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Towards a loophole free Bell tests with spin qubits in diamond

Anaïs Dréau

Jeudi 30 avril 2015

à 11h en salle C. Brot

Entanglement between space-like separated objects is one of the most intriguing phenomena in quantum science. Indeed, the outcomes of independent measurements on entangled objects can reveal strong correlations that cannot be explained by classical physics. This property, often called quantum non-locality, is demonstrated by the violation of the so-called Bell’s inequalities [1]. Fifty years after its first derivation, many experiments have violated Bell’s inequalities [2]. Ho- wever, all of these experiments rely on at least one additional assumption : the absence of signaling between the entangled particles or fair-sampling of the full dataset when using inefficient detection systems. Closing these two “loopholes” simultaneously is a current challenge in experimental quan- tum physics, with applications ranging from device independent quantum key distribution [3] to the generation of certified-random numbers [4]. In this seminar, I will present our latest result towards the first experimental realization of a loophole-free Bell test. This experiment relies on the efficient control achieved on the qubit asso- ciated with the electronic spin of a particular defect in diamond called the NV center. Thanks to a robust remote entanglement protocol [5], we generated high-fidelity entanglement between two NV centers located in two independent labs separated by 1.3 km on the TU Delft campus. This achieve- ment combined with the fast and high-fidelity single shot measurement [6] of our qubits could allow us in principle to violate Bell’s inequalities while closing the two previous loopholes at the same time.

[1] J.S. Bell, Physics 1, 195-200, (1964).

[2] N. Brunner et al., Rev. Mod. Phys. 86, 839 (2014).

[3] J. Barrett et al., Phys. Rev. Lett. 95, 010503 (2005).

[4] S. Pironio et al., Nature 464, 1021-1024 (2010).

[5] H. Bernien et al., Nature 497, 86-90 (2013).

[6] L. Robledo et al., Nature 574, 477 (2011).

Kavli Institute of Nanoscience Delft,

Delft University of Technology, P.O. Box 5046,

2600 GA Delft, The Netherlands