The Two-State Vector Formalism of Qauntum Mechanics: an Updated Review

TL;DR

This paper reviews the two-state vector formalism of quantum mechanics, emphasizing its time-symmetrized approach, analysis of weak measurements, and a thought experiment illustrating quantum time travel concepts.

Contribution

It provides an updated, comprehensive review of the two-state vector formalism, including new insights into weak measurements and a conceptual quantum time machine.

Findings

Weak measurements reveal unusual quantum effects.

The formalism clarifies time-symmetry in quantum mechanics.

A thought experiment illustrates quantum time travel possibilities.

Abstract

In this paper we present the two-state vector formalism of quantum mechanics. It is a time-symmetrized approach to standard quantum theory particularly helpful for the analysis of experiments performed on pre- and post-selected ensembles. Several peculiar effects which naturally arise in this approach are considered. In particular, the concept of ``weak measurements'' (standard measurements with weakening of the interaction) is discussed in depth revealing a very unusual but consistent picture. Also, a design of a gedanken experiment which implements a kind of quantum ``time machine'' is described. The issue of time-symmetry in the context of the two-state vector formalism is clarified.