Department of Nuclear Science and Engineering and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Phys Rev Lett. 2013 May 31;110(22):220503. doi: 10.1103/PhysRevLett.110.220503. Epub 2013 May 29.
We propose a method for Hamiltonian engineering that requires no local control but only relies on collective qubit rotations and field gradients. The technique achieves a spatial modulation of the coupling strengths via a dynamical construction of a weighting function combined with a Bragg grating. As an example, we demonstrate how to generate the ideal Hamiltonian for perfect quantum information transport between two separated nodes of a large spin network. We engineer a spin chain with optimal couplings starting from a large spin network, such as one naturally occurring in crystals, while decoupling all unwanted interactions. For realistic experimental parameters, our method can be used to drive almost perfect quantum information transport at room temperature. The Hamiltonian engineering method can be made more robust under decoherence and coupling disorder by a novel apodization scheme. Thus, the method is quite general and can be used to engineer the Hamiltonian of many complex spin lattices with different topologies and interactions.
我们提出了一种哈密顿工程方法，该方法不需要局部控制，而仅依赖于集体量子比特旋转和场梯度。该技术通过结合布拉格光栅的加权函数的动态构建来实现耦合强度的空间调制。作为示例，我们演示了如何在大型自旋网络的两个分离节点之间生成用于完美量子信息传输的理想哈密顿量。我们从大型自旋网络（例如晶体中自然存在的自旋网络）开始，通过最佳耦合来设计自旋链，同时消除所有不需要的相互作用。对于实际的实验参数，我们的方法可用于在室温下驱动几乎完美的量子信息传输。通过一种新颖的变迹方案，哈密顿工程方法可以在退相干和耦合无序下更加稳健。因此，该方法非常通用，可以用于工程具有不同拓扑和相互作用的许多复杂自旋晶格的哈密顿量。
