Atoms interact with each other through the electromagnetic field, creating collective states that can radiate faster or slower than a single atom, i.e. super- and sub-radiance. The generation control of such by engineering dipolar interactions between atoms enable new tools for atomic-based technologies. Atom-atom in free space are limited range, since amplitude radiated field decreases inversely distance. When is confined to one dimension it enables infinite-range interactions. This has...

We report ground-state quantum beats in spontaneous emission from a continuously driven atomic ensemble. Beats are visible only an intensity autocorrelation and evidence spontaneously generated coherence radiative decay. Our measurement realizes eraser where first photon detection prepares superposition second erases the "which path" information intermediate state.

Microscopic models based on multilevel atoms are central to optimizing nonlinear optical responses and the coherent control of light. These traditionally single-atom effects that parametrically extrapolated include collective effects, such as an enhanced response or propagation within atomic media. In this work, we present a systematic analysis cooperative arising in driven systems composed coupled via common electromagnetic environment. The is interplay between dressed states induced by...

We theoretically study the laser cooling of cavity optomechanics when mechanical resonance frequency and damping depend on time. In regime weak optomechanical coupling we extend theory using an adiabatic approximation. discuss modifications dynamics compare it with numerical simulations in a wide range modulation frequencies.

We study a system of two distant quantum emitters coupled via one-dimensional waveguide where the electromagnetic field has direction-dependent velocity. As consequence, onset collective emission is nonsimultaneous, and, for appropriate parameters, radiation could be enhanced one while inhibited other. Interference effects enable to radiate in preferential direction depending on atomic state and propagation phases. characterize such directional as function various delineating conditions...

Quantum chaos has recently received increasing attention due to its relationship with experimental and theoretical studies of nonequilibrium quantum dynamics, thermalization, the scrambling information. In an isolated system, refers properties spectrum that emerge when classical counterpart system is chaotic. However, despite progress leading longer coherence times, interactions environment can never be neglected, which calls for a definition in dissipative systems. Advances this direction...

We discuss the problem of finding best measurement strategy for estimating value a quantum system parameter. In general optimum measurement, in sense that it maximizes Fisher information and hence allows one to minimize estimation error, can only be determined if parameter is already known. A modification Van Trees inequality, which gives lower bound on error random parameter, proposed. The suggested inequality us assert particular together with an appropriate estimator, optimal. An adaptive...

We analyze the propagation of a pair quantized fields inside medium three-level atoms in Lambda configuration. calculate stationary quadrature noise spectrum field, case where probe field is squeezed state and show electromagnetically induced transparency. find an oscillatory transfer initial quantum properties between pump which most strongly pronounced when both have comparable intensities. This implies that measured after can be completely different from state, even though mean values are...

We study the modification of atomic spontaneous emission rate, i.e. Purcell effect, $^{87}$Rb in vicinity an optical nanofiber ($\sim$500 nm diameter). observe enhancement and inhibition decay rate depending on alignment induced dipole relative to nanofiber. Finite-difference time-domain simulations are quantitative agreement with measurements when considering atoms as simple oscillating linear dipoles. This is surprising since multi-level nature should produce a different radiation pattern,...

The interaction of a bichromatic quantized field with three-level atoms in $\ensuremath{\Lambda}$ configuration is analyzed. We calculate the correlation functions emitted by when driven coherent state. consider cases where are inside and outside cavity.

We present an analysis of chaos and regularity in the open Dicke model, when dissipation is due to cavity losses. Due infinite Liouville space this we also introduce a criterion numerically find complex spectrum which approximately represents system spectrum. The isolated model has well-defined classical limit with two degrees freedom. select case studies where shows appears. To characterize as regular or chaotic, study regions taking windows over absolute value its eigenvalues. Our results...

We investigate the collective non-Markovian dynamics of two fully excited two-level atoms coupled to a one-dimensional waveguide in presence delay. demonstrate that analogous well-known superfluorescence phenomena, where an inverted atomic ensemble synchronizes enhance its emission, there is “subfluorescence” effect into entangled dark state depending on interatomic separation. The phenomenon can lead two-photon bound continuum. Our results are pertinent long-distance quantum networks,...

It is shown how one can implement quantum feedback and probabilistic error correction in an open system consisting of a single atom, with ground- excited-state Zeeman structure, driven two-mode optical cavity. The ground-state superposition manipulated controlled through conditional measurements external fields, which shield the coherence correct errors. Modeling experimentally realistic situation demonstrates robustness proposal for realization laboratory.

