary condition, and as a function of this boundary condition, the number of qubits for error correction can be determined in each case. In this development of the invention, a measure of the logical qubits for implementing the solution algorithm can therefore be predetermined, and the error-freeness of the solution determined using the solution algorithm can be optimized, i.e., it can be selected to be as high as possible.

[0018] The quantum computer according to the invention has a configurable quantum circuit with a qubit arrangement, wherein the quantum computer has an interface for receiving a quantum computer problem, and wherein the quantum computer has a preferably classical computing device for configuring the configurable arrangement of qubits, the computing device being configured to determine a solution algorithm as a function of the received quantum computer problem, and to determine a configuration of the configurable quantum circuit as a function of the solution algorithm and the error susceptibility of the solution algorithm, that the configuration has a certain number of qubits for error correction as a function of the error susceptibility of the solution algorithm, wherein the quantum computer is configured to configure the quantum circuit as a function of the determined configuration. Particularly preferably, the quantum computer according to the invention is configured and designed to carry out the method according to the invention as described above.

[0019] In a preferred development of the invention, the quantum computer according to the invention is constructed in one piece, i.e. as an integrated single component. Alternatively and also preferably, the quantum computer according to the invention forms a system consisting of multiple parts, which at least includes a quantum circuit and a computing device, which form separate components that are in communication connection with each other.

[0020] The method according to the invention can be carried out with the aid of a quantum computer according to the invention. The same advantages as those already explained for the method according to the invention result for the quantum computer according to the invention. The advantageous refinements of the method according to the invention as already described above are preferably implemented in a meaningful manner in the case of a quantum computer according to the invention, i.e. the quantum computer according to the invention is designed and set up in a suitable manner specifically for the corresponding refinements of the method according to the invention.

[0021] In the case of the method according to the invention or in the case of the quantum computer according to the invention, the quantum computer problem is preferably a manufacturing problem and / or a maintenance problem and / or a logistics problem and / or a medical image recognition problem. In the case of applications in digital manufacturing and maintenance and logistics, complex problems often arise that can be solved with the aid of a quantum computer and a method for solving quantum computer problems. In these application cases, the use of the method according to the invention and / or the quantum computer according to the invention is therefore particularly advantageous. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawings. Figure 1 The sequence of the method according to the invention for solving a quantum computer problem by means of a quantum computer according to the invention having a configurable quantum circuit is schematically shown in a flow chart. DETAILED DESCRIPTION

[0023] exist Figure 1 The flowchart shown in the figure shows the flow of the method according to the invention for solving a quantum computer problem QCPROB in the form of a digital manufacturing task on a quantum computer according to the invention. The digital manufacturing task involves the efficient planning of a production process under predefined boundary conditions. In other embodiments, the quantum computer problem QCPROB is another problem, such as a maintenance problem or a logistics problem or a medical image recognition problem. For this quantum computer problem QCPROB, a series of quantum algorithms for execution on a quantum computer are known. The quantum computer problem QCPROB is transferred to the quantum computer according to the invention by means of an interface of the quantum computer.

[0024] With the method according to the invention, in a first step, a quantum computer problem QCPROB is received by a classical analysis computer ANA of a quantum computer and a quantum algorithm with the smallest possible number of required logical qubits is selected for solving the quantum computer problem QCPROB. For this purpose, the analysis computer ANA has a correspondingly programmed classical computing device with a database of known quantum algorithms. In the last step of the method, the selected quantum algorithm is implemented and solved on a configurable quantum circuit QC of the quantum computer.

[0025] For this purpose, in the case of this method, a logically ideal configuration of qubits is first set up which, in the case of error-free qubits, would solve the quantum computer problem QCPROB in such a way that the ideal configuration implements the selected quantum algorithm. However, this logically ideal configuration of qubits underestimates the number of qubits actually required. This is because for a practical realization, a large number of error-correcting qubits is required, which usually significantly exceeds the number of qubits for the ideal configuration, for example by several orders of magnitude, depending on the actual realization of the qubits.

