Long-distance distribution of qubit-qubit entanglement using Gaussian-correlated photonic beams

TL;DR

This paper explores a method for generating and distributing high-quality entanglement between distant qubits in large quantum networks using Gaussian-correlated photonic beams from a parametric amplifier, considering realistic experimental conditions.

Contribution

It introduces a scheme combining Gaussian two-mode squeezed states with qubit networks, analyzing optimal conditions for entanglement generation under practical limitations.

Findings

Optimal amplifier settings maximize qubit entanglement.

The scheme is robust against losses and delays.

Potential for scalable quantum network implementation.

Abstract

We investigate the deterministic generation and distribution of entanglement in large quantum networks by driving distant qubits with the output fields of a non-degenerate parametric amplifier. In this setting, the amplifier produces a continuous Gaussian two-mode squeezed state, which acts as a quantum-correlated reservoir for the qubits and relaxes them into a highly entangled steady state. Here we are interested in the maximal amount of entanglement and the optimal entanglement generation rates that can be achieved with this scheme under realistic conditions taking, in particular, the finite amplifier bandwidth, waveguide losses and propagation delays into account. By combining exact numerical simulations of the full network with approximate analytic results, we predict the optimal working point for the amplifier and the corresponding qubit-qubit entanglement under various conditions. Our findings show that this passive conversion of Gaussian- into discrete- variable entanglement offers a robust and experimentally very attractive approach for operating large optical, microwave or hybrid quantum networks, for which efficient parametric amplifiers are currently developed.