Quantum properties of a binary bosonic mixture in a double well

Author: Pere Mujal



Two condensates of identical bosons trapped in a double well, called a Bosonic Josephson Junction, present interesting quantum phenomena like Josephson oscillations and self-trapping [1] that have been observed experimentally [2]. The ground state of the system depends on atom-atom interactions and on the height of the barrier  between the two sites of the double well and can host relevant quantum spatial correlations [3]. What would happen if we had two bosonic species instead of one?
The physics of a binary mixture of Bose-Einstein condensates trapped in a double-well potential is captured by a two-component two-site Bose-Hubbard model [4]. A crucial aspect of this system is that it can host relevant  entangled many-body states, e.g., Schrödinger catlike states. The richness of the binary-mixture in a double-well is the possibility of having not only spatial entanglement but also quantum correlations between the two species. Taking the atom-atom interactions within each species and among the two species as variable parameters, the many-body properties of the ground state are fully characterized by means of quantum information tools, such as the Schmidt gap or the von Neumann entropy complemented by usual many-body techniques like the computation of the condensed fractions.

[1] A. Smerzi, S. Fantoni, S. Giovanazzi, and S. R. Shenoy, Phys. Rev. Lett. 79, 4950 (1997).
[2] M. Albiez, R. Gati, J. Fölling, S. Hunsmann, M. Cristiani, and M. K. Oberthaler, Phys. Rev. Lett. 95, 010402 (2005).
[3] B. Juliá-Díaz, D. Dagnino, M. Lewenstein, J. Martorell, and A. Polls, Phys. Rev. A 81, 023615 (2010).
[4] P. Mujal, B. Juliá-Díaz, and A. Polls, Phys. Rev. A 93, 043619 (2016).