26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Generation of a heralded three-mode NOON state

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral AIP | Quantum Science and Technology (QST)

Speaker

Dr Simon White (Queensland Quantum and Advanced Technologies Research Institute, Centre for Quantum Computation and Communication Technology, Griffith University, Yuggera Country, Brisbane, Queensland, 4111 Australia)

Description

The generation of entangled quantum states of photons is a key capability for a vast range of technologies and forms the foundations of quantum communication, computation, and metrology. In photonics, due to the lack of strong photon-photon interactions, the generation of the vast majority of entangled states is probabilistic. This typically requires post-selection to identify successful generation events, destroying the target state. Fortunately, there exists an alternative solution: Heralding. Here, the measurement of ancillary photons in auxiliary modes indicates that the generated state exists, without the need to measure and thereby destroy it.

In this work, we report a protocol for generating heralded multi-mode two-photon entangled NOON states [1], coherent superpositions of N photons across multiple modes, integral resources for applications including multiphase estimation and distributed sensing. We demonstrate the protocol by experimentally generating and verifying a three-mode two-photon NOON state, whose presence is signalled by the detection of a single photon in an auxiliary mode. To validate the generated state, we perform a tailored measurement to estimate its fidelity relative to an ideal three-mode NOON state, yielding $0.823\pm0.018$. Furthermore, with this achieved fidelity, the generated state exceeds the threshold for genuine multipartite entanglement by more than 8 standard deviations. We then theoretically show how to scale the protocol to generate arbitrary $d$-mode two-photon NOON states using a cascaded linear-optical scheme. Due to the low resource overhead (only one ancillary photon) and high success probability ($P=25\%$) of our demonstration, and the protocol's scalability, our work provides an experimental and theoretical advance for multi-mode entanglement generation. This generation of multimode entangled states represents a key milestone in linear-optical quantum information realisable with current technology and highlights these states as resources for entangled multi-qubit protocols.
[1] Singh, Sukhjit P., et al. "Heralded generation of a three-mode NOON state." arXiv preprint arXiv:2512.08458 (2025).