Compiler-assisted quantum processor architecture

Abstract

Techniques are provided relating to superconducting quantum processor architectures and / or VQE compiler optimizations. For example, one or more embodiments described herein may relate to an apparatus with a superconducting quantum processor topology that utilizes an X-tree architecture to define connections between superconducting qubits, where the total number of connections is less than the total number of superconducting qubits.

Description

[Technical Field]

[0001] The present disclosure relates to compiler support for variational quantum eigensolver (“VQE”) algorithms that can leverage multi-level hierarchical tree architectures, and more particularly to compiler optimizations that can map VQE algorithms to quantum processors with multi-level hierarchical tree architectures, such as X-tree architectures. Summary of the Invention

[0002] The following presents a summary to provide a basic understanding of one or more embodiments of the present invention. This summary is not intended to identify key or critical elements or to delineate the scope of particular embodiments or the claims. Its sole purpose is to present concepts in a simplified form as a prelude to the more detailed description that is presented later. In one or more embodiments described herein, systems, computer-implemented methods, apparatus, and / or computer program products are described that can leverage domain knowledge and / or program semantics to guide qubit connectivity architectures and / or compiler optimizations for one or more VQE algorithms.

[0003] According to one embodiment, an apparatus is provided. The apparatus may include a superconducting quantum processor topology that may utilize an X-tree architecture to define connections between superconducting qubits. The total number of connections may be less than the total number of superconducting qubits.

[0004] According to one embodiment, a system is provided. The system may include a memory that stores computer-executable components. The system may also include a processor operatively coupled to the memory that can execute the computer-executable components stored in the memory. The computer-executable components may include a compiler component that maps a variational quantum eigensolver algorithm to a superconducting quantum processor that may include qubit connectivity characterized by a multi-level hierarchical tree architecture.

[0005] According to one embodiment, a computer-implemented method is provided that may include mapping, by a system operatively coupled to a processor, a variational quantum eigensolver algorithm onto a superconducting quantum processor that may include qubit connectivity characterized by a multi-level hierarchical tree architecture. [Brief explanation of the drawings]

[0006] [Figure 1A] FIG. 1 is a diagram of an exemplary, non-limiting X-tree architecture for a superconducting quantum processor according to one or more embodiments described herein. [Figure 1B] FIG. 1 is a diagram of an exemplary, non-limiting X-tree architecture for a superconducting quantum processor according to one or more embodiments described herein.

[0007] [Figure 2] FIG. 10 is a diagram of an example, non-limiting graph that can demonstrate the effectiveness of one or more X-tree architectures for superconducting quantum processors, in accordance with one or more embodiments described herein.

[0008] [Figure 3]FIG. 1 is a block diagram of an example, non-limiting system that can perform one or more quantum compiler optimizations tailored to a VQE algorithm that can minimize mapping overhead on a sparse qubit-connected quantum processor, according to one or more embodiments described herein.

[0009] [Figure 4] FIG. 1 is a block diagram of an example, non-limiting system that can map physical and / or logical qubits represented by one or more Pauli strings into a multi-level hierarchical tree that characterizes qubit connectivity, according to one or more embodiments described herein.

[0010] [Figure 5] FIG. 1 is a diagram of an example, non-limiting layout and mapping technique that may be implemented by one or more quantum compilers according to one or more embodiments described herein.

[0011] [Figure 6] FIG. 1 is a block diagram of an example, non-limiting system that can utilize a merge-to-route compositing and routing approach that can perform combined compositing and routing of quantum circuits for a VQE algorithm, according to one or more embodiments described herein.

[0012] [Figure 7] FIG. 1 is a diagram of an example, non-limiting merge-to-route composition and routing approach that may be utilized by one or more quantum compilers according to one or more embodiments described herein.

[0013] [Figure 8] FIG. 1 is a diagram of an example, non-limiting chart that can demonstrate the effectiveness of one or more quantum compilers that can utilize a merge-to-route composition and routing approach, according to one or more embodiments described herein.

[0014] [Figure 9] FIG. 1 illustrates a computer-implemented method that can facilitate mapping a VQE algorithm to one or more superconducting quantum processors having a sparse qubit connection architecture while reducing mapping overhead, in accordance with one or more embodiments described herein.

[0015] [Figure 10] FIG. 1 illustrates a computer-implemented method that can facilitate mapping a VQE algorithm to one or more superconducting quantum processors having a sparse qubit connection architecture while reducing mapping overhead, in accordance with one or more embodiments described herein.

[0016] [Figure 11] FIG. 1 illustrates a cloud computing environment according to one or more embodiments described herein.

[0017] [Figure 12] FIG. 2 illustrates abstraction model layers according to one or more embodiments described herein.

[0018] [Figure 13] FIG. 1 is a block diagram of an example non-limiting operating environment that can facilitate one or more embodiments described herein. DETAILED DESCRIPTION OF THE INVENTION

[0019] The following detailed description is illustrative only and is not intended to limit the embodiments and / or the application or uses of the embodiments, nor is it intended to be bound by any expressed or implied information presented in the preceding Background or Summary sections or in the Detailed Description section.

[0020] One or more embodiments are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a more thorough understanding of one or more embodiments. It will be apparent, however, that in various instances, one or more embodiments may be practiced without these specific details.

[0021] As the number of hardware resources (e.g., qubits and / or qubit connections) utilized by a superconducting quantum processor increases, the manufacturing of the superconducting quantum processor becomes more difficult. For example, for each connected qubit pair, there is a possibility of frequency collisions (e.g., hardware failures). Also, increased qubit connectivity can result in a higher likelihood of crosstalk in quantum gates. Thus, quantum processors with dense qubit connections generally have lower yield rates and / or poorer performance.

[0022] In contrast, limiting the number of qubit connections may make some two-qubit gates in a quantum program not directly feasible because they can only be implemented between two nearby physical qubits. Conventional quantum compilers utilize qubit mapping and / or routing paths to insert additional operations to resolve these two-qubit dependencies. However, existing quantum compilers are typically at the gate level and cannot leverage higher-level domain knowledge, resulting in high mapping overhead.

[0023] Various embodiments of the present invention may be directed to computer processing systems, computer-implemented methods, apparatus, and / or computer program products that facilitate efficient, effective, and autonomous (e.g., without direct human guidance) synthesis of quantum circuits (e.g., Pauli string simulation quantum circuits) for VQE algorithms based on qubit connectivity mapping and / or underlying quantum hardware architectures. For example, one or more embodiments described herein may map one or more VQE algorithms to a sparsely connected superconducting quantum processor architecture with minimal mapping overhead.

[0024] The computer processing system, computer-implemented method, apparatus, and / or computer program product utilizes hardware and / or software (e.g., quantum processor architectures and / or quantum compiler optimizations tailored to VQE algorithms) to solve problems that are not abstract and are highly technical in nature, and cannot be performed as a set of mental acts by a human. For example, an individual or multiple individuals cannot map Pauli string compilations to one or more quantum processor architectures for executing one or more VQE algorithms in accordance with various embodiments described herein.

[0025] Moreover, one or more embodiments described herein may constitute a technical improvement over conventional quantum compilers by mapping Pauli strings for VQE algorithms to qubit connectivity characterized by a multi-level hierarchical tree architecture. Additionally, various embodiments described herein may demonstrate technical improvements over conventional quantum compilers by adaptively synthesizing each quantum circuit according to an evolving logical-to-physical qubit mapping. For example, various embodiments described herein may perform quantum circuit composition and routing in combination with one another to reduce mapping overhead.

[0026] Furthermore, one or more embodiments described herein may have practical application by considering high-level domain knowledge and / or program semantics to execute one or more VQE algorithms, e.g., for the analysis of one or more chemical simulations. For example, various embodiments described herein may enable the execution of complex VQE algorithms, such as quantum chemistry algorithms, on sparsely connected superconducting quantum processor architectures.

[0027] 1A-1B show diagrams of an example, non-limiting tree structure that may illustrate an X-Tree architecture 100 that may characterize the qubit connectivity of a superconducting quantum processor. X-Tree architecture 100 may illustrate one type of multi-level hierarchical tree architecture that may be utilized to reduce the mapping overhead performed by one or more quantum compilers according to one or more embodiments described herein.

[0028] The VQE algorithms can be implemented by one or more quantum computing programs that utilize Pauli string simulation circuits. For example, a variational quantum chemistry simulation program can use one or more VQE algorithms to discover the ground state energy of a chemical system (e.g., a molecule, etc.). In a variational quantum chemistry simulation program, the basic building block of a chemistry-inspired hypothesis can be a Pauli string simulation quantum circuit, which can parametrically simulate the time evolution of the Pauli string.

[0029] Quantum gates, such as two-qubit gates (e.g., controlled-NOT (“CNOT”) gates), in each of the Pauli string simulation quantum circuits can form a tree structure to define qubit connectivity. The tree structure can be utilized to guide the design of physical qubit connections within a superconducting quantum processor. Furthermore, quantum gates (e.g., CNOT gates) in each of the Pauli string simulation quantum circuits can be combined into a tree structure without affecting the functionality of the circuit. For example, the same Pauli string can be characterized by a variety of respective qubit connectivity layouts. Various embodiments described herein can leverage the flexibility of Pauli string simulation quantum circuits to design one or more compiler optimizations that can be tailored to the execution of a VQE algorithm (e.g., tailored to the execution of one or more variational quantum chemistry simulation programs).

[0030] The exemplary X-tree architecture 100 can characterize the qubit connectivity of a Pauli string simulation quantum circuit. As shown in FIGS. 1A-1B, the X-tree architecture 100 can represent a superconducting quantum processor topology with sparse qubit connectivity. As used herein, the term "sparse qubit connectivity" and / or grammatical variants thereof can refer to one or more superconducting quantum processor topologies in which the total number of connections between superconducting qubits is less than the total number of superconducting qubits. For example, the X-tree architecture 100 can characterize a superconducting quantum processor with sparse qubit connectivity because the X-tree architecture 100 utilizes at least one less inter-qubit connection than the total number of qubits. For example, for "N" qubits, the X-tree architecture 100 utilizes "N-1" connections to connect all of the qubits.

[0031] 1A-1B, an X-Tree architecture 100 can represent qubit connectivity as a tree structure with no loops. The X-Tree architecture 100 can include multiple nodes 102 (e.g., represented by circles) coupled together via multiple connections 104 (e.g., represented by straight lines). Each node 102 can represent a respective superconducting qubit, and each connection 104 can represent a qubit connection (e.g., via a two-qubit gate such as a CNOT gate). Among the nodes 102, one or more leaf nodes can be nodes 102 that branch off from a respective root node (e.g., via connections 104).

