Study On The Unified Generation And Fast Emission Of Arbitrary Single Photon Multimode W States

In the 1980s,the combination of quantum mechanics and classical information theory gave rise to a very active field--quantum information theory,which takes advantage of quantum mechanical systems to transmit,store and process information.The mathematical description of quantum systems have fundamental difference from the descriptions in the classic mode.Most of the information in general quantum mechanical systems is stored in the form of correlated subsystems,and the correlation can be very strong,namely the entanglement between the components of compound quantum system,which gives significantly different characteristics for quantum information.States with entangled properties are called entangled states.There are many types of entangled states.This thesis mainly studies the deterministc and fast preparation of arbitrary single photon multimode W states.Chapter 3 and Chapter 4 are our preparation schemes,and the specific arrangements are as follows:The first chapter introduces the purpose and significance of the research,the development status and existing problems at home and abroad.The second chapter briefly introduces the relevant theoretical basic knowledge,including qubit and multi-particle entanglement,cavity quantum electrodynamics,Rabi model,Lindblad master equation,etc.In chapter 3,the special dark states in the Rabi model of multi qubit multimode are briefly introduced,and the scheme of preparing and releasing arbitrary W states by using this special dark state is introduced.General solutions to the quantum Rabi model involve subspaces with an unbounded number of photons.However,for the multiqubit multimode case,we find special solutions with at most one photon for an arbitrary number of qubits and photon modes.Such solutions exist for arbitrary single qubit-photon coupling strength gi with constant eigenenergy,while still being qubitphoton entangled states.Taking advantage of their peculiarities and the reach of the ultrastrong coupling regime,we propose an adiabatic scheme for the fast and deterministic generation of a two-qubit Bell state and arbitrary single-photon multimode W states with nonadiabatic error less than 1%.Finally,we propose a superconducting circuit design to catch and release the W states,and shows the experimental feasibility of the multimode multi qubit quantum Rabi model.In chapter 4,the preparation and release of arbitrary W states by coupling a single superconducting qutrit(SQ)with several coplanar waveguide resonators(CWR)are described.A three-level system(qutrit)is driven by a pump-laser pulse and coupled to N spatially separated resonators.The coupling strength for each spatial mode gi totally decide the generated single-photon N-mode W state|WN>=1/AΣi=1 Ngi|0102…1i0i+1…ON>,so arbitrary |WN>can be generated inside resonators just by tuning gi.Moreover,such W states can be fast emitted with probability reaching 98.9%.The generation(or emission)time and fidelity can both be the same for arbitrary |WN>.Finally,the time evolution process is easy to control since only the pump pulse is time-dependent.The fifth chapter is the summary and prospect...