7,234 research outputs found
Entangled coherent states and squeezing in N trapped ions
We consider a resonant bichromatic excitation of N trapped ions that
generates displacement and squeezing in their collective motion conditioned to
their ionic internal state, producing eventually Scrhodinger cat states and
entangled squeezing. Furthermore, we study the case of tetrachromatic
illumination or producing the so called entangled coherent states in two
motional normal modes.Comment: 4 Revtex pages, no figures. To appear in Proceedings of "Mysteries,
Puzzles and Paradoxes in Quantum Mechanics", Garda Lake, Italy (2001
Field squeeze operators in optical cavities with atomic ensembles
We propose a method of generating unitarily single and two-mode field
squeezing in an optical cavity with an atomic cloud. Through a suitable laser
system, we are able to engineer a squeeze field operator decoupled from the
atomic degrees of freedom, yielding a large squeeze parameter that is scaled up
by the number of atoms, and realizing degenerate and non-degenerate parametric
amplification. By means of the input-output theory we show that ideal squeezed
states and perfect squeezing could be approached at the output. The scheme is
robust to decoherence processes.Comment: Four pages and one figure. Accepted in Physical Review Letter
Operational multipartite entanglement classes for symmetric photonic qubit states
We present experimental schemes that allow to study the entanglement classes
of all symmetric states in multiqubit photonic systems. In addition to
comparing the presented schemes in efficiency, we will highlight the relation
between the entanglement properties of symmetric Dicke states and a recently
proposed entanglement scheme for atoms. In analogy to the latter, we obtain a
one-to-one correspondence between well-defined sets of experimental parameters
and multiqubit entanglement classes inside the symmetric subspace of the
photonic system.Comment: 5 pages, 1 figur
Reliable teleportation in trapped ions
We study a method for the implementation of a reliable teleportation protocol
(theoretically, 100% of success) of internal states in trapped ions. The
generation of the quantum channel (any of four Bell states) may be done
respecting technical limitations on individual addressing and without claiming
the Lamb-Dicke regime. An adequate Bell analyzer, that transforms unitarily the
Bell basis into a completely disentangled one, is considered. Probable sources
of error and fidelity estimations of the teleportation process are studied.
Finally, we discuss experimental issues, proposing a scenario in which the
present scheme could be implemented.Comment: 8 Latex pages with five (ps,eps) figures included (EPJ style also
included). Accepted for publication in European Physical Journal
Unitary expansion of the time evolution operator
We propose an expansion of the unitary evolution operator, associated to a
given Schr\"odinger equation, in terms of a finite product of explicit unitary
operators. In this manner, this unitary expansion can be truncated at the
desired level of approximation, as shown in the given examples.Comment: 6 pages, 7 figures. Updated version, minor final change
Digitized-counterdiabatic quantum factorization
We factorize a 48-bit integer using 10 trapped-ion qubits on a Quantinuum's
quantum computer. This result outperforms the recent achievement by B. Yan et
al., arXiv:2212.12372 (2022), increasing the success probability by a factor of
6 with a non-hybrid digitized-counterdiabatic quantum factorization (DCQF)
algorithm. We expect better results with hybrid DCQF methods on our path to
factoring RSA-64, RSA-128, and RSA-2048 in this NISQ era, where the latter case
may need digital-analog quantum computing (DAQC) encoding
Singular Lagrangian Systems on Jet Bundles
The jet bundle description of time-dependent mechanics is revisited. The
constraint algorithm for singular Lagrangians is discussed and an exhaustive
description of the constraint functions is given. By means of auxiliary
connections we give a basis of constraint functions in the Lagrangian and
Hamiltonian sides. An additional description of constraints is also given
considering at the same time compatibility, stability and second-order
condition problems. Finally, a classification of the constraints in first and
second class is obtained using a cosymplectic geometry setting. Using the
second class constraints, a Dirac bracket is introduced, extending the
well-known construction by Dirac.Comment: 65 pages. LaTeX fil
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