Proposed Five-Electron Charge Quadrupole Qubit.

Area of Science:

• Quantum computing
• Semiconductor physics
• Quantum information science

Background:

• Charge qubits are susceptible to decoherence from electric field fluctuations due to their dipole moment coupling.
• Existing semiconductor spin qubits face limitations in quality factor and gate speed.

Purpose of the Study:

• To propose and analyze the p-orbital (pO) qubit, a novel quantum bit design for improved performance.
• To investigate the advantages of the pO qubit in terms of quality factor, gate speed, readout, and size.
• To demonstrate all-electrical control and two-qubit gate operations for the pO qubit.

Main Methods:

• Utilizing a phenomenological charge noise model to estimate decoherence times (T_{2}^{*}).
• Simulating Rabi frequencies to assess gate speeds.
• Modeling quadrupole-quadrupole interactions for two-qubit gates.
• Employing gradient ascent-based control pulse optimization for universal gate sets.

Main Results:

• The pO qubit couples to charge noise via its quadrupole moment, reducing decoherence.
• An estimated T_{2}^{*} of ~80 ns and Rabi frequencies of ~10 GHz suggest an order of magnitude improvement in qubit quality factor.
• All-electrical control is achieved by modulating the quantum dot's eccentricity.
• Two-qubit gates are feasible via quadrupole-quadrupole interactions.

Conclusions:

• The pO qubit offers significant advantages over current semiconductor spin qubits, including enhanced quality factor and gate speed.
• The proposed qubit architecture enables efficient all-electrical control and scalable two-qubit operations.
• The pO qubit represents a promising advancement for building robust quantum processors.