Recent advances in quantum hardware and error correction have paved the way for early fault-tolerant (EFT) quantum computing. We propose iSwitch, a hybrid system architecture for trapped-ion quantum computers (TIQC) that exploits ultra-high-fidelity single-qubit gates and efficient logical CNOTs enabled by ion shuttling. iSwitch employs bare qubits for single-qubit operations and QEC-encoded logical qubits for two-qubit gates, avoiding full logical encoding, gate synthesis, and magic state distillation. To enable this selective encoding, we develop a low-noise conversion protocol between bare and logical qubits, a hybrid instruction set tailored to 2D TIQC layouts, and a compiler that minimizes conversion overhead and optimizes scheduling. Evaluations on variational quantum algorithm benchmarks show that iSwitch achieves comparable fidelity to conventional QEC methods, while reducing qubit and operation counts by roughly 33–50%, offering a practical, resource-efficient path toward EFT quantum computing on trapped-ion platforms.

We present STQS, a unified system architecture for spatiotemporal quantum sensing that interlaces four key quantum components: sensing , memory , communication , and computation . By employing a comprehensive gate-based framework, we systemically explore the design space of quantum sensing schemes and probe the influence of noise at each state in a sensing workflow through simulation. We introduce a novel distance-based metric that compares reference states to sensing states and assigns a confidence level. We anticipate that the distance measure will serve as an intermediate step toward more advanced quantum signal processing techniques like quantum machine learning. To our knowledge, STQS is the first system-level framework to integrate quantum sensing within a coherent, unified architectural paradigm. STQS provides seamless avenues for unique state preparation, multi-user sensing requests, and addressing practical implementations. We demonstrate the versatility of STQS through evaluations of quantum radar and qubit-based dark matter detection. To highlight the near-term feasibility of our approach, we present results obtained from IBM’s Marrakesh and IonQ’s Forte devices, validating key STQS components on present day quantum hardware. We have made the simulation code and experimental data used in this work publicly available.

Quantum Error Correction (QEC) codes are essential for achieving fault-tolerant quantum computing (FTQC). However, their implementation faces significant challenges due to disparity between required dense qubit connectivity and sparse hardware architectures. Current approaches often either underutilize QEC circuit features or focus on manual designs tailored to specific codes and architectures, limiting their capability and generality. In response, we introduce QECC-Synth, an automated compiler for QEC code implementation that addresses these challenges. We leverage the ancilla bridge technique tailored to the requirements of QEC circuits and introduces a systematic classification of its design space flexibilities. We then formalize this problem using the MaxSAT framework to optimize these flexibilities. Evaluation shows that our method significantly outperforms existing methods while demonstrating broader applicability across diverse QEC codes and hardware architectures.

Quantum Error Correction (QEC) is essential for fault-tolerant, large-scale quantum computation.However, error drift in qubits undermines QEC performance during long computations, necessitating frequent calibration.Conventional calibration methods disrupt quantum states, requiring system downtime and rendering in situ calibration impractical.To address this challenge, we propose QECali, a novel framework that enables in situ calibration for surface codes.Our evaluation demonstrates that QECali introduces modest qubit overhead and negligible increases in execution time, offering the first practical solution for in situ calibration in surface code based quantum computation.

Distributed Quantum Computing (DQC) provides a scalable architecture by interconnecting multiple quantum processor units (QPUs).Among various DQC implementations, quantum data centers (QDCs) -where QPUs in different racks are connected through reconfigurable optical switch networks -are becoming feasible in the near term.However, the latency of cross-rack communications and dynamic switch reconfigurations poses unique challenges to communications in QDCs, significantly increasing the overall latency, thereby also reducing the overall fidelity.In this paper, we address these challenges by introducing a novel compiler that optimizes scheduling of communications across the program and network layers.Our evaluation shows that it reduces the overall latency by 8.02× over prior approaches with a small overhead and can be integrated with quantum error correction (QEC) to facilitate fault-tolerant quantum computing (FTQC).We have open-sourced our codes at https://zenodo.org/records/15377656.

Chiplet architecture is an emerging architecture for quantum computing that could significantly increase qubit resources with its great scalability and modularity. However, as the computing scale increases, communication between qubits would become a more severe bottleneck due to the long routing distances. In this paper, we propose a multi-entry communication highway (MECH) mechanism to trade ancillary qubits for program concurrency, and build a compilation framework to efficiently manage and utilize the highway resources. Our evaluation shows that this framework significantly outperforms the baseline approach in both the circuit depth and the number of operations on typical quantum benchmarks. This implies a more efficient and less error-prone compilation of quantum programs.

In this paper, we introduce Surf-Deformer, a code deformation framework that seamlessly integrates adaptive defect mitigation functionality into the current surface code workflow. It crafts several basic deformation instructions based on fundamental gauge transformations, which can be combined to explore a larger design space than previous methods. This enables more optimized deformation processes tailored to specific defect situations, restoring the QEC capability of deformed codes more efficiently with minimal qubit resources. Additionally, we design an adaptive code layout that accommodates our defect mitigation strategy while ensuring efficient execution of logical operations. Our evaluation shows that Surf-Deformer outperforms previous methods by significantly reducing the end-to-end failure rate of various quantum programs by 35× to 70×, while requiring only about 50% of the qubit resources compared to the previous method to achieve the same level of failure rate. Ablation studies show that Surf-Deformer surpasses previous defect removal methods in preserving QEC capability and facilitates surface code communication by achieving nearly optimal throughnut.