… , understood as a classical frame of reference. If we were to promote the reference frame to
the role of an quantum observer, we would need to account for the quantum character of the …

… as a quantum reference frame, because quantum theory … apparatus) as defining a reference
frame, and that this stipulation … back and describe that object quantum-mechanically again (…

… Here, we revisit one of their models and analyse its dynamics in more detail. We show how
their result follows from simple physical principles based on symmetries and conservation …

… reference frames fundamentally as quantum systems is inevitable in quantum gravity and also
in quantum … of how to describe physics relative to quantum reference systems and how the …

… The situation was revisited, and clarified, by Aharonov & Susskind [4,5], followed by … A
general quantum reference frame In this section, we construct a general quantum reference frame …

… perspective of quantum reference frames. We find a … reference frame transformations
correspond to reparametrizations of the constraint surface. We conclude by constructing a quantum …

… Jordan and Einstein conformal frames in scalar-tensor gravity is revisited, with the … quantum
gravity. In view of Dicke’s paper, many authors consider the issue of which conformal frame …

… a reference system. We provide a rigorous mathematical language to introduce and study
quantum reference … of observable relative quantities if the reference state is suitably localised. …

… The degrees of freedom ˆB can be identified as a quantum reference frame (QRF): the
physics of QG should be understood in terms of QRF. This new type of physics is extremely rich …

… It is the aim of this contribution to critically revisit the subject within two complementary
frameworks. First, in Secs. II and III, by suitably employing passive unitary transformations, we …