Experimental observation of a quantum Cheshire cat using a weak measuring device

Yosep Kim, Dong Gil Im, Yong Su Kim, Sang Yun Lee, Sang Wook Han, Sung Moon, Yoon Ho Kim, Young Wook Cho

Research output: Chapter in Book/Report/Conference proceedingConference contribution


In Alice's Adventures in Wonderland by Lewis Carroll, mischievous grin of a Cheshire cat is sometimes disembodied from her body. Quantum theory allows such a counterintuitive phenomenon, known as the quantum Cheshire cat effect [1], to happen for a pre- and post-selected (PPS) system. While observing the quantum Cheshire cat, the physical property and the carrier's location should be weakly probed with a measuring device to leave the quantum state with negligible disturbance. To date, experimental observations of the quantum Cheshire cat effect have been realized with a single neutron as well as with a single photon [2, 3]. However, their observations relied on weakly disturbing elements instead of a true weak measuring device. In this work, we report the experimental observation of the quantum Cheshire cat effect with a weak measuring device. To investigate the quantum Cheshire cat effect, we employ a photon pair generated by spontaneous parametric down conversion (SPDC). The elements of quantum Cheshire cat, namely the body (photon) and the grin (polarization), are indirectly probed with a quantum pointer using another single photon, where both the body and the grin are weakly measured without destroying the photon itself.

Original languageEnglish
Title of host publicationEuropean Quantum Electronics Conference, EQEC_2019
PublisherOptica Publishing Group (formerly OSA)
ISBN (Print)9781728104690
Publication statusPublished - 2019
EventEuropean Quantum Electronics Conference, EQEC_2019 - Munich, United Kingdom
Duration: 2019 Jun 232019 Jun 27

Publication series

NameOptics InfoBase Conference Papers
VolumePart F143-EQEC 2019
ISSN (Electronic)2162-2701


ConferenceEuropean Quantum Electronics Conference, EQEC_2019
Country/TerritoryUnited Kingdom

Bibliographical note

Publisher Copyright:
© 2019 IEEE

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Mechanics of Materials


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