Julio Gea-Banacloche

Bio: Julio Gea-Banacloche is an academic researcher from University of Arkansas. The author has contributed to research in topics: Photon & Field (physics). The author has an hindex of 28, co-authored 137 publications receiving 4799 citations. Previous affiliations of Julio Gea-Banacloche include University of New Mexico & Quaid-i-Azam University.

Electromagnetically induced transparency in ladder-type inhomogeneously broadened media: Theory and experiment

Abstract: We develop a theory of electromagnetically induced transparency in a three-level, ladder-type Doppler-broadened medium, paying special attention to the case where the coupling and probe beams are counterpropagating and have similar frequencies, so as to reduce the total Doppler width of the two-photon process. The theory is easily generalized to deal with the \ensuremath{\Lambda} configuration, where the ideal arrangement involves two copropagating beams. We discuss different possible regimes, depending on the relative importance of the various broadening mechanisms, and identify ways to optimize the absorption-reduction effect. The theory is compared to the results of a recent experiment (on a ladder-type system), using the Rb D2 line, with generally very good agreement. The maximum absorption reduction observed (64.4%) appears to be mostly limited by the relatively large (\ensuremath{\sim}5 MHz) linewidth of the diode lasers used in our experiment.

The ring laser gyro

Abstract: This paper presents a review of both active and passive ring laser devices. The operating principles of the ring laser are developed and discussed, with special emphasis given to the problems associated with the achievement of greater sensitivity and stability. First-principle treatments of the nature of quantum noise in the ring laser gyro and various methods designed to avoid low-rotation-rate lock-in are presented. Descriptions of state-of-the-art devices and current and proposed applications (including a proposed test of metric theories of gravity using a passive cavity ring laser) are given.

Measurement of Dispersive Properties of Electromagnetically Induced Transparency in Rubidium Atoms

Abstract: The dispersive properties of the atomic transition in the rubidium ${D}_{2}$ line ($5{S}_{\frac{1}{2}}\ensuremath{-}5{P}_{\frac{3}{2}}$) at 780.0 nm are measured with a Mach-Zehnder interferometer when an additional coupling field at 775.8 nm is applied to an upper transition ($5{P}_{\frac{3}{2}}\ensuremath{-}5{D}_{\frac{5}{2}}$). This ladder-type system is observed to exhibit electromagnetically induced transparency together with a rapidly varying refractive index. A reduction in group velocity for the probe beam (${v}_{g}=\frac{c}{13.2}$) is inferred from the measured dispersion curve with 52.5% suppressed absorption on resonance.

Collapse and revival of the state vector in the Jaynes-Cummings model: An example of state preparation by a quantum apparatus.

Abstract: The evolution of the atomic state in the resonant Jaynes-Cummings model (a two-level atom interacting with a single mode of the quantized radiation field) with the field initially in a coherent state is considered. It is shown that the atom is to a good approximation in a pure state in the middle of what has been traditionally called the "collapse region. This pure state exhibits no Rabi oscillations and is reached independently of the initial state of the atom. For most initial states a total or partial "collapse of the wave function" takes place early during the interaction, at the conventional collapse time, following which the state vector is recreated, over a longer time scale. PACS numbers: 42.50.— p, 03.65.— w, 42.52.+x The Jaynes-Cummings model' (JCM) is perhaps the simplest nontrivial example of two interacting quantum systems: a two-level atom and a single mode of the radiation field. In addition to its being exactly solvable, the physical system that it represents has recently become experimentally realizable with Rydberg atoms in high-Q microwave cavities. Comparison of the predictions of the model with those of its semiclassical version have served to identify a number of uniquely quantum properties of the electromagnetic field; indeed, the model displays some very interesting dynamics, and the differences with the semiclassical theory are both profound and unexpected. The JCM would also appear to be an excellent model with which to explore some of the more puzzling aspects of quantum mechanics, such as the possibility (or impossibility) to describe an interacting quantum system by a state vector undergoing unitary evolution; i.e., the socalled "collapse of the wave function. " In the semiclassical version, the atom interacting with the classical electromagnetic field may at all times be described by a state vector evolving unitarily. What happens, however, when it is recognized that the field is itself a quantum system (which leads inevitably to "entanglement" )? This is the question addressed in this Letter. It does not seem to have been addressed before in full generality, although entanglement in the JCM dynamics plays an essential role in a recent measurement-theory-related proposal of Scully and Walther, and preparation of a pure state of the field in the JCM has been the subject of several theoretical investigations and may be close to being achieved experimentally. The resonant JCM interaction Hamiltonian may be written as Ht = hg(~a&(b (a+ a'(b)(a ~ ), ' is a coupling constant (d is the atomic dipole matrix element for the transition, m is the transition frequency, and Vis the mode volume), ~a) and ~b) are the upper and lower atomic levels, respectively, and a and a are the annihilation and creation operators of the field mode, which in the semiclassical theory are simply replaced by c numbers. The solution to the Schrodinger equation for the atom initially in state y(0)).,&,~ =a~a)+ p b) and field initially in state ttt(0))fi iu g„-OC„n) is ~y(t)) = g [[aC„cos(gOn+1 t) — ipC„s+i l(gnawn +1 t)]~ a& +[ — iaC„~sin(gran t)+pC„cos(gran

Atom- and field-state evolution in the Jaynes-Cummings model for large initial fields.

