Fault-tolerant implementation of quantum gates is one of preconditions for realizing quantum computation. The platform of Rydberg atoms is one of the most promising candidates for achieving quantum computation. We propose to implement a controlled-$Z$ gate on Rydberg atoms where an amplitude-modulated field is employed to induce Rydberg antiblockade. Gate robustness against the fluctuations in the Rydberg-Rydberg interaction can be largely enhanced by adjusting amplitude-modulated field. Furthermore, we introduce a Landau-Zener-Stückelberg transition on the target atom so as to improve the gate resilience to the deviation in the gate time and the drift in the pulse amplitude. With feasible experimental parameters, one can achieve the gate with low fidelity errors caused by atomic decay, interatomic dipole-dipole force, and Doppler effects. Finally, we generalize the gate scheme into multiqubit cases, where resilient multiqubit phase gates can be obtained in one step with an unchanged gate time as the number of qubits increases.

Using a microwave-regime cyclic three-state configuration, enantiomer-selective state transfer (ESST) is carried out through two-path interference between a direct one-photon coupling and an effective two-photon coupling. A phase difference of $\pi$ in the one-photon process between the two enantiomers makes the interference constructive for one enantiomer but destructive for the other. Therefore only one enantiomer is excited into a higher rotational state, while the other remains in the ground state. The scheme allows flexibility in the pulse waveforms and the time order of the two paths. We simulate the scheme for a sample of cyclohexylmethanol (${\mathrm{C}}_7{\mathrm{H}}_{14}\mathrm{O}$) molecules. The simulation results show that robust high-fidelity ESST can be obtained when experimental concerns are considered. Finally, we propose to employ the ESST scheme to implement enantioseparation and determine enantiomeric excesses.

We propose to discriminate chiral molecules by combining one- and two-photon processes in a closed-loop configuration. The one-photon-coupling intrinsic $\pi$-phase difference between two enantiomers leads to their different superposition states, which is then followed by a two-photon process through three-mode parallel paths (3MPPs), enabling the discrimination of enantiomers by inducing their entirely different population distributions. The 3MPPs are constructed by “chosen paths,” a method of shortcuts to adiabaticity, exhibiting a fast two-photon process. As an example, we propose to perform the scheme in 1,2-propanediol molecules, which show relatively robust and highly efficient results under considering the experimental issues concerning unwanted transitions, imperfect initial state, pulse shaping, control errors, and the effect of energy relaxations. The present work may provide help for laboratory researchers in a robust separation of chiral molecules.

One scheme is presented to construct the robust multi-qubit arbitrary-phase controlled-phase gate (CPG) with one control and multiple target qubits in Rydberg atoms using the Lewis–Riesenfeld (LR) invariant method. The scheme is not limited by adiabatic condition while preserves the robustness against control parameter variations of adiabatic evolution. Comparing with the adiabatic case, our scheme does not require very strong Rydberg interaction strength. Taking the construction of two-qubit $\pi$ CPG as an example, our scheme is more robust against control parameter variations than non-adiabatic scheme and faster than adiabatic scheme.

The prevalent fashion of executing Rydberg-mediated two- and multi-qubit quantum gates in neutral atomic systems is to pump Rydberg excitations using multistep piecewise pulses in the Rydberg blockade regime. Here, we propose to synthesize a Λ -type Rydberg antiblockade (RAB) of two neutral atoms using periodic fields, which facilitates one-step implementations of SWAP and controlled-SWAP (CSWAP) gates with the same gate time. Besides, the RAB condition is modified so as to circumvent the sensitivity of RAB-based gates to infidelity factors, including atomic decay, motional dephasing, and interatomic distance deviation. Our work makes up the absence of one-step schemes of Rydberg-mediated SWAP and CSWAP gates and may pave a way to enhance the robustness of RAB-based gates.

Quantum holonomic gates hold built-in resilience to local noises and provide a promising approach for implementing fault-tolerant quantum computation. We propose to realize high-fidelity holonomic $(N+1)$-qubit controlled gates using Rydberg atoms confined in optical arrays or superconducting circuits. We identify the scheme, deduce the effective multibody Hamiltonian, and determine the working condition of the multiqubit gate. Uniquely, the multiqubit gate is immune to systematic errors, i.e., laser parameter fluctuations and motional dephasing, as the $N$ control atoms largely remain in the very stable qubit space during the operation. We show that $C_N$-not gates can reach the same level of fidelity at a given gate time for $N\le 5$ under a suitable choice of parameters, and the gate tolerance against errors in systematic parameters can be further enhanced through optimal pulse engineering. In the case of Rydberg atoms, the proposed protocol is intrinsically different from typical schemes based on Rydberg blockade or antiblockade. Our study paves an alternative way to build robust multiqubit gates with Rydberg atoms trapped in optical arrays or with superconducting circuits. It contributes to current efforts to develop scalable quantum computation with trapped atoms and fabricable superconducting devices.