Deterministic Free-Propagating Photonic Qubits with Negative Wigner Functions

TL;DR

This paper reports the first deterministic method to generate non-Gaussian, Wigner-negative free-propagating photonic states by mapping an intracavity Rydberg superatom's state onto an optical qubit, enabling advanced quantum applications.

Contribution

It introduces a novel deterministic technique for producing non-Gaussian Wigner-negative photonic states using a Rydberg superatom, overcoming probabilistic limitations of previous methods.

Findings

Achieved 60% photon generation efficiency in a controlled mode.

Observed transition from quadrature squeezing to Wigner negativity.

Maintained strong photon antibunching during state evolution.

Abstract

Engineering quantum states of free-propagating light is of paramount importance for quantum technologies. Coherent states ubiquitous in classical and quantum communications, squeezed states used in quantum sensing, and even highly-entangled cluster states studied in the context of quantum computing can be produced deterministically, but they obey quasi-classical optical field statistics described by Gaussian, positive Wigner functions. Fully harnessing the potential of many quantum engineering protocols requires using non-Gaussian Wigner-negative states, so far produced using intrinsically probabilistic methods. Here we describe the first fully deterministic preparation of non-Gaussian Wigner-negative free-propagating states of light, obtained by mapping the internal state of an intracavity Rydberg superatom onto an optical qubit encoded as a superposition of 0 and 1 photons. This approach allows us to reach a 60% photon generation efficiency in a well-controlled spatio-temporal mode, while maintaining a strong photon antibunching. By changing the qubit rotation angle, we observe an evolution from quadrature squeezing to Wigner negativity. Our experiment sets this new technique as a viable method to deterministically generate non-Gaussian photonic resources, lifting several major roadblocks in optical quantum engineering.