Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Nat Commun. 2017 Jun 23;8:15923. doi: 10.1038/ncomms15923.
Quantum computing promises significant speed-up for certain types of computational problems. However, robust implementations of semiconducting qubits must overcome the effects of charge noise that currently limit coherence during gate operations. Here we describe a scheme for protecting solid-state qubits from uniform electric field fluctuations by generalizing the concept of a decoherence-free subspace for spins, and we propose a specific physical implementation: a quadrupole charge qubit formed in a triple quantum dot. The unique design of the quadrupole qubit enables a particularly simple pulse sequence for suppressing the effects of noise during gate operations. Simulations yield gate fidelities 10-1,000 times better than traditional charge qubits, depending on the magnitude of the environmental noise. Our results suggest that any qubit scheme employing Coulomb interactions (for example, encoded spin qubits or two-qubit gates) could benefit from such a quadrupolar design.
量子计算有望为某些类型的计算问题带来显著的提速。然而，为了实现半导体量子比特的稳健应用，必须克服目前在门操作过程中限制相干性的电荷噪声的影响。在这里，我们通过推广用于自旋的无退相干子空间的概念，描述了一种保护固态量子比特免受均匀电场波动影响的方案，并提出了一种具体的物理实现方案：在三量子点中形成四极电荷量子比特。四极电荷量子比特的独特设计使得在门操作过程中抑制噪声影响的脉冲序列特别简单。根据环境噪声的大小，模拟得到的门保真度比传统电荷量子比特高出 10 到 1000 倍。我们的研究结果表明，任何采用库仑相互作用的量子比特方案（例如，编码的自旋量子比特或双量子比特门）都可以从这种四极设计中受益。
