Simulazione quantistica ed informazione quantistica con atomi ultra-freddi intrappolati

Responsabili di progetto

Luca Pezze, Nicolae Enaki

Accordo

MOLDOVA - ASM-not in force - Academy of Sciences of Moldova

Bando

CNR/ASM 2015-2016

Dipartimento

Scienze fisiche e tecnologie della materia

Area tematica

Scienze fisiche e tecnologie della materia

Stato del progetto

Nuovo

Proposta di ricerca

The collective processes in condense matter have many analogous properties with cooperative radiation effects in quantum optics. Following this concept, the authors of Refs.[1-3] describe the analogies between the cooperative effects in optics and theory of superconductivity. Using the possibilities offered by cooperation in quantum optics phenomena to form distinctive states in atomic emission-exchange pairs of quanta, we can make a transfer of optical quantic cooperative phenomenon such that superconducting couple pairs are formed by sharing two phonons [4]. Thus the appearance of Bose-Einstein condensation can become multi-quantum nonlinear in the sense of cooperation between particles.

In this project we intend to study the Bose-Einstein condensation taking into account the non-linear interaction of the atoms with local vibrational modes and laser modes of the optical lattices. The progress in manipulating and controlling trapped neutral in optical lattices by quantum optical means [5] opens novel applications of atomic collective phenomena and Bose Einstein condensation in quantum information processing [6], atom interferometry [7], and atomic and molecular physics [8]. The control by quantum optical techniques over the structure and the parameters of atomic interaction allows realizing and deploying a number of lattice Hamiltonian models [8] which are frequently used in strongly correlated condensed matter systems. Optical lattices formed by microscopic potentials induced by the AC Stark effect of interfering laser beams can be used to confine cold atoms. The quantized motion of such atoms is described by the vibrational motion within an individual well and the tunneling between neighboring wells, leading to a spectrum describable as a band structure [8]. Higher filling factors will require lower temperatures, and hence will also require minimization of the optical dissipation. This can be achieved in a far-detuned optical lattice (especially with blue detuning), where photon scattering times of many minutes have been demonstrated [9-11]. Thus the lattice then behaves as a conservative potential, which could be loaded with a Bose condensed atomic vapor [12]. This corresponds to tens of atoms per lattice site.
Similar to the above discussed quantum system, the cooperative superfluorescent system of radiators like Dicke systems also exhibits a phase transition from the phase where the radiators emit haotically (non-correlated) to the phase where the cooperative processes between the radiators is established in such a way that the intensity of emission becomes proportional to the square number of radiators, named as super-radiance. At the last time a peculiar interest presents the study of the phenomena which appear in physical systems when the electronic or atomic subsystems are in non-linear interaction with the thermostat (large subsystem): for example, the nonlinear mechanism of superconductivity [1,2] ferro-magnetism, two-photon super-radiance, and others. Recently, by authors were found some interesting results for the feature of phase transition for superconductivity in the case when the non-linear exchange interaction of electronic system with the phonon system exists. it was obtained the non critical temperature becomes possible in comparison with the usual BCS model [1,2]. So we concluded that the existence of dependence of two-phonon exchange integral of temperature by means of the average number of phonons change essentially the feature of phase transition and consequently the value of the critical temperature with possibility to enhance this [4].

Refereces:

[1] 1. N.A.Enaki, V.Eremeev "Specificity of Phase Transition of Quasi-Spin System in Two-Quantum Exchange with Thermostat" Phys. Lett. A 357, p.104-107. (2006).
[2] Enaki, N.A. Cooperative Two-Quanta Phase Transitions in Quantum Optics and Superconductivity. Journal of Low Temperature Physics. 2010, Vol. 160(5), 157-179.
[3] DiRienzo, D.Rogovin and M. Scully, in Coherence in Spectroscopy and Modern Physics, (New York: Plenum, 231, 1978).
[4] N. A. Enaki and V. V. Eremeev, Cooperative two-photon phenomena in superconductivity, New Journal of Physics 4, 80.1(2002).
[5] M. Greiner, O. Mandel, T. Esslinger, T.W. Haensch, I. Bloch, Nature 415, 39 (2002).
[6] G.K. Brennen, C.M. Caves, P.S. Jessen, and I.H. Deutsch, Phys. Rev. Lett. 82, 1060 (1999); G.K. Brennen, I.H. Deutsch, and P.S. Jessen, Phys. Rev. A 61, 062309 (2000), W. Hofstetter, J.I. Cirac, P. Zoller, E. Demler, and M. Lukin, Phys. Rev. Lett. 89, 220407 (2002).
[7] U. Dorner, P. Fedichev, D. Jaksch, M. Lewenstein, and P. Zoller, quant-ph/0212039
[8] D. Jaksch, V. Venturi, J.I. Cirac, C.J. Williams, and P. Zoller, Phys. Rev. Lett. 89, 040402 (2002).
[9] K. Molmer, Phys. Rev. Lett. 90, 110403 (2003).
[10] M Raizen, C. Salomon, and Q. Niu, Physics Today 50, 30 (1997).
[11] S. Friebel et al. Phys. Rev. A 57, R20 (1998).
[12] D.M. Stamper-Kurn et al. Phys. Rev. Lett. 80, 2027(1998); S. Inouye et al., Nature 392, 151 (1998)

Obiettivi della ricerca

This project will bring together two groups from Italy and Moldova in order to achieve a common research program concerning the application of second order coherence and entanglement in Quantum Information and Holography. In this project we intend to describe a new nonlinear collective phenomena like entangled and disentangled effects between large atomic systems, which appear in the muti-quantum processes of interaction of ultra-cold atoms with cavity electromagnetic field for further applications in quantum processing of information. Two mechanisms of non-linear cooperative interaction between the ultra-cold atoms through the electromagnetic and vibration states of thermostat will be examined. The first of them corresponds to the cooperative interaction between the ultra-cold atoms through the non-linear lattice vibration in exchange processes between them and the second takes into consideration the non-linear cooperative optical process. According to these models the ultra-cold Bose-Einstein condensation is created in the processes of the two- and single-photon simultaneous exchanges between radiators.
Objectives:
1. To propose a new non-linear phase transition, in which correlation function between the cold atoms anomalous increases after which decreases with increasing of temperature.
2. Examination of the coherence properties of emitted pairs of entangled photons in such Bose-Einstein condensate and their application in quantum communication an processing systems.

Ultimo aggiornamento: 30/04/2025