Coherent Transfer between Low-Angular-Momentum and Circular Rydberg States

Abstract

We realize a coherent transfer between a laser-accessible low-angular-momentum Rydberg state and the circular Rydberg level with maximal angular momentum. This transfer is induced by a radiofrequency field with a high-purity σ + polarization tuned at resonance on Stark transitions inside the hydrogenic Rydberg manifold. We observe over a few microseconds more than twenty coherent Rabi oscillations between the initial Rydberg state and the circular Rydberg level. We characterize in details these complex oscillations involving many Rydberg levels and find them to be in perfect agreement with a simple theoretical model. This coherent transfer procedure opens the way to hybrid quantum gates bridging the gap between optical communication and quantum information manipulations based on microwave Cavity and Circuit Quantum Electrodynamics.The long-lived Circular Rydberg Levels (CRLs) are ideal tools for quantum manipulation of microwave (mw) fields stored in ultra-high-Q 3D superconducting resonators. They led to early demonstrations of basic quantum information processing operations [1] and to the generation of non-classical field state superpositions [2]. More recently, they have been instrumental in the exploration of fundamental Cavity Quantum Electrodynamics (Cavity-QED) effects, such as QND measurements of the photon number [3] and quantum feedback [4]. Recent advances on the manipulation of Rydberg atoms near atom chips [5] indicate that they could also be interfaced with the resonant structures used in the flourishing field of Circuit-QED [6,7].However, the photons used in mw Cavity-and Circuit-QED are unable to propagate over long-range transmission lines [8]. Optical to mw interfaces are thus the focus of an intense activity [9,10]. A new realm for mw quantum information manipulation would open if the CRLs could be coherently interfaced with optical photons, which are ideal quantum information carriers over fiber and free-space communication networks [11]. Unfortunately, the CRLs, with their large orbital quantum number = n − 1 (n is the principal quantum number), do not couple directly to optical photons.In contrast, low-angular momentum Rydberg states are accessible from the ground state by coherent laser excitation [12][13][14]. They were recently used for optical quantum information processing operations such as photon-photon gates relying on single-photon optical non-linearities induced by the dipole blockade mechanism [15][16][17][18]. They could also lead to quantum gates entangling a mw photon with a collective hyperfine excitation in a ground state atomic ensemble [19] and hence, through the DLCZ protocol [20], to gates entangling optical and mw photons. However, the short lifetime of these levels, of the order of 100 µs, sets limits on the quantum transfer fidelity and on their use in CQED experiments.The missing link between mw and optical photons is a fast coherent transfer from a laser-accessible low-state to the CRLs. The most efficient CRL preparation technique so far involves a series of radiof...

State-selective electric-field ionization of Rydberg positronium

“…Thus, Ps circular states will have to be generated using the microwave transfer method; SFI will be invaluable in optimizing this process [41], which will likely have to be further developed (see, e.g., Refs. [45,46]) to work within the parameters of a Ps experiment. Circular states of Ps have the advantage that, in contrast to hydrogen, they do not possess a large magnetic moment, owing to the equal and opposite orbital magnetic moments of the electron and positron.…”

Controlling the Scattering Length of Ultracold Dipolar Molecules

“…The microwave energies available are in the range [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] which correspond exactly to the energies needed (twice the rotational constant of the alkali molecules). Finally, better control over circular polarization fields becomes nowadays possible [57]. Therefore, with the current improvement of the microwave technologies, the control of the scattering length of dipolar molecules seems experimentally realistic, and will certainly open a new regime of strongly interacting and correlated physics with ultracold dipolar molecules.…”

Towards quantum simulations with circular Rydberg atoms

“…Laser trapping allows us to straightforwardly remove these bottlenecks. One can even envision hybrid cavity QED experiments combining superconducting circuits and laser-trapped Rydberg atoms, which can be used to create a coherent interface between microwave and optical photons [163].…”