Deterministic entanglement of photons in two superconducting microwave resonators

TL;DR

This paper demonstrates the creation and measurement of entangled photon states in two linear microwave resonators using superconducting circuits, marking a significant step in quantum control of linear systems.

Contribution

It introduces a method to generate and fully characterize entangled photon states in linear microwave resonators with superconducting circuits, overcoming previous control challenges.

Findings

Successfully created N-photon NOON states

Achieved complete bipartite Wigner tomography

Demonstrated advanced quantum control in linear resonators

Abstract

Quantum entanglement, one of the defining features of quantum mechanics, has been demonstrated in a variety of nonlinear spin-like systems. Quantum entanglement in linear systems has proven significantly more challenging, as the intrinsic energy level degeneracy associated with linearity makes quantum control more difficult. Here we demonstrate the quantum entanglement of photon states in two independent linear microwave resonators, creating N-photon NOON states as a benchmark demonstration. We use a superconducting quantum circuit that includes Josephson qubits to control and measure the two resonators, and we completely characterize the entangled states with bipartite Wigner tomography. These results demonstrate a significant advance in the quantum control of linear resonators in superconducting circuits.