Geometric gates in atomic arrays without Rydberg blockade

Henning Labuhn, Sylvain Ravets, Daniel Barredo +4 more

Ming, Yue, Zhao-Xin Fu, Yan-Xiong Du

The Rydberg blockade effect plays an important role in realizing two-qubit gates in atomic arrays. Meanwhile, such mechanics will increase the crosstalk between atoms and enhance the decoherence. In this paper, we propose a new scheme to realize the controlled-phase gate without Rydberg blockade. The scheme works effectively with large atomic spacings and is insensitive to the thermal motions of atoms. The proposal is robust against random noises due to the geometric characteristic and operates fast based on the non-adiabatic evolution. The proposed gate is actually a new-type geometric gate that consolidates the non-adiabatic holonomic control and the unconventional geometric control simultaneously. The interference between two different types of geometric phases can be investigated. Furthermore, we show that the scheme with weak Rydberg interaction requires much less physical resources than the present Rydberg blockade scheme. Therefore, our proposal provides a fast and robust way to realize geometric quantum control, and it may trigger the discoveries of new geometric gates in high-dimensional Hilbert space.

Marco Cozzini, Tommaso Calarco, Alessio Recati +1 more

Yan-Xiong Du

In this manuscript we discuss the relationship between the gate time of Rydberg two-qubit gate and the Rydberg interaction strength. Different from the two-qbuit gates that directly depend on the interactions between the spins (or pseudo spins), the ones in atomic arrays are realized by driving the atoms to the Rydberg states. As a consequence, competition happens between shortening the gate time and decreasing the excitation probability of Rydberg states. For the case of Rydberg blockade, it is found that the gate time is irrelevant of the Rydberg interaction strength. In contrast, for the case of weak Rydberg interactions, the interactions will help to accelerate the two-qubit gates. This implies that the scheme of weak Rydberg interactions will be faster than the Rydberg blockade one to realize the two-qbuit gates under the same Rabi frequencies of Rydberg excitation. Through using the geometric control under the region of weak Rydberg interaction, fast and robust two-qubit gates can be achieved in atomic arrays, of which detailed discussion can be referred to the manuscript \textsl{arXiv:2412. 19193 (2024)}.

Mark E. Saffman

Ze-Rui He, Zhao-Xin Fu, Jia-Hao Liang +8 more

Abstract Connectivity between qubits plays an irreplaceable role in quantum computation. An urgent task of quantum computation based on atomic arrays is to generate effective coupling between two distant qubits, thereby enhancing connectivity. In this paper, we investigate the realization of two-qubit gates utilizing buffer-atomic configuration, where the non-coding atoms serve as quantum buses to connect the computational qubits. Geometric control is achieved through globally-shined laser pulses in the Rydberg blockade region. It is found that acceleration based on shortcut to adiabaticity can be realized by reshaping the original control waveforms. The proposed distant two-qubit gate demonstrates robustness against systematic errors and random noise. Further numerical simulations indicate that high-fidelity control is maintained even when considering next-nearest-neighbor coupling among the atoms. Thus, our proposal provides a fast and experimentally feasible method for realizing distant two-qubit gates in atomic arrays, which may contribute to improving the scalability of quantum computations.