Seventeen theoretical physics faculty across 12 institutions are members of the newly established Simons Collaboration called “Ultra-Quantum Matter”. This new effort is an $8M four-year award renewable for three additional years, funded by the Simons Foundation. The institutions supported are: Caltech, Harvard, the Institute for Advanced Study, MIT, Stanford, University of California Santa Barbara, University of California San Diego, University of Colorado at Boulder, the University of Chicago, the University of Innsbruck, University of Maryland, and University of Washington.  The collaboration, led by Professor Ashvin Vishwanath (Director) at Harvard, and Professor Michael Hermele (Deputy Director) at CU Boulder, is part of the Simons Collaborations in Mathematics and Physical Sciences program, which aims to “stimulate progress on fundamental scientific questions of major importance in mathematics, theoretical physics and theoretical computer science.”  The Simons Collaboration on Ultra-Quantum Matter will be one of 12 such collaborations ranging across these fields.

In the more than a century since its beginnings, quantum mechanics has enthralled and astounded with its dramatically non-intuitive nature. While quantum effects are all-important at atomic lengths, they are usually less evident at the human scale. A remarkable series of revolutionary developments in theoretical condensed matter physics and quantum information theory, however, has revealed that even large macroscopic systemswhich consist of many atoms or electrons – i.e. matter – can behave in an essentially quantum way.

The famous Schrödinger’s cat provides one ultimate large quantumsystem: a quantum superposition of two macroscopically distinct states. Such a state displays non-local entanglement: a measurement in one location is correlated with the outcome of a second measurement a macroscopic distance away. The Schrödinger cat is, unfortunately, exponentially unstable due to the ability of a local measurement anywhere in space to collapse the quantum superposition. We now know that there is a rich middle ground between ordinary classical matter and Schrödinger’s cat. These are stable phases of Ultra-Quantum Matter (UQM) that extend quantum effects in striking ways to the macro-world. The wavefunction of a state of UQM consists of a superposition of an infinite number of classical states, in such a way that non-local correlations persist but cannot be destroyed by local measurements. Emergent non-locality is the key property of UQM, as well as a resource that allows unique effects like distributed storage of information, fractional quantum numbers, and beyond. UQM is as fundamentally different from ordinary matter in its quantum aspects as a solid is from a liquid in classical terms.

It has become evident that the natural language for UQM is that of gauge theory, originally conceived as a notion of local symmetry and a guiding principle for quantum field theory of elementary particles. In the current era, the study of UQM is bringing new life to this venerable topic in diverse ways. In UQM, gauge theory arises not as a symmetry principle imposed on nature, but as an emergent structure necessary to describe our world. Moreover, in this context the framework of gauge theory itself becomes naturally enlarged to include richer mathematical structures from Chern- Simons terms to higher formgauge fields, fractons, and more. Our proposed Simons Collaboration on Ultra-Quantum Matter seeks to understand, classify and realize ultraquantum matter with an underlying gauge structure. Rapid progress toward this goal is now possible, due to the recent breakthrough in the understanding of dualities of 2+1 dimensional field theories which reveals deep connections amongst apparently different gauge theories. New dualities discovered only in the last few years forge these relations and imply non-manifest “quantum” symmetries without classical analogs. Finally, the AdS/CFT correspondence ties the improved understanding of critical gauge theories to that of gravity, further linked to UQM through the physics of “strange metals.”

The proposed Collaboration brings together experts in different aspects of UQM and gauge theory from high energy physics, condensed matter physics, and atomic and molecular physics – an unusual but timely trifecta that is essential to accomplish our program.