Dynamics of decoherence in continuous atom-optical quantum nondemolition measurements

Onofrio, Roberto; Viola, Lorenza

doi:10.1103/physreva.58.69

Cited by 19 publications

(20 citation statements)

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“…(10) preserves the total number of atoms, and corresponds to a quantum nondemolition coupling between the atom and the optical fields [18,19,[23][24][25]. If the measurement kernel were a local one, K(r 1 − r 2 ) ≃ δ(r 1 − r 2 ), Eq.…”

Section: Master Equation For Dispersive Imaging Of a Bose Condensatementioning

confidence: 99%

Continuous quantum measurement of a Bose-Einstein condensate: A stochastic Gross-Pitaevskii equation

2002

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We analyze the dynamics of a Bose-Einstein condensate undergoing a continuous dispersive imaging by using a Lindblad operator formalism. Continuous strong measurements drive the condensate out of the coherent state description assumed within the Gross-Pitaevskii mean-field approach. Continuous weak measurements allow instead to replace, for timescales short enough, the exact problem with its mean-field approximation through a stochastic analogue of the Gross-Pitaevskii equation. The latter is used to show the unwinding of a dark soliton undergoing a continuous imaging. 03.75.Fi,05.30.Jp,

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Section: Master Equation For Dispersive Imaging Of a Bose Condensatementioning

confidence: 99%

Continuous quantum measurement of a Bose-Einstein condensate: A stochastic Gross-Pitaevskii equation

2002

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“…(2). This equation preserves the total number of atoms, and corresponds to a quantum nondemolition [13] coupling between the atom and the optical fields [9,[14][15][16]. The measurement kernel K has the expression: (3) where ξ is the lengthscale of the condensate in the z direction, the width of the Gaussian state Λ(z) under the abovementioned approximation.…”

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confidence: 99%

Measurement-induced squeezing of a Bose-Einstein condensate

2002

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We discuss the dynamics of a Bose-Einstein condensate during its nondestructive imaging. A generalized Lindblad superoperator in the condensate master equation is used to include the effect of the measurement. A continuous imaging with a sufficiently high laser intensity progressively drives the quantum state of the condensate into number squeezed states. Observable consequences of such a measurementinduced squeezing are discussed. 03.75.Fi, 42.50.Md Since its birth, quantum mechanics has led to an interpretational debate on the role played by the measurement process in its structure and its relationship to classical mechanics developed for macroscopic systems [1]. This debate has been enriched by the realization of new experimental techniques spanning from quantum jumps in single ion traps to macroscopic entangled states in various quantum systems. Recently, the production of atomic Bose-Einstein condensates of dilute atomic gases has also paved the way to the study of dynamical phenomena of macroscopic quantum systems with the precision characteristic of atomic physics [2].Two optical techniques, absorption and dispersive imagings, have been used to monitor the dynamics of a Bose-Einstein condensate [2]. In the former the condensate interacts with a light beam resonant (or close to resonance) with an atomic transition. The output beam is attenuated proportionally to the column density of the condensate -the condensate density integrated along the line of sight of the imaging beam. The absorption of photons heats the condensate then strongly perturbing it, and in general a new replica of the condensate has to be produced to further study its dynamics. This measurement is, in the language of quantum measurement theory, of type-II since it destroys the state of the observed system and forbids the study of the dynamics of a single quantum system [3]. Repeated measurements on a Bose-Einstein condensate or, at the limit, its continuous monitoring are instead possible using its dispersive features, for instance through phase-contrast [4] or interference [5] imaging techniques. Off-resonance light is scattered by the condensate which induces phase-shifts thereby converted into light intensity modulations by homodyne or heterodyne detection. The off-resonant nature of the atom-photon interaction allows for a very low absorption rate and therefore low heating of the condensate. Thus, multiple shots of the same condensate can be taken -a type-I measurement -allowing to study with high accuracy several phenomena, like its formation in non-adiabatic conditions [6], short and long wavelength collective excitations [7], vortices and superfluid dynamics [8]. The effect of the measurement process is typically neglected in these analysis. A first attempt to include the measurement process in a two-mode configuration for the condensate has been discussed in [9]. Our main goal is to include the atom-photon interaction process present in dispersive imaging into the intrinsic dynamics of the condensate. We show that the measure...

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“…Such a measurement scheme was originally introduced in the context of the detection of gravitational waves [14,15,16,17,18,19,20]. The experimental progress on QND measurements has been summarized in the review [21] and the dynamics of decoherence in continuous atom-optical QND measurements studied in [22]. In addition to its relevance in ultrasensitive measurements, a QND scheme provides a way to prepare quantum mechanical states which may otherwise be difficult to create, such as Fock states with a specific number of particles.…”

Section: Introductionmentioning

confidence: 99%

Phase-diffusion pattern in quantum-nondemolition systems

Banerjee

Ghosh

2007

Phys. Rev. A

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We quantitatively analyze the dynamics of the quantum phase distribution associated with the reduced density matrix of a system, as the system evolves under the influence of its environment with an energy-preserving quantum nondemolition (QND) type of coupling. We take the system to be either an oscillator (harmonic or anharmonic) or a two-level atom (or equivalently, a spin-1/2 system), and model the environment as a bath of harmonic oscillators, initially in a general squeezed thermal state. The impact of the different environmental parameters is explicitly brought out as the system starts out in various initial states. The results are applicable to a variety of physical systems now studied experimentally with QND measurements.

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Dynamics of decoherence in continuous atom-optical quantum nondemolition measurements

Cited by 19 publications

References 47 publications

Continuous quantum measurement of a Bose-Einstein condensate: A stochastic Gross-Pitaevskii equation

Continuous quantum measurement of a Bose-Einstein condensate: A stochastic Gross-Pitaevskii equation

Measurement-induced squeezing of a Bose-Einstein condensate

Phase-diffusion pattern in quantum-nondemolition systems

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