Abstract
We consider the characterization of quantum superposition states beyond the pattern ‘dead and alive’. We propose a measure that is applicable to superpositions of multiple macroscopically distinct states, superpositions with different weights as well as mixed states. The measure is based on the mutual information to characterize the distinguishability between the multiple branches of the superposition. This allows us to overcome limitations of previous proposals, and to bridge the gap between general measures for macroscopic quantumness and measures for Schrödinger-cat type superpositions. We discuss a number of relevant examples, provide an alternative definition using basis-dependent quantum discord and reveal connections to other proposals in the literature. Finally, we also show the connection between the size of quantum states as quantified by our measure and their vulnerability to noise.
Highlights
When going from single microscopic particles to composite systems with many degrees of freedom, quantum mechanics shows enormous complexity
We propose a measure that is applicable to superpositions of multiple states with unequal weights and is readily extendable to mixed states, thereby overcoming the shortcomings of previous proposals
We formalize this idea into a general measure that is useful for mixed states
Summary
Pavel Sekatski1,4, Benjamin Yadin2, Marc-Olivier Renou3, Wolfgang Dür1, Nicolas Gisin3 and Florian Fröwis3 Original content from this Keywords: macrospic quantum effects and states, quantum to classical transition, Schrödinger-cat work may be used under the terms of the Creative Commons Attribution 3.0 licence.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
