How squeezed states both maximize and minimize the same notion of quantumness
Abstract
Beam splitters are routinely used for generating entanglement between modes in the optical and microwave domains, requiring input states that are not convex combinations of coherent states. This leads to the ability to generate entanglement at a beam splitter as a notion of quantumness. A similar, yet distinct, notion of quantumness is the amount of entanglement generated by twomode squeezers (i.e., fourwave mixers). We show that squeezedvacuum states, paradoxically, both minimize and maximize these notions of quantumness, with the crucial resolution of the paradox hinging upon the relative phases between the input states and the devices. Our notion of quantumness is intrinsically related to eigenvalue equations involving creation and annihilation operators, governed by a set of inequalities that leads to generalized cat and squeezedvacuum states.
 Publication:

Physical Review A
 Pub Date:
 September 2021
 DOI:
 10.1103/PhysRevA.104.032425
 arXiv:
 arXiv:2106.03862
 Bibcode:
 2021PhRvA.104c2425G
 Keywords:

 Quantum Physics;
 Physics  Optics
 EPrint:
 12 pages including 2 figures and 1 appendix. Comments welcome!