Large ion Coulomb crystals: A near-ideal medium for coupling optical cavity modes to matter

Abstract

We present an investigation of the coherent coupling of various transverse field modes of an optical cavity to ion Coulomb crystals. The obtained experimental results, which include the demonstration of identical collective coupling rates for different transverse modes of a cavity field to ions in the same large Coulomb crystal, are in excellent agreement with theoretical predictions. The results furthermore suggest that Coulomb crystals in the future may serve as near-ideal media for highfidelity multi-mode quantum information processing and communication purposes, including the generation and storage of single photon qubits encoded in different transverse modes.PACS numbers: 42.50. Pq,37.30.+i,42.50.Ct For the field of quantum information to mature to a practical stage, where complex computational tasks [1] and quantum information networks [2] can be realized, careful attention has to be paid to the actual quality of the physical systems involved. While the ideal system for carrying out serious quantum computational tasks has yet to be singled out, photons remain uncontested in their position as the ideal carriers of quantum information over large distances. Consequently, there is a clear need for identifying high quality physical media suitable for e.g. single photon generation and storage as well as for the realization of quantum repeaters.Among the systems under consideration (e.g systems discussed in Ref. [2,3]), a single ion in an optical cavity appears to be an excellent candidate for such realizations [4,5,6,7]. In addition, larger ensembles of cold trapped ions in the form of so-called Coulomb crystals [8,9,10] in cavities may afford new opportunities for not only single-, but also multi-mode quantum information purposes, due to the combination of their solid state properties, including long term stability and uniform ion density throughout the crystal, and their single isolated particle features, i.e. no significant internal state perturbations due to interactions between the individual ions [11]. These features are relevant for e.g. encoding quantum information in orthogonal transverse spatial modes in contrast to the usual application of frequency and polarization degrees of freedom [12,13]. In addition, coupling to multiple modes may have applications even outside of the context of quantum information, for e.g. quantum imaging [14,15] and cavity mediated cooling [16,17,18].Important steps towards the realization of high quality single-mode quantum devices based on an ion Coulomb crystal in a cavity were very recently taken, by demonstrating that the collective strong coupling regime of Cavity Quantum ElectroDynamics [19] can be reached with large ion Coulomb crystals interacting with a cavity field at the single photon level in the fundamental TEM 00 mode of an optical cavity [11].In this paper, the potential of ion Coulomb crystals as a media for multi-mode quantum interfaces is explored by a thorough experimental investigation characterizing the coupling of the TEM 00 and TEM 10,01 transverse ...

Finite-temperature crossover from a crystalline to a cluster phase for a confined finite chain of ions

“…For cold atomic ions, the formation of quasi-1D crystals with L ≈ 1 mm [39], N ≈ 100 ions, and, e.g., Z = 1 leads to a critical temperature T SI c ≈ 1.7 × 10 −1 K, which is easily accessible experimentally. Therefore, by tuning the values of L and N it is possible to study this crystalline-clustering crossover in laboratory experiments with cold ions assuming a 1D trapping geometry.…”

Cryogenic linear Paul trap for cold highly charged ion experiments

“…HCIs are also sensitive probes of quantum electrodynamics (QED) [31][32][33][34] and parity violating effects, [35][36][37] and could also serve as optical frequency standards. 38 Other applications of Paul traps include the investigation of cavity QED [39][40][41][42][43][44][45] and cold molecular ions. 18-20, 46, 47 Some of the open challenges in the field of ion trapping are the cooling of HCIs to temperatures necessary to a) Electronic mail: m.schwarz@mpi-hd.mpg.de.…”

Structural phase transitions and topological defects in ion Coulomb crystals

“…Such defects have been proposed for storage of quantum information, and for studies of the nonlinear physics of solitons and phase transitions [15,17,27,28,29].…”