Quantum circuit mapping method for distributed superconducting quantum computing architecture

Abstract

The invention provides a quantum circuit mapping method for a distributed superconducting quantum computing architecture, and belongs to the technical field of quantum computing. The problem that the quantum computing scale exceeds the capacity limit of a single QPU is solved. According to the technical scheme, the distributed quantum circuit mapping method oriented to the superconducting quantum network is characterized in that a quantum state is moved in a QPU through an SWAP gate, the quantum state is transmitted between the QPUs based on quantum state transmission operation of a microwave link, and the purpose of reducing inserted auxiliary quantum operands is achieved. The method has the advantages that a distributed calculation abstract model based on the low-temperature superconducting quantum network is constructed, and quantum states are transmitted between QPUs through quantum state transmission operation of microwave links.

Description

Technical Field

[0001] The present invention relates to the field of quantum computing technology, and in particular to a quantum circuit mapping method for a distributed superconducting quantum computing architecture. Background Art

[0002] Existing superconducting quantum computers are NISQ (Noisy Intermediate-Scale Quantum) devices, which have technical problems such as susceptibility to noise, short quantum state coherence time, and high quantum operation errors. Solving the above technical problems requires more quantum bit resources, but due to limitations in cooling, control, wiring, noise suppression, and chip manufacturing, it is difficult to meet the resource requirements of fault-tolerant computing by simply expanding the number of quantum bits in a single superconducting chip. In this context, the distributed computing model provides another effective way to continuously expand the scale of superconducting quantum computing.

[0003] Although there are some methods for distributed quantum circuit mapping, these methods are all oriented to a hypothetical distributed computing model based on the quantum Internet. The quantum Internet uses quantum teleportation technology to transmit data between QPUs, which is mainly aimed at remote quantum communication scenarios rather than quantum computing scenarios. It is difficult to meet the requirements of collaborative quantum computing in terms of transmission efficiency, fidelity, and latency. In addition, in this hypothetical model, any two QPUs are directly connected, and any pair of quantum bits in the QPU is also directly connected. Obviously, this hypothetical model is not suitable for quantum computing scenarios and does not conform to the current development status and future development trends of superconducting quantum computing. Therefore, the distributed quantum circuit mapping method based on this assumption cannot be directly applied to the emerging superconducting quantum computing network. Summary of the invention

[0004] The purpose of the present invention is to provide a quantum circuit mapping method (DQM for short) for a distributed superconducting quantum computing architecture. The distributed quantum circuit mapping method for superconducting quantum networks moves quantum states within a QPU through a SWAP gate, and transmits quantum states between QPUs based on quantum state transmission operations based on microwave links, with the goal of reducing the number of inserted auxiliary quantum operations.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is specifically: a quantum circuit mapping method for a distributed superconducting quantum computing architecture, the distributed quantum circuit mapping method takes minimizing the number of ST gates and SWAP gates required for circuit mapping as the main goal, and the specific steps are as follows:

[0006] Step 1: Generate a set of virtual quantum bits Q = {q0, q1, ..., qn-1} to the physical qubit set V = {v0, v0, ..., v n-1} mapping function π, so that π(q i )=v i ;

[0007] Step 2: Get the active gate set with in-degree 0 in the DAG model, and move all non-CNOT gates and CNOT gates with physical distance 1 to the physical line;

[0008] Step 3: Add all non-CNOT gates in the active gate set and CNOT gates with a physical distance of 1 to the executable gate set;

[0009] Step 4: If the executable gate set is not empty, move all executable gates to the physical circuit according to the mapping function π;

[0010] Step 5: Repeat Step 3 to Step 4 until there are no new executable gates added;

[0011] Step 6: Traverse the active gate set. If the physical quantum bits in the current active gates are all located in the same QPU, execute Step 7. Otherwise, execute Step 8.

[0012] Step 7: Insert the SWAP gate into the shortest physical path of the current active gate, so that the mapping of the two logical bits where the SWAP gate is located is swapped, and the mapping function π is updated, and Step 2 is executed;

[0013] Step8: Get the shortest physical path of the current active door and execute Step8.1 to Step8.3;

[0014] Step 8.1: Move the control bit to the communication bit v of the current QPU by inserting a SWAP gate i And update the mapping function π;

[0015] Step 8.2: Insert a SWAP gate on the shortest path to move the idle qubit in the QPU where the controlled bit is located closest to the communication bit to the communication bit v j And update the mapping function π;

[0016] Step8.3: Insert ST keeper communication bit v i Move to the communication position v j So that the physical qubits in the currently active gate are all located in the same QPU, and the mapping function π is updated;

[0017] Step8.4: Execute Step7.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention constructs an abstract model of distributed computing based on a low-temperature superconducting quantum network, and uses quantum state transfer (ST) operations of microwave links to transfer quantum states between QPUs.

