1,519 research outputs found
Adiabatic quantum search with atoms in a cavity driven by lasers
We propose an implementation of the quantum search algorithm of a marked item
in an unsorted list of N items by adiabatic passage in a cavity-laser-atom
system. We use an ensemble of N identical three-level atoms trapped in a
single-mode cavity and driven by two lasers. In each atom, the same level
represents a database entry. One of the atoms is marked by having an energy gap
between its two ground states. Appropriate time delays between the two laser
pulses allow one to populate the marked state starting from an initial
entangled state within a decoherence-free adiabatic subspace. The time to
achieve such a process is shown to exhibit the Grover speedup.Comment: 5 pages, 3 figure
Quantum search by parallel eigenvalue adiabatic passage
We propose a strategy to achieve the Grover search algorithm by adiabatic
passage in a very efficient way. An adiabatic process can be characterized by
the instantaneous eigenvalues of the pertaining Hamiltonian, some of which form
a gap. The key to the efficiency is based on the use of parallel eigenvalues.
This allows us to obtain non-adiabatic losses which are exponentially small,
independently of the number of items in the database in which the search is
performed.Comment: 7 pages, 4 figure
Analog Grover search by adiabatic passage in a cavity-laser-atom system
A physical implementation of the adiabatic Grover search is theoretically
investigated in a system of N identical three-level atoms trapped in a single
mode cavity. Some of the atoms are marked through the presence of an energy gap
between their two ground states. The search is controlled by two partially
delayed lasers which allow a deterministic adiabatic transfer from an initially
entangled state to the marked states. Pulse schemes are proposed to satisfy the
Grover speedup either exactly or approximately, and the success rate of the
search is calculated.Comment: 9 pages, 8 figure
Field-free two-direction alignment alternation of linear molecules by elliptic laser pulses
We show that a linear molecule subjected to a short specific elliptically
polarized laser field yields postpulse revivals exhibiting alignment
alternatively located along the orthogonal axis and the major axis of the
ellipse. The effect is experimentally demonstrated by measuring the optical
Kerr effect along two different axes. The conditions ensuring an optimal
field-free alternation of high alignments along both directions are derived.Comment: 5 pages, 4 color figure
On the topology of adiabatic passage
We examine the topology of eigenenergy surfaces characterizing the population
transfer processes based on adiabatic passage. We show that this topology is
the essential feature for the analysis of the population transfers and the
prediction of its final result. We reinterpret diverse known processes, such as
stimulated Raman adiabatic passage (STIRAP), frequency-chirped adiabatic
passage and Stark-chirped rapid adiabatic passage (SCRAP). Moreover, using this
picture, we display new related possibilities of transfer. In particular, we
show that we can selectively control the level which will be populated in
STIRAP process in Lambda or V systems by the choice of the peak amplitudes or
the pulse sequence
Fast and robust population transfer in two-level quantum systems with dephasing noise and/or systematic frequency errors
We design, by invariant-based inverse engineering, driving fields that invert
the population of a two-level atom in a given time, robustly with respect to
dephasing noise and/or systematic frequency shifts. Without imposing
constraints, optimal protocols are insensitive to the perturbations but need an
infinite energy. For a constrained value of the Rabi frequency, a flat
pulse is the least sensitive protocol to phase noise but not to systematic
frequency shifts, for which we describe and optimize a family of protocols.Comment: 7 pages, 2 figure
Optimized time-dependent perturbation theory for pulse-driven quantum dynamics in atomic or molecular systems
We present a time-dependent perturbative approach adapted to the treatment of
intense pulsed interactions. We show there is a freedom in choosing secular
terms and use it to optimize the accuracy of the approximation. We apply this
formulation to a unitary superconvergent technique and improve the accuracy by
several orders of magnitude with respect to the Magnus expansion.Comment: 4 pages, 2 figure
Reaching optimally oriented molecular states by laser kicks
We present a strategy for post-pulse orientation aiming both at efficiency
and maximal duration within a rotational period. We first identify the
optimally oriented states which fulfill both requirements. We show that a
sequence of half-cycle pulses of moderate intensity can be devised for reaching
these target states.Comment: 4 pages, 3 figure
Acute Abdomen: A Rare Presentation of Lung Cancer Metastasis
Surgical emergencies caused by bowel metastases from carcinoma of the lung are very rare. We describe two cases of symptomatic gastrointestinal metastatic small cell carcinoma: the first one concerns a 69-year-old man with an acute abdomen and the second is a 72-year-old man complaining of a gastric ulcer symptoms. We also discuss the current management and the prognosis of these patients
Laser control for the optimal evolution of pure quantum states
Starting from an initial pure quantum state, we present a strategy for
reaching a target state corresponding to the extremum (maximum or minimum) of a
given observable. We show that a sequence of pulses of moderate intensity,
applied at times when the average of the observable reaches its local or global
extremum, constitutes a strategy transferable to different control issues.
Among them, post-pulse molecular alignment and orientation are presented as
examples. The robustness of such strategies with respect to experimentally
relevant parameters is also examined.Comment: 16 pages, 9 figure
- âŠ