Abstract Using the convex structure of positive operator value measurements and several quantities used in quantum metrology, such as Fisher information or Van Trees information, we present an efficient numerical method to find best strategy allowed by mechanics estimate a parameter. This explores extremal thus providing significant advantage over previously methods. We exemplify for different cost functions qubit harmonic oscillator strong when desired target error is sufficiently small.

We consider the Lindblad equation for a collection of multilevel systems coupled to independent environments. The is symmetric under exchange labels associated with each system and thus open-system dynamics takes place in permutation-symmetric subspace operator space. dimension this space grows polynomially number systems. construct basis set superoperators whose action on easily specified. For given levels, $M$, these are written terms bosonic realization generators Lie algebra $\sln{M^2}$....

An anomalous light shift in the precession of a ground-state Zeeman coherence is observed: Larmor frequency increases with strength drive that blue (red) detuned from transition out lower (upper) energy level. Our measurements are made on Rb 85 atoms traversing an optical cavity containing few photons; shifts as large 1% per photon recorded. The arises accumulation phase driven by quantum jumps. It stochastic and accompanied broadening.

The spontaneous creation and persistence of ground-state coherence in an ensemble intracavity Rb atoms has been observed as a quantum beat. Our system realizes eraser, where the detection first photon prepares superposition Zeeman sublevels, while second erases stored information. Beats appear time-delayed photon-photon coincidence rate (intensity correlation function). We study beats theoretically experimentally function parameters, find them remarkably robust against perturbations such...

We implement a simple feedback mechanism on two-mode cavity QED system to preserve the Zeeman coherence of ground state superposition that generates quantum beats second-order correlation function. Our investigation includes theoretical and experimental studies show how prevent shift away from Larmor frequency associated decoherence caused by Rayleigh scattering. The protocol consists turning off drive after detection first photon letting it evolve in dark. Turning back pre-set time reveals...

The interaction of a quantized field with three-level atoms in $\ensuremath{\Lambda}$ configuration inside two-mode cavity is analyzed the small-noise approximation. are two-photon detuning respect to carriers field. We calculate stationary quadrature noise spectrum outside case where input probe squeezed state and pump coherent state. mean value unaltered all analysis: shows electromagnetically induced transparency. effect atoms' base level decoherence output also studied. It found that...

We present a family of many-body models which are exactly solvable analytically. The an extended n-body interaction Lipkin-Meshkov-Glick model considers spin-flip terms associated with the external classical field coherently manipulates state system in order to, for example, process quantum information. also describe two-mode Bose-Einstein condensate Josephson-type includes n-particle elastic and inelastic collisions. One corresponds to canonical Hamitonian plus term we argue must be...

Estimating correctly the quantum phase of a physical system is central problem in parameter estimation theory due to its wide range applications from metrology cryptography. Ideally, optimal estimator given by so-called Cramér-Rao bound, so any measurement strategy aims obtain estimations as close possible it. However, more often than not, current state-of-the-art methods estimate phases fail reach this bound they rely on maximum likelihood estimators non-identifiable functions. In work we...

The interaction of a quantized field with three-level atoms in $\ensuremath{\Lambda}$ configuration inside two mode cavity is analyzed. We calculate the stationary quadrature noise spectrum outside case where input probe squeezed state and show electromagnetically induced transparency. If Rabi frequencies both dipole transitions are different from zero, we that output has four maxima squeezing absorption. some cases these can be very close to transition frequency atom, region mean value...

We study the effects of three-body collisions in basic physical properties a two-mode Bose-Einstein condensate. By finding exact analytical solution model which includes two-body and elastic mode-exchange collisions, we show analytically that interactions produce observable probability distribution ground state dynamics relative population. In particular, find under certain circumstances inhibit collapse

Mode-exchange collisions occur in multimode Bose-Einstein condensates, some cases, producing particle loss the system. Nevertheless, little is known about mode-exchange case when particles do not escape trap. We show that these processes are relevant quantum properties of system such as evolution relative population, self-trapping effect, and probability distribution particles. Surprisingly, including terms model two-mode condensate allows for an exact analytical solution. Using this...

Abstract Physical realizations of the canonical phase measurement for optical are unknown. Single-shot estimation, which aims to determine an field in a single shot, is critical quantum information processing and metrology. Here we present family strategies single-shot estimation coherent states based on adaptive non-Gaussian, photon counting, measurements with displacements that maximize gain as progresses, have higher sensitivities over best known Gaussian strategies. To understanding...