[0032] 1A shows a first exemplary X-tree architecture 100a including five nodes 102 to represent connectivity among five superconducting qubits. For clarity, the nodes 102 are further numbered using respective numerals (e.g., first node 102, second node 102, third node 102, fourth node 102, and / or fifth node 102). In the first exemplary X-tree architecture 100a, the second node 102, the third node 102, the fourth node 102, and / or the fifth node 102 may be leaf nodes relative to the first node 102, and the first node 102 may therefore be the root node. For example, the second node 102, the third node 102, the fourth node 102, and / or the fifth node 102 may branch from the first node 102. Thus, the first exemplary X-tree architecture 100a may define a first qubit (e.g., represented by the first node 102) connected to a second qubit (e.g., represented by the second node 102) via a first quantum gate (e.g., a CNOT gate); to a third qubit (e.g., represented by the third node 102) via a second quantum gate (e.g., a CNOT gate); to a fourth qubit (e.g., represented by the fourth node 102) via a third quantum gate (e.g., a CNOT gate); and / or to a fifth qubit (e.g., represented by the fifth node 102) via a fourth quantum gate (e.g., a CNOT gate). As shown in FIG. 1A, the first exemplary X-tree architecture 100a may feature qubit connectivity capable of coupling five qubits via four qubit connections to facilitate a superconducting quantum processor with sparse qubit connections.

[0033] Additionally, the size of the X-tree architecture 100 can be increased by adding one or more additional nodes 102 to one or more of the leaf nodes. For example, the second exemplary X-tree architecture 100b shown in FIG. 1A comprises eight nodes 102 to represent connectivity between eight superconducting qubits. In particular, a sixth node 102, a seventh node 102, and / or an eighth node 102 can be further connected to the fifth node 102. Thus, the fifth node 102 can be considered a leaf node with respect to the first node 102 (e.g., the first node 102 can therefore be the root node of the pairing), and can be considered a root node with respect to the sixth node 102, the seventh node 102, and / or the eighth node 102 (e.g., the sixth node 102, the seventh node 102, and / or the eighth node 102 can therefore be the respective leaf nodes of the pairing). As shown in FIG. 1A, a second exemplary X-tree architecture 100b can feature qubit connectivity that can couple eight qubits through seven qubit connections to facilitate a superconducting quantum processor with sparse qubit connections.

[0034] Furthermore, by adding additional leaf nodes, the X-Tree architecture 100 can continue to grow to feature superconducting quantum processor topologies with even more qubits. For example, the third exemplary X-Tree architecture 100c shown in FIG. 1A can represent 26 qubits coupled via 25 qubit connections. As illustrated by FIG. 1A, the X-Tree architecture 100 is not limited to a particular number of qubits; rather, the X-Tree architecture 100 can be scaled to accommodate any desired number of qubits by adding leaf nodes to expand the branching of the X-Tree architecture 100. In one or more embodiments, each node 102 can be coupled via four or fewer connections 104 (e.g., a node 102 can function as a root node for four or fewer leaf nodes).

[0035] As shown in FIG. 1B , the X-Tree architecture 100 can be further segmented into multiple levels (e.g., extending from a central region of the X-Tree architecture 100 toward a peripheral region of the X-Tree architecture 100). For example, a fourth exemplary X-Tree architecture 100d is shown in FIG. 1B . The fourth exemplary X-Tree architecture 100d can comprise 17 nodes 102 (e.g., representing 17 qubits) connected via 16 connections 104 (e.g., representing 16 qubit connections). Further, the fourth exemplary X-Tree architecture 100d can be segmented into three levels: Level 0, Level 1, and / or Level 2. For clarity, the boundaries of Level 0 are defined using dark gray shading in FIG. 1B , the boundaries of Level 1 are defined using light gray shading in FIG. 1B , and the boundaries of Level 2 are defined by a white background in FIG. 1B . The boundaries of each level can be such that the connections 104 between root node and leaf node pairings span different levels. In various embodiments, the physical qubits represented in the X-Tree architecture 100 may be located at different levels from the root node to the leaf nodes. In addition, each of the nodes 102 located at the outermost level (e.g., the highest level) of the X-Tree architecture 100 may be a leaf node.

[0036] For example, with respect to the fourth exemplary X-Tree architecture 100d, the second node 102, the third node 102, the fourth node 102, and / or the fifth node 102 may be leaf nodes relative to the first node 102 (e.g., the root node). Further, the first node 102 may be positioned within level 0; and the second node 102, the third node 102, the fourth node 102, and / or the fifth node 102 may be positioned within level 1. Thus, the connections 104 between the second node 102, the third node 102, the fourth node 102, and / or the fifth node 102 (e.g., leaf nodes) and the first node 102 (e.g., the root node) may traverse between level 0 and level 1 (e.g., may span between level 0 and level 1).

[0037] Similarly, the second node 102, the third node 102, the fourth node 102, and / or the fifth node 102 may be a root node for the nodes 102 located in level 2. For example, the second node 102 may be a root node for the fifteenth node 102, the sixteenth node 102, and / or the seventeenth node 102. As shown in FIG. 1B , the second node 102 may be located in level 1; while the fifteenth node 102, the sixteenth node 102, and / or the seventeenth node 102 may be located in level 2. Thus, the connections 104 between the 15th node 102, the 16th node 102, and / or the 17th node 102 (e.g., leaf nodes) and the second node 102 (e.g., root nodes for the 15th node 102, the 16th node 102, and / or the 17th node 102) can be traversed between level 1 and level 2 (e.g., can span between level 1 and level 2).

[0038] As the branching of the X-Tree architecture 100 increases, the number of levels in the X-Tree architecture 100 can increase. For example, if an additional node 102 is added to the fourth exemplary X-Tree architecture 100d, the additional node 102 can be added as a leaf node and positioned within level 3 (not shown) in the X-Tree architecture 100. Thus, the X-Tree architecture 100 can be embodied as a multi-level hierarchical tree architecture.

[0039] FIG. 2 shows a diagram of an exemplary, non-limiting graph 200 that can demonstrate the effectiveness of a superconducting quantum processor topology characterized by an X-tree architecture 100 according to one or more embodiments described herein. Repeated descriptions of similar elements utilized in other embodiments described herein are omitted for brevity. Graph 200 can compare the fourth exemplary X-tree architecture 100d with a conventional grid architecture “Grid17Q” (e.g., a conventional 17-node grid, where each node is coupled via at least two connections). Graph 200 demonstrates that a superconducting quantum processor characterized by an X-tree architecture 100 (e.g., a 17-qubit superconducting quantum processor characterized by the fourth exemplary X-tree architecture 100d) can achieve an approximately 8-fold higher yield rate compared to a superconducting quantum processor characterized by a conventional two-dimensional grid connection (e.g., a 17-qubit superconducting quantum processor characterized by a 17-node grid connection). Thus, the X-tree architecture 100 can enable efficient superconducting quantum processor architectures with sparse qubit connections and high yield rates.

[0040] 3 shows a block diagram of an exemplary, non-limiting system 300 that can map one or more VQE algorithms to a multi-level hierarchical architecture of qubit connectivity (e.g., X-tree architecture 100) to generate one or more quantum circuits for execution of a quantum program (e.g., a variational quantum chemistry simulation). Repeated descriptions of similar elements utilized in other embodiments described herein are omitted for brevity. System (e.g., system 300, etc.), apparatus, or process aspects of various embodiments of the invention may constitute one or more machine-executable components embodied within one or more machines (e.g., embodied in one or more computer-readable media associated with one or more machines). When executed by one or more machines (e.g., computers, computing devices, virtual machines, combinations thereof, etc.), such components can cause the machines to perform the operations described.

[0041] As shown in FIG. 3 , system 300 can include one or more servers 302, a network 304, an input device 306, and / or a quantum processor 308. Server 302 can include a compiler component 310. Compiler component 310 can further include a communications component 312 and / or a layout component 314. Server 302 can also include or be otherwise associated with at least one memory 316. Server 302 can also include a system bus 318 that can couple to various components, such as, but not limited to, compiler component 310 and associated components, memory 316, and / or processor 320. While server 302 is shown in FIG. 3 , in other embodiments, multiple devices of various types can be associated with or include the features shown in FIG. 3 . Additionally, server 302 can be in communication with one or more cloud computing environments.

[0042] The one or more networks 304 may include wired and wireless networks, including, but not limited to, a cellular network, a wide area network (WAN) (e.g., the Internet), or a local area network (LAN). For example, the server 302 may communicate with the one or more input devices 306 and / or quantum processor 308 (and vice versa) using substantially any desired wired or wireless technology, including, but not limited to, cellular, WAN, Wireless Fidelity (Wi-Fi), Wi-Max, WLAN, Bluetooth technology, combinations thereof, etc. Furthermore, in the illustrated embodiment, the compiler component 310 may be provided on one or more servers 302, although it should be appreciated that the architecture of the system 300 is not so limited. For example, the compiler component 310, or one or more components of the compiler component 310, may be located on another computing device (e.g., another server device, a client device, a combination thereof, etc.).

[0043] The one or more input devices 306 may include one or more computerized devices, including, but not limited to: a personal computer, a desktop computer, a laptop computer, a mobile phone (e.g., a smartphone), a computerized tablet (e.g., including a processor), a smartwatch, a keyboard, a touchscreen, a mouse, combinations thereof, etc. The one or more input devices 306 may be utilized to input one or more VQE algorithm inputs (e.g., Hamiltonians, quantum programs, quantum circuits, Pauli strings, combinations thereof, etc.) into the system 300, so that such data is shared with the server 302 (e.g., via a direct connection and / or over one or more networks 304). For example, the one or more input devices 306 may transmit data to the communications component 312 (e.g., via a direct connection and / or over one or more networks 304). Additionally, the one or more input devices 306 may include one or more displays that may present one or more outputs generated by the system 300 to a user. For example, the one or more displays may include, but are not limited to: a cathode ray tube display ("CRT"), a light emitting diode display ("LED"), an electroluminescent display ("ELD"), a plasma display panel ("PDP"), a liquid crystal display ("LCD"), an organic light emitting diode display ("OLED"), combinations thereof, and the like.

[0044] In various embodiments, one or more input devices 306 and / or one or more networks 304 may be utilized to input one or more settings and / or commands into system 300. For example, in various embodiments described herein, one or more input devices 306 may be utilized to operate and / or manipulate server 302 and / or associated components. Additionally, one or more input devices 306 may be utilized to display one or more outputs (e.g., displays, data, visualizations, etc.) generated by server 302 and / or associated components. Furthermore, in one or more embodiments, one or more input devices 306 may be comprised within and / or operably coupled to a cloud computing environment.

