Hideaki Matsueda

Dynamic dipole-dipole interactions between excitons in quantum dots of different sizes

A model of the resonance dynamic dipole-dipole interaction between excitons confined in quantum dots (QDs) of different sizes at close enough distance is given in terms of parity inheritance and exchange of virtual photons. Microphotoluminescence spectra of GaAs-AlGaAs coupled QDs are proposed to be analyzed by this model, including features created by high-speed random switching, depending on the carrier configuration in and around the QD pair, between the dipole-dipole split states and the nonsplit states to give double peaks at both of the QDs.

Solid State Coherent Quantum Dot System for Quantum Computing and Quantum Transmission

Recent progress in nano-metre structure and measurements is capable of providing us with the freedom to harness fast and seemingly weak correlations between atoms in an ensemble, manifesting them at macroscopic level. So we have investigated a prospective model of solid state integrated circuits for quantum computation, based on our coherence retentive resonance dynamic dipole–dipole interaction (RDDDI) theory. In this model, each qubit is a block consisting of an ensemble of quantum dots, and the energetics of which suggests stability up to room temperature. Here, we propose a qubit swap (∏4) gate applying our RDDDI. Moreover, integration of the ∏4 gate is proposed to form quantum circuits that can transfer a qubit state to any position within them, realizing bit reversal permutation circuits with even and odd bits, and a shuffling circuit. Copyright

Reduction of Theoretical Uncertainty in Quantum Computing

A theoretical framework is developed to evaluatethe amount of intrinsic uncertainty, as distinguishedfrom operational uncertainty (noise), inherent inquantum computation. The temporal evolution of states in quantum computing is analyzeddiagramatically, providing a visual tool for therefining of quantum algorithms to help achieve minimaluncertainty and maximal efficiency, as well as forbetter understanding of the quantum entanglements crucial to quantumcomputing.

Integrated solid circuits for quantum computing

Recent progress in nanometre structure and measurements is going to provide us with the freedom to domesticate fast correlations between atoms in an ensemble, manifesting them at macroscopic level. So we propose a prospective model of a solid state integrated circuit for quantum computation, based on our coherence generating dynamic dipole–dipole interaction theory. In this model, each qubit is a block consisting of an ensemble of quantum dots, and the energetics of which suggests stability up to room temperature. Moreover, a quantum controlled–controlled not (CCN) gate of the block structure is given as an essential unit. The spatiotemporal dynamics of the quantum entangled pure states, which is crucial for the execution of the quantum super-parallelism, is illustrated for the proposed quantum CCN gate. Copyright

Possibility of room-temperature solid state quantum computer winning coherence against noise by quantum ensemble resonance

Recent progress in nano-meter structure and measurements is going to provide us the freedom to domesticate fast correlations between atoms in an ensemble, manifesting them at macroscopic level. Here, we show a possibility to generate an electron coherence within an atomic ensemble, via the quantum resonance due to parity inheriting dynamic dipole-dipole interaction. We built up a realistic Hamiltonian having a combinatorial probability factors for the dynamic dipole-dipole quantum resonance. This leads to the precise simulation of the process that will actually occur in nature obeying the energy conservation law. We also show a preliminary experimental data suggestive of the dynamic dipole-dipole mode. These results lead to our proposal of solid state room temperature quantum computer, e.g. by a solid state qubit system of arrayed quantum dots designed to resist against phase errors as well as bit errors.

Physical Basis of Optoelectronic Integration

It is not an exaggeration to say that the technological developments of our civilization have been done by the activity of integration. In other words, most of the products of our civilization are constituted in a numbers of parts. And it is hard to find parts, each of which works by itself alone. Therefore, it is natural to believe that the optoelectronic integration is the next target of the technology of optical devices and electronic circuits.

Estimation of Photonic Couplings among Electric Multipoles in Quantum Dots for Nanometer Scale Devices

A comparison among the possible nonlinear photonic interactions for scalable nanometer networks and quantum gates as well as for coherence retention in solids is made theoretically, and then numerical plottings are given, on the basis of the dipole length estimated from our μ-PL (microphotoluminescence) spectra of GaAs/AlGaAs coupled quantum dots (QDs) having a pair of 0.3 meV splittings. Furthermore, prospective device concepts based on these nonlinear multipolar interactions are given.

Multipolar Photonic Interactions for Interconnections and Logical Operations in Nanostructure Networks

Multipolar interactions involving real and virtual photons are compared, and suggested as the principle of intra-device, inter-device, and inter-chip interconnections and logical operations, with the device concepts for solid state nano-networks and a quantum computer

Atomic Operator Formalism of Elementary Gates for Quantum Computation and Impurity-Induced Exciton Quantum Gates

The information-processing capability of quantum systems has long been of theoretical interest in physics and computer science. Feynman considered gate arrays with computing operations based on principles of quantum mechanics1. Deutch and his co-workers sought formulating quantum Turing machines2,3 and quantum complexity theory4. Recently, considerable progress has been achieved in the latter line of approach where quantum computers were shown to be qualitatively much stronger than classical ones, culminating in Shor’s discovery of quantum polynomial time algorithms for factoring and discrete logarithm5. This has led several-physicist groups to make attempts to. implement quantum computers by using trapped ions6,7, quantum dots, nuclear spins using multiple pulse resonance techniques8 and so on. Appreciation of the power of quantum computing was quickly tempered by the realization that preserving quantum coherence made the implementation of practical quantum computers unlikely within decades.

Spatiotemporal Dynamics of Quantum Computing Solid Dipole-Dipole Block Systems

This paper enstimates the stability of dipole-dipole interaction in quantum dot array, and proposes a novel solid state quantum CCN (controlled controlled not) gate having a block structure, which is effective to maintain quantum mechanical coherence and reduce both the bit error and the phase error. The spatiotemporal dynamics of quantum computation process involving the quantum entangled pure states is illustrated.