We show that excitons in $K$ and $K^{\prime }$ valleys of transition metal dichalcogenide monolayers can be entangled with respect to their valley degree of freedom by absorbing linearly polarized single photons. This effect does not require any interaction between $K$ and $K^{\prime }$ excitons in contrast to conventional mechanisms of entanglement that are mediated by coupling between quantum systems (e.g., entanglement of photons in nonlinear optical interactions). The valley entanglement of excitons and free carriers can be verified by measuring the polarization of their photoluminescence or fluctuations of the photocurrent under an applied in-plane dc bias.

• Received 20 March 2015
• Revised 21 May 2015

DOI:https://doi.org/10.1103/PhysRevB.92.075409