[0045] For example, in various embodiments, one or more input devices 306 can be utilized to input one or more initial quantum Hamiltonians into system 300 for analysis via one or more VQE algorithms. For example, the initial quantum Hamiltonian can include a summation of Pauli matrices and / or can be obtained by applying one or more versions of Jordan-Wigner encoding. The initial quantum Hamiltonian can characterize the interparticle interactions of a chemical system, which can be a set of separable or non-separable operators that can evolve a wave function into stationary eigenstates (e.g., where the eigenvalues ​​are energies). In one or more embodiments, system 300 can be initialized with atomic coordinates (e.g., internal or absolute) of one or more given molecules and / or atom types / basis sets from which the initial quantum Hamiltonian can be derived.

[0046] In various embodiments, one or more quantum processors 308 may include quantum hardware devices that can utilize the laws of quantum mechanics (e.g., superposition and / or entanglement, etc.) to facilitate computational processing (e.g., while satisfying the DiVincenzo criterion). In one or more embodiments, one or more quantum processors 308 may include a quantum data plane, a control processor plane, a control and measurement plane, and / or qubit technology.

[0047] In one or more embodiments, a quantum data plane can include one or more quantum circuits, including physical qubits, structures for fixing the positioning of the qubits, and / or support circuitry. The support circuitry can, for example, facilitate measurement of the qubit states and / or perform gate operations on the qubits (e.g., for gate-based systems). In some embodiments, the support circuitry can include a wiring network that can enable multiple qubits to interact with one another. Furthermore, the wiring network can facilitate transmission of control signals via direct electrical connections and / or electromagnetic radiation (e.g., optical, microwave, and / or low-frequency signals). For example, the support circuitry can include one or more superconducting resonators operably coupled to one or more qubits. As described herein, the term “superconducting” can characterize a material that exhibits superconducting properties at or below a superconducting critical temperature, such as aluminum (e.g., a superconducting critical temperature of 1.2 Kelvin) or niobium (e.g., a superconducting critical temperature of 9.3 Kelvin). In addition, those skilled in the art will recognize that other superconductor materials (e.g., hydride superconductors such as lithium / magnesium hydride alloys) may be used in the various embodiments described herein.

[0048] In one or more embodiments, the control processor plane can identify and / or trigger Hamiltonian sequences of quantum gate operations and / or measurements, where the sequences execute programs (e.g., provided by a host processor, such as server 302, via compiler component 310) to implement quantum algorithms (e.g., VQE algorithms). For example, the control processor plane can translate compiled code into commands for the control and measurement planes. In one or more embodiments, the control processor plane can further execute one or more quantum error correction algorithms.

[0049] In one or more embodiments, the control and measurement plane can convert digital signals generated by the control processor plane, which can define the quantum operation to be performed, into analog control signals for performing operations on one or more qubits in the quantum data plane. The control and measurement plane can also convert one or more analog measurement outputs of qubits in the data plane into standard binary data that can be shared with other components of system 300.

[0050] Those skilled in the art will recognize that a variety of qubit technologies can provide the basis for one or more qubits in one or more quantum processors 308. Two exemplary qubit technologies can include trapped ion qubits and / or superconducting qubits. For example, if quantum processor 308 utilizes trapped ion qubits, the quantum data plane can include a plurality of ions that function as qubits and one or more traps that function to hold the ions in specific locations. Additionally, the control and measurement plane can include: a laser or microwave source directed at one or more of the ions to affect their quantum state; a laser to cool and / or enable measurement of the ions; and / or one or more photon detectors to measure the state of the ions. In another example, a superconducting qubit (e.g., a superconducting quantum interference device "SQUID," etc.) can be a lithographically defined electronic circuit that can be cooled to millikelvin temperatures to exhibit quantized energy levels (e.g., due to quantized states of charge or magnetic flux). The superconducting qubit can be Josephson junction-based, such as a transmon qubit. Superconducting qubits may also be compatible with microwave-controlled electronics and may be utilized with gate-based technologies or integrated cryogenic control. Additional exemplary qubit technologies may include, but are not limited to: photonic qubits, quantum dot qubits, gate-based neutral atom qubits, semiconductor qubits (e.g., optically gated or electrically gated), topological qubits, combinations thereof, and the like.

[0051] In one or more embodiments, communications component 312 may receive one or more initial quantum Hamiltonians from one or more input devices 306 (e.g., via a direct electrical connection and / or through one or more networks 304) and share the data with various associated components of compiler component 310. Additionally, communications component 312 may facilitate the sharing of data between compiler component 310 and one or more quantum processors 308, and / or vice versa (e.g., via a direct electrical connection and / or through one or more networks 304).

[0052] In various embodiments, one or more quantum processors 308 may include one or more VQE components 322 (e.g., included in a control processor plane) that may execute one or more VQE algorithms on the quantum processors 308. In one or more embodiments, one or more VQE components 322 and compiler component 310 may function in combination to execute an iterative VQE algorithm based on one or more initial quantum Hamiltonians. For example, one or more VQE components 322 and / or compiler component 310 may function in combination to execute one or more variational quantum chemistry simulations.

[0053] As used herein, the term “variational quantum eigensolver (“VQE”) algorithm” and its grammatical variants can refer to one or more hybrid quantum-standard computing algorithms that can share computational work between standard computing hardware (e.g., one or more servers 302 via compiler component 310) and quantum computing hardware (e.g., one or more quantum processors 308 via VQE component 322) to reduce the long coherence times required by all quantum phase estimation algorithms. The VQE algorithm can be initialized with one or more assumptions about the form of the target wave function. Based on the one or more assumptions, hypotheses with one or more adjustable parameters can be constructed, and quantum circuits capable of generating the hypotheses can be designed (e.g., Pauli string simulation quantum circuits). Throughout the execution of the VQE algorithm, the hypothesis parameters can be variationally adjusted to minimize the expectation value of the resulting Hamiltonian matrix. Standard computing hardware (e.g., one or more servers 302 via compiler component 310) can precompute one or more terms in the Hamiltonian matrix and / or update parameters during quantum circuit optimization. Quantum hardware (e.g., one or more quantum processors 308 via VQE component 322) can prepare a quantum state (e.g., defined by the current iteration's set of hypothetical parameter values) and / or perform measurements of various interaction terms in the Hamiltonian matrix. State preparation can be repeated over multiple iterations until each individual operator has been measured a sufficient number of times to derive sufficient statistics. Additionally, the efficiency of the VQE algorithm can be improved by using particle-hole mapping of the quantum Hamiltonian to generate improved starting points for the trail wavefunction.Furthermore, methods for reducing the number of qubits required for electronic structure calculations (eg, qubit tapering, etc.) can reduce redundant degrees of freedom in the Hamiltonian.

[0054] In various embodiments, compiler component 310 can map one or more VQE algorithms to one or more quantum processors 308, where one or more quantum processors 308 can have qubit connectivity characterized by a multi-layer hierarchical tree architecture. Further, in various embodiments, one or more quantum processors 308 can have sparse qubit connectivity. For example, one or more quantum processors 308 can have a topology characterized by an X-tree architecture 100. For example, one or more quantum processors 308 can have sparse qubit connectivity characterized by an X-tree architecture 100, which can be exploited by compiler component 310 to minimize mapping overhead while synthesizing and / or routing one or more quantum circuits for execution of VQE algorithms (e.g., for performing variational quantum chemistry simulations).

[0055] In one or more embodiments, the layout component 314 may generate a hierarchical layout for both the physical qubits of one or more quantum processors 308 and / or the logical qubits contained within one or more Pauli strings utilized by one or more VQE algorithms. For example, given that one or more quantum processors 308 have a multi-level hierarchical tree architecture for qubit connectivity (e.g., X-tree architecture 100), the hierarchical layout generated by the layout component 314 may first assign program qubits of one or more VQE algorithms to one or more hardware qubits contained within the one or more quantum processors 308 and / or characterized by the multi-level hierarchical tree architecture (e.g., X-tree architecture 100). In various embodiments, the layout component 314 may analyze one or more Pauli strings utilized by one or more VQE algorithms to execute a quantum program (e.g., a variational quantum chemistry simulation) and first assign the qubits described by the Pauli strings to nodes 102 of the multi-level hierarchical tree architecture. Thus, the hierarchical layout generated by layout component 314 may first map logical qubits (e.g., qubits described by Pauli strings utilized by the VQE algorithm) to physical qubits (e.g., represented by a multi-level hierarchical tree architecture, such as nodes 102 of X-tree architecture 100) of one or more quantum processors 308.

[0056] 4 shows a diagram of an example, non-limiting system 300 further comprising a mapping component 402, according to one or more embodiments described herein. Repetitive descriptions of similar elements utilized in other embodiments described herein are omitted for brevity. In various embodiments, the mapping component 402 can further facilitate the layout component 314 in determining the distribution of logical qubits across multiple levels of a multi-level hierarchical tree architecture (e.g., the X-Tree architecture 100).

[0057] For example, mapping component 402 may analyze the Pauli strings of one or more VQE algorithms to determine the amount of connectivity associated with logical qubits during execution of a quantum program. In various embodiments, the amount of connectivity may be characterized by the number of occurrences a logical qubit makes in the Pauli string. For example, each Pauli string may describe a respective quantum computation performed by a VQE algorithm. Thus, the number of quantum computations involving a given logical qubit may be characterized by the number of occurrences of the given logical qubit in the Pauli string. As a logical qubit is included in more quantum computations, the connectivity of the logical qubit may be considered to increase. For example, as the number of occurrences increases, the amount of connectivity experienced by the associated logical qubit during execution of a quantum program may also increase. For example, a logical qubit with the greatest number of occurrences in a Pauli string may be determined to have the greatest connectivity within a multi-level hierarchical tree architecture (e.g., X-tree architecture 100).

[0058] In various embodiments, mapping component 402 can assign logical qubits to different levels of a multi-level hierarchical tree architecture (e.g., X-tree architecture 100) based on an associated amount of connectivity. For example, if the levels of the tree architecture increase with branching iterations (e.g., as illustrated in FIG. 1B with respect to fourth example X-tree architecture 100d), logical qubits can be assigned to levels of the tree architecture in order of connectivity; where logical qubits with the greatest amount of connectivity can be assigned to the lowest levels (e.g., closest to the center of the tree architecture) and logical qubits with the lowest amount of connectivity can be assigned to the highest levels (e.g., closest to the periphery of the tree architecture).

[0059] 5 shows a diagram of an example, non-limiting initial hierarchical layout 500 that may be generated by the layout component 314 and / or the mapping component 402, according to one or more embodiments described herein. Repetitive descriptions of similar elements utilized in other embodiments described herein are omitted for brevity. Quantum computations executable according to the VQE algorithm may be defined via multiple Pauli strings.