[0020] 2. The present invention constructs a heuristic mapping method to map the logic circuit LC(Q, G), where Q represents the set of all quantum bits in the logic circuit, and G represents the set of quantum gates in the logic circuit, into the physical circuit PC(V, G′), where V is the set of physical quantum bits contained in the distributed model, and G′ is the set of quantum gates in the physical circuit, so that the number of inserted ST gates and SWAP gates is minimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0022] Figure 1 This is a schematic diagram of the abstract model of distributed computing based on low-temperature superconducting quantum network of the present invention.

[0023] Figure 2 Schematic diagram of quantum gate for quantum state movement within / between QPUs in the present invention.

[0024] Figure 3 Schematic diagram of the quantum circuit and its DAG model in the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Of course, the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0026] Example 1

[0027] See also Figure 1 As shown, there are 4 superconducting QPUs, each QPU contains 9 data quantum bits and 4 communication quantum bits, the QPUs are connected through quantum channels, all quantum bits can be used to store quantum states and execute quantum basic gates, in addition, the communication quantum bits are also used to perform quantum state transmission operations between QPUs.

[0028] It is assumed that all QPUs in this model support the Clifford+T gate library, which is a commonly used universal quantum gate library, including several single-qubit gates and two-qubit CNOT gates, such as Figure 2As shown in (a), quantum circuit mapping requires inserting a series of quantum state movement operations into the original circuit. In a distributed scenario, quantum state movement can occur on neighboring quantum bit pairs within a QPU and between QPUs. Among them, quantum state transmission within a QPU can be achieved through a SWAP gate, such as Figure 2 In addition, the quantum state movement between QPUs is realized through quantum channel transmission technology similar to the cryogenic microwave link. We use Figure 2 In the figure, the circuit symbol (ST gate) shown in (c) represents this quantum channel-based cross-QPU quantum state transmission operation, and the arrow in the figure represents the transmission direction of the quantum state. The ST gate is only allowed to act on a pair of neighboring communication qubits. It moves the quantum state of the source qubit to the destination qubit, and requires that the destination qubit must be in the |0> state before transmission.

[0029] Two models are used to represent quantum circuits, namely the circuit model and the DAG (Directed Acyclic Graph) model. Figure 3 A circuit model of a quantum circuit and its corresponding DAG model are given.

[0030] In order to prove the effectiveness of the method, the routing cost and time performance required by the proposed distributed quantum circuit mapping method are evaluated through experiments on the benchmark quantum circuit library, namely the number of ST gates and the number of SWAP gates. In order to reflect the diversity, 10 circuits of different sizes and the distributed quantum circuit mapping method (DQP) based on the hypothetical model are selected for comparison. The specific experimental data are as follows:

[0031] Table 1 Performance comparison between the DQP algorithm and the method of this embodiment

[0032]

[0033] As shown in Table 1, DQM is far superior to DQP in terms of the number of SWAP gates and ST gates. On all benchmark lines, the SWAP gates required by the present invention are reduced by up to 80.28% and 69.56% on average compared with DQP; similarly, the ST gates required by DQM are reduced by up to 92.47% and 84.93% on average.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A quantum circuit mapping method for distributed superconducting quantum computing architecture, characterized in that: The method aims to minimize the number of ST gates and SWAP gates required for line mapping, and includes the following steps: S1: Generate a virtual quantum bit set Q = {q0, q1, ..., q n-1 } to the physical qubit set V = {v0, v0, ..., v n-1 } mapping function π, so that π(q i )=v i ; S2: Get the active gate set with in-degree 0 in the DAG model, and move all non-CNOT gates and CNOT gates with physical distance 1 to the physical line; S3: Add all non-CNOT gates in the active gate set and CNOT gates with a physical distance of 1 to the executable gate set; S4: If the executable gate set is not empty, move all executable gates to the physical circuit according to the mapping function π; S5: Repeat steps S3 to S4 until there is no new executable gate added; S6: Traverse the active gate set. If the physical quantum bits in the current active gates are all located in the same QPU, execute step S7; otherwise, execute step S8. S7: insert the SWAP gate into the shortest physical path of the current active gate, so that the mapping of the two logic bits where the SWAP gate is located is swapped, and the mapping function π is updated, and step S2 is executed; S8: Obtain the shortest physical path of the current active door and execute steps S8.1 to S8.

3.

2. The quantum circuit mapping method for distributed superconducting quantum computing architecture according to claim 1 is characterized in that: The step S8 specifically includes the following steps: S8.1: Move the control bit to the communication bit v of the current QPU by inserting a SWAP gate i And update the mapping function π; S8.2: Insert a SWAP gate on the shortest path to move the idle qubit in the QPU where the controlled bit is located closest to the communication bit to the communication bit v j And update the mapping function π; S8.3: Insert ST keeper communication bit v i Move to the communication position v j So that the physical qubits in the currently active gate are all located in the same QPU, and the mapping function π is updated; S8.4: Execute step S7.

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