26,477 research outputs found
Quantum reference frames and deformed symmetries
In the context of constrained quantum mechanics, reference systems are used
to construct relational observables that are invariant under the action of the
symmetry group. Upon measurement of a relational observable, the reference
system undergoes an unavoidable measurement "back-action" that modifies its
properties. In a quantum-gravitational setting, it has been argued that such a
back-action may produce effects that are described at an effective level as a
form of deformed (or doubly) special relativity. We examine this possibility
using a simple constrained system that has been extensively studied in the
context of quantum information. While our conclusions support the idea of a
symmetry deformation, they also reveal a host of other effects that may be
relevant to the context of quantum gravity, and could potentially conceal the
symmetry deformation.Comment: 11 pages, revtex. Comments are welcom
Quantum communication, reference frames and gauge theory
We consider quantum communication in the case that the communicating parties
not only do not share a reference frame but use imperfect quantum communication
channels, in that each channel applies some fixed but unknown unitary rotation
to each qubit. We discuss similarities and differences between reference frames
within that quantum communication model and gauge fields in gauge theory. We
generalize the concept of refbits and analyze various quantum communication
protocols within the communication model.Comment: pretty pointless, published nonetheles
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