# What weak measurements and weak values really mean - Reply to Kastner

## TL;DR

This paper defends the meaning and significance of weak measurements against recent criticism, clarifying misconceptions and highlighting experimental results that support their practical utility in quantum physics.

## Contribution

The author provides a detailed rebuttal to Kastner's critique, clarifies the interpretation of weak measurements, and discusses recent experimental findings supporting their validity.

## Key findings

- Weak measurements have practical significance in quantum metrology.
- Recent experiments clarify the meaning of weak values.
- Weak measurements can be replaced by strong projective measurements in some cases.

## Abstract

Despite their important applications in metrology and in spite of numerous experimental demonstrations, weak measurements are still confusing for part of the community. This sometimes leads to unjustified criticism. Recent papers have experimentally clarified the meaning and practical significance of weak measurements, yet in [R.E. Kastner, Found. Phys. 47, 697-707 (2017)], Kastner seems to take us many years backwards in the debate, casting doubt on the very term "weak value" and the meaning of weak measurements. Kastner appears to ignore both the basics and frontiers of weak measurements and misinterprets the weak measurement process and its outcomes. In addition, she accuses the authors of [Y. Aharonov et al., Ann. Phys. 355, 258-268 (2015)] in statements completely opposite to the ones they have actually made. There are many points of disagreement between Kastner and us, but in this short reply I will leave aside the ontology (which is indeed interpretational and far more complex than that described by Kastner) and focus mainly on the injustice in her criticism. I shall add some general comments regarding the broader theory of weak measurements and the Two-State-Vector Formalism (TSVF), as well as supporting experimental results. Finally, I will point out some recent promising results, which can be proven by (strong) projective measurements, without the need of employing weak measurements.