[0060] 5, one or more exemplary Pauli strings 502 may include a group of Pauli operators (e.g., “X,” “Y,” “Z,” and “I”) associated with each logical qubit utilized by a VQE algorithm to perform a quantum computation. For example, the exemplary Pauli string 502 shown in FIG. 5 considers a six-member group having Pauli operators associated with six qubits (e.g., where the qubits are represented as “q0,” “q1,” “q2,” “q3,” “q4,” “q5,” and / or “q6”). In the exemplary Pauli string 502, qubit q0 has the greatest number of occurrences (e.g., the greatest number of “X,” “Y,” and / or “Z” Pauli operator associations within the set of exemplary Pauli strings 502). In contrast, qubit q5 has the least number of occurrences (e.g., the least number of “X,” “Y,” and / or “Z” Pauli operator associations within the set of exemplary Pauli strings 502).

[0061] 5, compiler component 310 (e.g., via layout component 314 and / or mapping component 402) can assign logical qubits to different levels of a tree architecture (e.g., X-tree architecture 100) based on the connectivity of the qubits (e.g., as determined based on the number of occurrences in the Pauli string). In various embodiments, mapping component 402 can determine the number of times a quantum computation can utilize each of the logical qubits in a VQE algorithm, and therefore the amount of connectivity associated with each logical qubit, based on the number of occurrences of each logical qubit in the Pauli string (e.g., the number of “X,” “Y,” and / or “Z” Pauli operator associations in a set Pauli string).

[0062] For example, the qubit associated with the greatest number of occurrences in the exemplary Pauli string 502 (e.g., qubit q0) may be assigned by the mapping component 402 to the lowest level (e.g., level 0) of the tree architecture (e.g., X-tree architecture 100). Also, the qubit associated with the least number of occurrences in the exemplary Pauli string 502 (e.g., qubit q5) may be assigned by the mapping component 402 to the highest level (e.g., level 2) of the tree architecture (e.g., X-tree architecture 100). Furthermore, the qubits not associated with the greatest or least number of occurrences in the exemplary Pauli string 502 (e.g., qubit q1, qubit q2, qubit q3, and / or qubit q4) may be assigned by the mapping component 402 to one or more intermediate levels (e.g., level 1) of the tree architecture (e.g., X-tree architecture 100).

[0063] Additionally, compiler component 310 (e.g., via layout component 314 and / or mapping component 402) may map qubits to nodes 102 of a tree architecture (e.g., X-Tree architecture 100) based on the level assignments. For clarity, the boundaries of level 0 within the tree architecture of exemplary hierarchical layout 500 are defined by dark gray shading in FIG. 5, the boundaries of level 1 within the tree architecture of exemplary hierarchical layout 500 are defined by light gray shading in FIG. 5, and the boundaries of level 2 within the tree architecture of exemplary hierarchical layout 500 are defined by white background shading in FIG. 5. In various embodiments, as the positioning of a mapped qubit approaches the center of the multi-level hierarchical tree architecture (e.g., X-Tree architecture 100), the number of qubit connections that the mapped qubit receives throughout execution of the VQE algorithm increases. For example, in the exemplary set of Pauli strings 502, qubit q0 is shown to be involved in the most quantum computations throughout the execution of the VQE algorithm (e.g., as evidenced by the number of occurrences in the Pauli strings), and therefore can be located within the most central level (e.g., level 0) of the multilevel hierarchical tree architecture (e.g., X-tree architecture 100). In contrast, in the exemplary set of Pauli strings 502, qubit q5 is shown to be involved in the fewest quantum computations throughout the execution of the VQE algorithm (e.g., as evidenced by the number of occurrences in the Pauli strings), and therefore can be located within the most remote level (e.g., level 2) of the multilevel hierarchical tree architecture (e.g., X-tree architecture 100).

[0064] As a result of mapping qubits based on level assignments within a tree architecture (e.g., X-tree architecture 100), qubits mapped to nodes 102 closest to the center of the multi-level hierarchical tree architecture may be qubits that can experience the greatest amount of qubit connection diversity during execution of the VQE algorithm. In contrast, qubits mapped to nodes 102 furthest from the center of the multi-level hierarchical tree architecture may be qubits that can be expected to experience the least amount of qubit connection diversity during execution of the VQE algorithm.

[0065] With each composition of quantum circuits utilized by the VQE algorithm, logical qubits can be routed to new physical qubit mappings that facilitate different qubit connectivity schemes defined by the respective quantum circuits. As the number of routing operations utilized to establish the desired connectivity increases, the mapping overhead also increases. However, the initial hierarchical layout described herein can enable a reduction in the number of routing operations, and therefore closer proximity to each other, by mapping high-traffic qubits (e.g., qubits involved in numerous quantum computations) to one or more central levels of the tree architecture (e.g., X-tree architecture 100). In other words, qubits initially mapped to a central level in the tree architecture (e.g., level 0 in the fourth exemplary X architecture 100d) can be routed to a desired qubit connection (e.g., a desired root-to-leaf node pairing) via fewer operations than qubits initially mapped to a peripheral level in the tree architecture (e.g., level 2 in the fourth exemplary X architecture 100d).

[0066] 6 shows a diagram of an example, non-limiting system 300 further comprising a composition component 602 and / or a routing component 604 according to one or more embodiments described herein. Repeated descriptions of similar elements utilized in other embodiments described herein are omitted for brevity. In various embodiments, the compiler component 310 (e.g., via the composition component 602 and / or the routing component 604) can utilize a merge-to-route composition and routing approach to generate one or more quantum circuits (e.g., Pauli string simulation quantum circuits) for execution of one or more VQE algorithms (e.g., execution of variational quantum chemistry simulations).

[0067] For example, with each iteration of the VQE algorithm, compiler component 310 (e.g., via composition component 602 and / or routing component 604) can synthesize respective quantum circuits (e.g., Pauli string simulation quantum circuits) to represent respective Pauli strings and can route the current logical-to-physical qubit mappings utilized to enable qubit connectivity for the synthesized quantum circuits. In one or more embodiments, composition component 602 can synthesize a quantum circuit representing one Pauli string from multiple Pauli strings through a series of qubit connection selections. Furthermore, composition component 602 can select each qubit connection (e.g., between logical qubits) based on the effect that previously selected qubit connections have on the mapping of physical qubits to logical qubits. In addition, routing component 604 can alter the position of the logical qubits on the multi-level hierarchical tree architecture based on the qubit connection selections performed by composition component 602. For example, routing component 604 may perform one or more routing operations that define a rearrangement of one or more logical qubits from one node 102 to another node 102 in the tree architecture, thereby moving the logical qubits to one or more nodes 102 with which selected qubit connections can be established (e.g., and thus physical qubit assignments). In various embodiments, the composition of quantum circuits and the execution of routing operations may be performed in combination. For example, the routing operations employed by routing component 604 may modify the logical-to-physical qubit mapping, whereupon the next composition operation (e.g., defining qubit connections) employed by composition component 602 may be selected based on the modified state of the qubit mapping.

[0068] 7 shows a diagram of an exemplary, non-limiting merge-to-route composing and routing technique 700 that may be implemented by the composing component 602 and / or the routing component 604, according to one or more embodiments described herein. Repeated descriptions of similar elements utilized in other embodiments described herein are omitted for brevity. The exemplary merge-to-route composing and routing technique 700 shown in FIG. 7 may illustrate features of the composing component 602 and / or the routing component 604 with respect to an exemplary quantum circuit. In various embodiments, the merge-to-route composing and routing technique performed by the compiler component 310 (e.g., the exemplary merge-to-route composing and routing technique 700, etc.) may be implemented using a quantum processor 308 having qubit connectivity characterized by a multi-level hierarchical tree architecture (e.g., the X-tree architecture 100). For example, layout component 314 and / or mapping component 402 may first generate an initial hierarchical layout of logical-to-physical qubit mappings that map logical qubits that are likely to experience multiple different qubit connections during execution of a VQE algorithm at a central level of the tree architecture (e.g., a central level such as exemplary levels 0 and / or 1 in the fourth exemplary X-tree architecture 100d); thus facilitating merge-to-route composition and routing technique 700 by allowing a variety of quantum circuit synthesis options to be achievable using minimal routing operations.

[0069] As described herein, the same Pauli string can be represented by multiple different Pauli string simulation quantum circuits, each describing a variation scheme of qubit connectivity that can be utilized to achieve quantum computation of the Pauli string. Therefore, for a given Pauli string, multiple quantum circuits may be available for composition. Due to the positioning of high-traffic logical qubits (e.g., qubits likely to experience the greatest amount of qubit connectivity throughout the VQE algorithm) at least within the central level of the tree architecture (e.g., X-tree architecture 100), multiple qubit connection options may be available for selection by composition component 602 to compose a quantum circuit. Thus, composition component 602 can select qubit connections in conjunction with routing operations utilized by routing component 604 to adaptively compose a quantum circuit representing a given Pauli string with minimal mapping overhead.

[0070] The exemplary merge-to-route composition and routing technique 700 shown in FIG. 7 illustrates the composition of an exemplary Pauli string simulation quantum circuit 702 (e.g., as described in a quantum assembly ("QASM") code) from an exemplary input Pauli string 704. For example, the exemplary input Pauli string 704 may consider a quantum computation including four logical qubits (e.g., represented in FIG. 7 by qubit q1, qubit q2, qubit q3, and qubit q4). As shown in FIG. 7, the logical qubits may already be mapped to a multi-level hierarchical tree architecture (e.g., X-tree architecture 100) of a given quantum processor 308. For example, the currently mapped position of the logical qubit may be a residual position from a previous iteration of the VQE algorithm. In another example, the currently mapped position of the logical qubit may be a position established by an initial hierarchical layout according to one or more embodiments described herein. The composition component 602 and / or the routing component 604 can operate in combination with one another to remap logical qubits to nodes 102 that enable qubit connections described by a composed quantum circuit (e.g., exemplary Pauli string simulation quantum circuit 702) that represents a given Pauli string (e.g., exemplary input Pauli string 704).

[0071] As shown in FIG. 7 , combining operations utilized by combining component 602 are indicated with “S” arrows, and routing operations utilized by routing component 604 are indicated with “R” arrows. For clarity, combining and routing operations are shown with respect to an illustration of at least a portion of a multi-level hierarchical tree architecture (e.g., X-tree architecture 100). Additionally, combining and routing operations are shown as QASM code that, when compiled, can describe a combined quantum circuit (e.g., exemplary Pauli string simulation quantum circuit 702). In various embodiments, combining component 602 can utilize one or more combining operations to define selected qubit connections. For example, one or more combining operations can define one or more quantum logic gates between qubits, such as two-qubit gates (e.g., CNOT gates, etc.). In various embodiments, routing component 604 can utilize one or more routing operations to route logical qubits to alter nodes 102 in the tree architecture. For example, a routing operation may route a given logical qubit from an initial node 102 to another node 102 that can establish a qubit connection defined by one or more combining operations. For example, one or more routing operations may define one or more quantum logic gates that adjust the qubit basis state, such as a swap ("SWAP") gate.

