"Doubly-magic" conditions in magic-wavelength trapping of ultracold alkalis

In experiments with trapped atoms, atomic energy levels are shifted by the trapping optical and magnetic fields. Regardless of this strong perturbation, precision spectroscopy may be still carried out using specially crafted, "magic" trapping fields. Finding these conditions for particularly valuable microwave clock transitions in alkalis has so far remained an open challenge. Here I demonstrate that the microwave clock transitions for alkalis may be indeed made impervious to both trapping laser intensity and fluctuations of magnetic fields. I consider driving multiphoton transitions between the clock levels and show that these "doubly-magic" conditions are realized at special values of trapping laser wavelengths and fixed values of relatively weak magnetic fields. This finding has implications for precision measurements and quantum information processing with qubits stored in hyperfine manifolds.Comment: 4 pages, 3 figs, 1 tabl

Magic composite pulses

I describe composite pulses during which the average dipolar interactions within a spin ensemble are controlled while realizing a global rotation. The construction method used is based on the average Hamiltonian theory and rely on the geometrical properties of the spin-spin dipolar interaction only. I present several such composite pulses robust against standard experimental defects in NRM: static or radio-frequency field miscalibration, fields inhomogeneities. Numerical simulations show that the magic sandwich pulse sequence, a pulse sequence that reverse the average dipolar field while applied, is plagued by defects originating from its short initial and final \pi/2 radio-frequency pulses. Using the magic composite pulses instead of \pi/2 pulses improves the magic sandwich effect. A numerical test using a classical description of NMR allows to check the validity of the magic composite pulses and estimate their efficiency.Comment: 22 pages, 6 figure

Theory of "magic" optical traps for Zeeman-insensitive clock transitions in alkalis

Precision measurements and quantum information processing with cold atoms may benefit from trapping atoms with specially engineered, "magic" optical fields. At the magic trapping conditions, the relevant atomic properties remain immune to strong perturbations by the trapping fields. Here we develop a theoretical analysis of a recently observed magic trapping for especially valuable Zeeman-insensitive clock transitions in alkali-metal atoms. The involved mechanism relies on applying "magic" bias B-field along circularly polarized trapping laser field. We map out these B-fields as a function of trapping laser wavelength for all commonly-used alkalis.Comment: 4 pages, 2 fig, 1 table (v3: added discussion of the correct way of computing polarizabilities

Magic conditions for multiple rotational states of bialkali molecules in optical lattices

We investigate magic-wavelength trapping of ultracold bialkali molecules in the vicinity of weak optical transitions from the vibrational ground state of the X 1 Σ + potential to low-lying rovibrational states of the b 3 Π 0 potential, focusing our discussion on the 87 Rb 133 Cs molecule in a magnetic field of B = 181 G. We show that a frequency window exists between two nearest-neighbor vibrational poles in the dynamic polarizability where the trapping potential is “near magic” for multiple rotational states simultaneously. We show that the addition of a modest DC electric field of E = 0.13 kV/cm leads to an exact magic-wavelength trap for the lowest three rotational states at a angular-frequency detuning of Δ v ′ = 0 = 2 π × 218.22 GHz from the X 1 Σ + ( v = 0 , J = 0 ) → b 3 Π 0 ( v ′ = 0 , J = 1 ) transition. We derive a set of analytical criteria that must be fulfilled to ensure the existence of such magic frequency windows and present an analytic expression for the position of the frequency window in terms of a set of experimentally measurable parameters. These results should inform future experiments requiring long coherence times on multiple rotational transitions in ultracold polar molecules

Possibility of "magic" co-trapping of two atomic species in optical lattices

Much effort has been devoted to removing differential Stark shifts for atoms trapped in specially tailored "magic" optical lattices, but thus far work has focused on a single trapped atomic species. In this work, we extend these ideas to include two atomic species sharing the same optical lattice. We show qualitatively that, in particular, scalar J = 0 divalent atoms paired with non-scalar state atoms have the necessary characteristics to achieve such Stark shift cancellation. We then present numerical results on "magic" trapping conditions for 27Al paired with 87Sr, as well as several other divalent atoms.Comment: 5 pages, 2 figures, 1 tabl

Possibility of "magic" trapping of three-level system for Rydberg blockade implementation

The Rydberg blockade mechanism has shown noteworthy promise for scalable quantum computation with neutral atoms. Both qubit states and gate-mediating Rydberg state belong to the same optically-trapped atom. The trapping fields, while being essential, induce detrimental decoherence. Here we theoretically demonstrate that this Stark-induced decoherence may be completely removed using powerful concepts of "magic" optical traps. We analyze "magic" trapping of a prototype three-level system: a Rydberg state along with two qubit states: hyperfine states attached to a J=1/2 ground state. Our numerical results show that, while such a "magic" trap for alkali metals would require prohibitively large magnetic fields, the group IIIB metals such as Al are suitable candidates.Comment: 5 pages, 3 figure