Quantum Information Processing Based On Rydberg Atom

The features of the interatomic Rydberg interactions open many possibilities to explore neutral atoms in the research of few-and many-body physics and quantum information applications.One of the critical effects resulting from the long-range interactions is the Rydberg blockade: it will significantly suppress the simultaneous excitation of multiple Rydberg atoms in a small volume.Based on the Rydberg blockade effect,a variety of proposals were designed theoretically and experimentally for quantum computation,entanglement generation,quantum algorithms,quantum simulators,and quantum repeaters.In addition,the combination of interatomic Rydberg interactions and two-photon detuning leads to an opposite effect,the Rydberg antiblockade.It will achieve the simultaneous excitations of two Rydberg atoms and can restrain the Rydberg blockade.The corresponding exploration is of particular interest,not only for two-qubit or multiqubit logic gates,but also for preparations of quantum entanglement.In this dissertation,we focus on the new schemes about the quantum information processing based on the Rydberg atoms.First,based on the Rydberg antiblockade effect,we successfully generate the Knill-Laflamme-Milburn(KLM)state with a high fidelity,where the system consists of two Rydberg atoms.Utilizing the combination of Rydberg antiblockade effect,the microwave field and the quantum dissipation,the KLM state becomes the unique steady state for the total system.Therefore,the system will be steady at the target state without precise time-dependent operations,and the scheme regards the atomic spontaneous emission as an important resource.Then,we use an organic combination of quantum Zeno dynamics,Rydberg antiblockade,and atomic spontaneous emission to prepare the tripartite W state.Besides the dissipative generation of the entanglement,we also propose a dissipation-assisted scheme to directionally transfer an arbitrary quantum state by the Rydberg antiblockade mechanism,the laser-induced Raman transition,and the photon loss of an optical cavity.Secondly,by virtue of the Rydberg-antiblockade effect,the Raman transition,and the quantum Zeno effect,we propose a new mechanism between two N-type Rydberg atoms: the ground-state blockade effect of Rydberg atoms.It can inhibit the double or more Rydberg atoms simultaneously occupying a certain ground state.Moreover,once the relevant parameters are suitable,the excited states can be adiabatically eliminated and the adverse effect of the atomic spontaneous emission can be significantly suppressed.In previous work,our group has used this effect to obtain the Bell state and the W state.In this work,we make use of this effect and the stimulated Raman adiabatic passage(STIRAP)to generate the multipartite Greenberger-Horne-Zeilinger(GHZ)state.After investigating the feasibility of the proposal,we show a 3-qubit GHZ state can be generated in a wide range of relevant parameters and a fidelity above 98% is achievable with the current experimental technologies.Finally,benefiting from the Rydberg interaction,we put forward a new mechanism,unconventional Rydberg pumping(URP),which differs from the general Rydberg blockade or Rydberg antiblockade.This effect is closely related to the ground states of atoms,i.e.,two atoms in the same ground state are stable while two atoms in different ground states are resonantly excited.Due to URP,we achieve a three-qubit controlledPHASE gate.And combining URP with the quantum dissipation,we provide the possibility to dissipatively prepare the two-and three-dimensional entangled states.Furthermore,we also exploit the URP to realize the autonomous quantum error correction in a Rydberg-atom-cavity system,where the bit-flip noise can be autonomously and continuously corrected.