State Transfer in Latent-Symmetric Networks

TL;DR

This paper introduces a novel class of quantum networks based on latent symmetries that enable high-fidelity state transfer without relying on conventional spatial symmetries, expanding design possibilities for quantum communication.

Contribution

The work demonstrates the design and experimental realization of latent-symmetric networks supporting efficient quantum state transfer, even without traditional symmetries, and explores their potential applications.

Findings

Achieved 75% fidelity in state transfer between two sites.

Observed preservation of quantum interference with two-photon states.

Validated the theoretical advantage of latent symmetries in quantum networks.

Abstract

The transport of quantum states is a crucial aspect of information processing systems, facilitating operations such as quantum key distribution and inter-component communication within quantum computers. Most quantum networks rely on symmetries to achieve an efficient state transfer. A straightforward way to design such networks is to use spatial symmetries, which severely limits the design space. Our work takes a novel approach to designing photonic networks that do not exhibit any conventional spatial symmetries, yet nevertheless support an efficient transfer of quantum states. Paradoxically, while a perfect transfer efficiency is technically unattainable in these networks, a fidelity arbitrarily close to unity is always reached within a finite time of evolution. Key to this approach are so-called latent, or 'hidden', symmetries, which are embodied in the spectral properties of the network. Latent symmetries substantially expand the design space of quantum networks and hold significant potential for applications in quantum cryptography and secure state transfer. We experimentally realize such a nine-site latent-symmetric network and successfully observe state transfer between two sites with a measured fidelity of 75%. Furthermore, by launching a two-photon state, we show that quantum interference is preserved by the network. This demonstrates that the latent symmetries enable efficient quantum state transfer, while offering greater flexibility in designing quantum networks.