Quantum computing with dangling bond pairs on a Si surface

If, one day, a quantum computer is built, it would be able to efficiently solve some intractable computational problems such as factorizing large integers; this is something that would never be possible with today's classical computers. Despite all impressive progress that has been achieved in developing silicon quantum computing (QC) implementations for both spin and charge qubits, there are still serious obstacles remained for realizing such schemes where decoherence effects in charge qubit and read-out in spin qubit cases are at the heart of these challenges. A promising approach in overcoming the spin-qubit problem is to convert it to a charge qubit before doing the measurement. Thus, looking for a practical Si-based charge qubit is important not only as a quantum information carrier but also as an intercessor for spin-qubit measurement. We propose a feasible charge qubit QC scheme but on a Si surface rather than in crystal bulk. In our scheme charge qubit is an excess electron shared between two nearby dangling bonds (DBs). A DB is a bond created by removing a hydrogen atom by means of a scanning tunneling microscope tip from the hydrogen-terminated Si(100)2x1 surface. Signature of coupled DBs for a distance between 4 to 15 angstroms has already been shown experimentally in the demonstration of a quantum cellular automata unit cell on Si(100)2x1 surface and the implementation of our scheme is in fact leveraged on this success. Our scheme has a couple of significant advantages over the other proposed bulk silicon QC schemes: long coherence time, and direct manipulation and measurement of qubits on the surface. In my talk, I will address DiVincenzo criteria and demonstrate how our proposed scheme fulfill these criteria