Continuous-variable square-ladder cluster states in a microwave frequency comb

TL;DR

This paper reports the experimental generation of large-scale continuous-variable cluster states in a microwave frequency comb using a Josephson Parametric Amplifier, demonstrating significant squeezing and entanglement at a large number of modes.

Contribution

The work introduces a method to generate large-scale square-ladder continuous-variable cluster states in the microwave regime with up to 94 modes using a Josephson Parametric Amplifier.

Findings

Achieved up to 1.4 dB of nullifier squeezing verifying the cluster state.

Demonstrated up to 5.42 dB of two-mode squeezing with a single pump.

Generated three independent cluster states with up to 94 modes.

Abstract

We describe an experiment demonstrating the generation of three independent square-ladder continuous-variable cluster states with up to 94 qumodes of a microwave frequency comb. This entanglement structure at a large scale is realized by injecting vacuum fluctuations into a Josephson Parametric Amplifier pumped by three coherent signals around twice its resonance frequency, each having a particular well-defined phase relation. We reach up to 1.4 dB of squeezing of the nullifier which verifies the cluster state on the square ladder graph. Our results are consistent with a more familiar measure of two-mode squeezing, where we find up to 5.42 dB for one pump, and up to 1 dB for three pumps.