Enhancement of on-site interactions of tunneling ultracold atoms in optical potentials using radio-frequency dressing

Abstract

We show how it is possible to more than double the on-site interaction energy of neutral atoms in optical potentials by the technique of radio-frequency (rf) dressing, while maintaining interwell dynamics. We calculate Bose-Hubbard parameters for rf dressed optical lattices and arrays of rf dressed dipole traps. We show that decreasing the distance between wells, by the interpolation of wells confining different mF states, increases the interaction energy more than decreasing the height of the classically forbidden region between existing wells. The schemes we propose have negligible Landau-Zener losses caused by atomic motion; this was a dominant effect in the first experimental demonstration of the modification of an optical potential by radio-frequency dressing.PACS numbers: 03.75. Lm, 34.50.Cx, 37.10.Jk, 64.70.Tg, 67.85.Hj The study of complex nonlinear quantum systems is a major area of research in the fields of atomic and condensed matter physics. A subject of current interest is the effect of the nonlinear interaction term on the behaviour of ultracold atoms confined in optical lattices. The dynamics of ultracold bosonic atoms in such a system has been shown to be described by the Bose-Hubbard Hamiltonian [1]where i and j denote lattice sites of a homogeneous lattice. The ground state of the Bose-Hubbard Hamiltonian passes from superfluid to Mott insulator as the parameters controlling U and J are varied; this behaviour has been demonstrated experimentally [2]. The on-site interaction energy, the Hubbard U , is the dominant parameter characterising interactions between ultracold atoms in optical lattices. As such it plays a pivotal role in phase transitions [2] and entanglement [3]. The ability to generate complex entangled states has drawn interest to these systems for the purposes of quantum computing [4] and quantum simulation [5]. Typically, the magnitude of U controls the purity of the resulting many-particle state, or the speed at which this entanglement may be generated [6]. It is likely that there are a significant number of 'impurity' atoms present in the Mott insulator states currently being made [3,7]; for applications such as quantum computing and simulation it is desirable to reduce the number of these impurities as much as possible. Furthermore, by increasing the on-site interaction relative to the tunnelling energy, it may be possible to push optical lattice systems into new regimes, for example where the on-site interaction energy is greater than the band gap [8]. * Electronic address: m.shotter@physics.ox.ac.ukIn this paper we study ways to increase the on-site interaction energy, U , while still maintaining slow interwell dynamics, using the technique of radio-frequency (rf) dressing of optical potentials. We study both optical lattices and arrays of highly focused laser dipole spots, both seen as promising systems for quantum information processing [5,9]. We restrict our study to dressing the optical potential along a single direction of the lattice. The atoms in these potentials wil...

Radio-frequency dressed atoms beyond the linear Zeeman effect

“…The use of radio-frequency (RF) fields for the manipulation of ultra-cold atomic samples [1][2][3][4][5][6] is underpinning important developments in areas such as matter-wave interferometry [4,[7][8][9][10][11] which are beyond the original use of RF fields for evaporative cooling [12]. Nowadays, in combination with atom-chip technology [13] or optical lattices [14,15] RF dressing is a wellestablished technique that allows us routinely to control and engineer atomic quantum states and potential landscapes on micron scales [13,16]. Furthermore, RF dressing plays a central role in several proposals for extending the scope of functions and applications of ultra-cold atomic gases, including reduced dimensionality and connected geometries (ring and toroidal traps) [3,5,[17][18][19][20][21][22], cooling and probing of RF dressed atom traps [6,23,24], sub-wavelength tailoring of potentials [14] and transporting atoms in dressed atom traps [25].…”

Inelastic losses in radio-frequency-dressed traps for ultracold atoms

“…The atoms are trapped using a combination of magnetic and radio frequency (rf) fields, and are confined in an adiabatic potential obtained by diagonalizing a simple Hamiltonian in a basis set of rf-dressed atomic states. Radio frequency dressing has also been used to form new structures in optical lattices [8,9].…”

Observations ofλ/4structure in a low-loss radio-frequency-dressed optical lattice

“…[16] stems from a tripling of the gap Ω * which permits a new regime of dressed lattice structure. One possible route to avoid these losses altogether would be to use the lowest adiabatic potentials [18], and sweep the detuning downward rather than upward in order to distort the lattice; in this case the degree to which the system was adiabatic would be difficult to observe, as the atoms transitioning to the bare lattice would not be lost, but rather occupy the same space while obeying a different band structure. In the limit of strong enough dressing such that the experimenter was sure that losses were minimal this would perhaps be an attractive technique.…”

“…Taking a wholly different approach, other work [16][17][18] introduced a method of altering lattice geometry and topology based on the notion of radiofrequency (rf) dressing of spin-dependent lattice potentials [19]. The theoretical work [17,18] aimed at the exploitation of the resulting adiabatic potentials' faster tunnelling timescales and higher interaction energies, as well as the associated higher temperature scale.…”

“…The theoretical work [17,18] aimed at the exploitation of the resulting adiabatic potentials' faster tunnelling timescales and higher interaction energies, as well as the associated higher temperature scale. The experimental work [16] showed that it was possible to generate 2D dressed lattices that in principle had tailored subwavelength structure, in particular pointing the way to toroidal singlesite wavefunctions [20].…”