Strain-Controlled Quantum Dot Fine Structure for Entangled Photon Generation at 1550 nm
Thomas Lettner, Samuel Gyger, Katharina D. Zeuner, Lucas Schweickert, Stephan Steinhauer, Carl Reuterskiöld Hedlund, Sandra Stroj, Armando Rastelli, Mattias Hammar, Rinaldo Trotta, Klaus D. Jöns, Val Zwiller
Abstract
Entangled photon generation at 1550 nm in the telecom C-band is of critical importance as it enables the realization of quantum communication protocols over long distance using deployed telecommunication infrastructure. InAs epitaxial quantum dots have recently enabled on-demand generation of entangled photons in this wavelength range. However, time-dependent state evolution, caused by the fine-structure splitting, currently limits the fidelity to a specific entangled state. Here, we show fine-structure suppression for InAs quantum dots using micromachined piezoelectric actuators and demonstrate generation of highly entangled photons at 1550 nm. At the lowest fine-structure setting, we obtain a maximum fidelity of 90.0 ± 2.7% (concurrence of 87.5 ± 3.1%). The concurrence remains high also for moderate (weak) temporal filtering, with values close to 80% (50%), corresponding to 30% (80%) of collected photons, respectively. The presented fine-structure control opens the way for exploiting entangled photons from quantum dots in fiber-based quantum communication protocols.