[0072] 7, an input Pauli string 704 can be expressed via multiple different qubit connection combinations. The combine component 602 can select a first qubit connection from a first pool of qubit connections included in a quantum circuit variant that can express a given Pauli string (e.g., the input Pauli string 704). Furthermore, the combine component 602 can select the first qubit connection based on the number of routing operations that need to be utilized to enable the first qubit connection on an existing logical-to-physical qubit mapping. For example, for the initial logical-to-physical qubit mapping shown in FIG. 7, if the first pool of qubit connections includes a qubit connection between qubits q2 and q3 and a qubit connection between qubits q3 and q1; combine component 602 can select the qubit q3 and q1 connection because at least qubits q3 and q1 have already been mapped to the node 102 to which they are connected; therefore, the combine operation (e.g., a CNOT gate) utilized by combine component 602 to define the qubit connection does not require an association routing operation to be enabled (e.g., as shown in FIG. 7).

[0073] Additionally, combiner component 602 may select a second qubit connection from a second pool of qubit connections included within a quantum circuit variant having a first qubit connection and capable of expressing a given Pauli string (e.g., input Pauli string 704). Furthermore, combiner component 602 may select the second qubit connection based on the number of routing operations that need to be utilized to enable the second qubit connection on the state of the logical-to-physical qubit mapping after establishment of the first qubit connection. If the first qubit connection can be established without one or more routing operations (e.g., as shown in FIG. 7 ), the state of the logical-to-physical qubit mapping may remain unchanged. For example, if the second pool of qubit connections includes a qubit connection between qubits q0 and q1 and a qubit connection between qubits q0 and q2, combiner component 602 may utilize a combining operation (e.g., a CNOT gate) to define the qubit q0 and q2 connection because at least the qubit q0 and q2 connection can be established using fewer routing operations than the qubit q0 and q1 connection. For example, qubit q2 may be routed to node 102 connected to qubit q's node via a single routing operation, while qubit q1 requires at least two routing operations to be routed to node 102 connected to qubit q's node. As shown in Figure 7, routing component 604 may utilize a single routing operation (e.g., a SWAP gate) to reposition qubit q2 to the root node in the tree architecture connected to qubit q's node 102.

[0074] Additionally, combining component 602 may select a third qubit connection from a third pool of qubit connections included within a quantum circuit variant having first and second qubit connections and capable of expressing a given Pauli string (e.g., input Pauli string 704). Additionally, combining component 602 may select the third qubit connection based on the number of routing operations that need to be utilized to enable the third qubit connection on the state of the logical-to-physical qubit mapping after establishment of the second qubit connection. In the illustrated example, the state of the logical-to-physical map was altered by the last routing operation (e.g., a SWAP gate for qubit q2) utilized by routing component 604. For example, if the third pool of qubit connections includes a qubit connection between qubits q2 and q3 and a qubit connection between qubits q2 and q1, combining component 602 may select a combining operation (e.g., a CNOT gate) that defines the qubit q2 and q1 connection because at least the qubit q2 and q1 connection can be established using fewer routing operations than the qubit q2 and q3 connection. For example, qubit q1 or q2 can be routed to a node 102 connected to the other respective qubit's node 102 via a single routing operation, while multiple routing operations are required to achieve a connection between qubits q2 and q3 without disturbing the first and second qubit connections described above. As shown in Figure 7, routing component 604 can utilize a single routing operation (e.g., a SWAP gate) to route qubit q1 to a root node in a tree architecture connected to qubit q2's node 102.

[0075] Those skilled in the art will recognize that the exemplary merge-to-route combining and routing technique 700 is described herein to illustrate various features of compiler component 310 (e.g., via combining component 602 and / or routing component 604), and that the architecture of the merge-to-route combining and routing technique implemented by compiler component 310 is not so limited. For example, embodiments including more than three qubit connection selections and / or more than four logical qubits are also contemplated. For example, the various features described herein can be scaled to meet one or more demands of a VQE algorithm.

[0076] By adaptively selecting composition operations based on the initial mapping states and / or how the mapping states evolve throughout the circuit composition, composition component 602 can synthesize a quantum circuit that represents a given Pauli string with minimal routing operations (e.g., minimal mapping overhead). Furthermore, mapping high-traffic logical qubits to central levels in a multilevel hierarchical tree architecture in the initial hierarchical layout can increase the number of candidate qubit connections that can be selected with minimal routing operations, according to various embodiments described herein. Moreover, in various embodiments, a multilevel hierarchical tree architecture, such as X-tree architecture 100, can enable the generation of an initial hierarchical layout for a quantum processor 308 with sparse qubit connections and therefore a high yield rate.

[0077] 8 illustrates an exemplary, non-limiting table 800 that can demonstrate the effectiveness of the merge-to-route compositing and routing technique utilized by compiler component 310 for X-Tree architecture 100 according to one or more embodiments described herein. Repetitive descriptions of similar elements utilized in other embodiments described herein are omitted for brevity. Table 800 can demonstrate the effectiveness of various features of compiler component 310 described herein with respect to mapping overhead (e.g., number of routing operations). Column 802 shows the mapping overhead resulting from running a variational quantum chemistry simulation for the illustrated molecules (e.g., hydrogen gas (“H”), lithium hydride (“LiH”), sodium hydride (“NaH”), hydrogen fluoride (“HF”), beryllium hydride (“BeH”), water (“H O”), borane (“BH”), ammonia (“NH”), and methane (“CH”)) using the compiler component 310 described herein on the fourth example X-tree architecture 100d. Column 804 shows the mapping overhead resulting from running the same variational quantum chemistry simulation for the illustrated molecules using a conventional VQE compiler (e.g., the sabre compiler) on the fourth example X-tree architecture 100d. As shown in FIG. 8, the compiler component 310 can execute the VQE algorithm while reducing the mapping overhead by approximately 99% compared to conventional compilers.

[0078] 9 shows a flow diagram of an exemplary, non-limiting computer-implemented method 900 that can map one or more VQE algorithms to a sparse qubit-connected quantum processor 308 with reduced mapping overhead, according to one or more embodiments described herein. Repeated descriptions of similar elements utilized in other embodiments described herein are omitted for brevity.

[0079] At 902, the computer-implemented method 900 may comprise mapping, by the system 300 operatively coupled to the processor 320, one or more VQE algorithms to one or more superconducting quantum processors 308 (e.g., via the layout component 314 and / or the mapping component 402), which may include qubit connectivity characterized by a multi-level hierarchical tree architecture (e.g., the X-tree architecture 100). In various embodiments, the mapping at 902 may include generating a hierarchical layout (e.g., the exemplary hierarchical layout 500) based on an amount of connectivity expected for each of the logical qubits. For example, logical qubits with high connectivity throughout the VQE algorithms (e.g., as evidenced by their various occurrences in the Pauli string) may be mapped to physical qubits positioned at a central level of the tree architecture (e.g., high-traffic qubits may be mapped to the root node).

[0080] At 904, the computer-implemented method 900 may include synthesizing, by the system 300 (e.g., via the synthesis component 602 and / or the routing component 604), a quantum circuit (e.g., a Pauli string simulation quantum circuit) capable of expressing the Pauli string of the VQE algorithm through a series of qubit connection selections, where each qubit connection selection may be based on an effect on the logical-to-physical qubit mapping resulting from a previous qubit connection selection. For example, a first selected qubit connection may be enabled by one or more routing operations. As a result of the achieved routing, establishing the first selected qubit connection may modify the current logical-to-physical qubit mapping (e.g., may modify the mapping initially established in 902 and / or established during a previous iteration of the VQE algorithm). A second qubit connection in the series of selections compiled to synthesize the quantum circuit may be selected based on the modified mapping; thus, taking into account how previous routing operations may affect the routing operation associated with each possible qubit connection candidate. By adaptively selecting qubit connections based on the evolving state of the logical-to-physical qubit mapping, the computer-implemented method 900 can synthesize a quantum circuit that represents a given Pauli string while also minimizing mapping overhead (e.g., as demonstrated by the exemplary merge-to-route composition and routing technique 700 shown in FIG. 7 ).

[0081] 10 shows a flow diagram of an exemplary, non-limiting computer-implemented method 1000 that can map one or more VQE algorithms to a sparse qubit-connected quantum processor 308 with reduced mapping overhead, according to one or more embodiments described herein. Repeated descriptions of similar elements utilized in other embodiments described herein are omitted for brevity.

[0082] At 1002, computer-implemented method 1000 may comprise mapping (e.g., via layout component 314 and / or mapping component 402) by system 300 operably coupled to processor 320 physical qubits of superconducting quantum processor 308 with logical qubits contained within multiple Pauli strings utilized by the VQE algorithm. In various embodiments, superconducting quantum processor 308 may have qubit connectivity characterized by a multi-level hierarchical tree architecture, such as X-tree architecture 100 described herein. In various embodiments, mapping at 902 may comprise generating a hierarchical layout (e.g., exemplary hierarchical layout 500) based on the amount of connectivity expected for each of the logical qubits. For example, logical qubits with high connectivity throughout the VQE algorithm (e.g., as evidenced by their various occurrences in the Pauli strings) may be mapped to physical qubits positioned at a central level of the tree architecture (e.g., high-traffic qubits may be mapped to the root node).

[0083] Furthermore, the computer-implemented method 1000 can synthesize a quantum circuit (e.g., a Pauli string simulation quantum circuit) for each Pauli string, and the quantum circuit can be made executable by the superconducting quantum processor 308 by routing qubits through a logical-to-physical qubit mapping. Various quantum circuits, each with a respective qubit connectivity, can represent the same Pauli string. However, quantum circuit variants can be associated with respective amounts of routing operations to enable execution on the superconducting quantum processor 308. Selecting a quantum circuit variant that requires the least amount of routing to be achieved can reduce the mapping overhead associated with running a VQE algorithm. According to various embodiments described herein, the computer-implemented method 1000 can synthesize a quantum circuit while minimizing mapping overhead by synthesizing the quantum circuit through a series of qubit connection selections, where each qubit connection is adaptively selected based on how the logical-to-physical qubit mapping evolves in response to previous selections (e.g., as demonstrated in the exemplary merge-to-route synthesis and routing technique 700 shown in FIG. 7 ).

