Ion Trap Experiments Research Articles

Shelving and probe efficiency in trapped ion experiments

A generalized probe sequence typical of trapped ion experiments using shelving is studied. Detection efficiency is analyzed for finite shelved state lifetimes and using multi-modal count distributions. Multi-modal distributions are more appropriate for measurements that use a small number of ions than the simple Poisson counting statistics usually considered and have a larger variance that may be significant in determining uncertainties and in making weighted fits. Optimal probe times and the resulting state detection efficiency and sensitivity are determined for arbitrary cooling rates, initial states, and shelved state lifetimes in terms of a probe coherence time τp. A universal optimal probe time of is shown to give close to the optimal probe sensitivity for most systems.

Modified Orbital Atomic Study of Dominant Rydberg Series in the Photoionization Spectra of Halogen-like Kr^+ and Xe^+ Ions

We report in this paper the energy positions of the 4s^24p^4 (^1D2)nd and 4s^24p^4 (^1S_0) nd dominant Rydberg states originating from the ns^2np^5 ^2P^◦_3/2 ground-state and the ns^2np^5 ^2P^◦_1/2 metastable state of Kr^+ and Xe^+ ions. Calculations are performed using the modified orbital atomic theory (MAOT). Analysis of the present data is done using the standard quantum defect expansion formula. The results obtained agree very well with recent combined merged-beam set up and ion trap experiments [Bizau et al., J. Phys. B: At. Mol. Phys. 44, 055205 (2011)] and theoretical multi-channel R-matrix eigenphase derivative (QB) calculations [McLaughlin and Ballance, J. Phys. B: At. Mol. Phys. 45, 085701 (2012)].

Damage-free single-mode transmission of deep-UV light in hollow-core PCF.

Transmission of UV light with high beam quality and pointing stability is desirable for many experiments in atomic, molecular and optical physics. In particular, laser cooling and coherent manipulation of trapped ions with transitions in the UV require stable, single-mode light delivery. Transmitting even ~2 mW CW light at 280 nm through silica solid-core fibers has previously been found to cause transmission degradation after just a few hours due to optical damage. We show that photonic crystal fiber of the kagomé type can be used for effectively single-mode transmission with acceptable loss and bending sensitivity. No transmission degradation was observed even after >100 hours of operation with 15 mW CW input power. In addition it is shown that implementation of the fiber in a trapped ion experiment increases the coherence time of the internal state transfer due to an increase in beam pointing stability.

Size-dependent self-limiting oxidation of free palladium clusters.

Temperature-dependent gas phase ion trap experiments performed under multicollision conditions reveal a strongly size-dependent reactivity of Pd(x)(+) (x = 2-7) in the reaction with molecular oxygen. Yet, a particular stability and resistance to further oxidation is generally observed for reaction products with two oxygen molecules, Pd(x)O4(+). Complementary first-principles density functional theory simulations elucidate the details of the size-dependent bonding of oxygen to the small palladium clusters and are able to assign the pronounced occurrence of Pd(x)O4(+) complexes to a dissociatively chemisorbed bridging oxygen atomic structure which impedes the chemisorption of further oxygen molecules. The molecular physisorption of additional O2 is only observed at cryogenic temperatures. Additional experiments and simulations employing preoxidized clusters Pd(x)O(+) (x = 2-8) and Pd(x)O2(+) (x = 4-7) confirm the formation of the two different oxygen species.

Laser induced rovibrational cooling of the linear polyatomic ion C2H2(+).

The laser-induced blackbody-assisted rotational cooling of a linear polyatomic ion, C2H2(+), in its (2)Π ground electronic state in the presence of the blackbody radiation field at 300 K and 77 K is investigated theoretically using a rate-equations model. Although pure rotational transitions are forbidden in this non-polar species, the ν5 cis-bending mode is infrared active and the (1-0) band of this mode strongly overlaps the 300 K blackbody spectrum. Hence the lifetimes of state-selected rotational levels are found to be short compared to the typical timescale of ion trapping experiments. The ν5 (1-0) transition is split by the Renner-Teller coupling of vibrational and electronic angular momentum, and by the spin-orbit coupling, into six principal components and these effects are included in the calculations. In this paper, a rotational-cooling scheme is proposed that involves simultaneous pumping of a set of closely spaced Q-branch transitions on the (2)Δ5/2 - (2)Π3/2 band together with two Q-branch lines in the (2)Σ(+) - (2)Π1/2 band. It is shown that this should lead to >70% of total population in the lowest rotational level at 300 K and over 99% at 77 K. In principle, the multiple Q-branch lines could be pumped with just two broad-band (∼Δν = 0.4-3 cm(-1)) infrared lasers.

