Witnessing light-driven entanglement using time-resolved resonant inelastic X-ray scattering

Abstract

Characterizing and controlling entanglement in quantum materials is crucial for the development of next-generation quantum technologies. However, defining a quantifiable figure of merit for entanglement in macroscopic solids is theoretically and experimentally challenging. At equilibrium the presence of entanglement can be diagnosed by extracting entanglement witnesses from spectroscopic observables and a nonequilibrium extension of this method could lead to the discovery of novel dynamical phenomena. Here, we propose a systematic approach to quantify the time-dependent quantum Fisher information and entanglement depth of transient states of quantum materials with time-resolved resonant inelastic x-ray scattering. Using a quarter-filled extended Hubbard model as an example, we benchmark the efficiency of this approach and predict a light-enhanced many-body entanglement due to the proximity to a phase boundary. Our work sets the stage for experimentally witnessing and controlling entanglement in light-driven quantum materials via ultrafast spectroscopic measurements.

Vibrational Entanglement through the Lens of Quantum Information Measures

“…For an experimental measurement, however, entanglement witnesses such as those based on the quantum Fisher information are likely to be more suitable candidates, as this quantity can be evaluated also for mixed quantum states and measured through spectroscopic observables. 50 Although we performed the vibrational entanglement analysis on MPS wave functions calculated with the vDMRG algorithm in the present work, the modal entropy descriptors introduced in this Letter are completely general and can be easily transferred to other types of second-quantized multiconfigurational vibrational methods such as those based on vibrational configuration interaction or vibrational coupled cluster. 51 As a consequence, the vibrational entanglement analysis can be applied to compare the results of different vibrational structure methods, PES parametrizations, vibrational coordinates, and modal basis sets.…”

“…They could, in principle, also be exploited for the construction of suitable entanglement witnesses to experimentally verify whether a given vibrational state is entangled or not. For an experimental measurement, however, entanglement witnesses such as those based on the quantum Fisher information are likely to be more suitable candidates, as this quantity can be evaluated also for mixed quantum states and measured through spectroscopic observables …”

“…For an experimental measurement, however, entanglement witnesses such as those based on the quantum Fisher information are likely to be more suitable candidates, as this quantity can be evaluated also for mixed quantum states and measured through spectroscopic observables. 50 …”