[0084] For example, at 1004, computer-implemented method 1000 may include selecting, by system 300 (e.g., via composition component 602), a first qubit connection in the composition of the quantum circuit. The first qubit connection may be a qubit connection that requires a minimum amount of routing operations to achieve compared to other candidate qubit connections in a pool of qubit connections included in one or more of the quantum circuit variants that can represent Pauli strings. In one or more embodiments, computer-implemented method 1000 may include modifying, by system 300 (e.g., via routing component 604), the logical-to-physical qubit mapping by routing the logical qubit to a target node of the multi-level hierarchical tree architecture to enable the first qubit connection. At 1008, computer-implemented method 1000 may then include selecting, by system 300 (e.g., via composition component 602), a second qubit connection in the composition of the quantum circuit. The second qubit connection may be a qubit connection that requires a minimum amount of routing operations to be achieved on the modified logical-to-physical qubit mapping compared to other candidate qubit connections in a pool of qubit connections included in one or more of the quantum circuit variants that further include the first qubit connection and that can represent Pauli strings. Further, computer-implemented method 1000 may repeat steps 1004-1008 until a synthesis of a quantum circuit that represents a given Pauli string is achieved.

[0085] Although this disclosure includes detailed descriptions of cloud computing, it should be understood that implementation of the teachings described herein is not limited to cloud computing environments. Rather, embodiments of the present invention can be implemented in conjunction with any other type of computing environment now known or later developed.

[0086] Cloud computing is a model of service delivery that enables convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, network bandwidth, servers, processing, memory, storage, applications, virtual machines, and services) that can be rapidly provisioned and released with minimal administrative effort or interaction with a service provider. The cloud model can include at least five characteristics, at least three service models, and at least four deployment models.

[0087] The properties are as follows:

[0088] On-Demand Self-Service: Cloud consumers can unilaterally provision computing capacity, such as server time and network storage, automatically as needed, without the need for human interaction with the service provider.

[0089] Wide network access: This capability is available over the network and accessed through standard mechanisms that facilitate use by heterogeneous thin or thick client platforms (eg, cell phones, laptops, and PDAs).

[0090] Resource Pooling: A provider's computing resources are pooled to serve multiple consumers using a multi-tenant model, with different physical and virtual resources dynamically allocated and reallocated according to demand. There is location independence in that consumers generally have no control or knowledge over the exact location of the provided resources, but may be able to specify location at a higher level of abstraction (e.g., country, state, or data center).

[0091] Rapid Elasticity: This capacity can be rapidly and elastically provisioned, in some cases automatically, to rapidly scale out, and rapidly released to rapidly scale in. To the consumer, the capacity available for provisioning often appears unlimited, and can be purchased in any quantity at any point in time.

[0092] Measured Services: Cloud systems automatically control and optimize resource usage by leveraging metering capabilities at a level of abstraction appropriate to the type of service (e.g., storage, processing, bandwidth, and active user accounts). Resource usage can be monitored, controlled, and reported, providing transparency to both providers and consumers of the services utilized.

[0093] The service model is as follows:

[0094] Software as a Service (SaaS): The consumer is offered the ability to use a provider's applications running on a cloud infrastructure. The applications are accessible from a variety of client devices through a thin-client interface such as a web browser (e.g., web-based email). The consumer does not manage or control the underlying cloud infrastructure, including the network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited user-specific application configuration settings.

[0095] Platform as a Service (PaaS): The ability offered to consumers is to deploy applications they create or acquire, written using programming languages ​​and tools supported by the provider, onto a cloud infrastructure. The consumer does not manage or control the underlying cloud infrastructure, including networks, servers, operating systems, or storage, but does control the deployed applications and, in some cases, the application hosting environment configuration.

[0096] Infrastructure as a Service (IaaS): The ability offered to consumers is to provision processing, storage, network, and other basic computing resources, on which they can deploy and run any software, which may include operating systems and applications. The consumer does not manage or control the underlying cloud infrastructure, but does control the operating systems, storage, deployed applications, and possibly limited control over selected networking components (e.g., host firewalls).

[0097] The deployment model is as follows:

[0098] Private Cloud: This cloud infrastructure operates solely for an organization. It may be managed by that organization or a third party and may exist on-premise or off-premise.

[0099] Community Cloud: This cloud infrastructure is shared by several organizations and supports a specific community with shared concerns (e.g., mission, security requirements, policies and compliance considerations). It may be managed by those organizations or a third party and may exist on-premises or off-premises.

[0100] Public Cloud: This cloud infrastructure is made available to the general public or large industry groups and is owned by an organization that sells cloud services.

[0101] Hybrid Cloud: This cloud infrastructure is a composite of two or more clouds (private, community, or public) that remain distinct entities but are bound together by standard or proprietary technologies that allow for data and application portability (e.g., cloud bursting for load balancing between clouds).

[0102] Cloud computing environments are service-oriented with a focus on statelessness, low coupling, modularity, and semantic interoperability. At the core of cloud computing is an infrastructure that includes a network of interconnected nodes.

[0103] 11 , an exemplary cloud computing environment 1100 is shown. As shown, the cloud computing environment 1100 comprises one or more cloud computing nodes 1102 with which local computing devices used by cloud consumers, such as, for example, a personal digital assistant (PDA) or mobile phone 1104, a desktop computer 1106, a laptop computer 1108, and / or an automobile computer system 1110, may communicate. The nodes 1102 may communicate with each other. They may be physically or virtually grouped in one or more networks (not shown), such as a private cloud, a community cloud, a public cloud, or a hybrid cloud, or combinations thereof, as described hereinabove. This enables the cloud computing environment 1100 to provide infrastructure, a platform, and / or software as a service for which the cloud consumer does not need to maintain resources on their local computing device. It will be understood that the types of computing devices 1104-1110 shown in FIG. 11 are intended to be illustrative only, and that computing node 1102 and cloud computing environment 1100 can communicate with any type of computerized device via any type of network and / or network-addressable connection (e.g., using a web browser).

[0104] Referring now to Figure 12, a set of functional abstraction layers provided by cloud computing environment 1100 (Figure 11) is shown. Repetitive descriptions of similar elements utilized in other embodiments described herein will be omitted for brevity. It should be understood in advance that the components, layers, and functions shown in Figure 12 are intended to be merely exemplary, and embodiments of the present invention are not limited thereto. As shown, the following layers and corresponding functions are provided:

[0105] Hardware and software layer 1202 comprises hardware and software components. Examples of hardware components include: mainframe 1204; RISC (reduced instruction set computer) architecture-based server 1206; server 1208; blade server 1210; storage device 1212; and network and networking components 1214. In some embodiments, software components include network application server software 1216 and database software 1218.

[0106] The virtualization layer 1220 provides an abstraction layer over which the following examples of virtual entities can be provided: virtual servers 1222; virtual storage 1224; virtual networks 1226, including virtual private networks; virtual applications and operating systems 1228; and virtual clients 1230.

[0107] In one example, management layer 1232 may provide the functions described below. Resource provisioning 1234 provides dynamic procurement of computing and other resources utilized to execute tasks within the cloud computing environment. Metering and pricing 1236 provides cost tracking as resources are utilized within the cloud computing environment and billing or invoicing for the consumption of these resources. In one example, these resources may include application software licenses. Security provides identity verification for cloud consumers and tasks, as well as protection for data and other resources. User portal 1238 provides access to the cloud computing environment for consumers and system administrators. Service level management 1240 provides cloud computing resource allocation and management to ensure required service levels are met. Service level agreement (SLA) planning and fulfillment 1242 provides advance arrangements and procurement of cloud computing resources where future requirements are anticipated according to SLAs.

[0108] Workload tier 1244 provides examples of functionality for which a cloud computing environment may be utilized. Examples of workloads and functionality that may be provided from this tier include: mapping and navigation 1246; software development and lifecycle management 1248; virtual classroom instruction delivery 1250; data analytics processing 1252; transaction processing 1254; and VQE algorithm processing 1256. Various embodiments of the present invention may utilize the cloud computing environment described with reference to Figures 11 and 12 to map VQE algorithms to one or more quantum processors 308 having a multi-level hierarchical tree architecture, such as an X-tree architecture.

[0109] The present invention may be a system, method, and / or computer program product at any possible level of technical detail of integration. The computer program product may include a computer-readable storage medium (or media) having computer-readable program instructions for causing a processor to perform aspects of the present invention. The computer-readable storage medium may be a tangible device capable of holding and storing instructions for use by an instruction-execution device. The computer-readable storage medium may be, for example, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of computer-readable storage media includes the following: portable computer diskettes, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disk read-only memory (CD-ROM), digital versatile disk (DVD), memory stick, floppy disk, mechanically encoded devices such as punch cards or raised structures in grooves that record instructions, and any suitable combination of the foregoing. Computer-readable storage media, as used herein, should not be construed as a transitory signal per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission medium (e.g., light pulses passing through a fiber optic cable), or electrical signals transmitted through wires.

[0110] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device or to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network may include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and transfers the computer-readable program instructions to a computer-readable storage medium in the respective computing / processing device for storage.

[0111] The computer-readable program instructions for carrying out the operations of the present invention may be either assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, configuration data for an integrated circuit, or source or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk®, C++, etc., and procedural programming languages ​​such as the “C” programming language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be to an external computer (e.g., via the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA) can execute computer readable program instructions to personalize the electronic circuitry by utilizing state information of the computer readable program instructions to perform aspects of the present invention.

[0112] Aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0113] These computer-readable program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus to produce a machine, whereby the instructions, executed by the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in one or more blocks of the flowcharts and / or block diagrams. These computer-readable program instructions can also be stored on a computer-readable storage medium, whereby the instructions can instruct a computer, programmable data processing apparatus, and / or other device to function in a particular manner, whereby the computer-readable storage medium having the instructions stored thereon comprises an article of manufacture including instructions that implement aspects of the functions / acts specified in one or more blocks of the flowcharts and / or block diagrams.

[0114] The computer-readable program instructions may also be loaded into a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be executed on the computer, other programmable apparatus, or other device to generate a computer-implemented process, whereby the instructions executing on the computer, other programmable apparatus, or other device implement the functions / operations specified in one or more blocks of the flowcharts and / or block diagrams.

[0115] The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of instructions, including one or more executable instructions, that implements the specified logical function(s). In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending on the functionality involved. It should also be noted that each block of the block diagrams and / or flowchart diagrams, and combinations of blocks in the block diagrams and / or flowchart diagrams, may be implemented by a dedicated hardware-based system that performs the specified functions or operations or executes a combination of dedicated hardware and computer instructions.

