Quantum Non-Gaussianity From An Indefinite Causal Order of Gaussian Operations

TL;DR

This paper explores how indefinite causal order of Gaussian operations, controlled by a qubit, can generate highly non-Gaussian states useful for quantum information tasks, outperforming traditional schemes.

Contribution

It introduces a novel method to engineer non-Gaussian states using quantum switch with Gaussian operations, leveraging non-convexity and postselection for deterministic non-Gaussianity.

Findings

Deterministic generation of non-Gaussian states from Gaussian operations.

Enhanced non-classicality of states via indefinite causal order.

Potential applications in quantum communication and sensing.

Abstract

Quantum Non-Gaussian states are considered as a useful resource for many tasks in quantum information processing, from quantum metrology and quantum sensing to quantum communication and quantum key distribution. Another useful tool that is growing attention is the newly constructed quantum switch. Its applications in many tasks in quantum information have been proved to be outperforming many existing schemes in quantum communication and quantum thermometry. In this contribution, we are addressing this later to be very useful to engineer highly non-Gaussian states from Gaussian operations whose order is controlled by degrees of freedom of a control qubit. The non-convexity of the set of Gaussian states and the set of Gaussian operations guarantees the emergence of non-Gaussianity after postselection on the control qubit deterministically, in contrast to existing protocols in the literature. The non-classicality of the resulting states is discussed accordingly.