Variational waveguide QED simulators

Abstract

Waveguide QED simulators are analogue quantum simulators made by quantum emitters interacting with one-dimensional photonic band-gap materials. One of their remarkable features is that they can be used to engineer tunable-range emitter interactions. Here, we demonstrate how these interactions can be a resource to develop more efficient variational quantum algorithms for certain problems. In particular, we illustrate their power in creating wavefunction ansätze that capture accurately the ground state of quantum critical spin models (XXZ and Ising) with less gates and optimization parameters than other variational ansätze based on nearest-neighbor or infinite-range entangling gates. Finally, we study the potential advantages of these waveguide ansätze in the presence of noise. Overall, these results evidence the potential of using the interaction range as a variational parameter and place waveguide QED simulators as a promising platform for variational quantum algorithms.

Trainability Enhancement of Parameterized Quantum Circuits via Reduced-Domain Parameter Initialization

“…The core idea is exploiting PQCs to delegate classically difficult computation and variationally updating the parameters in PQCs with a powerful classical optimizer [28,29,30,31,32]. With error mitigation techniques [33,34,35,36,37,38,39,40], VQAs have been applied to various fields and the corresponding specific algorithms have been developed, including variational quantum eigensolver (VQE) [41,42,43,44,45], quantum approximate optimization algorithm [46,47,48,15,49], variational quantum simulator [50,51,52,53], quantum neural network (QNN) [54,55,56,57,58,59,60,61,62,63], and others [64,65,66,67,68,69,70,71,72,...…”