Linear simultaneous measurements of position and momentum with minimum error-trade-off in each minimum uncertainty state

TL;DR

This paper demonstrates the construction of linear simultaneous measurements of position and momentum that achieve the theoretical error-trade-off bound in minimum uncertainty states, advancing the understanding of quantum measurement limits.

Contribution

It introduces a method to realize optimal simultaneous measurements of position and momentum that attain the Branciard-Ozawa error-trade-off relation in minimum uncertainty states.

Findings

Achieved the Branciard-Ozawa error-trade-off bound in minimum uncertainty states.

Constructed linear measurement models for position and momentum.

Analyzed probability distributions and posterior states post-measurement.

Abstract

So-called quantum limits and their achievement are important themes in physics. Heisenberg's uncertainty relations are the most famous of them but are not universally valid and violated in general. In recent years, the reformulation of uncertainty relations is actively studied, and several universally valid uncertainty relations are derived. On the other hand, several measuring models, in particular, spin-1/2 measurements, are constructed and quantitatively examined. However, there are not so many studies on simultaneous measurements of position and momentum despite their importance. Here we show that an error-trade-off relation (ETR), called the Branciard-Ozawa ETR, for simultaneous measurements of position and momentum gives the achievable bound in minimum uncertainty states. We construct linear simultaneous measurements of position and momentum that achieve the bound of the Branciard-Ozawa ETR in each minimum uncertainty state. To check their performance, we then calculate probability distributions and families of posterior states, sets of states after the measurements, when using them. The results of the paper show the possibility of developing the theory of simultaneous measurements of incompatible observables. In the future, it will be widely applied to quantum information processing.