Controlling photons in a box and exploring the quantum to classical boundary

Microwave photons trapped in a superconducting cavity constitute an ideal system to realize some of the thought experiments imagined by the founding fathers of quantum physics. The interaction of these trapped photons with Rydberg atoms crossing the cavity illustrates fundamental aspects of measurement theory. The experiments performed with this "photon box" at the Ecole Normale Supérieure (ENS) belong to the domain of quantum optics called "Cavity Quantum Electrodynamics." We have realized the non-destructive counting of photons, the recording of field quantum jumps, the preparation and reconstruction of "Schrödinger cat" states of radiation and the study of their decoherence, which provides a striking illustration of the transition from the quantum to the classical world. These experiments have also led to the demonstration of basic steps in quantum information processing, including the deterministic entanglement of atoms and the realization of quantum gates using atoms and photons as quantum bits. This lecture starts with an introduction stressing the connection between the ENS photon box and the ion trap experiments of David Wineland, whose accompanying lecture recalls his own contribution to the field of single particle control. I give then a personal account of the early days of Cavity Quantum Electrodynamics before describing the main experiments performed at ENS during the last twenty years and concluding with a discussion comparing our work to other research dealing with the control of single quantum particles.

Frequency stabilization of a 369 nm diode laser by nonlinear spectroscopy of Ytterbium ions in a discharge

We demonstrate stabilization of an ultraviolet diode laser via Doppler-free spectroscopy of Ytterbium ions in a discharge. Our technique employs polarization spectroscopy, which produces a natural dispersive lineshape whose zero-crossing is largely immune to environmental drifts, making this signal an ideal absolute frequency reference for Yb+ ion trapping experiments. We stabilize an external-cavity diode laser near 369 nm for cooling Yb+ ions, using amplitude modulated polarization spectroscopy and a commercial PID feedback system. We achieve stable, low-drift locking with a standard deviation of measured laser frequency ∼ 400 kHz over 10 minutes, limited by the instantaneous linewidth of the diode laser. These results and the simplicity of our optical setup makes our approach attractive for stabilization of laser sources in atomic physics applications.

Probabilistic simulation of mesoscopic “Schrödinger cat” states

We carry out probabilistic phase-space sampling of mesoscopic Schr\"odinger cat quantum states, demonstrating multipartite Bell violations for up to 60 qubits. We use states similar to those generated in photonic and ion-trap experiments. These results show that mesoscopic quantum superpositions are directly accessible to probabilistic sampling, and we analyze the properties of sampling errors. We also demonstrate dynamical simulation of super-decoherence in ion traps. Our computer simulations can be either exponentially faster or slower than experiment, depending on the correlations measured.

Управление фотонами в ящике и изучение границы между квантовым и классическим

Microwave photons trapped in a superconducting cavity constitute an ideal system to realize some of the thought experiments imagined by the founding fathers of quantum physics. The interaction of these trapped photons with Rydberg atoms crossing the cavity illustrates fundamental aspects of measurement theory. The experiments performed with this at the Ecole Normale Superieure (ENS) belong to the domain of quantum optics called Quantum Electrodynamics. We have realized the non-destructive counting of photons, the recording of field quantum jumps, the preparation and reconstruction of Schrodinger cat states of radiation and the study of their decoherence, which provides a striking illustration of the transition from the quantum to the classical world. These experiments have also led to the demonstration of basic steps in quantum information processing, including the deterministic entanglement of atoms and the realization of quantum gates using atoms and photons as quantum bits. This lecture starts with an introduction stressing the connection between the ENS photon box and the ion trap experiments of David Wineland, whose accompanying lecture recalls his own contribution to the field of single particle control. I give then a personal account of the early days of Cavity Quantum Electrodynamics before describing the main experiments performed at ENS during the last twenty years and concluding with a discussion comparing our work to other research dealing with the control of single quantum particles.

Quantum Synchronization of Quantum van der Pol Oscillators with Trapped Ions

The van der Pol oscillator is the prototypical self-sustained oscillator and has been used to model nonlinear behavior in biological and other classical processes. We investigate how quantum fluctuations affect phase locking of one or many van der Pol oscillators. We find that phase locking is much more robust in the quantum model than in the equivalent classical model. Trapped-ion experiments are ideally suited to simulate van der Pol oscillators in the quantum regime via sideband heating and cooling of motional modes. We provide realistic experimental parameters for 171Yb+ achievable with current technology.

