In this work quantum dot fluorescence thermometry, in combination with double-beam confocal microscopy, has been applied to determine the thermal loading of gold nanorods when subjected to an optical excitation at the longitudinal surface plasmon resonance. The absorbing/heating efficiency of low (%3) aspect ratio gold nanorods has been experimentally determined to be close to 100%, in excellent agreement with theoretical simulations of the extinction, absorption, and scattering spectra based on the discrete dipole approximation. Gold nanorods (GNRs) are one of the most popular metallic nanoparticles with numerous applications in a great variety of fields including data storage, solar energy, catalysis, photonic devices, and microscopy.

We exploit the nondissipative dynamics of a pair of electrons in a large square quantum dot to perform singlet-triplet spin measurement through a single charge detection and show how this may be used for entanglement swapping and teleportation. The method is also used to generate the Affleck-Kennedy-LiebTasaki ground state, a further resource for quantum computation. We justify, and derive analytic results for, an effective charge-spin Hamiltonian which is valid over a wide range of parameters and agrees well with exact numerical results of a realistic effective-mass model. Our analysis also indicates that the method is robust to the choice of dot-size and initialization errors, as well as decoherence. [3,4] and ideas exist for quantum gates based on single qubits encoded in two QDs [5]. As it is timely for ''proof of principle'' demonstrations of multiqubit processes, it would be highly desirable to establish a coherent two qubit process in a single quantum dot.Bell measurement is a key ingredient that makes possible some important tasks such as teleportation [6] and entanglement swapping [7]. In this Letter, we propose a mechanism for singlet-triplet measurement based on the coherent dynamics of two electrons in a large square QD, followed by a single charge detection. Such spin filtering will give a perfect Bell measurement in the S z ¼ 0 subspace of two spins. This projection is made possible due to the existence of a ground manifold of two singlets and two triplets, separated from higher-lying states by a large energy gap. To a very good approximation this enables the low-energy coherent dynamics to be confined to the ground manifold in which the singlets rotate around the quantum dot whereas the triplets are frozen at their initial locations. By initializing the system in an unentangled superposition state, we are then able to project onto a singlet or triplet state simply by a charge measurement to detect whether or not the charge has moved during the evolution. We use this property to propose some quantum information applications such as entanglement swapping and generating the Affleck-Kennedy-Lieb-Tasaki (AKLT) state, which is a resource for measurement-based quantum computation [8].From a practical perspective a large square QD is easier to fabricate than a small one and will also be modeled more accurately by our effective Hamiltonian, since the energy gap between the ground manifold and the lowest excited

We show that a large entangled current can be produced from a very simple passive device: a cluster of three resonant quantum dots, tunnel coupled to one input lead and two output leads. Through a rapid first order resonant process within the cluster, entangled electrons pairs are emitted into separate leads. We show that the process is remarkably robust to variants in systems parameters. An ideal 'clean' mode gives way to a 'dirty' mode as we relax system constraints, but even the latter produces useful entanglement. The simplicity and robustness should permit experimental demonstration in the immediate future. Applications include quantum repeaters and unconditionally secure interfaces. arXiv:0801.4411v2 [quant-ph]

We propose a scheme for implementing quantum gates and entanglement between spin qubits in the outer dots of a triple-dot system with an empty central dot. The voltage applied to the central dot can be tuned to realize the gate. Our scheme exemplifies the possibility of quantum gates outside the regime where each dot has an electron, so that spin-spin exchange interaction is not the only relevant mechanism. Analytic treatment is possible by mapping the problem to a t-J model. The fidelity of the entangling quantum gate between the spins is analyzed in the presence of decoherence stemming from a bath of nuclear spins, as well as from charge fluctuations. Our scheme provides an avenue for extending the scope of two-qubit gate experiments to triple dots, while requiring minimal control, namely that of the potential of a single dot, and may enhance the qubit separation to ease differential addressability.