Qubit state tomography in superconducting circuit via weak measurements

TL;DR

This paper explores a direct method for qubit state tomography in superconducting circuits using weak measurements, extending the approach beyond traditional limits and aligning with current experimental capabilities.

Contribution

It introduces a finite-strength weak measurement scheme for qubit tomography in circuit QED, applicable under broad parameter conditions and beyond previous limiting assumptions.

Findings

Formulation for finite-strength weak measurement in circuit QED.

Analysis applicable beyond bad-cavity and weak-response limits.

Accessible to current circuit-QED experimental setups.

Abstract

The standard method of "measuring" quantum wavefunction is the technique of {\it indirect} quantum state tomography. Owing to conceptual novelty and possible advantages, an alternative {\it direct} scheme was proposed and demonstrated recently in quantum optics system. In this work we present a study on the direct scheme of measuring qubit state in the circuit QED system, based on weak measurement and weak value concepts. To be applied to generic parameter conditions, our formulation and analysis are carried out for finite strength weak measurement, and in particular beyond the bad-cavity and weak-response limits. The proposed study is accessible to the present state-of-the-art circuit-QED experiments.