arXiv subjects

Ross Jenkinson

Publications and source records attributed to Ross Jenkinson.

4 recordsLinked to original sources

arXiv2026

Quantum simulation of real-time Yukawa dynamics with qubits and qumodes

Real-time quantum simulation of field theories offers access to scattering and decay dynamics, circumventing the limitations of Euclidean lattice methods. However, representing bosonic fields on qubits requires a finite-dimensional approximation and can entail costly multi-qubit operations. Hybrid qubit-qumode architectures avoid this by encoding bosonic fields directly in oscillators. We formulate scattering in the (1+1)-dimensional Yukawa theory for such a device, with staggered fermions on qubits and the scalar on qumodes. Trapped ions are a natural candidate, with the fermions on the internal states of the ions and the scalar on their collective motion, so that the Yukawa coupling becomes a native spin-dependent displacement. Emulating the device with tensor networks, we study the decay of a single scalar particle and fermion-antifermion scattering around the resonance region, using observables that can be measured on the device natively. We compare the results with those obtained using lattice perturbation theory. The emulation is able to resolve corrections beyond the Dyson summation of the one-loop self-energy.

quant-ph↗

arXiv2025

A Manifestly Causal Approach to Quantum Field Theory

We develop a probability-level, manifestly causal formalism for calculations in QFT. The approach involves an implicit summation over final states, which makes causality manifest since retarded propagators emerge naturally. This inclusive summation over final states may also offer insights into the cancellation of IR divergences in physical observables within gauge theories, in accordance with the BN and KLN theorems. To study this, we first conduct particle scattering calculations using conventional methods, determining the quark-antiquark production cross section at first-order in gluon corrections, with careful tracking and cancellation of both IR and UV divergences. We then apply the causal formalism to analogous processes in scalar field theory, introducing novel diagrams that represent algebraic terms at the probability level, akin to Feynman diagrams at the amplitude level. We present a list of rules that generate all probability-level diagrams for particle scattering processes in which one is fully inclusive over final states that contain no initial-state particles. We also investigate the Unruh effect through the lens of the causal formalism. We calculate the transition rate of an accelerating UdW detector coupled to a massive scalar field, from both the perspective of an inertial observer and an accelerating observer. We confirm that the two perspectives give the same transition rate, despite the Rindler observer describing the Minkowski vacuum state as a thermal bath of particles. Numerical results for the transition rate are presented, highlighting the transient effects caused by forcing the field to initially be in the Minkowski vacuum state. Finally, we review the literature regarding the response of an UdW detector on various trajectories in the spacetime of a (3+1)-D Schwarzschild black hole, with a view to extending the analysis in the future using our causal formalism.

hep-th↗

arXiv2025

Towards a Manifestly Causal Approach to Particle Scattering

We introduce a new, probability-level approach to calculations in scalar field particle scattering. The approach involves the implicit summation over final states, which makes causality manifest since retarded propagators emerge naturally. Novel diagrams represent algebraic terms at the probability level, akin to Feynman diagrams at the amplitude level. We conjecture a list of rules that generate all probability-level diagrams for particle scattering processes in which one is fully inclusive over final states that contain no initial-state particles. These rules are confirmed using some fixed-order examples. The inclusivity and causal structure of this formalism may offer insights into the cancellation of infrared divergences if applied to gauge theory calculations.

hep-ph↗

arXiv2025

A new study of the Unruh effect

We revisit the Unruh effect within a general framework based on direct, probability-level calculations. We rederive the transition rate of a uniformly accelerating Unruh-DeWitt monopole detector coupled to a massive scalar field, from both the perspective of an inertial (Minkowski) observer and an accelerating (Rindler) observer. We show that, for a measurement at a finite time after the initial state is prepared, the two perspectives give the same transition rate. We confirm that an inertial detector in a thermal bath of Minkowski particles responds differently to the accelerated detector (which perceives a thermal bath of Rindler particles), except in the case of a massless field where there is agreement at all times. Finally, new numerical results for the transition rate are presented and explained, highlighting the transient effects caused by forcing the field to initially be in the Minkowski vacuum state.

hep-th↗