Quantum theory is a mathematically coherent and beautiful theory that lies at the heart of our current understanding of nature. However, whether it is *the* fundamentally correct description of nature remains uncertain. We have no conceptually well-defined and empirically tested theory that unifies quantum theory and gravity and rigorously explains cosmological data. Nor is there even a consensus that the appearance of the quasiclassical world can be explained from within standard quantum theory. Alternatives to quantum theory have been increasingly explored in recent decades, partly in the hope of resolving these problems, and partly with the aim of better understanding quantum theory itself and identifying the strongest experimental tests. In parallel with these developments, advances in matter interferometry and other areas have also made new tests possible. We aim at this meeting to explore the most attractive current theoretical ideas, to make progress towards a systematic understanding of the landscape of possible theories to which quantum theory belongs, and to review and advance the prospects for experimental tests of quantum theory in new regimes.
Sponsorship for this conference has been provided by: