Hui Deng

Quantum mechanics is the language in the microscopic world where single or few particles and quasi-particles are fully described by their complex wavefunctions and a Hermitian system Hamiltonian. When the number of particles grows large, phase correlation among the particles is lost due to interaction with the environment — and we enter the classical world of human scales. In some special systems, however, phase correlations survive among a macroscopic number of particles over macroscopic distances, and remarkable collective quantum phenomena emerge. Those are the systems that we study.