0 Charge based quantum computer without charge transfer

A novel implementation of a charge based quantum computer is proposed. There is no charge transfer during calculation, therefore, uncontrollable entan-glement between qubits due to long-range Coulomb forces is suppressed. High-speed computation with 1ps per an operation looks as feasible. Almost all recent experimental realizations of quantum computation accomplished on several qubits and even theoretical proposals of new devices were based on spin states. Much cited papers of Kane [1] and DiVincenzo et al. [2, 3, 4] just concerned nucleus or electron spin encoding in solid state implementation of a quantum computer (QC). The attractiveness of spin states in solid state QC was mainly caused by quite long decoherence time: hours for a nucleus spin and milliseconds for electron spin seem attainable [1, 4]. Nevertheless, space or charge states for quantum encoding do not seem less prospective [5–13] although two main disadvantages are commonly mentioned [3]. Firstly, much less decoherence time is expected for charge states. Secondly, charge transfer results in uncontrollable interaction between even distant qubits due to long-range Coulomb forces. However, as it was shown recently [11, 12], for fairly small energy gap between different charge (or space) states decoherence caused by acoustic phonons might be very weak. Here we withdraw the second reproach for charge based QC offering a construction where no charge transfer occurs during computation. Besides, the computation may be much faster than that in spin based QC.