Single-qubit quantum gate at an arbitrary speed

• URL: http://arxiv.org/abs/2412.19561v1
• Date: Fri, 27 Dec 2024 10:05:27 GMT
• Title: Single-qubit quantum gate at an arbitrary speed
• Authors: Seongjin Ahn, Kichan Park, Daehee Cho, Mikyoung Lim, Taeyoung Choi, Andrey S. Moskalenko,
• Abstract summary: We show that it is possible to construct a universal set of single-qubit gates at a strong-coupling and ultrafast regime. We observe a transition in the scaling behavior of the central frequency from the long-gate time regime to the short-gate time regime.
• Score: 0.7256915467062314
• License:
• Abstract: Quantum information processing comprises physical processes, which obey the quantum speed limit (QSL): high speed requires strong driving. Single-qubit gates using Rabi oscillation, which is based on the rotating wave approximation (RWA), satisfy this bound in the form that the gate time $T$ is inversely proportional to the Rabi frequency $\Omega$, characterizing the driving strength. However, if the gate time is comparable or shorter than the qubit period $T_{0} \equiv 2\pi / \omega_{0}$, the RWA actually breaks down since the Rabi frequency has to be large compared to the qubit frequency $\omega_{0}$ due to the QSL, which is given as $T \gtrsim \pi/\Omega$. We show that it is possible to construct a universal set of single-qubit gates at this strong-coupling and ultrafast regime, by adjusting the central frequency $\omega$ and the Rabi frequency $\Omega$ of the driving pulse. We observe a transition in the scaling behavior of the central frequency from the long-gate time regime ($T \gg T_{0}$) to the short-gate time ($T \ll T_{0}$) regime. In the former, the central frequency is nearly resonant to the qubit, i.e., $\omega \simeq \omega_{0}$, whereas in the latter, the central frequency is inversely proportional to the gate time, i.e., $\omega \sim \pi/T$. We identify the transition gate time at which the scaling exponent $n$ of the optimal central frequency $\omega \sim T^{n}$ changes from $n=0$ to $n=-1$.

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