We study the effect of particle losses on dynamical phase diffusion in a two-mode Bose-Einstein condensate.Starting with an equal-population coherent state, the single-particle coherence is solved analytically by the Monte Carlo wave function method.We show that decoherence slows down the loss of single-particle coherence.Moreover, we find that the bigger phase diffusion is, the more sensitive to the noise it becomes.Finally, we discuss the effect of the losses on the spin squeezing and show that the squeezing angle is robust to the decoherence even though the value of the squeezing is greatly affected.We study the effect of particle losses on dynamical phase diffusion in a two-mode Bose-Einstein condensate.Starting with an equal-population coherent state, the single-particle coherence is solved analytically by the Monte Carlo wave function method.We show that decoherence slows down the loss of single-particle coherence.Moreover, we find that the bigger phase diffusion is, the more sensitive to the noise it becomes.Finally, we discuss the effect of the losses on the spin squeezing and show that the squeezing angle is robust to the decoherence even though the value of the squeezing is greatly affected.

Acta Physica Polonica AOct 1, 20220 citations

Coherence and squeezing in superpositions of spin coherent states

Xiaoguang Wang

arXiv:quant-ph/0109125Optics CommunicationsDec 1, 200124 citations

Relationship between spin squeezing and single-particle coherence in two-component Bose-Einstein condensates with Josephson coupling

Guangri Jin, C. K. Law

We investigate spin squeezing of a two-mode boson system with a Josephson coupling. An exact relation between the squeezing and the single-particle coherence at the maximal-squeezing time is discovered, which provides a more direct way to measure the squeezing by readout of the coherence in atomic interference experiments. We prove explicitly that the strongest squeezing is along the ${J}_{z}$ axis, indicating the appearance of an atom number-squeezed state. Power laws of the strongest squeezing and the optimal coupling with particle number $N$ are obtained based upon a wide range of numerical simulations.We investigate spin squeezing of a two-mode boson system with a Josephson coupling. An exact relation between the squeezing and the single-particle coherence at the maximal-squeezing time is discovered, which provides a more direct way to measure the squeezing by readout of the coherence in atomic interference experiments. We prove explicitly that the strongest squeezing is along the ${J}_{z}$ axis, indicating the appearance of an atom number-squeezed state. Power laws of the strongest squeezing and the optimal coupling with particle number $N$ are obtained based upon a wide range of numerical simulations.

arXiv:0808.1957Physical Review ADec 29, 200837 citations

Ultrasensitive Two-Mode Interferometry with Single-Mode Number Squeezing

Luca Pezzè, Augusto Smerzi

A major challenge of the phase estimation problem is the engineering of high-intensity entangled probe states. The goal is to significantly enhance above the shot-noise limit the sensitivity of two-mode interferometers. Here we show that this can be achieved by squeezing in input, and then measuring in output, the population fluctuations of a single mode. The second input mode can be left as an arbitrary nonvacuum (e.g., a bright coherent) state. This two-mode state belongs to a novel class of particle-entangled states which are not spin squeezed. Already a 2.4 db gain above shot noise can be obtained when just a single-particle Fock state is injected into the empty input port of a classical interferometer configuration. Higher gains, up to the Heisenberg limit, can be reached with squeezed states of a larger number of particles. We finally study the robustness of this protocol with respect to detection noise.A major challenge of the phase estimation problem is the engineering of high-intensity entangled probe states. The goal is to significantly enhance above the shot-noise limit the sensitivity of two-mode interferometers. Here we show that this can be achieved by squeezing in input, and then measuring in output, the population fluctuations of a single mode. The second input mode can be left as an arbitrary nonvacuum (e.g., a bright coherent) state. This two-mode state belongs to a novel class of particle-entangled states which are not spin squeezed. Already a 2.4 db gain above shot noise can be obtained when just a single-particle Fock state is injected into the empty input port of a classical interferometer configuration. Higher gains, up to the Heisenberg limit, can be reached with squeezed states of a larger number of particles. We finally study the robustness of this protocol with respect to detection noise.

Physical Review LettersApr 16, 2013132 citations

{J}_{z}

axis, indicating the appearance of an atom number-squeezed state. Power laws of the strongest squeezing and the optimal coupling with particle number

N

are obtained based upon a wide range of numerical simulations.