SGER: A Self Assembled Spintronic Quantum Gate

本研究将利用电化学方法在孔径约为10 nm的自组装多孔薄膜的孔内依次电沉积铁磁层和半导体层，实现新型量子门结构的自组装。量子位将通过从铁磁接触注入耗尽半导体层并通过库仑阻塞捕获在那里的单个电子的自旋极化来编码。利用Rashba效应，通过外部静电门电势调制半导体层中的自旋分裂能量来实现单量子比特旋转。这种方法的独特之处在于它利用了自组装结构（从而避免了对复杂光刻的需要;输入/输出连接和栅极接触需要一些光刻），并且它依赖于量子位的电气控制，而不是其他类似方案中设想的磁场控制。由于电开关在芯片上更快、更方便，这种模式具有明显的优势。该项目的风险在于穿过铁磁/半导体界面的相干自旋注入的不确定性。然而，由于自旋注入在小面积界面上更容易，并且存在穿过碳纳米管和铁磁金属的界面的自旋注入的实验证据，这与我们在制造方案中预期的质量相当或更差，因此减轻了风险。如果成功，这个项目将导致唯一的自组装，全电自旋电子量子门。自组装自旋电子量子门将最终允许创建一个自组装量子电路，量子连接器连接不同的门，以及量子存储元件。由于自组装结构非常致密，预计量子位密度超过10 E11/cmE 2，这相当于1 cmE 2区域中2**{10 E9}个经典位的存储密度，这超过了宇宙中所有材料在宇宙寿命期间可以制造的所有硬盘的存储容量。

A small grant is requested for exploratory research leading to the possible demonstration of a critical element for a nanoscale universal quantum gate.A novel gate structure will be electrochemically self assembled by sequential electrodeposition of ferromagnetic and semiconducting layers inside the pores of a self-assembled porous film with ~ 10-nm sized pores. A qubit will be encoded by the spin polarization of a single electron injected into the depleted semiconductor layer from the ferromagnetic contact and trapped there by Coulomb blockade. Single qubit rotations will be effectedby modulating the spin splitting energy in the semiconductor layer with an external electrostatic gate potential, utilizing the Rashba effect. The uniqueness of this approach is that it utilizes a self-assembled structure (thereby obviating the need for complicated lithography; some lithography is needed for input/output connections and gate contacts) and it relies on electrical control of the qubit as opposed to magnetic field control envisaged in other comparable schemes. Since electrical switching is faster and moreconvenient on a chip, this paradigm has distinct advantages.The risk involved in the project is the uncertainty of coherent spin injectionacross a ferromagnetic/semiconductor interface. The risk is however mitigated by the fact that spin injection is easier across small area interfaces and there exists experimental evidence of spin injection across the interface of carbon nanotubes and ferromagnetic metals which is ofa quality comparable to or worse than what we expect in our fabrication scheme. If successful, this project will lead to the only self-assembled, all-electric spintronic quantum gate.A self assembled spintronic quantum gate will ultimately allow the creation of a self-assembled quantum circuit with quantum connectors linking different gates,as well as quantum memory elements. Since the self assembled structures are extremely dense, it is expect a qubit density ofmore than 10E11/cmE2 that translates to a storage density equivalent tothat of 2**{10E9} classical bits in a 1-cmE2 area which exceeds the storage capacity of all the hard disks that could be made with all the material in the universe over the life of the universe.