Implementation of quantum phase gate between two atoms via Rydberg antiblockade and adiabatic passage

Abstract

Combining adiabatic passage and Rydberg antiblockade, we propose a scheme to implement a two-qubit phase gate between two Rydberg atoms. Detuning parameters between frequencies of atomic transitions and those of the corresponding driving lasers are carefully chosen to offset the blockade effect of two Rydberg atoms, so that an effective Hamiltonian, representing a single-photon detuning Λ-type three-level system and concluding the quantum state of two Rydberg atoms excited simultaneously, is obtained. The adiabatic-passage technique, based on the effective Hamiltonian, is adopted to implement a two-atom phase gate by using two time-dependent Rabi frequencies. Numerical simulations indicate that a high-fidelity two-qubit π-phase gate is constructed and its operation time does not have to be controlled accurately. Besides, owing to the long coherence time of the Rydberg state, the phase gate is robust against atomic spontaneous emission.

Dissipative preparation of multipartite Greenberger-Horne-Zeilinger states of Rydberg atoms*

“…Ever since the seminal scheme was pro-posed by Jaksch and coworkers, [42] a variety of proposals were designed for quantum information processing using the Rydberg blockade, such as quantum algorithms, [43,44] entanglement generation, [45][46][47][48] quantum repeaters, [49][50][51] singlephoton transistors. [52] In contrast to the blockade regime, the Rydberg antiblockade, which can achieve the simultaneous excitations of two Rydberg atoms, offers many new possibilities in the research of quantum logic gate [53][54][55][56][57][58][59][60][61][62][63] and quantum entanglement. [64][65][66][67][68][69][70][71][72] Quite recently, the authors of Ref.…”

Generation of three-dimensional entanglement between two antiblockade Rydberg atoms with detuning-compensation-induced effective resonance

“…On the other hand, Rydberg atom systems are one of the most promising candidates for implementing quantum computing [42][43][44][45][46][47][48][49][50][51][52] and quantum information processing [53][54][55][56][57][58][59][60][61][62] due to the long coherence time of Rydberg states and the natural and powerful interatomic interactions [63]. Rydberg atoms that are the neutral atoms with high lying excited states exhibit strong Rydberg-Rydberg interaction (RRI) with their adjacent ones.…”

“…In addition, the direct measurement of the RRI has also been reported [66]. Beyond the Rydberg blockade, the Rydberg antiblockade (RAB) has also great potential applications in quantum physics, such as gaining the quantitative strength information of the RRI [67], quantum computing [43,45,47,51,52], and creating steady entangled states [28-31, 57, 59, 61].…”

“…On the other hand, the existing Rydberg-atom-based schemes of the highdimensional entanglement are almost based on dissipative dynamics that requires very long evolution time [28][29][30][31], while the present scheme uses the unitary dynamics which can ensure the fast generation of the 3D entanglement. In addition, in order to obtain the desired dynamics the Stark shifts induced by off-resonant transitions are usually eliminated through introducing the additional auxiliary levels and laser fields yielding opposite shifts of energy levels [51,58,59,68], which is complicated and difficult to implement. Here we propose to offset Stark shifts with detuning compensation by slightly modifying the frequencies of two laser fields.…”

A method to calculate effective Hamiltonians in quantum information*

“…[1,2] As the development of quantum information and quantum optics, it becomes common to use effective Hamiltonians in quantum entangled state preparation and quantum gate construction. [3][4][5][6][7][8][9] The method to calculate effective Hamiltonians presented by James and Jerke has been widely used in the fields of quantum information and quantum optics. [10,11] Their basic idea is to consider a time-dependent Hamiltonian in the interaction picture and to delete the high frequency terms of the corresponding time evolution operator.…”