# Nondestructive Measurement of Orbital Angular Momentum for an Electron Beam

## TL;DR

This paper introduces a nondestructive method to measure the orbital angular momentum of twisted electrons by detecting induced currents in a conductive loop, preserving the electron's OAM and minimizing energy loss.

## Contribution

It proposes a novel nondestructive measurement technique for electron OAM based on magnetic dipole interactions with a conductive loop.

## Key findings

- Induced currents are proportional to the electron's OAM.
- The measurement process does not alter the electron's OAM.
- Minimal energy loss occurs during measurement.

## Abstract

Free electrons with a helical phase front, referred to as "twisted" electrons, possess an orbital angular momentum (OAM) and, hence, a quantized magnetic dipole moment along their propagation direction. This intrinsic magnetic moment can be used to probe material properties. Twisted electrons thus have numerous potential applications in materials science. Measuring this quantity often relies on a series of projective measurements that subsequently change the OAM carried by the electrons. In this Letter, we propose a nondestructive way of measuring an electron beam's OAM through the interaction of this associated magnetic dipole with a conductive loop. Such an interaction results in the generation of induced currents within the loop, which are found to be directly proportional to the electron's OAM value. Moreover, the electron experiences no OAM variations and only minimal energy losses upon the measurement, and, hence, the nondestructive nature of the proposed technique.