SGER: A Self Assembled Spintronic Quantum Gate

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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.