0501048v1

related topics
{group, space, representation}
{time, decoherence, evolution}
{equation, function, exp}
{operator, operators, space}
{entanglement, phys, rev}
{qubit, qubits, gate}
{level, atom, field}
{let, theorem, proof}
{spin, pulse, spins}
{states, state, optimal}
{time, wave, function}
{cos, sin, state}
{energy, state, states}
{bell, inequality, local}
{observables, space, algebra}

Four-level and two-qubit systems, sub-algebras, and unitary integration

A. R. P. Rau, G. Selvaraj, D. Uskov

abstract: Four-level systems in quantum optics, and for representing two qubits in quantum computing, are difficult to solve for general time-dependent Hamiltonians. A systematic procedure is presented which combines analytical handling of the algebraic operator aspects with simple solutions of classical, first-order differential equations. In particular, by exploiting $su(2) \oplus su(2)$ and $su(2) \oplus su(2) \oplus u(1)$ sub-algebras of the full SU(4) dynamical group of the system, the non-trivial part of the final calculation is reduced to a single Riccati (first order, quadratically nonlinear) equation, itself simply solved. Examples are provided of two-qubit problems from the recent literature, including implementation of two-qubit gates with Josephson junctions.

oai_identifier:
oai:arXiv.org:quant-ph/0501048
categories:
quant-ph
comments:
1 gzip file with 1 tex and 9 eps figure files. Unpack with command: gunzip RSU05.tar.gz
doi:
10.1103/PhysRevA.71.062316
arxiv_id:
quant-ph/0501048
journal_ref:
Phys.Rev.A71:062316,2005
created:
2005-01-11

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