Department of Photonics Engineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark.
Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Phys Rev Lett. 2019 Oct 4;123(14):140502. doi: 10.1103/PhysRevLett.123.140502.
Coupling a qubit coherently to an ensemble is the basis for collective quantum memories. A single driven electron in a quantum dot can deterministically excite low-energy collective modes of a nuclear spin ensemble in the presence of lattice strain. We propose to gate a quantum state transfer between this central electron and these low-energy excitations-spin waves-in the presence of a strong magnetic field, where the nuclear coherence time is long. We develop a microscopic theory capable of calculating the exact time evolution of the strained electron-nuclear system. With this, we evaluate the operation of quantum state storage and show that fidelities up to 90% can be reached with a modest nuclear polarization of only 50%. These findings demonstrate that strain-enabled nuclear spin waves are a highly suitable candidate for quantum memory.
将量子位相干地耦合到一个集合体是集体量子存储器的基础。在晶格应变存在的情况下，量子点中的单个被驱动电子可以确定性地激发核自旋集合体的低能集体模式。我们建议在强磁场下，对这个中心电子和这些低能激发——自旋波——之间的量子态转移进行门控，在这种情况下，核相干时间较长。我们开发了一种微观理论，能够计算应变电子-核系统的精确时间演化。通过这种方法，我们评估了量子态存储的操作，并表明仅需 50%的适度核极化，就可以达到高达 90%的保真度。这些发现表明，应变能核自旋波是量子存储器的一个非常合适的候选者。
