Optical schemes for quantum computation in quantum dot molecules

Abstract

We give three methods for entangling quantum states in quantum dots. We do this by showing how to tailor the resonant energy (Förster-Dexter) transfer mechanisms and the biexciton binding energy in a quantum dot molecule. We calculate the magnitude of these two electrostatic interactions as a function of dot size, interdot separation, material composition, confinement potential and applied electric field by using an envelope function approximation in a two-cuboid dot molecule. In the first implementation, we show that it is desirable to suppress the Förster coupling and to create entanglement by using the biexciton energy alone. We show how to perform universal quantum logic in a second implementation which uses the biexciton energy together with appropriately tuned laser pulses: by selecting appropriate materials parameters high fidelity logic can be achieved. The third implementation proposes generating quantum entanglement by switching the Förster interaction itself. We show that the energy transfer can be fast enough in certain dot structures that switching can occur on a timescale which is much less than the typical decoherence times.

Plasmon-Mediated Radiative Energy Transfer across a Silver Nanowire Array via Resonant Transmission and Subwavelength Imaging

“…1Ϫ14 For instance, the excitation energy transfer between semiconductor quantum dots (QDs) is employed to demonstrate quantum operations, 4 and the stimulated interactions between active optical dipoles and surface plasmons are used to generate plasmonic lasing. 5Ϫ8 Comparing with nonradiative energy transfer (such as Dexter and Fö rster processes), 15,16 radiative energy transfer has sufficient distance range but poor efficiency and directionality.…”

Temporal resources for global quantum computing architectures

“…The first column of Table III shows the general result associated to an arbitrary coupling intensity J F . The last column shows the result for J F = 1.5 THz ≈ 1 meV, which is a representative estimate for exchange interactions between quantum dots [23][24][25][26]. In this case, the parameters of "transport" g 1 and g 2 decrease by a factor of one half, expressing the fact that the Förster interaction is a more efficient interaction for energy transfer.…”

“…The latter equation is directly deduced from Table IV. Next, we compute the optimal additional time for general computational two-qubit gates for the case of a generic physical system where the qubits interact via the Förster coupling: J XY ≡ J F , J = 0 in Eq. (6) [23][24][25][26]. We do so for the model BM1.…”

“…The calculation for the models LM3 and BM2 remains an open question due to the fact that optimal simulation for three qubit quantum gates under Förster interaction is still, hitherto, an unsolved problem. The J F coupling appears in many different physical systems, ranging from nanostructures such as quantum dots and wells [23][24][25][26] through to biomolecular systems [27][28][29]. The first column of Table III shows the general result associated to an arbitrary coupling intensity J F .…”

On the conveyance of angular momentum in electronic energy transfer

“…More significantly still, the use of circularly polarized excitation can populate specific exciton spin states, enabling the coding of additional information. [26][27][28][29][30][31][32][33] It has been shown by quantum electrodynamics (QED) analysis that the spin state of an exciton can be transmitted through RET between quantum dots; 34,35 the plots in Fig. 2 illustrate the effect of rotating one quantum dot relative to another.…”