arXiv subjects

Ian Gill

Publications and source records attributed to Ian Gill.

2 recordsLinked to original sources

arXiv2026

Generalized matching decoders for 2D topological translationally-invariant codes

Two-dimensional topological translationally-invariant (TTI) quantum codes, such as the toric code (TC) and bivariate bicycle (BB) codes, are promising candidates for fault-tolerant quantum computation. For such codes to be practically relevant, their decoders must successfully correct the most likely errors while remaining computationally efficient. For the TC, graph-matching decoders satisfy both requirements and, additionally, admit provable performance guarantees. Given the equivalence between TTI codes and (multiple copies of) the TC, one may then ask whether TTI codes also admit analogous graph-matching decoders. In this work, we develop a graph-matching approach to decoding general TTI codes. Intuitively, our approach coarse-grains the TTI code to obtain an effective description of the syndrome in terms of TC excitations, which can then be removed using graph-matching techniques. We prove that our decoders correct errors of weight up to a constant fraction of the code distance and achieve non-zero code-capacity thresholds. We further numerically study a variant optimized for practically relevant BB codes and observe performance comparable to that of the belief propagation with ordered statistics decoder. Our results indicate that graph-matching decoders are a viable approach to decoding BB codes and other TTI codes.

quant-ph↗

arXiv2025

Probing the Dependence of Partonic Energy Loss on the Initial Energy Density of the Quark Gluon Plasma

Considerable evidence now exists for partonic energy loss due to interaction with the hot, dense medium created in ultra-relativistic heavy-ion collisions. A primary signal of this energy loss is the suppression of high transverse momentum $p_{\mathrm{T}}$ hadron yields in A-A collisions relative to appropriately scaled $pp$ collisions at the same energy. Measuring the collision energy dependence of this energy loss is vital to understanding the medium, but it is difficult to disentangle the medium-driven energy loss from the natural kinematic variance of the steeply-falling $p_{\mathrm{T}}$ spectra across different $\sqrt{s_{\mathrm{NN}}}$. To decouple these effects, we utilize a phenomenologically motivated spectrum shift model to estimate the average transverse momentum loss $\Delta p_{\mathrm{T}}$ imparted on high $p_{\mathrm{T}}$ partons in A-A collisions, a proxy for the medium induced energy loss. We observe a striking correlation between $\Delta p_{\mathrm{T}}$ and Glauber-derived estimates of initial state energy density $\varepsilon_{\mathrm{Bj}}$, consistent across two orders of magnitude in collision energy for a variety of nuclear species. To access the path-length dependence of energy loss, we couple our model to geometric event shape estimates extracted from Glauber calculations to produce predictions for high-$p_{\mathrm{T}}$ hadron elliptic flow $v_2$ that agree reasonably with data.

nucl-th↗