Mesoscopic quantum switching of a Bose-Einstein condensate in an optical lattice governed by the parity of the number of atoms

TL;DR

This paper demonstrates that the parity of the number of atoms in a Bose-Einstein condensate causes a qualitative difference in quantum switching behavior within an optical lattice, observable on a mesoscopic scale.

Contribution

It introduces a parity-dependent quantum switching mechanism in a boson model for BECs in optical lattices, revealing novel quantum effects related to atom number parity.

Findings

Parity determines the system's response to parameter variation.

Even and odd atom numbers lead to different switching behaviors.

Proposed experimental scheme for observing the parity effect.

Abstract

It is shown that for a $N$-boson system the parity of $N$ can be responsible for a qualitative difference in the system response to variation of a parameter. The nonlinear boson model is considered, which describes tunneling of boson pairs between two distinct modes $X_{1,2}$ of the same energy and applies to a Bose-Einstein condensate in an optical lattice. By varying the lattice depth one induces the parity-dependent quantum switching, i.e. $X_1\to X_2$ for even $N$ and $X_1\to X_1$ for odd $N$, for arbitrarily large $N$. A simple scheme is proposed for observation of the parity effect on the \textit{mesoscopic scale} by using the bounce switching regime, which is insensitive to the initial state preparation (as long as only one of the two $X_l$ modes is significantly populated), stable under small perturbations and requires an experimentally accessible coherence time.