[0026] An optimization algorithm is now applied with the aid of an analytical computer ANA, which calculates the share of error-correcting qubits required for the required reliable solution of the quantum computer problem QCPROB. To this end, an ideal configuration of qubits is first used, and the qubits of the ideal configuration are weighted, i.e., it is determined for which qubits error correction is very important and for which qubits error correction is not necessary. Therefore, a certain share of error-correcting qubits actually required for the actual realization of the ideal configuration of qubits can be determined. Therefore, the qubits and error-correcting qubits set for the ideal configuration can be set in a corresponding proportion for the configuration of the quantum circuit QC. In particular, in this way it can be determined how many qubits are available in the case of a configurable quantum circuit QC, and therefore the complexity of the ideal configuration can be appropriately selected according to the ratio of qubits used for the ideal configuration to error-correcting qubits, so that as large a number of qubits as possible are available for the ideal configuration, and a sufficiently high number of error-correcting qubits is set.

[0027] According to the previously performed weighting, in the case of a configurable quantum circuit QC, a configuration comprising an ideal configuration and a specific share of error correction qubits is configured by means of a configuration step OPTCONF. For this purpose, the analysis computer ANA outputs the configuration by means of an output interface and transfers the configuration to the quantum circuit. The quantum computer is set up to configure the quantum circuit by means of the configuration transferred to the quantum circuit. Subsequently, the quantum computer problem QCPROB is solved in a solution step SOL using the configured quantum circuit QC.

[0028] In another embodiment not specifically shown, a plurality of ideal configurations are used to solve the quantum computer problem QCPROB, wherein each of the ideal configurations is a configuration for solving the quantum computer problem QCPROB assuming non-error-containing qubits. Here, the plurality of ideal configurations differ in the complexity of the quantum computer problem QCPROB, and the ideal configurations can respectively solve the quantum computer problem. For each of the ideal configurations, the required error correction qubits are determined, and the total number of qubits required for realizing the ideal configuration and realizing the error correction qubits is determined, so that a plurality of configuration candidates can be used to configure the configurable quantum circuit QC. Then, the configuration candidate that makes the best possible use of the available qubits of the quantum circuit QC is used, and the configurable quantum circuit QC is configured using the configuration candidate. In this embodiment, the quantum computer problem QCPROB is then solved using the quantum circuit QC configured in this way.

Claims

1. A method for solving a quantum computer problem, wherein a configurable quantum circuit (QC) with a qubit arrangement is used, and a quantum computer problem (QCPROB) is received, wherein a solution algorithm is determined as a function of the received quantum computer problem, and a configuration of the qubits is determined as a function of the solution algorithm and the error susceptibility of the solution algorithm, which configuration has a certain number of qubits for error correction as a function of the error susceptibility of the solution algorithm, and wherein the configurable quantum circuit (QC) is configured with the determined configuration, and the quantum computer problem is solved (SOL) with the aid of the configured quantum circuit (QC).

2. The method according to the preceding claim, wherein the error susceptibility of the solution algorithm relative to errors of the individual steps of the solution algorithm is determined, and the configuration of the qubits is determined as a function of the error susceptibility of the solution algorithm relative to errors of the individual steps.

3. A method according to any one of the preceding claims, wherein the configuration has different numbers of physical qubits for different logical qubits used to implement the solution algorithm.

4. The method according to any of the preceding claims, wherein such a configuration is determined that fully utilizes the available amount of qubits of the quantum circuit (QC). 5 . The method according to claim 1 , wherein a measure of the error-freeness of a solution is predetermined and a configuration is determined which takes into account or satisfies the measure of the error-freeness of the solution. 6 . The method according to claim 1 , wherein a measure of the complexity of the quantum computer problem is predetermined and the configuration is determined as a function of the measure of the complexity.

7. A quantum computer having a configurable quantum circuit with an arrangement of qubits, wherein the quantum computer has an interface for receiving a quantum computer problem (QCPROB), and wherein the quantum computer (QC) has a computing device for configuring the quantum circuit, the computing device being configured to determine a solution algorithm as a function of the received quantum computer problem (QCPROB), and to determine a configuration of the quantum circuit as a function of the solution algorithm and the error susceptibility of the solution algorithm, wherein the configuration has a certain number of qubits for error correction as a function of the error susceptibility of the solution algorithm, wherein the quantum computer (QC) is configured to configure the quantum circuit as a function of the determined configuration.

8. The quantum computer according to the preceding claim, which is designed to carry out the method according to any one of claims 1 to 7.

9. A method or quantum computer, wherein the quantum computer problem is a manufacturing problem and / or a maintenance problem and / or a logistics problem and / or a medical image recognition problem.

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