Quantum Simulation of a Lattice Schwinger Model in a Chain of Trapped Ions

We discuss how a lattice Schwinger model can be realized in a linear ion trap, allowing a detailed study of the physics of Abelian lattice gauge theories related to one-dimensional quantum electrodynamics. Relying on the rich quantum-simulation toolbox available in state-of-the-art trapped-ion experiments, we show how one can engineer an effectively gauge-invariant dynamics by imposing energetic constraints, provided by strong Ising-like interactions. Applying exact diagonalization to ground-state and time-dependent properties, we study the underlying microscopic model, and discuss undesired interaction terms and other imperfections. As our analysis shows, the proposed scheme allows for the observation in realistic setups of spontaneous parity- and charge-symmetry breaking, as well as false-vacuum decay. Besides an implementation aimed at larger ion chains, we also discuss a minimal setting, consisting of only four ions in a simpler experimental setup, which enables to probe basic physical phenomena related to the full many-body problem. The proposal opens a new route for analog quantum simulation of high-energy and condensed-matter models where gauge symmetries play a prominent role.

ChemInform Abstract: Controlling Photons in a Box and Exploring the Quantum to Classical Boundary (Nobel Lecture)

AbstractReview: 118 refs.

Spread of Correlations in Long-Range Interacting Quantum Systems

The nonequilibrium response of a quantum many-body system defines its fundamental transport properties and how initially localized quantum information spreads. However, for long-range-interacting quantum systems little is known. We address this issue by analyzing a local quantum quench in the long-range Ising model in a transverse field, where interactions decay as a variable power law with distance ∝r(-α), α>0. Using complementary numerical and analytical techniques, we identify three dynamical regimes: short-range-like with an emerging light cone for α>2, weakly long range for 1<α<2 without a clear light cone but with a finite propagation speed of almost all excitations, and fully nonlocal for α<1 with instantaneous transmission of correlations. This last regime breaks generalized Lieb-Robinson bounds and thus locality. Numerical calculation of the entanglement spectrum demonstrates that the usual picture of propagating quasiparticles remains valid, allowing an intuitive interpretation of our findings via divergences of quasiparticle velocities. Our results may be tested in state-of-the-art trapped-ion experiments.

Structure, dynamics and bifurcations of discrete solitons in trapped ion crystals

We study discrete solitons (kinks) accessible in the state-of-the-art trapped ion experiments, considering zigzag crystals and quasi-three-dimensional configurations, both theoretically and experimentally. We first extend the theoretical understanding of different phenomena predicted and recently experimentally observed in the structure and dynamics of these topological excitations. Employing tools from topological degree theory, we analyze bifurcations of crystal configurations in dependence on the trapping parameters, and investigate the formation of kink configurations and the transformations of kinks between different structures. This allows us to accurately define and calculate the effective potential experienced by solitons within the Wigner crystal, and study how this (so-called Peierls–Nabarro) potential gets modified to a non-periodic globally trapping potential in certain parameter regimes. The kinks' rest mass (energy) and spectrum of modes are computed and the dynamics of linear and nonlinear kink oscillations are analyzed. We also present novel, experimentally observed, configurations of kinks incorporating a large-mass defect realized by an embedded molecular ion, and of pairs of interacting kinks stable for long times, offering the perspective for exploring and exploiting complex collective nonlinear excitations, controllable on the quantum level.

Controlling Photons in a Box and Exploring the Quantum to Classical Boundary (Nobel Lecture)

Microwave photons trapped in a superconducting cavity constitute an ideal system to realize some of the thought experiments imagined by the founding fathers of quantum physics. The interaction of these trapped photons with Rydberg atoms crossing the cavity illustrates fundamental aspects of measurement theory. The experiments performed with this "photon box" at Ecole Normale Supérieure (ENS) belong to the domain of quantum optics called "Cavity Quantum Electrodynamics". We have realized the non-destructive counting of photons, the recording of field quantum jumps, the preparation and reconstruction of "Schrödinger cat" states of radiation and the study of their decoherence, which provides a striking illustration of the transition from the quantum to the classical world. These experiments have also led to the demonstration of basic steps in quantum information processing, including the deterministic entanglement of atoms and the realization of quantum gates using atoms and photons as quantum bits. This lecture starts by an introduction stressing the connection between the ENS photon box and the ion trap experiments of David Wineland, whose accompanying lecture recalls his own contribution to the field of single particle control. I give then a personal account of the early days of Cavity Quantum Electrodynamics before describing the main experiments performed at ENS during the last twenty years and concluding by a discussion comparing our work to other researches dealing with the control of single quantum particles.

