Spin-Photon Entanglement of a Single <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msup> <mml:mrow> <mml:mi>Er</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> <mml:mo>+</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> Ion in the Telecom Band
Mehmet T. Uysal, Łukasz Dusanowski, Haitong Xu, Sebastian P. Horvath, Salim Ourari, R. J. Cava, Nathalie P. de Leon, Jeff D. Thompson
Abstract
Entanglement between photons and a quantum memory is a key component of quantum repeaters, which allow long-distance quantum entanglement distribution in the presence of fiber losses. Spin-photon entanglement has been implemented with a number of different atomic and solid-state qubits with long spin coherence times, but none directly emit photons into the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mn>1.5</a:mn> <a:mtext>−</a:mtext> <a:mi mathvariant="normal">μ</a:mi> <a:mi mathvariant="normal">m</a:mi> </a:mrow> </a:math> telecom band where losses in optical fibers are minimized. Here, we demonstrate spin-photon entanglement using a single rare earth ion in the solid-state <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mrow> <e:msup> <e:mrow> <e:mi>Er</e:mi> </e:mrow> <e:mrow> <e:mn>3</e:mn> <e:mo>+</e:mo> </e:mrow> </e:msup> </e:mrow> </e:math> coupled to a silicon nanophotonic cavity, which directly emits photons at 1532.6 nm. We infer an entanglement fidelity of 73(3)% after propagating through 15.6 km of optical fiber. This work opens the door to large-scale quantum networks based <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mrow> <g:msup> <g:mrow> <g:mi>Er</g:mi> </g:mrow> <g:mrow> <g:mn>3</g:mn> <g:mo>+</g:mo> </g:mrow> </g:msup> </g:mrow> </g:math> ions, leveraging scalable silicon device fabrication and spectral multiplexing.