[0116] To provide additional context for the various embodiments described herein, Figure 13 and the following discussion are intended to provide a general description of a suitable computing environment 1300 in which various embodiments of the embodiments described herein may be implemented. While the embodiments have been described above in the general context of computer-executable instructions that may be executed on one or more computers, those skilled in the art will recognize that the embodiments may also be implemented in combination with other program modules and / or as a combination of hardware and software.

[0117] Generally, program modules include routines, programs, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Moreover, those skilled in the art will appreciate that the methods of the present invention can be practiced with other computer system configurations, including single-processor or multi-processor computer systems, minicomputers, mainframe computers, Internet of Things ("IoT") devices, distributed computing systems, as well as personal computers, handheld computing devices, microprocessor-based or programmable consumer electronics, etc., each of which can be operatively coupled to one or more associated devices.

[0118] The illustrated embodiments of the embodiments herein may also be practiced in distributed computing environments where certain tasks are performed by remote processing devices linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote memory storage devices. For example, in one or more embodiments, computer-executable components may execute from a memory that may include or be comprised of one or more distributed memory units. As used herein, the terms "memory" and "memory unit" are interchangeable. Furthermore, one or more embodiments described herein may execute code of computer-executable components in a distributed manner, e.g., multiple processors working in combination or concertedly to execute code from one or more distributed memory units. As used herein, the term "memory" may encompass a single memory or memory unit in one location or multiple memories or memory units in one or more locations.

[0119] A computing device typically includes a variety of media, which may include computer-readable storage media, machine-readable storage media, and / or communication media, and the two terms are used interchangeably herein as follows. A computer-readable storage medium or machine-readable storage medium may be any available storage medium that can be accessed by a computer and includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, a computer-readable storage medium or machine-readable storage medium may be implemented in connection with any method or technology for storage of information, such as computer-readable or machine-readable instructions, program modules, structured or unstructured data, etc.

[0120] A computer-readable storage medium may include, but is not limited to, random access memory ("RAM"), read-only memory ("ROM"), electrically erasable programmable read-only memory ("EEPROM"), flash memory or other memory technology, compact disc read-only memory ("CD-ROM"), digital versatile disc ("DVD"), Blu-ray disc ("BD") or other optical disc storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device, solid-state drive or other solid-state storage device, or other tangible and / or non-transitory medium that may be used to store the desired information. In this regard, the terms "tangible" or "non-transitory" herein as applied to storage, memory, or computer-readable medium should be understood as qualifiers to exclude only the propagating transitory signal per se, and do not waive any right to all standard storage, memory, or computer-readable medium that is not merely the propagating transitory signal per se.

[0121] The computer-readable storage medium may be accessed by one or more local or remote computing devices for various operations on the information stored by the medium, for example, via access requests, queries, or other data retrieval protocols.

[0122] Communication media typically embodies computer-readable instructions, data structures, program modules, or other structured or unstructured data in a modulated data signal, such as a carrier wave or other transport mechanism, and includes any information delivery or transport medium. The term "modulated data signal" or signal refers to a signal that has one or more of its characteristics set or changed in such a manner as to encode information in one or more signals. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media.

[0123] 13 , an exemplary environment 1300 for implementing various embodiments of the aspects described herein includes a computer 1302 having a processing unit 1304, a system memory 1306, and a system bus 1308. The system bus 1308 couples system components including, but not limited to, the system memory 1306 to the processing unit 1304. The processing unit 1304 can be any of a variety of commercially available processors. Dual processors and other multi-processor architectures can also be utilized as the processing unit 1304.

[0124] The system bus 1308 may be any of several types of bus structures that may be further interconnected to a memory bus, a peripheral bus, and a local bus (with or without a memory controller) using any of a variety of commercially available bus architectures. The system memory 1306 includes ROM 1310 and RAM 1312. The basic input / output system ("BIOS") may be stored in non-volatile memory such as ROM, erasable programmable read-only memory ("EPROM"), or EEPROM, which contains the basic routines that the BIOS helps to transfer information between elements within the computer 1302, such as during start-up. The RAM 1312 may also include high-speed RAM such as static RAM for caching data.

[0125] The computer 1302 further comprises an internal hard disk drive (“HDD”) 1314 (e.g., EIDE, SATA), one or more external storage devices 1316 (e.g., a magnetic floppy disk drive (“FDD”) 1316, a memory stick or flash drive reader, a memory card reader, etc.), and an optical disk drive 1320 (e.g., capable of reading from or writing to CD-ROM disks, DVDs, BDs, etc.). While the internal HDD 1314 is shown as located within the computer 1302, the internal HDD 1314 could also be configured for external use in a suitable chassis (not shown). Additionally, although not shown in the environment 1300, a solid state drive (“SSD”) could be used in addition to or in place of the HDD 1314. HDD 1314, external storage device 1316, and optical disk drive 1320 may be connected to system bus 1308 by HDD interface 1324, external storage interface 1326, and optical drive interface 1328, respectively. Interface 1324 for external drive implementations may include at least one or both of Universal Serial Bus ("USB") and Institute of Electrical and Electronics Engineers ("IEEE") 1394 interface technologies. Other external drive connection technologies are within the contemplation of the embodiments described herein.

[0126] The drives and their associated computer-readable storage media provide non-volatile storage of data, data structures, computer-executable instructions, etc. For the computer 1302, the drives and storage media accommodate the storage of any data in a suitable digital format. While the above description of computer-readable storage media refers to each type of storage device, it should be understood by those skilled in the art that other types of computer-readable storage media, whether now existing or developed in the future, may be used in the exemplary operating environment, and further that any such storage media may include computer-executable instructions for performing the methods described herein.

[0127] A number of program modules may be stored in the drives and RAM 1312, including an operating system 1330, one or more application programs 1332, other program modules 1334, and program data 1336. All or portions of the operating system, applications, modules, and / or data may also be cached in RAM 1312. The systems and methods described herein may be implemented using various commercially available operating systems or combinations of operating systems.

[0128] Computer 1302 may optionally include emulation technology. For example, a hypervisor (not shown) or other intermediary may emulate a hardware environment for operating system 1330, where the emulated hardware may optionally differ from the hardware shown in FIG. 13 . In one such embodiment, operating system 1330 may comprise one virtual machine (“VM”) of multiple VMs hosted on computer 1302. Additionally, operating system 1330 may provide a runtime environment, such as the Java Runtime Environment or the .NET Framework, for application 1332. A runtime environment is a consistent execution environment that allows application 1332 to run on any operating system that includes the runtime environment. Similarly, operating system 1330 may support containers, where application 1332 may be in the form of a container, which is a lightweight, standalone executable package of software that includes, for example, code, runtime, system tools, system libraries, and settings for the application.

[0129] Additionally, computer 1302 can be enabled with a security module such as a trusted processing module ("TPM"). For example, with a TPM, a boot component hashes the chronologically succeeding boot component and waits for the resulting match to a protected value before loading the next boot component. This process can occur at any layer in the code execution stack of computer 1302, for example, applied at the application execution level or the operating system ("OS") kernel level, thereby enabling security at any level of code execution.

[0130] A user can enter commands and information into the computer 1302 through one or more wired / wireless input devices, such as a keyboard 1338, a touch screen 1340, and a pointing device such as a mouse 1342. Other input devices (not shown) can include a microphone, an infrared ("IR") remote control, a radio frequency ("RF") remote control, or other remote control, a joystick, a virtual reality controller and / or headset, a game pad, a stylus pen, an image input device such as a camera, a gesture sensor input device, a vision movement sensor input device, an expression or face detection device, a biometric input device such as a fingerprint or iris scanner, etc. These and other input devices are often connected to the processing unit 1304 through an input device interface 1344, which can be coupled to the system bus 1308, but can also be connected by other interfaces, such as a parallel port, an IEEE 1394 serial port, a game port, a USB port, an IR interface, a BLUETOOTH interface, etc.

[0131] A monitor 1346 or other type of display device may also be connected to the system bus 1308 via an interface, such as a video adapter 1348. In addition to the monitor 1346, computers typically include other peripheral output devices (not shown), such as speakers, printers, etc.

[0132] The computer 1302 may operate in a networked environment using logical connections via wired and / or wireless communications to one or more remote computers, such as a remote computer 1350. The remote computer 1350 can be a workstation, a server computer, a router, a personal computer, a portable computer, a microprocessor-based entertainment device, a peer device, or other common network node, and typically includes many or all of the elements described relative to the computer 1302, although for simplicity, only a memory / storage device 1352 is shown. The logical connections shown include wired / wireless connectivity to a local area network (“LAN”) 1354 and / or larger networks, e.g., a wide area network (“WAN”) 1356. Such LAN and WAN networking environments are commonplace in offices and businesses and facilitate enterprise-wide computer networks, such as intranets, all of which may connect to a global communications network, e.g., the Internet.

[0133] When used in a LAN networking environment, the computer 1302 may be connected to the local network 1354 through a wired and / or wireless communication network interface or adapter 1358. The adapter 1358 may facilitate wired or wireless communication to the LAN 1354, which may also include a wireless access point (“AP”) disposed thereon for communicating with the adapter 1358 in a wireless mode.

[0134] When used in a WAN networking environment, the computer 1302 may include a modem 1360 or may be connected to a communications server on the WAN 1356 via other means for establishing communications over the WAN 1356, such as via the Internet. The modem 1360, which may be internal or external and a wired or wireless device, may be connected to the system bus 1308 via the input device interface 1344. In a networked environment, program modules depicted for the computer 1302, or portions thereof, may be stored in the remote memory / storage device 1352. It will be appreciated that the network connections shown are examples and other means of establishing a communications link between computers may be used.

[0135] When used in either a LAN or WAN networking environment, computer 1302 may access a cloud storage system or other network-based storage system in addition to, or instead of, external storage device 1316, as described above. Generally, the connection between computer 1302 and the cloud storage system may be established over LAN 1354 or WAN 1356, for example, by adapter 1358 or modem 1360, respectively. Upon connecting computer 1302 to an associated cloud storage system, external storage interface 1326, with the aid of adapter 1358 and / or modem 1360, can manage the storage provided by the cloud storage system as it manages other types of external storage. For example, external storage interface 1326 can be configured to provide access to cloud storage sources as if those sources were physically connected to computer 1302.

[0136] The computer 1302 may be operable to communicate with any wireless device or entity operably arranged in wireless communication, such as a printer, a scanner, a desktop and / or portable computer, a personal digital assistant, a communications satellite, any equipment or location associated with a wirelessly detectable tag (e.g., a kiosk, a newsstand, a store shelf, etc.), and a telephone. This may include Wireless Fidelity ("Wi-Fi") and BLUETOOTH wireless technologies. Thus, communication may be in a predefined structure, similar to a traditional network, or may simply be ad-hoc communication between at least two devices.

