# Direct measurement of the quantum state of photons in a cavity

## TL;DR

This paper introduces a novel method for directly measuring the quantum state of photons in a cavity using weak values, enabling access to superposition components without full state reconstruction.

## Contribution

It presents a new direct measurement scheme based on quantum weak values applicable to cavity QED systems, bypassing the need for quantum state tomography.

## Key findings

- Allows direct access to superposition components in Fock basis
- Eliminates the need for global quantum state reconstruction
- Applicable to solid-state and atomic cavity QED systems

## Abstract

We propose a scheme to measure the quantum state of photons in a cavity. The proposal is based on the concept of quantum weak values and applies equally well to both the solid-state circuit and atomic cavity quantum electrodynamics (QED) systems. The proposed scheme allows us to access directly the superposition components in Fock state basis, rather than the Wigner function as usual in phase space. Moreover, the separate access feature held in the direct scheme does not require a global reconstruction for the quantum state, which provides a particular advantage beyond the conventional method of quantum state tomography.