Pascal Eich

Experimental protocol for high-fidelity heralded photon-to-atom quantum state transfer.

A quantum network combines the benefits of quantum systems regarding secure information transmission and calculational speed-up by employing quantum coherence and entanglement to store, transmit and process information. A promising platform for implementing such a network are atom-based quantum memories and processors, interconnected by photonic quantum channels. A crucial building block in this scenario is the conversion of quantum states between single photons and single atoms through controlled emission and absorption. Here we present an experimental protocol for photon-to-atom quantum state conversion, whereby the polarization state of an absorbed photon is mapped onto the spin state of a single absorbing atom with >95% fidelity, while successful conversion is heralded by a single emitted photon. Heralded high-fidelity conversion without affecting the converted state is a main experimental challenge, in order to make the transferred information reliably available for further operations. We record >80 s(-1) successful state transfer events out of 18,000 s(-1) repetitions.

Telecom-heralded single-photon absorption by a single atom

We present, characterize, and apply the architecture of a photonic quantum interface between the near infrared and telecom spectral regions. A singly resonant optical parametric oscillator (OPO) operated below threshold, in combination with external filters, generates high-rate (

High-fidelity entanglement between a trapped ion and a telecom photon via quantum frequency conversion

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Programmable atom-photon quantum interface

) narrowband photon pairs (

Quantum interference in absorption and emission of single photons by a single ion

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Doubly heralded single-photon absorption by a single atom

MHz bandwidth); the signal photons are tuned to resonance with an atomic transition in

High-fidelity heralded polarization-state transfer of a photon onto a single atom

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Quantum State Teleportation from a Single Ion to a Single Photon by Heralded Absorption

, while the idler photons are at telecom wavelength. Interface operation is demonstrated through high-rate absorption of single photons by a single trapped ion (

Photon-photon to atom-photon entanglement transfer

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Double-heralded single-photon absorption by a single atom

), heralded by coincident telecom photons.