[0137] What has been described above includes merely examples of systems, computer program products, and computer-implemented methods. Of course, for purposes of describing the present disclosure, it is not possible to describe every conceivable combination of components, products, and / or computer-implemented methods, and those skilled in the art will recognize that many further combinations and permutations of the present disclosure are possible. Furthermore, to the extent that terms such as "includes," "has," "possesse," and the like are used in the detailed description, claims, appendices, and drawings, such terms are intended to be inclusive in a manner similar to the term "comprising," as "comprising" is interpreted when used as a transitional term in a claim. The description of various embodiments has been presented for illustrative purposes and is not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein has been selected to best explain the principles, practical applications, or technical improvements of the embodiments over those found in the marketplace, or to enable others skilled in the art to understand the embodiments disclosed herein. According to this specification, the following items are also disclosed. [Item 1] a superconducting quantum processor topology that utilizes an X-tree architecture to define connections between superconducting qubits; wherein the total number of connections is less than the total number of superconducting qubits. [Item 2] Item 10. The apparatus of item 1, wherein the superconducting qubit is represented in the X-tree architecture as at least one member selected from the group consisting of a root node and a leaf node. [Item 3] Item 3. The apparatus of item 2, wherein the X-tree architecture is segmented into a plurality of levels, and the connection between the root node and the leaf node spans between two levels from the plurality of levels. [Item 4] 4. The apparatus of claim 2, wherein the superconducting quantum processor topology includes five superconducting qubits, a first superconducting qubit from the five superconducting qubits represented as the root node in a first level of the X-tree architecture, and four other superconducting qubits from the five superconducting qubits represented as leaf nodes in a second level of the X-tree architecture. [Item 5] memory for storing computer-executable components; and a processor operatively coupled to the memory for executing the computer-executable components stored in the memory; the computer-executable components comprising: A compiler component that maps variational quantum eigensolver algorithms to superconducting quantum processors containing qubit connectivity characterized by a multilevel hierarchical tree architecture. A system having: [Item 6] a layout component that generates an initial hierarchical layout that maps physical qubits of the superconducting quantum processor with logical qubits contained within a plurality of Pauli strings utilized by the variational quantum eigensolver algorithm; Item 6. The system of item 5, further comprising: [Item 7] 7. The system of any one of items 5 to 6, wherein the multi-level hierarchical tree architecture includes a root node connected to leaf nodes across different levels, the root node being connected to multiple leaf nodes. [Item 8] 8. The system according to any one of items 5 to 7, wherein the multi-level hierarchical tree architecture is an X-tree architecture. [Item 9] The variational quantum eigensolver algorithm defines a quantum computation executable by the superconducting quantum processor, and the system: a mapping component that determines the number of quantum computations that utilize a first logical qubit from the logical qubits and the number of quantum computations that utilize a second logical qubit from the logical qubits. The system according to item 6 or item 7 or 8 dependent on item 6, further comprising: [Item 10] 10. The system of claim 9, wherein the first logical qubit is mapped to a more central level of the multilevel hierarchical tree architecture in the initial hierarchical layout than the second logical qubit based on the first logical qubit being utilized in more quantum computations than the second logical qubit. [Item 11] a synthesis component that synthesizes a quantum circuit that represents one Pauli string from the plurality of Pauli strings through a series of qubit connection selections, where the synthesis component selects qubit connections between the logical qubits based on the effect of previously selected qubit connections on the mapping of the physical qubits with the logical qubits; and a routing component that alters the position of logical qubits on the multi-level hierarchical tree architecture based on the qubit connections. The system according to item 6 or items 7 to 10 dependent on item 6, further comprising: [Item 12] 12. The system of claim 11, wherein synthesizing the quantum circuit and modifying the positions of the logical qubits are performed in combination with each other. [Item 13] mapping, by a system operatively coupled to the processor, a variational quantum eigensolver algorithm onto a superconducting quantum processor including qubit connectivity characterized by a multilevel hierarchical tree architecture. A computer-implemented method comprising: [Item 14] generating, by the system, an initial hierarchical layout that maps physical qubits of the superconducting quantum processor with logical qubits contained within a plurality of Pauli strings utilized by the variational quantum eigensolver algorithm; Item 14. The computer-implemented method of item 13, further comprising: [Item 15] 15. The computer-implemented method of any one of items 13 to 14, wherein the multi-level hierarchical tree architecture includes a root node connected to leaf nodes across different levels, the root node being connected to multiple leaf nodes. [Item 16] 16. The computer-implemented method according to any one of items 13 to 15, wherein the multi-level hierarchical tree architecture is an X-tree architecture. [Item 17] The variational quantum eigensolver algorithm defines a quantum computation executable by the superconducting quantum processor, and the computer-implemented method comprises: determining, by the system, a number of quantum computations that utilize a first logical qubit from the logical qubits and a number of quantum computations that utilize a second logical qubit from the logical qubits; Item 14 or Item 15 or 16, which is dependent on Item 14, further comprising: [Item 18] Item 18. The computer-implemented method of item 17, wherein the first logical qubit is mapped to a more central level of the multilevel hierarchical tree architecture in the initial hierarchical layout than the second logical qubit based on the first logical qubit being utilized in more quantum computations than the second logical qubit. [Item 19] synthesizing, by the system, a quantum circuit that represents one Pauli string from the plurality of Pauli strings through a series of qubit connection selections, where the selection from the series of qubit connection selections is based on the effect of previously selected qubit connections on the mapping of the physical qubits with the logical qubits; and modifying, by the system, the positions of the logical qubits on the multi-level hierarchical tree architecture based on the selection. The computer-implemented method according to item 14 or items 15 to 18 dependent on item 14, further comprising: [Item 20] 20. The computer-implemented method of claim 19, wherein the steps of synthesizing the quantum circuit and performing the modification of the positions of the logical qubits are performed in combination with each other.

Claims

1. A superconducting quantum processor topology that utilizes an X-tree architecture to define hardware connections between physical superconducting qubits. wherein the total number of connections is less than the total number of superconducting qubits.

2. 10. The apparatus of claim 1, wherein the superconducting qubit is represented in the X-tree architecture as at least one member selected from the group consisting of a root node and a leaf node.

3. The apparatus of claim 2 , wherein the X-tree architecture is segmented into a plurality of levels, and the connection between the root node and the leaf node spans between two levels from the plurality of levels.

4. 4. The apparatus of claim 2, wherein the superconducting quantum processor topology includes five superconducting qubits, a first superconducting qubit from the five superconducting qubits being represented as the root node in a first level of the X-tree architecture, and four other superconducting qubits from the five superconducting qubits being represented as leaf nodes in a second level of the X-tree architecture.

5. memory for storing computer-executable components; and a processor operatively coupled to the memory for executing the computer-executable components stored in the memory; the computer-executable components comprising: A compiler component that maps a variational quantum eigensolver algorithm to a superconducting quantum processor that includes qubit connectivity characterized by a multilevel hierarchical tree architecture to define hardware-implemented connections between physical superconducting qubits. A system having:

6. a layout component that generates an initial hierarchical layout that maps physical qubits of the superconducting quantum processor with logical qubits contained within a plurality of Pauli strings utilized by the variational quantum eigensolver algorithm; The system of claim 5 further comprising:

7. The system of any one of claims 5 to 6, wherein the multi-level hierarchical tree architecture includes a root node connected to leaf nodes across different levels, the root node being connected to multiple leaf nodes.

8. The system according to any one of claims 5 to 7, wherein the multi-level hierarchical tree architecture is an X-tree architecture.

9. The variational quantum eigensolver algorithm defines a quantum computation executable by the superconducting quantum processor, and the system: a mapping component that determines a number of quantum computations that utilize a first logical qubit from the logical qubits and a number of quantum computations that utilize a second logical qubit from the logical qubits. The system according to claim 6 or claim 7 or 8 depending on claim 6, further comprising:

10. 10. The system of claim 9, wherein the first logical qubit is mapped to a more central level of the multilevel hierarchical tree architecture in the initial hierarchical layout than the second logical qubit on the basis that the first logical qubit is utilized in more quantum computations than the second logical qubit.

11. a synthesis component that synthesizes a quantum circuit that represents one Pauli string from the plurality of Pauli strings through a series of qubit connection selections, where the synthesis component selects qubit connections between the logical qubits based on the effect of previously selected qubit connections on the mapping of the physical qubits with the logical qubits; and a routing component that alters the position of logical qubits on the multi-level hierarchical tree architecture based on the qubit connections. The system according to claim 6 or any of claims 7 to 10 depending on claim 6, further comprising:

12. 12. The system of claim 11, wherein the combining of the quantum circuits and the modifying of the positions of the logical qubits are performed in combination with one another.

13. mapping, by a system operatively coupled to the processor, the variational quantum eigensolver algorithm onto a superconducting quantum processor including qubit connectivity characterized by a multilevel hierarchical tree architecture to define hardware-implemented connections between physical superconducting qubits. A computer-implemented method comprising:

14. generating, by the system, an initial hierarchical layout that maps physical qubits of the superconducting quantum processor with logical qubits contained within a plurality of Pauli strings utilized by the variational quantum eigensolver algorithm; The computer-implemented method of claim 13 further comprising:

15. 15. The computer-implemented method of claim 13, wherein the multi-level hierarchical tree architecture includes a root node connected to leaf nodes across different levels, the root node being connected to multiple leaf nodes.

16. The computer-implemented method of any one of claims 13 to 15, wherein the multi-level hierarchical tree architecture is an X-tree architecture.

17. The variational quantum eigensolver algorithm defines a quantum computation executable by the superconducting quantum processor, and the computer-implemented method comprises: determining, by the system, a number of quantum computations that utilize a first logical qubit from the logical qubits and a number of quantum computations that utilize a second logical qubit from the logical qubits; 17. The computer-implemented method of claim 14 or claim 15 or 16 depending from claim 14, further comprising:

18. 18. The computer-implemented method of claim 17, wherein the first logical qubit is mapped to a more central level of the multilevel hierarchical tree architecture in the initial hierarchical layout than the second logical qubit on the basis that the first logical qubit is utilized in more quantum computations than the second logical qubit.

19. synthesizing, by the system, a quantum circuit that represents a Pauli string from the plurality of Pauli strings through a series of qubit connection selections, where the selection from the series of qubit connection selections is based on the effect of previously selected qubit connections on the mapping of the physical qubits with the logical qubits; and modifying, by the system, the positions of the logical qubits on the multi-level hierarchical tree architecture based on the selection. The computer-implemented method of claim 14 or any of claims 15 to 18 depending on claim 14, further comprising:

20. 20. The computer-implemented method of claim 19, wherein the steps of synthesizing the quantum circuit and performing the modification of the positions of the logical qubits are performed in combination with one another.

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