ABSTRACT Hybrid quantum–classical architectures demonstrate significant potential for efficiently solving complex physical models. This study focuses on developing and implementing a hybrid quantum–classical algorithm to solve the Muskat–Leverett model by reformulating it as a system of linear equations. By expressing the Muskat–Leverett model in matrix form , we enable the application of quantum algorithms. We leverage classical computational platforms (CPU and GPU) alongside quantum computing to efficiently solve the model, achieving competitive accuracy and demonstrating potential for scalability compared to traditional methods. The Harrow–Hassidim–Lloyd algorithm and the variational quantum linear solver were utilised to design quantum circuits and variational ansatz. The study evaluates quantum solutions with classical optimisation, variational methods, fully classical solutions on graphical processors and purely quantum solutions. Experimental results show that the hybrid architecture, utilising cuQuantum and CUDA‐Q, achieves up to 6.42× faster execution compared to CPU implementations and provides a comparable speedup to GPU‐based solvers. When applied for large‐scale problems, the hybrid approach is also ∼10× faster than standard quantum simulators. Key factors, such as qubits, optimisers and cost functions, were analysed to determine optimal parameters. These results highlight the advantages of hybrid architecture in accelerating and optimising numerical solutions for complex physical models.
ABSTRACT Hybrid quantum–classical architectures demonstrate significant potential for efficiently solving complex physical models. This study focuses on developing and implementing a hybrid quantum–classical algorithm to solve the Muskat–Leverett model by reformulating it as a system of linear equations. By expressing the Muskat–Leverett model in matrix form , we enable the application of quantum algorithms. We leverage classical computational platforms (CPU and GPU) alongside quantum computing to efficiently solve the model, achieving competitive accuracy and demonstrating potential for scalability compared to traditional methods. The Harrow–Hassidim–Lloyd algorithm and the variational quantum linear solver were utilised to design quantum circuits and variational ansatz. The study evaluates quantum solutions with classical optimisation, variational methods, fully classical solutions on graphical processors and purely quantum solutions. Experimental results show that the hybrid architecture, utilising cuQuantum and CUDA‐Q, achieves up to 6.42× faster execution compared to CPU implementations and provides a comparable speedup to GPU‐based solvers. When applied for large‐scale problems, the hybrid approach is also ∼10× faster than standard quantum simulators. Key factors, such as qubits, optimisers and cost functions, were analysed to determine optimal parameters. These results highlight the advantages of hybrid architecture in accelerating and optimising numerical solutions for complex physical models.
Efficiently solving large-scale sparse linear systems poses a significant challenge in computational science, especially in fields such as physics, engineering, machine learning, and finance. Traditional classical algorithms face scalability issues as the size of these systems increases, leading to performance degradation. On the other hand, quantum algorithms, like the Harrow-Hassidim-Lloyd (HHL) algorithm, offer exponential speedups for solving linear systems, yet they are constrained by the current state of quantum hardware and sensitivity to matrix condition numbers. This paper introduces a hybrid classical-quantum algorithm that combines CUDA-accelerated preconditioning techniques with the HHL algorithm to solve sparse linear systems more efficiently. The classical GPU parallelism is utilised to preprocess and precondition the matrix, reducing its condition number, while quantum computing is employed to solve the preconditioned system using the HHL algorithm. Additionally, the algorithm integrates machine learning models, particularly reinforcement learning, to dynamically optimise system parameters, such as block sizes and preconditioning stratgies, based on real-time performance data. Our experimental results show that the proposed approach not only surpasses traditional methods in speed and scalability but also mitigates some of the inherent limitations of quantum algorithms. This work pushes the boundaries of efficient computing and provides a foundation for future advancements in hybrid computational frameworks.
Recent advancements in quantum computing provide opportunities to address the challenges of computational resource limitations in computational fluid dynamics (CFD). This work presents a hybrid quantum-classical CFD framework that leverages quantum linear algorithms to practical flow simulations. By transforming nonlinear fluid dynamics problems into linear systems, the framework employs quantum linear algorithms to compute solutions, effectively integrating quantum and classical computing approaches. Furthermore, this framework employs subspace methods to map the original large-scale linear systems to small ones solved by quantum linear algorithms, thereby enabling the solution of large-scale problems using the currently limited quantum resources. We applied the famous Harrow–Hassidim–Lloyd (HHL) algorithm and variational quantum linear solver to simulate complex flows, including unsteady flows around a cylinder, simulation of an aircraft with turbulence model, and combustion flows. The performance and quantum resource consumption of these algorithms were evaluated in practical flow scenarios, demonstrating their effectiveness with an average relative error lower than 0.001%. We conducted quantum resource and convergence analyses to adapt this framework for use with near-term quantum computers. Our framework supports simulations of up to 9.4 × 106 grid cells, marking a significant advancement from previous quantum approaches limited to simple flows. This paper not only offers a way for employing quantum linear algorithms in solving complex flow problems but also provides insights into optimizing quantum algorithms for CFD applications, pushing forward the practical utilization of quantum CFD.