Abstract: An asymptotic result is derived for the Jaynes-Cummings model of a two-level atom interacting with a quantized single-mode field, which is valid when the field is initially in a coherent state with a large average photon number. It is shown that for certain initial atomic states the joint atom-field wave function factors into an atomic and a field part throughout the interaction, so that each system remains separately in a pure state. The atomic part of the wave function displays a crossing of trajectories in the atom Hilbert space that leads to a unique state for the atom, independent of its initial state, at a specific time to (equal to half the revival time). The field part of the wave function resembles a crescent squeezed state. The well-known collapses and revivals are investigated from this perspective. The collapse appears to be associated with a "measurement" of the initial state of the atom with the field as the measuring apparatus. The measurement is not complete for finite average photon number: the system is instead left in a coherent superposition of macroscopically distinct states. At the half-revival time to this superposition of states is entirely in the field part of the state vector, so that the (pure) state of the field at that time is of the form sometimes referred to as a "Schrodinger cat. " The revivals of the population inversion are seen to be entirely due to the fact that the linear superposition of the two macroscopically distinct field states is coherent (i.e., a pure state), as opposed to an incoherent mixture.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Many-Body Physics with Ultracold Gases

Abstract: This paper reviews recent experimental and theoretical progress concerning many-body phenomena in dilute, ultracold gases. It focuses on effects beyond standard weak-coupling descriptions, such as the Mott-Hubbard transition in optical lattices, strongly interacting gases in one and two dimensions, or lowest-Landau-level physics in quasi-two-dimensional gases in fast rotation. Strong correlations in fermionic gases are discussed in optical lattices or near-Feshbach resonances in the BCS-BEC crossover.

Electromagnetically induced transparency : Optics in coherent media

Abstract: Coherent preparation by laser light of quantum states of atoms and molecules can lead to quantum interference in the amplitudes of optical transitions. In this way the optical properties of a medium can be dramatically modified, leading to electromagnetically induced transparency and related effects, which have placed gas-phase systems at the center of recent advances in the development of media with radically new optical properties. This article reviews these advances and the new possibilities they offer for nonlinear optics and quantum information science. As a basis for the theory of electromagnetically induced transparency the authors consider the atomic dynamics and the optical response of the medium to a continuous-wave laser. They then discuss pulse propagation and the adiabatic evolution of field-coupled states and show how coherently prepared media can be used to improve frequency conversion in nonlinear optical mixing experiments. The extension of these concepts to very weak optical fields in the few-photon limit is then examined. The review concludes with a discussion of future prospects and potential new applications.

Light speed reduction to 17 metres per second in an ultracold atomic gas

Abstract: Techniques that use quantum interference effects are being actively investigated to manipulate the optical properties of quantum systems1. One such example is electromagnetically induced transparency, a quantum effect that permits the propagation of light pulses through an otherwise opaque medium2,3,4,5. Here we report an experimental demonstration of electromagnetically induced transparency in an ultracold gas of sodium atoms, in which the optical pulses propagate at twenty million times slower than the speed of light in a vacuum. The gas is cooled to nanokelvin temperatures by laser and evaporative cooling6,7,8,9,10. The quantum interference controlling the optical properties of the medium is set up by a ‘coupling’ laser beam propagating at a right angle to the pulsed ‘probe’ beam. At nanokelvin temperatures, the variation of refractive index with probe frequency can be made very steep. In conjunction with the high atomic density, this results in the exceptionally low light speeds observed. By cooling the cloud below the transition temperature for Bose–Einstein condensation11,12,13 (causing a macroscopic population of alkali atoms in the quantum ground state of the confining potential), we observe even lower pulse propagation velocities (17?m?s−1) owing to the increased atom density. We report an inferred nonlinear refractive index of 0.18?cm2?W−1 and find that the system shows exceptionally large optical nonlinearities, which are of potential fundamental and technological interest for quantum optics.

Electromagnetically Induced Transparency

Abstract: Electromagnetically induced transparency is a technique for eliminating the effect of a medium on a propagating beam of electromagnetic radiation EIT may also be used, but under more limited conditions, to eliminate optical self‐focusing and defocusing and to improve the transmission of laser beams through inhomogeneous refracting gases and metal vapors, as figure 1 illustrates The technique may be used to create large populations of coherently driven uniformly phased atoms, thereby making possible new types of optoelectronic devices