arXiv subjects

John Stack

Publications and source records attributed to John Stack.

4 recordsLinked to original sources

arXiv2026

A Heterogeneous Distributed Architecture for Quantum Simulation

Architectural specialization and distribution can help scale fault-tolerant quantum computers, but may also introduce substantial overheads from communication, routing, and resource duplication. We introduce a heterogeneous distributed architecture in which a magic core is connected to an extensible storage system composed of one-dimensional lanes of specialized cold-storage nodes. The storage system supports parallel random access to Pauli string parities. This organization is particularly well suited to fermionic quantum simulation, enabling parallel execution of the highly non-local Pauli strings arising from these systems. We evaluate the architecture on fault-tolerant simulations of the dynamics of the Fermi-Hubbard and sparse Sachdev-Ye-Kitaev (SYK) models on systems of up to 450 logical qubits. These workloads exhibit complementary communication structures: Fermi-Hubbard produces a spectrum of interactions from local to non-local shaped by lattice geometry, whereas sparse SYK produces highly non-local and overlapping Pauli operators. For a Trotter step of a 450-logical-qubit Fermi-Hubbard workload, a six-lane system with 30 T-state factories is within approximately $1.4\times$ the wall-clock time of a homogeneous distributed architecture with 4 times as many T-state factories and substantially greater connectivity and sites for injecting magic. For matched T-factory counts, our architecture is $\sim 2\times$ faster.

quant-ph↗

arXiv2026

Remote Entanglement in Lattice Surgery: To Distill, or Not to Distill

Distributed quantum computing can potentially address the scalability challenge by networking processors through photon-mediated remote entanglement. Prior approaches assumed that remote Bell pairs require distillation before use, incurring substantial overhead, to achieve sufficiently high fidelity. However, recent results show that lattice-surgery operations at logical qubit boundaries tolerate significantly higher error rates than previously assumed. We quantify the resource trade-offs between distillation overhead and surface-code distance requirements under realistic constraints including probabilistic entanglement generation and memory decoherence. We identify the fidelity crossover point separating the two regimes. Below this threshold, the distillation strategy dominates, reducing resource overhead by up to two orders of magnitude. Above it, no-distillation becomes the more efficient choice, reducing resource overhead by more than half. We briefly describe the application of these methods to ion-trap and neutral-atom platforms. These results provide joint design guidelines for optimizing photonic interconnects and fault-tolerant architectures in distributed quantum computing.

quant-ph↗

arXiv2025

Transversal Fault Tolerant Distributed Quantum Computing Operations

Distributed architectures are a route to scalable quantum computing, but the performance of fault-tolerant operations across noisy inter-module links remains poorly characterized. We present circuit-level simulations of two key distributed primitives: transversal non-local CNOT and logical teleportation using surface and bivariate-bicycle codes. We then simulate the use of these distributed primitives in a major subroutine of common quantum algorithms. The results, enabled by our scalable library Transversal Multiple CodeBlock Simulator, demonstrate that on appropriate devices distributed qLDPC transversal operations can outperform surface code lattice surgery and enable efficient parallel computation with lower Bell pair consumption. Notably, we find that the non-local CNOT achieves up to an order of magnitude lower logical error rates than teleportation at the same code distance and noise levels. We further show that code distances of $d \approx 11$ at physical error rate $p \sim 10^{-4}$ and $d \approx 29$ at $p \sim 10^{-3}$, with $p_{\mathrm{ebit}}=10p$, are sufficient to achieve logical error rates below $10^{-12}$, enabling large-scale algorithms. These results provide critical guidance for architecture and code selection in distributed quantum computing.

quant-ph↗

arXiv2000

Monopoles, Vortices and Confinement is SU(3) Lattice Gauge Theory

We present results for the heavy quark potential computed in SU(3) from magnetic monopoles and from center vortices. The monopoles are identified after fixing SU(3) lattice configurations to the maximal abelian gauge. The center vortices are identified after using an indirect center gauge fixing scheme which we describe for SU(3). Z(3) center vortices are extracted and used to compute the potential. The values of the string tensions from monopoles and vortices are compared to the full SU(3) string tension.

hep-lat↗