arXiv subjects

Drishti Gupta

Publications and source records attributed to Drishti Gupta.

4 recordsLinked to original sources

arXiv2026

Perturbation theory, irrep truncations, and state preparation methods for quantum simulations of SU(3) lattice gauge theory

We study methods for efficient preparation of approximate ground states of $SU(3)$ lattice gauge theory on quantum hardware. Working in a variant of the electric basis, we introduce a refinement of the irrep truncation based on the energy density of site singlets, which provides a finer gradation of simulation complexity. Using strong-coupling perturbation theory as a guide, we develop simple ansatz circuits for ground state preparation and test them via classical simulation on small lattices, including the $2\times 2$ plaquette lattice in $d=2$ and the cube in $d=3$. We contrast state fidelities and resource requirements of variational methods against adiabatic state preparation and introduce a method that hybridizes the two approaches. Finally, we report on the public release of \texttt{ymcirc} -- a package of tools for building $SU(3)$ circuits and processing measurements -- and \texttt{pyclebsch}, a package for efficiently computing $SU(N)$ Clebsch-Gordan coefficients.

hep-lat↗

arXiv2026

Resurgence in the two-field scalar and spinor Quantum Electrodynamics Euler-Heisenberg Lagrangian

We present the first systematic resurgent analysis of the Euler-Heisenberg Lagrangian in spinor and scalar quantum electrodynamics for the most general constant background field configuration. In contrast to the extensively studied single-field cases, the two-field case exhibits unique asymptotic structures, leading to a substantially richer pattern of singularities in the Borel plane. Explicit large-order asymptotic formulas for the weak-field coefficients in both spinor and scalar quantum electrodynamics are derived. These reveal a nontrivial interplay between alternating and non-alternating factorial growth, governed by distinct structures associated with electric and magnetic contributions, and smoothly interpolating between the known single-field limits. Using Borel dispersion techniques, we demonstrate that the complete instanton structure underlying Schwinger pair production in two-field backgrounds is encoded in the divergent perturbative coefficients. We then construct resurgent approximants using Padé-Borel and Padé-Conformal-Borel resummation schemes adapted to the two-field case. For the spinor case, conformal improvement results in a significant enhancement in reconstructing both the real and imaginary parts of the effective Lagrangian across a wide range of field ratios, accurately capturing the subtle sign-changing features in the strong-field regime while in the scalar case, it yields minor improvement. Detailed comparisons with exact special-function representations demonstrate the reliability of reconstructions from a modest number of weak-field coefficients. This work establishes a natural completion of the resurgence programme for constant electromagnetic backgrounds, providing a robust analytic framework for exploring nonperturbative physics and strong-field phenomena in spinor and scalar quantum electrodynamics, from finite perturbative data.

hep-th↗

arXiv2025

Quantum Circuits for SU(3) Lattice Gauge Theory

Lattice gauge theories in varying dimensions, lattice volumes, and truncations offer a rich family of targets for Hamiltonian simulation on quantum devices. In return, formulating quantum simulations can provide new ways of thinking about the quantum structure of gauge theories. In this work, we consider pure $SU(3)$ gauge theory in two and three spatial dimensions in a streamlined version of the electric basis. We use a formulation of the theory that balances locality of the Hamiltonian and size of the gauge-invariant state space, and we classically pre-compute dictionaries of plaquette operator matrix elements for use in circuit construction. We build circuits for simulating time evolution on arbitrary lattice volumes, spanning circuits suitable for NISQ era hardware to future fault-tolerant devices. Relative to spin models, time evolution in lattice gauge theories involves more complex local unitaries, and the Hilbert space of all quantum registers may have large unphysical subspaces. Based on these features, we develop general, volume-scalable tools for optimizing circuit depth, including pruning and fusion algorithms for collections of large multi-controlled unitaries. We describe scalings of quantum resources needed to simulate larger circuits and some directions for future algorithmic development.

hep-lat↗

arXiv2025

Resurgence in the Scalar Quantum Electrodynamics Euler-Heisenberg Lagrangian

We explore the ideas of resurgence and Padé-Borel resummation in the Euler-Heisenberg Lagrangian of scalar quantum electrodynamics, which has remained largely unexamined in these contexts. We thereby extend the related seminal works in spinor quantum electrodynamics, while contrasting the similarities and differences in the two cases. We investigate in detail the efficacy of resurgent extrapolations starting from just a finite number of terms in the weak-field expansions of the 1-loop and 2-loop scalar quantum electrodynamics Euler-Heisenberg Lagrangian. While we re-derive some of the well-known 1-loop and 2-loop contributions in representations suitable for Padé-Borel analyses, other contributions have been derived for the first time. For instance, we find a closed analytic form for the one-particle reducible contribution at 2-loop, which until recently was thought to be zero. It is pointed out that there could be an interesting interplay between the one-particle irreducible and one-particle reducible terms in the strong-field limit. The 1-loop scalar electrodynamics contribution may be effectively mapped into two copies of the spinor quantum electrodynamics, and the particle reducible contribution may be mapped to the 1-loop contribution. It is suggested that these mappings cannot be trivially used to map the corresponding resurgent structures. The singularity structures in the Padé-Borel transforms at 1-loop and 2-loop are examined in some detail. Analytic continuation to the electric field case and the generation of an imaginary part is also studied. We compare the Padé-Borel reconstructions to closed analytic forms or to numerically computed values in the full theory.

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