The spontaneous localization mechanism of collapse models induces a Brownian motion in all physical systems. This effect is very weak, but experimental progress in creating ultracold atomic systems can be used to detect it. In this paper, we considered a recent experiment (Kovachy et al., 2015), where an atomic ensemble was cooled down to picokelvins. Any Brownian motion induces an extra increase of the position variance of the gas. We study this effect by solving the dynamical equations for the Continuous Spontaneous Localizations (CSL) model, as well as for its non-Markovian and dissipative extensions. The resulting bounds, with a 95% of confidence level, are beaten only by measurements of spontaneous X-ray emission and by experiments with cantilever (in the latter case, only for r(C) >= 10(-7) m, where r(C) is one of the two collapse parameters of the CSL model). We show that, contrary to the bounds given by X-ray measurements, non-Markovian effects do not change the bounds, for any reasonable choice of a frequency cutoff in the spectrum of the collapse noise. Therefore the bounds here considered are more robust. We also show that dissipative effects are unimportant for a large spectrum of temperatures of the noise, while for low temperatures the excluded region in the parameter space is the more reduced, the lower the temperature. (C) 2016 Elsevier B.V. All rights reserved.

Bounds on collapse models from cold-atom experiments

BILARDELLO, MARCO MARIA;DONADI, SANDRO;BASSI, ANGELO
2016

Abstract

The spontaneous localization mechanism of collapse models induces a Brownian motion in all physical systems. This effect is very weak, but experimental progress in creating ultracold atomic systems can be used to detect it. In this paper, we considered a recent experiment (Kovachy et al., 2015), where an atomic ensemble was cooled down to picokelvins. Any Brownian motion induces an extra increase of the position variance of the gas. We study this effect by solving the dynamical equations for the Continuous Spontaneous Localizations (CSL) model, as well as for its non-Markovian and dissipative extensions. The resulting bounds, with a 95% of confidence level, are beaten only by measurements of spontaneous X-ray emission and by experiments with cantilever (in the latter case, only for r(C) >= 10(-7) m, where r(C) is one of the two collapse parameters of the CSL model). We show that, contrary to the bounds given by X-ray measurements, non-Markovian effects do not change the bounds, for any reasonable choice of a frequency cutoff in the spectrum of the collapse noise. Therefore the bounds here considered are more robust. We also show that dissipative effects are unimportant for a large spectrum of temperatures of the noise, while for low temperatures the excluded region in the parameter space is the more reduced, the lower the temperature. (C) 2016 Elsevier B.V. All rights reserved.
http://www.sciencedirect.com/science/article/pii/S0378437116304095
File in questo prodotto:
File Dimensione Formato  
Expansion_Gas.pdf

embargo fino al 29/06/2018

Descrizione: Articolo principale
Tipologia: Bozza finale post-referaggio (post-print)
Licenza: Creative commons
Dimensione 603.01 kB
Formato Adobe PDF
603.01 kB Adobe PDF Visualizza/Apri
1-s2.0-S0378437116304095-main.pdf

non disponibili

Tipologia: Documento in Versione Editoriale
Licenza: Digital Rights Management non definito
Dimensione 1.37 MB
Formato Adobe PDF
1.37 MB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/2884103
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 45
  • ???jsp.display-item.citation.isi??? 36
social impact