Gerardo Ortiz (Indiana U.)
Fundamentals of Entangled Probes for Entangled Matter

Advancing the frontiers of science often requires the creation of new probes to uncover the underlying microscopic 
mechanisms giving rise to exotic macroscopic phenomena, such as high-temperature superconductivity. Can quantum entangled 
probes uncover the inherent entanglement of the target matter? We have recently [1,2] developed an entangled neutron beam 
where individual neutrons can be entangled in spin, trajectory and energy. 
To demonstrate entanglement in these beams we crafted neutron interferometric measurements of contextuality inequalities 
whose violation provided an  indication of  the breakdown of Einstein's local realism. In turn, the tunable entanglement 
(spin-echo) length of the neutron beam from nanometers to microns and energy differences from peV to neV opens a pathway 
to a future era of entangled neutron scattering in matter.  What kind of information can be extracted with this novel entangled probe? 
A recent general quantum many-body entangled-probe scattering theory [3] provides a framework to respond to this question. Interestingly, by 
carefully tuning the probe's entanglement and inherent coherence properties, one can directly access the intrinsic entanglement 
of the target material. This theoretical framework supports the view that our entangled beam can be used as a multipurpose 
scientific tool.  We are currently [4] pursuing several ideas and developing new spin-textured entangled beams with OAM for future 
experiments in candidate quantum spin liquids, unconventional superconductors, and chiral quantum materials. 

[1] J. Shen {\it et. al.}, Nature Commun. {\bf 11}, 930 (2020). 
[2] S. Lu  {\it et. al.}, Phys. Rev. A  {\bf 101}, 042318 (2020). 
[3] A. A. Md. Irfan, P. Blackstone, R. Pynn, and G. Ortiz, New J. Phys. {\bf 23},  083022 (2021).
[4] Q. Le Thien, S. McKay, R. Pynn, and G. Ortiz,  arXiv:2207.12419.