Quantum reference frames, revisited

Understand

The topic of quantum reference frames (QRFs) has attracted a great deal of attention in the recent literature.

• Potentially, the correct description of such frames is important for both the technological applications of quantum mechanics and for its foundations, including the search for a future theory of quantum gravity.
• In this letter, we point out potential inconsistencies in the mainstream approach to this subject and propose an alternative definition that avoids these problems.
• Crucially, we reject the notion that transformations between QRFs can be represented by unitary operators and explain the clear physical reasons for this.