31 research outputs found
Quantum computing with an inhomogeneously broadened ensemble of ions: Suppression of errors from detuning variations by specially adapted pulses and coherent population trapping
The proposal for quantum computing with rare-earth-ion qubits in inorganic
crystals makes use of the inhomogeneous broadening of optical transitions in
the ions to associate individual qubits with ions responding to radiation in
selected frequency channels. We show that a class of Gaussian composite pulses
and complex sech pulses provide accurate qubit pi-rotations, which are at the
same time channel selective on a 5 MHz frequency scale and tolerant to 0.5 MHz
deviations of the transition frequency of ions within a single channel.
Rotations in qubit space of arbitrary angles and phases are produced by
sequences of pi-pulses between the excited state of the ions and coherent
superpositions of the qubit states.Comment: 6 pages, 6 figures. Revised, extended version. More detailed
discussion of frequency toleranc
Quantum computing with a single molecular ensemble and a Cooper pair box
We propose to encode quantum information in rotational excitations in a
molecular ensemble. Using a stripline cavity field for quantum state transfer
between the molecular ensemble and a Cooper pair box two-level system, our
proposal offers a linear scaling of the number of qubits in our register with
the number of rotationally excited states available in the molecules.Comment: 4 pages, 3 figures Minor corrections from reviewing proces
Pairwise entanglement in symmetric multi-qubit systems
The concurrence, a quantitative measure of the entanglement between a pair of
particles, is determined for the case where the pair is extracted from a
symmetric state of N two-level systems. Examples are given for both pure and
mixed states of the N-particle system, and for a pair extracted from two
ensembles with correlated collective spins.Comment: 7 pages, 3 figure
Polarization squeezing by optical Faraday rotation
We show that it is possible to generate continuous-wave fields and pulses of
polarization squeezed light by sending classical, linearly polarized laser
light twice through an atomic sample which causes an optical Faraday rotation
of the field polarization. We characterize the performance of the process, and
we show that an appreciable degree of squeezing can be obtained under realistic
physical assumptions.Comment: 4 pages, 4 figure