Wei Chen, Z. D. Wang, R. Shen, D. Y. Xing
We investigate spin entangled electron pairs transporting separately in the helical edge channels of two quantum spin Hall systems. Both dc and ac Aharonov-Bohm (AB) effects of the crossed current correlation are studied. In the dc case, it is found that the visibility of the AB oscillation of differential noise is equal to entanglement concurrence, and a {\pi} phase difference indicates singlet and triplet entangled states. More remarkably, when an ac flux with frequency {\Omega} is introduced, the differential noise exhibits nontrivial step structures as the voltage bias V increases, with the step edges being located at eV = n{\hbar}{\Omega}. The concurrence can be probed directly by measuring the heights of these steps. We also show that the relation between differential noise and concurrence is general even when spin dephasing exists.
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http://arxiv.org/abs/1304.5933
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