A charge qubit couples to environmental electric field fluctuations through its dipole moment, resulting in fast decoherence. We propose the $p$-orbital ($pO$) qubit, formed by the single-electron, $p$-like valence states of a five-electron Si quantum dot, which couples to charge noise through the quadrupole moment. We demonstrate that the $pO$ qubit offers distinct advantages in quality factor, gate speed, readout, and size. We use a phenomenological, dipole two-level-fluctuator charge noise model to estimate a $T_2^{*}\sim 80\mathrm{ns}$. In conjunction with Rabi frequencies of order 10 GHz, an order of magnitude improvement in qubit quality factor is expected relative to state-of-the-art semiconductor spin qubits. The $pO$ qubit features all-electrical control via modulating the dot’s eccentricity. We also show how to perform two-qubit gates via the $1/r^5$ quadrupole-quadrupole interaction. We find a universal gate set using gradient ascent-based control pulse optimization, subject to 10 GHz maximum allowable bandwidth and 1 ns pulse times.

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• Charge dynamics
• Quantum information architectures & platforms
• Qubits
• Quantum dots
• Semiconductors