no code implementations • 11 Aug 2019 • Leonardo Andreta de Castro, Olímpio Pereira de Sá Neto, Carlos Alexandre Brasil
The clear separation between quantum system and classical apparatus that causes these restrictions is subverted in von Neumann's paradigmatic model of quantum measurements, a subject whose concepts we explain, while also providing the mathematical tools necessary to apply it to new problems.
Quantum Physics History and Philosophy of Physics
no code implementations • 19 Mar 2018 • Leonardo Andreta de Castro, Carlos Alexandre Brasil, Reginaldo de Jesus Napolitano
Weak measurements have an increasing number of applications in contemporary quantum mechanics.
Quantum Physics
no code implementations • 25 May 2016 • Leonardo Andreta de Castro, Carlos Alexandre Brasil, Reginaldo de Jesus Napolitano
The energy levels of hydrogen-like atoms are obtained from the phase-space quantization, one of the pillars of the old quantum theory, by three different methods - (i) direct integration, (ii) Sommerfeld's original method, and (iii) complex integration.
Quantum Physics
no code implementations • 17 Aug 2015 • Carlos Alexandre Brasil, Leonardo Andreta de Castro
Employing a simple physical model consisting of a pair of two-level systems -- one representing the main system, the other the measurement apparatus -- and a thermal bath -- representing the environment -- we show how pointer states emerge, explaining its contributions to the question of measurement in quantum mechanics, as well as its limitations.
Quantum Physics
no code implementations • 14 Sep 2013 • Carlos Alexandre Brasil, Leonardo Andreta de Castro, Reginaldo de Jesus Napolitano
Contrary to conventional quantum mechanics, which treats measurement as instantaneous, here we explore a model for finite-time measurement.
Quantum Physics
no code implementations • 21 Sep 2011 • Carlos Alexandre Brasil, Leonardo Andreta de Castro, Reginaldo de Jesus Napolitano
Analysing the behavior of the coherence, which tends to a value asymptotically close to zero, we obtain an expression for the time of measurement which depends only on the system-measurer coupling, and which does not depend on whether the observable commutes with the system-bath interaction.
Quantum Physics
no code implementations • 22 Jun 2011 • Carlos Alexandre Brasil, Leonardo Andreta de Castro, Reginaldo de Jesus Napolitano
We have tested the validity of the analytical predictions against an exact numerical approach, based on the superoperator-splitting method, that confirms the protection of the initial state of the system.
Quantum Physics
