Entanglement Concentration with Quantum Non Demolition Hamiltonians

TL;DR

This paper introduces two new entanglement concentration protocols using Quantum Non Demolition Hamiltonians in continuous variable systems, expanding the experimental toolkit for entanglement distillation.

Contribution

It develops and analyzes two novel protocols employing QND interactions with different ancillary states, enhancing the versatility and feasibility of entanglement concentration methods.

Findings

Protocols successfully increase entanglement as measured by Logarithmic Negativity.

Explicit density matrix calculations demonstrate the protocols' effectiveness.

Performance comparison shows advantages of each protocol in different scenarios.

Abstract

We devise and examine two procrustean entanglement concentration schemes using Quantum Non- Demolition (QND) interaction Hamiltonians in the continuous variable regime, applicable for light, for atomic ensembles or in a hybrid setting. We thus expand the standard entanglement distillation toolbox to the use of a much more general, versatile and experimentally feasible interaction class. The first protocol uses Gaussian ancillary modes and a non-Gaussian post-measurement, the second a non-Gaussian ancillary mode and a Gaussian post-measurement. We explicitly calculate the density matrix elements of the non-Gaussian mixed states resulting from these protocols using an elegant Wigner-function based method in a numerically efficient manner. We then quantify the entanglement increase calculating the Logarithmic Negativity of the output state and discuss and compare the performance of the protocols.