Over the past five years, there has been much interest in a new kind of "unspeakable" quantum information which is to regular quantum information what a classical clock or gyroscope is to a classical message. While the latter is indifferent to the physical nature of the information carriers, the former requires the carrier to have a particular degree of freedom -- a spatial orientation in the case of a gyroscope, or a natural oscillation in the case of a clock. Systems serving this purpose are referred to generically as reference frames, and constitute a quantifiable resource in quantum information theory. They play a central role in the tasks of direction and frame alignment, phase estimation, clock synchronization, and global positioning. The community has only just begun a systematic study of how this resource can be manipulated, quantified, and used optimally in both information-processing protocols and physical parameter estimation.
At the same time, there have been investigations into the information theory that is appropriate for parties that lack any system that could serve as a reference frame for some degree of freedom, or lack correlations among such systems. Such restrictions on the parties quantum operations result in local and global superselection rules (SSRs). How to contend with such SSRs, particularly in the context of computation, cryptography, communication, and the definition of entanglement, has also received a great deal of attention of late.
The community is currently struggling to develop a deeper understanding of these issues. Indeed, many of the confusions and controversies that spawned present research efforts in this field have yet to be completely resolved. These include: the interpretation of quantum states exhibiting coherence between number states in a single mode (a subject of controversy in optics, Bose-Einstein condensation and superconductivity); the quantification of entanglement in systems of bosons or fermions; the efficiency with which frames may be aligned, clocks synchronized, etcetera; and the significance of SSRs on the possibility of implementing various quantum information-processing tasks.
The goal of the workshop is to bring together leaders in this field to share their approaches and results, draw connections between research efforts, develop a broader perspective on the issues, focus on outstanding problems, foster an interactive community, and set objectives for future research.
Please take note of the conference on Quantum information and quantum control which takes place immediately following this workshop in the nearby city of Toronto.