2,763 research outputs found
Universal control of quantum subspaces and subsystems
We describe a broad dynamical-algebraic framework for analyzing the quantum
control properties of a set of naturally available interactions. General
conditions under which universal control is achieved over a set of
subspaces/subsystems are found. All known physical examples of universal
control on subspaces/systems are related to the framework developed here.Comment: 4 Pages RevTeX, Some typos fixed, references adde
Computation on a Noiseless Quantum Code and Symmetrization
Let be the state-space of a quantum computer coupled with the
environment by a set of error operators spanning a Lie algebra
Suppose admits a noiseless quantum code i.e., a subspace annihilated by We show that a universal set of
gates over is obtained by any generic pair of -invariant
gates. Such gates - if not available from the outset - can be obtained by
resorting to a symmetrization with respect to the group generated by Any computation can then be performed completely within the coding
decoherence-free subspace.Comment: One result added, to appear in Phys. Rev. A (RC) 4 pages LaTeX, no
figure
Quantum Entanglement in Fermionic Lattices
The Fock space of a system of indistinguishable particles is isomorphic (in a
non-unique way) to the state-space of a composite i.e., many-modes, quantum
system. One can then discuss quantum entanglement for fermionic as well as
bosonic systems. We exemplify the use of this notion -central in quantum
information - by studying some e.g., Hubbard,lattice fermionic models relevant
to condensed matter physics.Comment: 4 Pages LaTeX, 1 TeX Figure. Presentation improved, title changed. To
appear in PR
Quantum Computing of Classical Chaos: Smile of the Arnold-Schrodinger Cat
We show on the example of the Arnold cat map that classical chaotic systems
can be simulated with exponential efficiency on a quantum computer. Although
classical computer errors grow exponentially with time, the quantum algorithm
with moderate imperfections is able to simulate accurately the unstable chaotic
classical dynamics for long times. The algorithm can be easily implemented on
systems of a few qubits.Comment: revtex, 4 pages, 4 figure
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