Full electrical control of quantum bits could enable fast, low-power, scalable quantum computation. Although electric dipoles are highly attractive to couple spin qubits electrically over long distances, mechanisms identified to control two-qubit couplings do not permit single-qubit operations while two-qubit couplings are off. Here we identify a mechanism to modulate electrical coupling of spin qubits that overcomes this drawback for hole spin qubits in acceptors,that is based on the electrical tuning of the direction of the spin-dependent electric dipole by a gate. In this way, inter-qubit coupling can be turned off electrically by tuning to a "magic angle" of vanishing electric dipole-dipole interactions, while retaining the ability to manipulate the individual qubits. This effect stems from the interplay of the $\rm T_d$ symmetry of the acceptor state in the Si lattice with the magnetic field orientation, and the spin-3/2 characteristic of hole systems. Magnetic field direction also allows to greatly suppress spin relaxation by phonons that limit single qubit performance, while retaining sweet spots where the qubits are insensitive to charge noise. Our findings can be directly applied to state-of-the-art acceptor based architectures, for which we propose suitable protocols to practically achieve full electrical tunability of entanglement and the realization of a decoherence-free subspace.

中文翻译：

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Si中受体量子位的纠缠控制和魔角

量子位的完全电气控制可以实现快速、低功耗、可扩展的量子计算。尽管电偶极子对于长距离电耦合自旋量子位非常有吸引力，但已确定用于控制双量子位耦合的机制不允许在双量子位耦合关闭时进行单量子位操作。在这里，我们确定了一种调节自旋量子位电耦合的机制，该机制克服了受体中空穴自旋量子位的这一缺点，即基于栅极对自旋相关电偶极子方向的电调谐。通过这种方式，可以通过调谐到消失的电偶极-偶极相互作用的“魔角”来关闭量子位间耦合，同时保留操纵单个量子位的能力。这种效应源于 Si 晶格中受主态的 $\rm T_d$ 对称性与磁场方向的相互作用，以及空穴系统的自旋 3/2 特性。磁场方向还允许通过限制单个量子位性能的声子极大地抑制自旋弛豫，同时保留量子位对电荷噪声不敏感的最佳位置。我们的发现可以直接应用于最先进的基于受体的架构，为此我们提出了合适的协议来实际实现纠缠的完全电可调性和无退相干子空间的实现。磁场方向还允许通过限制单个量子位性能的声子极大地抑制自旋弛豫，同时保留量子位对电荷噪声不敏感的最佳位置。我们的发现可以直接应用于最先进的基于受体的架构，为此我们提出了合适的协议来实际实现纠缠的完全电可调性和无退相干子空间的实现。磁场方向还允许通过限制单个量子位性能的声子极大地抑制自旋弛豫，同时保留量子位对电荷噪声不敏感的最佳位置。我们的发现可以直接应用于最先进的基于受体的架构，为此我们提出了合适的协议来实际实现纠缠的完全电可调性和无退相干子空间的实现。