A configuration interaction analysis of exchange in double quantum dots

Abstract

We describe in detail a full configuration interaction (CI) method designed to analyze systems of quantum dots. This method is capable of exploring large regions of parameter space, like more approximate approaches such as Heitler London and Hund Mulliken, though it is not limited to weakly coupled dots. In particular, this method is well-suited to the analysis of solid state quantumdot-based qubits, and we consider the case of a double quantum dot (DQD) singlet-triplet qubit. Past analyses have used techniques which are either substantially restricted in the regimes they can be used, or device specific and unsuited to exploration of a large regions of parameter space. We analyze how the DQD exchange energy, which is central to the operation of qubit rotation gates, depends on a generic set of system parameters including magnetic field, DQD detuning, dot size, and dot separation. We discuss the implications of these results to the construction of real devices. We provide a benchmark of the CI by directly comparing results from the CI method with exact results for two electrons in a single parabolic potential (dot).

Coherent electrical rotations of valley states in Si quantum dots using the phase of the valley-orbit coupling

“…[36][37][38][39][40][41][42][43][44][45][46][47][48] Theoretical research on Si QDs has also evolved at a brisk pace. [49][50][51][52][53][54][55][56][57][58][59][60][61] Concomitantly, QDs in other group IV elements are being explored for QC: carbon, [62][63][64][65][66][67] including nitrogen-vacancy centers in diamond, 68 and Ge. 69 Group IV materials (C, Si, Ge) are notable for having equivalent conduction band minima known as valleys.…”

Quantum theory of the charge-stability diagram of semiconductor double-quantum-dot systems

“…As discussed in Refs. 50 and 51, the microscopic calculation 39,72,[82][83][84][85][86][87] is required to constrain the parameters of the Hubbard model in the physically relevant regime. In other words, although the Hubbard model by itself can have arbitrary parameters, a given physical double-dot system is restricted by the realistic confinement potential which would severely restrict the physical Hubbard parameters for the system.…”

“…The classical aspect of the change stability diagram is well understood using the capacitance circuit model. [46][47][48][49] On the other hand, microscopic calculations are usually carried out for other aspects of the quantum dot system 39,72,[82][83][84][85][86][87] but only rarely for the charge stability diagram. 56 This means that our understanding of the quantum aspect of the charge stability diagram has largely been limited to the quantum-mechanical two-level model, 37,[52][53][54][55] with only a few exceptions.…”

QCAD Simulation and Optimization of Semiconductor Quantum Dots

“…Details about the Poisson, Schrodinger, and self-consistent S-P solvers are described in the following subsections, and the CI method can be found in Ref. 19. We note that the current version of the QCAD simulator solves one or a system of equations in the full number of dimensions of the problem, and does not make any separability assumptions that allow a higher dimensional problem (e.g.…”