Two-Qubit State Tomography using a Joint Dispersive Read-Out

TL;DR

This paper presents a method for two-qubit state tomography using joint dispersive read-out in superconducting qubits, enabling full state reconstruction without single-shot measurements of individual qubits.

Contribution

It introduces a novel joint measurement technique that simplifies two-qubit state tomography by leveraging dispersive coupling and standard tomographic methods.

Findings

Successful reconstruction of two-qubit density matrices

Demonstration of joint read-out without single-shot measurements

Extraction of two-qubit correlations effectively

Abstract

Quantum state tomography is an important tool in quantum information science for complete characterization of multi-qubit states and their correlations. Here we report a method to perform a joint simultaneous read-out of two superconducting qubits dispersively coupled to the same mode of a microwave transmission line resonator. The non-linear dependence of the resonator transmission on the qubit state dependent cavity frequency allows us to extract the full two-qubit correlations without the need for single shot read-out of individual qubits. We employ standard tomographic techniques to reconstruct the density matrix of two-qubit quantum states.