Non-Markovian dynamics of generation of bound states in the continuum via single-photon scattering

TL;DR

This paper demonstrates a method to generate bound states in the continuum (BICs) in waveguide quantum systems using single-photon scattering with engineered qubit detuning, outperforming traditional relaxation strategies in non-Markovian regimes.

Contribution

It introduces a novel approach combining single-photon scattering and time-varying qubit detuning to efficiently generate BICs in non-Markovian regimes, supported by tensor network simulations.

Findings

Single-photon scattering with engineered detuning can generate BICs.

Non-Markovian photon delays enhance BIC generation efficiency.

Tensor network methods enable full quantum system simulation.

Abstract

The excitation of bound states in the continuum (BICs) in two- or multi-qubit systems lies at the heart of entanglement generation and harnessing in Waveguide Quantum Electrodynamics platforms. However, the generation of qubit pair BICs through single-photon scattering is hindered by the fact that these states are effectively decoupled from propagating photons. We prove that scattering of a parity-invariant single photon on a qubit pair, combined with a properly engineered time variation of the qubit detuning, is not only feasible, but also more effective than strategies based on the relaxation of the excited states of the qubits when the distance between the qubits gives rise to non-negligible photon delays (non-Markovian regime). The use of tensor network methods to simulate the proposed scheme enables to include such photon delays in collision models, thus opening the possibility to follow the time evolution of the full quantum system, including qubits and field, and to efficiently implement and characterize the dynamics hence identifying optimal working points for the BIC generation.