On-chip distribution of quantum information using traveling phonons

TL;DR

This paper demonstrates on-chip quantum information distribution using traveling phonons, creating entanglement and a time-bin encoded phononic qubit, advancing scalable quantum processing and hybrid quantum system integration.

Contribution

It experimentally shows quantum entanglement between traveling phonons and the creation of a phononic qubit on a chip, a novel step in quantum information transfer.

Findings

Successfully generated and launched phononic quantum states in a waveguide.

Demonstrated violation of a Bell-type inequality with phononic and photonic qubits.

Achieved propagation of quantum states over approximately 200 micrometers.

Abstract

Distributing quantum entanglement on a chip is a crucial step towards realizing scalable quantum processors. Using traveling phonons - quantized guided mechanical wavepackets - as a medium to transmit quantum states is currently gaining significant attention, due to their small size and low propagation speed compared to other carriers, such as electrons or photons. Moreover, phonons are highly promising candidates to connect heterogeneous quantum systems on a chip, such as microwave and optical photons for long-distance transmission of quantum states via optical fibers. Here, we experimentally demonstrate the feasibility of distributing quantum information using phonons, by realizing quantum entanglement between two traveling phonons and creating a time-bin encoded traveling phononic qubit. The mechanical quantum state is generated in an optomechanical cavity and then launched into a phononic waveguide in which it propagates for around two hundred micrometers. We further show how the phononic, together with a photonic qubit, can be used to violate a Bell-type inequality.