Engineering topics

Smerzi, Augusto

Publications and source records attributed to Smerzi, Augusto.

4 records

DOE OSTI2016

On the dispute between Boltzmann and Gibbs entropy

The validity of the concept of negative temperature has been recently challenged by arguing that the Boltzmann entropy (that allows negative temperatures) is inconsistent from a mathematical and statistical point of view, whereas the Gibbs entropy (that does not admit negative temperatures) provides the correct definition for the microcanonical entropy. Here we prove that the Boltzmann entropy is thermodynamically and mathematically consistent. Analytical results on two systems supporting negative temperatures illustrate the scenario we propose. In addition we numerically study a lattice system to show that negative temperature equilibrium states are accessible and obey standard statistical mechanics prediction.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2011

Mach-Zehnder interferometry with interacting trapped Bose-Einstein condensates

We theoretically analyze a Mach-Zehnder interferometer with trapped condensates and find that it is surprisingly stable against the nonlinearity induced by interparticle interactions. The phase sensitivity, which we study for number-squeezed input states, can overcome the shot noise limit and be increased up to the Heisenberg limit provided that a Bayesian or maximum-likelihood phase estimation strategy is used. We finally demonstrate the robustness of the Mach-Zehnder interferometer in the presence of interactions against condensate oscillations and a realistic atom-counting error.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2010

Phase estimation with interfering Bose-Einstein-condensed atomic clouds

We investigate how to estimate from atom-position measurements the relative phase of two Bose-Einstein condensates released from a double-well potential. We demonstrate that the phase-estimation sensitivity via the fit of the average density to the interference pattern is fundamentally bounded by shot noise. The shot noise can be overcome by estimating the phase from the measurement of order {radical}(N) (or higher) correlation functions. The optimal estimation strategy, saturating the quantum Fisher information, requires the measurement of the Nth-order correlation function. We demonstrate that a different estimation method--based on the detection of the center of mass of the interference pattern--also provides sub-shot-noise sensitivity. The implementation of both protocols, however, might be experimentally challenging.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2010

Rabi interferometry and sensitive measurement of the Casimir-Polder force with ultracold gases

We show that Rabi oscillations of a degenerate fermionic or bosonic gas trapped in a double-well potential can be exploited for the interferometric measurement of external forces at micrometer length scales. The Rabi interferometer is less sensitive but easier to implement than the Mach-Zehnder, since it does not require dynamical beam-splitting or recombination processes. As an application we propose a measurement of the Casimir-Polder force acting between the atoms and a dielectric surface. We find that even if the interferometer is fed with a coherent state of relatively small number of atoms, and in the presence of realistic experimental noise, the force might be measured with a sensitivity sufficient to discriminate between thermal and zero-temperature regimes of the Casimir-Polder potential. Higher sensitivities can be reached with bosonic spin squeezed states.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