Quantum Simulation In Room-Temperature Atoms

Quantum simulation is to use artificially controllable systems to simulate uncontrollable quanturm systems or a certain type of Hamiltonians.In recent years,quantum simulation has been widely used to study condensed-matter problems.Ultracold atoms in an optical lattice are an important platform for studying condensed-matter physics.In an optical lattice,atoms are trapped in a periodic potential formed by light fields,and their degrees of freedom of motion can be used to simulate electrons in solids.However,in the quantum simulation in optical lattices,atoms need to be cooled at extremely low temperatures,which accordingly require complex cooling devices and control technologies.Room-temperature atoms are an important platform in the field of quantum optics,and have important applications in electromagnetically induced transparency,multi-wave mixing,squeezed light and nonlinear interferometers.Compared to cold atoms in optical lattices,roomtemperature atoms are easier to obtain and do not require complex cooling technologies and equipment.Quantum simulation in room-temperature atoms is of great scientific significance as it not only overcomes limitations of temperature on atom-based quantum simulation,but also broadens the range of quantum simulation.Superradiance lattices are tight-binding lattices formed by timed Dicke states in momentum space.The timed Dicke state is the collective excited state of atoms with phase correlations and can be realized in moving atoms.Therefore,superradiance lattice is a room-temperature platform for quantum simulation.This thesis mainly focuses on quantum simulation based on superradiance lattices.The first two chapters introduce the background of quantum simulation and the theory of superradiance lattice.The last three chapters are the main content of this thesis.In Chapter 3,we synthesis a quasi-one-dimensional zigzag superradiance lattice by using two standing-wave light fields with spatial phase difference to couple three-level atoms.The spatial phase difference between the two standing-wave fields induces synthetic magnetic fields in the lattice.The chiral edge currents are experimentally observed by comparing the directional superradiant emissions of two timed Dicke states in the lattice.In Chapter 4,we study the flat-band localization in Creutz superradiance lattices.We synthesis Creutz lattices with tunable synthetic magnetic fields in superradiance lattices.The energy band structure of the Creutz lattice exhibits a flat band and a dispersive band,which are distinguished by localized and delocalized excitations,respectively.In the experiment,the hopping strengths can be tuned to selectively excite the particular band.We observe the interplay between the localization due to the flat band and edge currents due to the dispersive band,while the relation between flat-band localization and the synthetic gauge fields is investigated.In Chapter 5,we introduce the feasibility of superradiance lattice in achieving anti-parity-time symmetry.We construct an anti-parity-time-symmetric photonic lattice in standing wave coupled room-temperature atoms.Such a lattice possesses anti-parity-time-symmetric probe susceptibility,of which the real and imaginary parts are an odd and even function of position,respectively.We experimentally observe unidirectional reflectionless light propagation at the exceptional point.A summary of this thesis and future perspectives are given in Chapter 6.