Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
Network for Computational Nanotechnology, Birck Nanotechnology Center, Purdue University, 1205 West State Street, West Lafayette, Indiana 47907, USA.
Nat Nanotechnol. 2014 Jun;9(6):430-5. doi: 10.1038/nnano.2014.63. Epub 2014 Apr 13.
Electron spins confined to phosphorus donors in silicon are promising candidates as qubits because of their long coherence times, exceeding seconds in isotopically purified bulk silicon. With the recent demonstrations of initialization, readout and coherent manipulation of individual donor electron spins, the next challenge towards the realization of a Si:P donor-based quantum computer is the demonstration of exchange coupling in two tunnel-coupled phosphorus donors. Spin-to-charge conversion via Pauli spin blockade, an essential ingredient for reading out individual spin states, is challenging in donor-based systems due to the inherently large donor charging energies (∼45 meV), requiring large electric fields (>1 MV m(-1)) to transfer both electron spins onto the same donor. Here, in a carefully characterized double donor-dot device, we directly observe spin blockade of the first few electrons and measure the effective exchange interaction between electron spins in coupled Coulomb-confined systems.
束缚在硅中磷施主中的电子自旋由于其长相干时间而成为有前途的量子比特候选者，在同位素纯化的体硅中超过秒。随着最近对单个施主电子自旋的初始化、读出和相干操纵的演示，实现基于 Si:P 施主的量子计算机的下一个挑战是演示两个隧道耦合磷施主之间的交换耦合。通过 Pauli 自旋阻塞进行的自旋到电荷转换是读出单个自旋状态的基本要素，但由于施主固有较大的充电能（约 45 meV），在基于施主的系统中难以实现，这需要大的电场（>1 MV m(-1)) 才能将两个电子自旋都转移到同一个施主上。在这里，在一个经过精心表征的双施主点器件中，我们直接观察到前几个电子的自旋阻塞，并测量了耦合库仑受限系统中电子自旋之间的有效交换相互作用。
