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Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres

par Caroline CHAMPENOIS - publié le , mis à jour le

séminaire du laboratoire
jeudi 2 mars, 11:00 service 322 campus Saint-Jérôme

Anais Dréau

former affiliation : QuTech and Kavli Institute of Nanoscience Delft, Delft University of Technology, The Netherlands.

Current affiliation : CNRS, Laboratoire Charles Coulomb, Montpellier, France.

abstract :

Since its inception, quantum mechanics theory has been challenging our way of conceiving reality. In 1964, John Bell proved that no theory of nature that obeys locality and realism can reproduce all the predictions of quantum theory [1]. Under this framework, the correlations between distant measurements satisfy an inequality that can be violated according to quantum theory if the measurements are performed on entangled particles. Over the last decades, the violation of Bell inequality has been demonstrated in many ingenious experiments. However, due to practical limitations, all these experimental implementations required additional assumptions to account for a conflict with local realism. Inefficient detection systems create the detection loophole by relying on the fair-sampling assumption to hold, and the locality loophole is arisen when any sub-luminal communication during the measurements is allowed.

Here, I will present the first experiment that tests the violation of Bell inequality while being free of those loopholes [2]. By use of a robust remote entanglement protocol [3- 4], we generated high-fidelity entanglement between two electron spins in diamond located in independent labs separated by 1.3 km. Efficient spin readout enabled us to close the detection loophole while a space-like separation of the setups allowed us to fulfill the required locality conditions. The observed Bell inequality violation allows to reject large classes of local realist theories and constitutes a step towards the implementation of device-independent quantum-secure communication [5] and randomness certification [6].

[1] J.S. Bell, Physics 1, 195-200, (1964).
[2] B. Hensen et al. arXiv:1508.05949 (2015).
[3] S. D. Barrett and P. Kok, Phys. Rev. A 71, 060310 (2005). [4] H. Bernien et al., Nature 497, 86-90 (2013).
[5] A. Acín, et al., Phys. Rev. Lett. 98, 230501 (2007).
[6] S. Pironio et al., Nature 464, 1021-1024 (2010).

contact : Caroline Champenois

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