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Compute eXpress Link (CXL) is a pivotal technology for memory disaggregation in future heterogeneous computing systems, enabling on-demand memory expansion and improved resource utilization. Despite its potential, CXL is in its early stages with limited market products, highlighting the need for a reliable system-level simulation tool. This paper introduces CXL-DMSim, an open-source, high-fidelity full-system simulator for CXL disaggregated memory systems, comparable in speed to gem5. CXL-DMSim includes a flexible CXL memory expander model, device driver, and support for CXL\.io and CXL\.mem protocols. It supports both app-managed and kernel-managed modes, with the latter featuring a NUMA-compatible mechanism. Rigorous verification against real hardware testbeds with FPGA-based and ASIC-based CXL memory prototypes confirms CXL-DMSim's accuracy, with an average simulation error of 4.1%. Benchmark results using LMbench and STREAM indicate that CXL-FPGA memory has approximately ~2.88x higher latency than local DDR, while CXL-ASIC latency is about ~2.18x. CXL-FPGA achieves 45-69% of local DDR's memory bandwidth, and CXL-ASIC reaches 82-83%. The performance of CXL memory is significantly more sensitive to Rd/Wr patterns than local DDR, with optimal bandwidth at a 74%:26% ratio rather than 50%:50% due to the current CXL+DDR controller design. The study also shows that CXL memory can markedly enhance the performance of memory-intensive applications, with the most improvement seen in Viper (~23x) and in bandwidth-sensitive scenarios like MERCI (16%). CXL-DMSim's observability and expandability are demonstrated through detailed case studies, showcasing its potential for research on future CXL-interconnected hybrid memory pools., Comment: 15 pages, 19 figures

Biologically-inspired computing models have made significant progress in recent years, but the conventional von Neumann architecture is inefficient for the large-scale matrix operations and massive parallelism required by these models. This paper presents Spin-NeuroMem, a low-power circuit design of Hopfield network for the function of associative memory. Spin-NeuroMem is equipped with energy-efficient spintronic synapses which utilize magnetic tunnel junctions (MTJs) to store weight matrices of multiple associative memories. The proposed synapse design achieves as low as 17.4% power consumption compared to the state-of-the-art synapse designs. Spin-NeuroMem also encompasses a novel voltage converter with 60% less transistor usage for effective Hopfield network computation. In addition, we propose an associative memory simulator for the first time, which achieves a 5.05Mx speedup with a comparable associative memory effect. By harnessing the potential of spintronic devices, this work sheds light on the development of energy-efficient and scalable neuromorphic computing systems. The source code will be publicly available after the manuscript is reviewed.

High-quality random numbers are very critical to many fields such as cryptography, finance, and scientific simulation, which calls for the design of reliable true random number generators (TRNGs). Limited by entropy source, throughput, reliability, and system integration, existing TRNG designs are difficult to be deployed in real computing systems to greatly accelerate target applications. This study proposes a TRNG circuit named RHS-TRNG based on spin-transfer torque magnetic tunnel junction (STT-MTJ). RHS-TRNG generates resilient and high-speed random bit sequences exploiting the stochastic switching characteristics of STT-MTJ. By circuit/system co-design, we integrate RHS-TRNG into a RISC-V processor as an acceleration component, which is driven by customized random number generation instructions. Our experimental results show that a single cell of RHS-TRNG has a random bit generation speed of up to 303 Mb/s, which is the highest among existing MTJ-based TRNGs. Higher throughput can be achieved by exploiting cell-level parallelism. RHS-TRNG also shows strong resilience against PVT variations thanks to our designs using bidirectional switching currents and dual generator units. In addition, our system evaluation results using gem5 simulator suggest that the system equipped with RHS-TRNG can achieve 3.4-12x higher performance in speeding up option pricing programs than software implementations of random number generation., Comment: Published in: IEEE Transactions on Very Large Scale Integration (VLSI) Systems ( Volume: 31, Issue: 10, October 2023)

Unidirectional photon emission is crucial for constructing quantum networks and realizing scalable quantum information processing. In the present work an efficient scheme is developed for the unidirectional emission of a tunable squeezed microwave field. Our scheme is based on a chiral cavity magnonic system, where a magnon mode in a single-crystalline yttrium iron garnet (YIG) sphere is selectively coupled to one of the two degenerate rotating microwave modes in a torus-shaped cavity with the same chirality. With the YIG sphere driven by a two-color Floquet field to induce sidebands in the magnon-photon coupling, we show that the unidirectional emission of a tunable squeezed microwave field can be generated via the assistance of the dissipative magnon mode and a waveguide. Moreover, the direction of the proposed one-way emitter can be controlled on demand by reversing the biased magnetic field. Our work opens up an avenue to create and manipulate one-way nonclassical microwave radiation field and could find potential quantum technological applications., Comment: to appear in Phys. Rev. A

Coherent long-range interactions between atoms are a prerequisite for numerous applications in the field of quantum information science, but they usually decrease exponentially with the increase in atomic separation. Here we present an appealing method to dramatically enhance the long-range atom-atom interaction mediated by a coupled-cavity array that is subjected to two-photon (parametric) drives. Our method allows one to greatly amplify both the localization length of the single-photon bound-state wavefunction and the effective atom-photon coupling strength, resulting in a significant improvement of photon-mediated coherent interaction between two distant atoms. Additionally, we illustrate this effect by analyzing how it facilitates the transfer of information and the creation of entanglement between the atoms.

The intercalated iron selenide (Li,Fe)OHFeSe has a strongly layered structure analogous to the quasi two-dimensional (2D) bismuth cuprate superconductors, and exhibits both high-temperature (Tc) and topological superconductivity. However, the issue of its superconductivity dimensionality has not yet been fully investigated so far. Here we report that the quasi-2D superconductivity features, including the high anisotropy {\gamma} = 151 and the associated quasi-2D vortices, are also revealed for (Li,Fe)OHFeSe, based on systematic experiments of the electrical transport and magnetization and model fittings. Thus, we establish a new vortex phase diagram for (Li,Fe)OHFeSe, which delineates an emergent quasi-2D vortex-liquid state, and a subsequent vortex-solid dimensional crossover from a pancake-like to a three-dimensional state with decreasing temperature and magnetic field. Furthermore, we find that all the quasi-2D characteristics revealed here for the high-Tc iron selenide superconductor are very similar to those reported for the high-Tc bismuth cuprate superconductors., Comment: 20 pages, 6 figures