Quantum computing has emerged as a transformative paradigm capable of solving complex computational problems that are intractable for classical computers. Central to the advancement of this technology is the development of efficient quantum algorithms and high fidelity simulations that enable the design, testing, and optimization of quantum solutions before deployment on physical hardware. This study focuses on the design and implementation of quantum algorithms tailored for solving a variety of quantum problems, including quantum chemistry, optimization, and cryptography. Using state of the art simulation platforms such as Qiskit, Cirq, and Pennylane, algorithm performance was evaluated in terms of accuracy, execution time, scalability, and resilience to noise. Benchmarks demonstrate that algorithms such as the Variational Quantum Eigensolver (VQE) and Quantum Approximate Optimization Algorithm (QAOA) achieve significant speedups in problem specific domains, while hybrid quantum–classical methods provide robust pathways for near term quantum advantage. Simulation results reveal that algorithmic efficiency can be significantly improved through optimized circuit depth, qubit connectivity mapping, and advanced error mitigation techniques. The findings highlight the potential of simulation driven quantum algorithm development in accelerating the practical realization of quantum computing applications across disciplines such as materials discovery, molecular modeling, secure communications, and complex optimization tasks.
One of the primary focuses in the rapidly changing scenery of quantum computing is one of the most promising methodologies for transgressing the current feat of quantum technologies: a better mix of quantum and classical paradigms of computations.This paper suggests a new hybrid quantum-classical processor architecture that augments the computational speed and enhances efficiency by utilizing powers emanating from the quantum and classical processing units.The architecture proposed in the study incorporates quantum processing units with classical processing units, with CPUs interfaced tightly to support dynamic task allocation with a view toward computational requirements.Hybrid processor design caters to the performance of quantum algorithms that usually involve classical preprocessing and postprocessing, such as the Variational Quantum Eigensolver and Quantum Approximate Optimization Algorithm.These algorithms are essential for any complicated optimization, the simulation of quantum systems, and applications in machine learning.We provide an insightful processor architecture design, understanding the communication protocol details between QPU and CPU, the scheduling mechanism for hybrid tasks, and the optimization techniques employed to minimize data transfer overhead while maximizing computational throughput.A lot of these implementation challenges, like quantum error correction, managing the coherence time, and classical-quantum data conversion, are something that innovations in hardware design and software algorithms can achieve.In this paper, the performance of the hybrid processor is, for the first time, fully benchmarked based on simulation and experimental setups.Resultsshow that this hybrid approach outperforms standalone quantum and classical processors on specific computational tasks by ten times in optimization problems and five times for machine learning.These include case studies showing that for some problems, the processor can solve real-world problems much more efficiently than any existing quantum or classical system.Such case studies include quantum chemistry simulations, cryptographic tasks, and training machine learning models.We turn to the scalability and flexibility of the hybrid processor to extend the horizon of these case studies and to bridge the gap between the current quantum computing capabilities and the race toward fully functional quantum computers.This new hybrid quantum-classical processor architecture makes significant progress in quantum computing by providing a pragmatic, workable solution for harnessing quantum mechanics but using the maturity of classical computing.The results show how to proceed with the research involving the hybrid system and the many potential applications of such systems across optimization, cryptography, and artificial intelligence.This study is significant as it offers a practical approach to overcoming the limitations of current quantum and classical processors, providing a pathway to more efficient and scalable computational solutions.
Quantum chemistry and materials science are among the most promising areas for demonstrating algorithmic quantum advantage and quantum utility due to their inherent quantum mechanical nature. Still, large-scale simulations of quantum circuits are essential for determining the problem size at which quantum solutions outperform classical methods. In this work, we present a novel hybrid simulation approach, forming a hybrid of a fullstate and a Clifford simulator, specifically designed to address the computational challenges associated with the time evolution of quantum chemistry Hamiltonians. Our method focuses on the efficient emulation of multi-qubit rotations, a critical component of Trotterized Hamiltonian evolution. By optimizing the representation and execution of multi-qubit operations leveraging the Pauli frame, our approach significantly reduces the computational cost of simulating quantum circuits, enabling more efficient simulations. Beyond its impact on chemistry applications, our emulation strategy has broad implications for any computational workload that relies heavily on multi-qubit rotations. By increasing the efficiency of quantum simulations, our method facilitates more accurate and cost-effective studies of complex quantum systems. We quantify the performance improvements and computational savings for this emulation strategy, and we obtain a speedup of a factor ≈18 (≈22 with MPI) for our evaluated chemistry Hamiltonians with 24 qubits. Thus, we evaluate our integration of this emulation strategy into the Intel Quantum SDK, further bridging the gap between theoretical algorithm development and practical quantum software implementations.
Gaussian processes are widely known for their ability to provide probabilistic predictions in supervised machine learning models. Their non-parametric nature and flexibility make them particularly effective for regression tasks. However, training a Gaussian process model using standard methods requires matrix inversions with a cubic time complexity, which poses significant computational challenges for inference on larger datasets. Quantum algorithms, such as the HHL algorithm, have been proposed as solutions that overcome the need for classical matrix inversions by efficiently solving linear systems of equations using quantum computers. However, to gain a computational advantage over classical algorithms, these algorithms require fault-tolerant quantum computers with a large number of qubits, which are not yet available. The Variational Quantum Linear Solver is a hybrid quantum-classical algorithm that solves linear systems of equations by optimizing the parameters of a variational quantum circuit using a classical computer. This method is especially suitable for noisy intermediate-scale quantum computers, as it does not require many qubits. It can be used to compute the posterior distribution of a Gaussian process by reformulating the matrix inversion into a set of linear systems of equations. We empirically demonstrate that using the Variational Quantum Linear Solver to perform inference for Gaussian process regression delivers regression quality comparable to that of classical methods.