Spatial modes for testing indefinite causal order

Jacquiline Romero; Kaumudibikash Goswami; Christina Giarmatzi; Fabio Costa; Cyril Branciard; Andrew G. White

doi:10.1117/12.2292732

22 February 2018 Spatial modes for testing indefinite causal order

Jacquiline Romero, Kaumudibikash Goswami, Christina Giarmatzi, Fabio Costa, Cyril Branciard, Andrew G. White

Proceedings Volume 10549, Complex Light and Optical Forces XII; 1054908 (2018) https://doi.org/10.1117/12.2292732
Event: SPIE OPTO, 2018, San Francisco, California, United States

Abstract

The fundamental notion of fixed order between two events is challenged by formulations of quantum mechanics that makes no reference to a global time. The indefinite causal order arising from these formalisms can be realised using the quantum switch, a device where two operations can act in two different orders simultaneously. Similar to entanglement verification which employ entanglement witness, we verify indefinite causal order using a causal witness. In our experiment, we use polarisation as a control for the order of the operations that act on the spatial mode of a photon. We measure a causal witness value of -0.16±0.013, below the threshold of zero, thus demonstrating indefinite causal order in the quantum switch.

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Citation Download Citation

Jacquiline Romero, Kaumudibikash Goswami, Christina Giarmatzi, Fabio Costa, Cyril Branciard, and Andrew G. White "Spatial modes for testing indefinite causal order", Proc. SPIE 10549, Complex Light and Optical Forces XII, 1054908 (22 February 2018); https://doi.org/10.1117/12.2292732

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