Adiabatically-controlled two quibit gates using quantum dot hybrid qubits.

Adam Frees

Tetsufumi Tanamoto

A. A. Setser, J. P. Kestner

We theoretically examine the capacitive coupling between two quantum dot hybrid qubits, each consisting of three electrons in a double quantum dot, as a function of the energy detuning of the double dot potentials. We show that a shaped detuning pulse can produce a two-qubit maximally entangling operation in $\ensuremath{\sim}50\phantom{\rule{0.28em}{0ex}}\mathrm{ns}$ without having to simultaneously change tunnel couplings. Simulations of the entangling operation in the presence of experimentally realistic charge noise yield two-qubit fidelities over 90%.

S. N. Coppersmith, Teck Seng Koh, John King Gamble +2 more

Tetsufumi Tanamoto

David E. Logan, Martin R. Galpin

We consider the simplest example of a double quantum dot system: two equivalent, capacitively coupled single-level dots, each coupled to its own lead. Focussing on a regime of two electrons on the double dot, a rich range of behaviour is found on increasing the interdot coupling: first a crossover from spin- to charge-Kondo physics, via an intermediate SU(4) state with entangled spin and charge degrees of freedom; followed by a quantum phase transition of Kosterlitz-Thouless type to a non-Fermi liquid 'charge-ordered' phase with finite residual entropy and anomalous transport properties. The numerical renormalization group method, coupled with simple physical arguments, is employed to obtain a detailed understanding of the problem.