94 research outputs found
Spin-based optical quantum gates via Pauli blocking in semiconductor quantum dots
We present a solid-state implementation of ultrafast conditional quantum
gates. Our proposal for a quantum-computing device is based on the spin degrees
of freedom of electrons confined in semiconductor quantum dots, thus benefiting
from relatively long decoherence times. More specifically, combining Pauli
blocking effects with properly tailored ultrafast laser pulses, we are able to
obtain sub-picosecond spin-dependent switching of the Coulomb interaction,
which is the essence of our conditional phase-gate proposal. This allows us to
realize {\it a fast two qubit gate which does not translate into fast
decoherence times} and paves the road for an all-optical spin-based quantum
computer.Comment: 14 Pages RevTeX, 3 eps figures include
Quantum information processing in bosonic lattices
We consider a class of models of self-interacting bosons hopping on a
lattice. We show that properly tailored space-temporal coherent control of the
single-body coupling parameters allows for universal quantum computation in a
given sector of the global Fock space. This general strategy for encoded
universality in bosonic systems has in principle several candidates for
physical implementation.Comment: 4 pages, 2 figs, RevTeX 4; updated to the published versio
Semiconductor-based Geometrical Quantum Gates
We propose an implementation scheme for holonomic, i.e., geometrical, quantum
information processing based on semiconductor nanostructures. Our quantum
hardware consists of coupled semiconductor macroatoms addressed/controlled by
ultrafast multicolor laser-pulse sequences. More specifically, logical qubits
are encoded in excitonic states with different spin polarizations and
manipulated by adiabatic time-control of the laser amplitudes . The two-qubit
gate is realized in a geometric fashion by exploiting dipole-dipole coupling
between excitons in neighboring quantum dots.Comment: 4 Pages LaTeX, 3 Figures included. To appear in PRB (Rapid Comm.
Non-adiabatic geometrical quantum gates in semiconductor quantum dots
In this paper we study the implementation of non-adiabatic geometrical
quantum gates with in semiconductor quantum dots. Different quantum information
enconding/manipulation schemes exploiting excitonic degrees of freedom are
discussed. By means of the Aharanov-Anandan geometrical phase one can avoid the
limitations of adiabatic schemes relying on adiabatic Berry phase; fast
geometrical quantum gates can be in principle implementedComment: 5 Pages LaTeX, 10 Figures include
Optimal quantum control in nanostructures: Theory and application to generic three-level system
Coherent carrier control in quantum nanostructures is studied within the
framework of Optimal Control. We develop a general solution scheme for the
optimization of an external control (e.g., lasers pulses), which allows to
channel the system's wavefunction between two given states in its most
efficient way; physically motivated constraints, such as limited laser
resources or population suppression of certain states, can be accounted for
through a general cost functional. Using a generic three-level scheme for the
quantum system, we demonstrate the applicability of our approach and identify
the pertinent calculation and convergence parameters.Comment: 7 pages; to appear in Phys. Rev.
Holonomic quantum gates: A semiconductor-based implementation
We propose an implementation of holonomic (geometrical) quantum gates by
means of semiconductor nanostructures. Our quantum hardware consists of
semiconductor macroatoms driven by sequences of ultrafast laser pulses ({\it
all optical control}). Our logical bits are Coulomb-correlated electron-hole
pairs (excitons) in a four-level scheme selectively addressed by laser pulses
with different polarization. A universal set of single and two-qubit gates is
generated by adiabatic change of the Rabi frequencies of the lasers and by
exploiting the dipole coupling between excitons.Comment: 10 Pages LaTeX, 10 Figures include
Exploiting lipid metabolism by HSV-1: a challenge to rethink new therapies for Alzheimer’s disease
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