Measurement of the Entanglement of Two Superconducting Qubits via State Tomography

TLDR

Demonstration of quantum entanglement, a key resource in quantum computation arising from a nonclassical correlation of states, requires complete measurement of all states in varying bases. The study demonstrates entanglement between two solid‑state qubits using simultaneous measurement and state tomography. Entanglement was generated by single‑qubit operations and capacitive coupling between two superconducting phase qubits to produce a Bell‑type state. Full two‑qubit tomography yielded a density matrix showing an entangled state with fidelity up to 87%, demonstrating a high degree of unitary control and indicating that larger implementations are within reach.

Abstract

Demonstration of quantum entanglement, a key resource in quantum computation arising from a nonclassical correlation of states, requires complete measurement of all states in varying bases. By using simultaneous measurement and state tomography, we demonstrated entanglement between two solid-state qubits. Single qubit operations and capacitive coupling between two super-conducting phase qubits were used to generate a Bell-type state. Full two-qubit tomography yielded a density matrix showing an entangled state with fidelity up to 87%. Our results demonstrate a high degree of unitary control of the system, indicating that larger implementations are within reach.