Composition and size dependent methane dehydrogenation on binary gold–palladium clusters

Methane adsorption and possible dehydrogenation mediated by the free gold–palladium clusters Au2Pd+, AuPd2+, and Au2Pd2+ have been investigated in an ion trap experiment under multi-collision conditions. Temperature dependent kinetic measurements identify the palladium-rich AuPd2+ as the only one among these clusters which is able to dehydrogenate methane. The comparison with previously measured reactions of the bare gold Aun+ (n=2–4) as well as the bare palladium Pdm+ (m=2–4) clusters allows to obtain insights into cluster size and composition dependent reaction mechanisms, kinetics, and methane binding energies.

Nobel Lecture: Controlling photons in a box and exploring the quantum to classical boundary

Microwave photons trapped in a superconducting cavity constitute an ideal system to realize some of the thought experiments imagined by the founding fathers of quantum physics. The interaction of these trapped photons with Rydberg atoms crossing the cavity illustrates fundamental aspects of measurement theory. The experiments performed with this ``photon box'' at Ecole Normale Sup\'erieure (ENS) belong to the domain of quantum optics called ``cavity quantum electrodynamics.'' We have realized the nondestructive counting of photons, the recording of field quantum jumps, the preparation and reconstruction of ``Schr\"odinger cat'' states of radiation and the study of their decoherence, which provides a striking illustration of the transition from the quantum to the classical world. These experiments have also led to the demonstration of basic steps in quantum information processing, including the deterministic entanglement of atoms and the realization of quantum gates using atoms and photons as quantum bits. This lecture starts by an introduction stressing the connection between the ENS photon box and the ion-trap experiments of David Wineland, whose accompanying lecture recalls his own contribution to the field of single particle control. I give then a personal account of the early days of cavity quantum electrodynamics before describing the main experiments performed at ENS during the last 20 years and concluding by a discussion comparing our work to other researches dealing with the control of single quantum particles.

Scalable Reconstruction of Density Matrices

Recent contributions in the field of quantum state tomography have shown that, despite the exponential growth of Hilbert space with the number of subsystems, tomography of one-dimensional quantum systems may still be performed efficiently by tailored reconstruction schemes. Here, we discuss a scalable method to reconstruct mixed states that are well approximated by matrix product operators. The reconstruction scheme only requires local information about the state, giving rise to a reconstruction technique that is scalable in the system size. It is based on a constructive proof that generic matrix product operators are fully determined by their local reductions. We discuss applications of this scheme for simulated data and experimental data obtained in an ion trap experiment.

A high-power 626 nm diode laser system for Beryllium ion trapping

We describe a high-power, frequency-tunable, external cavity diode laser system near 626 nm useful for laser cooling of trapped (9)Be(+) ions. A commercial single-mode laser diode with rated power output of 170 mW at 635 nm is cooled to ≈-31°C, and a single longitudinal mode is selected via the Littrow configuration. In our setup, involving two stages of thermoelectric cooling, we are able to obtain ≈130 mW near 626 nm, sufficient for efficient frequency doubling to the required Doppler cooling wavelengths near 313 nm in ionized Beryllium. In order to improve nonlinear frequency conversion efficiency, we achieve larger useful power via injection locking of a slave laser. In this way the entirety of the slave output power is available for frequency doubling, while analysis may be performed on the master output. We believe that this simple laser system addresses a key need in the ion trapping community and dramatically reduces the cost and complexity associated with Beryllium ion trapping experiments.

Activation and Catalytic Dehydrogenation of Methane on Small Pdx+ and PdxO+ Clusters

The temperature-dependent adsorption as well as the possible activation and dehydrogenation of methane mediated by small free palladium Pdx+ (x = 2–4) and palladium mono-oxide PdxO+ (x = 2–4) clusters have been studied in an ion trap experiment under multicollision conditions. The smallest clusters Pd2+ and Pd3+ are found to readily dehydrogenate methane, while Pd4+ is completely nonreactive within the whole investigated temperature range between 220 and 300 K. In the case of the oxides PdxO+, a critical number of at least three coadsorbed CD4 is required before methane dehydrogenation can be observed. Temperature-dependent kinetic studies of the reaction of Pd2+ and Pd2O+ with methane allow for the determination of catalytic reaction mechanisms that involve C–D bond cleavage and C–C bond formation processes. The catalytic activity of these two clusters is compared in terms of active species, cooperative effects, and activation barriers. Finally, the possible methane oxidation on PdxO+ is discussed.