Experimental quantum telecloning across silicon photonic chips

Research Question and Background

The fundamental laws of quantum mechanics—specifically the no-cloning theorem—prohibit the creation of perfect copies of an unknown quantum state. However, quantum theory permits approximate cloning, where imperfect copies are produced with a maximum allowed fidelity. Quantum telecloning combines quantum teleportation and cloning to distribute approximate copies of an unknown state to multiple spatially separated recipients. While theoretically proposed decades ago, realizing symmetric telecloning experimentally has remained challenging because it requires generating complex multipartite entangled resource states and maintaining stable multi-photon interference across distributed nodes. This paper investigates whether an integrated silicon photonic platform can overcome these experimental hurdles to perform interchip quantum telecloning.

Experimental Approach

The authors designed and utilized two independent silicon-on-insulator (SOI) photonic chips linked by an optical fiber. Chip 1 acts as the sender, utilizing a nanowire photon-pair source driven by a pulsed laser to generate a heralded input photon state. Chip 2 serves as the resource generator, employing two additional photon-pair sources and interferometric networks to prepare a four-photon entangled resource state known as the telecloning resource. One photon from this resource state is transmitted via fiber to Chip 1, where an on-chip Bell-state measurement (BSM) is performed between the input photon and the received resource photon. Conditioned on successful BSM outcomes, the input state is nonlocally distributed and cloned into two output modes on Chip 2, which are then analyzed using quantum state tomography.

The system-level performance was validated through heralded Hong-Ou-Mandel interference, quantum state tomography, and fidelity measurements of the resulting clones. The reconstructed four-photon resource state exhibited an interchip fidelity of 81.12%. Following the interchip BSM and subsequent quantum state reconstruction of the clone photons, the researchers observed an average cloning fidelity of 78.45%. This result exceeds the classical cloning limit of 2/3 by eight standard deviations, confirming the genuine quantum mechanical nature of the distributed telecloning process across integrated chips.