Abstract Quantum phase gates serve as core fundamental resources for quantum information processing, and their preparation effciency and structural stability directly determine the overall performance of quantum computing and quantum communication. The traditional adiabatic preparation method is prone to the influence of decoherence due to its excessive time consumption, while superadiabatic shortcut technology can significantly shorten the evolution time while retaining the advantages of the adiabatic process. In this paper, we propose a scheme for rapidly implementing a quantum phase gate by combining superadiabatic scheme and quantum Zeno dynamics to construct shortcuts to adiabatic passage. We demonstrate the superadiabatic shortcut by using Rydberg superatoms in distant-atom-cavity system. Furthermore, we utilize the controlled π phase gate to achieve the preparation of N-particles cluster states. Additionally, the impact of decoherence and operational imperfections are discussed. Numerical simulation demonstrates the proposed scheme has high fidelities and robustness against both cavity leakage and atomic spontaneous emission.
Fast implementation of controlled π phase gate using superadiabatic shortcuts with Rydberg superatoms
Abstract Quantum phase gates serve as core fundamental resources for quantum information processing, and their preparation effciency and structural stability directly determine the overall performance of quantum computing and quantum communication. The traditional adiabatic preparation method is prone to the influence of decoherence due to its excessive time consumption, while superadiabatic shortcut technology can significantly shorten the evolution time while retaining the advantages of the adiabatic process. In this paper, we propose a scheme for rapidly implementing a quantum phase gate by combining superadiabatic scheme and quantum Zeno dynamics to construct shortcuts to adiabatic passage. We demonstrate the superadiabatic shortcut by using Rydberg superatoms in distant-atom-cavity system. Furthermore, we utilize the controlled π phase gate to achieve the preparation of N-particles cluster states. Additionally, the impact of decoherence and operational imperfections are discussed. Numerical simulation demonstrates the proposed scheme has high fidelities and robustness against both cavity leakage and atomic spontaneous emission.
In this paper, we propose a scheme for rapidly implementing a controlled- π phase gate by combining the Lewis–Riesenfeld invariant and quantum Zeno dynamics. We demonstrate the adiabatic shortcut by using Rydberg superatoms in distant-atom–cavity systems. Furthermore, we utilize the controlled- π phase gate to achieve the preparation of N -particle cluster states. Additionally, the impact of decoherence and operational imperfections is discussed. Numerical simulation demonstrates that the proposed scheme has high fidelities and robustness against both cavity leakage and atomic spontaneous emission.
The ``Lewis-Riesenfeld phases'' which play a crucial role in constructing shortcuts to adiabaticity may be a resource for the implementation of quantum phase gates. By combining ``Lewis-Riesenfeld invariants'' with ``quantum Zeno dynamics,'' we propose an effective scheme of rapidly implementing $\ensuremath{\pi}$ phase gates via constructing shortcuts to adiabatic passage in a two-distant-atom-cavity system. The influence of various decoherence processes such as spontaneous emission and photon loss on the fidelity is discussed. It is noted that this scheme is insensitive to both error sources. Additionally, a creation of N-atom cluster states is put forward as a typical example of the applications of the fast and noise-resistant phase gates. The study results show that the shortcuts idea is not only applicable in other logic gates with different systems, but also propagable for many quantum information tasks.
The W state, as a robust multipartite entangled state, plays an important role in quantum information processing, quantum network construction and quantum computing. In this paper, a three-level ladder-type Rydberg atomic system is placed into a Rydberg blocking sphere to form a superatom. Each superatom has many collective states including just one Rydberg excitation constrained by the Rydberg blockade effect. In the weak cavity field limit, at most one atom can be pumped into excited state, then we can describe the superatom by using a three-level ladder-type system. Afterwards we encode quantum information about the effective energy levels of Rydberg superatoms and propose a fast scheme for preparing the Rydberg superatom W state based on the superadiabatic iterative technique and quantum Zeno dynamics.This scheme can be achieved in only one step by controlling the laser pulses. In this scheme, the superatoms are trapped in spatially separated cavities connected by optical fibers, thereby greatly improving the feasibility of experimental manipulation. A remarkable feature is that it does not need to accurately control experimental parameters and interaction time. Meanwhile, the form of counterdiabatic Hamiltonian is the same as that of the effective Hamiltonian. Through numerical simulations, the fidelity of this scheme can reach 99.94%. Even considering decoherence effects, including atomic spontaneous emission and photon leakage, the fidelity can still exceed 97.5%, thereby further demonstrating the strong robustness of the solution. In addition, the Rabi frequency can be characterized as a linear superposition of Gaussian functions, and this representation significantly alleviates the complexity encountered in practical experiments. Futhermore, we also analyze the influence of parameter fluctuations on the fidelity, and the results show that this scheme is robust against parameter fluctuations. Finally, the present scheme is extended to the case of N Rydberg superatoms, which shows the scalability of our scheme.
Abstract Through combining ‘Lewis–Riesenfeld invariants’ and ‘transitionless quantum driving’ with ‘quantum zeno subspace’ and ‘second-order perturbation approximation’, respectively, we put forward two different methods to construct shortcuts via nonadiabatic processes to present robust quantum phase gates in a two-atom system. The influence of various decoherence processes such as spontaneous emission and photon loss on the fidelity is discussed. The result shows that this scheme is insensitive to both the two error sources. Moreover, the interaction time of the scheme is very short and precise control is not required. Additionally, this scheme is not only implemented without requiring extra complex conditions, but is also insensitive to variations of the parameters. Therefore, this scheme may provide a new perspective for quantum computation.
Quantum entanglement is a basic resource of quantum information processing and quantum computation. The simple and efficient generation of entangled states is always one of the hot research topics. As one of the ideal carriers of quantum information encoding, neutral Rydberg atom occupies a place in the field of generation of entangled state with its unique advantages. For example, Rydberg atom has a large volume and is easily ionized by an external electric field, so it is very sensitive to the change in the external electric field. Therefore, the interaction strength between Rydberg atoms can be changed by altering the external electric field. Rydberg state is a highly excited state, but its radiation attenuation is very small: the radiation lifetime can reach a millisecond level or even longer. The distance between the atomic kernel and the outermost electron is relatively long, and the electric dipole moment is very large. In this paper, the four-level inverted “Y”-type Rydberg atomic system is introduced into the Rydberg blocking ball to form a superatom, and the quantum information is encoded on the effective energy level of the superatom under the condition of weak cavity field. We construct shortcuts to adiabatic passage in a three-superatom system. Combined with quantum Zeno dynamics and shortcuts to adiabatic passage, the three-particle singlet state is simply and effectively generated. In addition, the influence of decoherence factors (including cavity decay and spontaneous emission of superatoms) on the fidelity is considered in this scheme. Numerical simulation results show that the proposed scheme can obtain high fidelity without precisely controlling the evolution time, and the fidelity of singlet state is robust to decoherence factors, since no cavity-photon population is involved in the whole process because of the quantum Zeno dynamics.
Abstract W states play an important role in quantum information processing and quantum computing. Here, it proposes a scheme for preparing W states by designing the evolution operators with Rydberg superatoms. It encodes quantum information on the effective energy level of the superatom, and construct shortcuts to adiabatic passages (STAP) by designing the evolution operators. Combined with Quantum Zeno dynamics and STAP, it can prepare three‐particle W states quickly and efficiently. In addition, the Rabi frequency in this scheme can be described as a linear superposition of Gaussian functions, which reduces the difficulty of practical experiment. The numerical simulation shows that the scheme is robust against decoherence, operational imperfection, and noise. At last, it generalizes this scheme to preparation of N ‐particle W states.