Entanglement of distant atoms by a continuous supply of quantum correlated photons

Klaus Mølmer

Jan Huwer, Nicolás Piro, Michael Schug +2 more

The emission and absorption of single photons by single atomic particles is a fundamental limit of light-matter interaction. As a controlled process, it is a tool for quantum optical information technology. A key task in quantum networks is to establish entanglement between distant atomic qubits that serve as nodes. Until now this has only been experimentally demonstrated [1] through an approach that uses a projective measurement of the photons emitted by the two distant atoms, to entangle them. Another strategy is to generate entangled photon pairs by spontaneous parametric down-conversion (SPDC), and make them interact with the distant atoms, transferring the entanglement from photon to atomic qubits [2,3]. We have recently demonstrated for the first time the heralded absorption of a single down-conversion photon by a single40Ca+ion [4]. Here we show that besides the time and frequency correlation that the photon pairs share, also their polarization entanglement is preserved during the absorption of one of the photons by a single atom.

Harald Weinfurter, Michael H. W. Weber, Jürgen Volz +4 more

Sang-Kyung Choi, Hee Su Park

Felix Rohde, Nicolás Piro, Carsten Schuck +7 more

Entanglement distribution between distant nodes is a critical requirement for the realization of quantum networks. Recently, entanglement between distant atomic qubits has been demonstrated experimentally [1]. This scheme uses the projective measurement of the photons emitted by the two distant atoms to entangle them. Another strategy is to generate entangled photon pairs by a parametric down-conversion process, and make them interact with the distant atoms, transferring the entanglement from photon to atomic qubits [2, 3]. Here we describe our activities towards studying this second kind of entanglement distribution scheme.

Hudson Leone, S. Srikara, Peter P. Rohde +1 more

Despite recent advances in quantum repeater networks, entanglement distribution on a continental scale remains prohibitively difficult and resource intensive. Using satellites to distribute maximally entangled photons (Bell pairs) between distant stations is an intriguing alternative. Quantum satellite networks are known to be viable for quantum key distribution, but the question of if such a network is feasible for fault tolerant distributed quantum computation (FTDQC) has so far been unaddressed. In this paper we determine a closed form expression for the rate at which logical Bell pairs can be produced between distant surface code encoded qubits using a satellite network to supply imperfect physical Bell pairs. With generous parameter assumptions, our results show that FTDQC with satellite networks over statewide distances (500--999 km) is possible up to a collective clock rate on the order of 1 MHz, while continental (1000--4999 km) and transcontinental ($5000+$ km) distances run on the order of 10 kHz and 100 Hz, respectively.