Optimal model for fewer-qubit CNOT gates with Rydberg atoms

Abstract

Fewer-qubit quantum logic gate, serving as a basic unit for constructing universal multiqubit gates, has been widely applied in quantum computing and quantum information. However, traditional constructions for fewer-qubit gates often utilize a multi-pulse protocol which inevitably suffers from serious intrinsic errors during the gate execution. In this article, we report an optimal model about universal two-and three-qubit CNOT gates mediated by excitation to Rydberg states with easily-accessible van der Waals interactions. This gate depends on a global optimization to implement amplitude and phase modulated pulses via genetic algorithm, which can facilitate the gate operation with fewer optical pulses. Compared to conventional multi-pulse piecewise schemes, our gate can be realized by simultaneous excitation of atoms to the Rydberg states, saving the time for multi-pulse switching at different spatial locations. Our numerical simulations show that a single-pulse two(three)-qubit CNOT gate is possibly achieved with a fidelity of 99.23%(90.39%) for two qubits separated by 7.10 µm when the fluctuation of Rydberg interactions is excluded. Our work is promising for achieving fast and convenient multiqubit quantum computing in the study of neutral-atom quantum technology.

Single Gaussian temporal pulse modulated controlled-Z gate of neutral atoms under symmetrically optical pumping

“…According to the frequency range of the external driving field, the resulting long-range resonant (Förster) and off-resonant dipolar (van der Waals) interactions can give rise to Rydberg blockade effect [3][4][5][6][7], Rydberg facilitation (or antiblockade) dynamics [8][9][10][11], and Rydberg dressing mechanism [12][13][14][15][16] which constitute the basic principle for performing most quantum computing and quantum simulation tasks in neutral-atom system . Nevertheless, it should be worth emphasizing that although the above three mechanisms have their own advantages for the realization of neutral atomic logic gates in theory, the characteristic of Rydberg blockade makes it stand out in experimental implementation since the fidelity of such schemes is independent of the first-order large blockade shift [52][53][54][55][56][57][58][59][60][61][62][63][64][65].…”

“…Recently, Levine et al improve the traditional gate protocol by selecting a specific detuning parameter of laser light, and the two-qubit controlled-phase gate is implemented in a faster way after two global pulses [60,63]. In addition, compared with the constant-amplitude pulses, the temporal modulation of the laser field is more helpful to avoid unwanted transitions of quantum states and then suppresses the population leakage error [61,[65][66][67][68][69]. Very recently in experiment, Fu et al have achieved the C z gate with fidelity F = 0.980 (7) after correcting the state preparation and measurement (SPAM) errors using the single-modulated-pulse off-resonant modulated driving (SORMD) [64].…”