arXiv subjects

Chr. Wunderlich

Publications and source records attributed to Chr. Wunderlich.

8 recordsLinked to original sources

arXiv2010

Resonance enhanced isotope-selective photoionization of YbI for ion trap loading

Neutral Ytterbium (YbI) and singly ionized Ytterbium (YbII) is widely used in experiments in quantum optics, metrology and quantum information science. We report on the investigation of isotope selective two-photoionisation of YbI that allows for efficient loading of ion traps with YbII. Results are presented on two-colour (399 nm and 369 nm) and single-colour (399 nm) photoionisation and their efficiency is compared to electron impact ionisation. Nearly deterministic loading of a desired number of YbII ions into a linear Paul trap is demonstrated.

physics.atom-ph↗

arXiv2009

Individual addressing of trapped ions and coupling of motional and spin states using rf radiation

Individual electrodynamically trapped and laser cooled ions are addressed in frequency space using radio-frequency radiation in the presence of a static magnetic field gradient. In addition, an interaction between motional and spin states induced by an rf field is demonstrated employing rf-optical double resonance spectroscopy. These are two essential experimental steps towards realizing a novel concept for implementing quantum simulations and quantum computing with trapped ions.

quant-ph↗

arXiv2006

Error-resistant Single Qubit Gates with Trapped Ions

Coherent operations constitutive for the implementation of single and multi-qubit quantum gates with trapped ions are demonstrated that are robust against variations in experimental parameters and intrinsically indeterministic system parameters. In particular, pulses developed using optimal control theory are demonstrated for the first time with trapped ions. Their performance as a function of error parameters is systematically investigated and compared to composite pulses.

quant-ph↗

arXiv2006

Electrodynamically trapped Yb+ ions for quantum information processing

Highly efficient, nearly deterministic, and isotope selective generation of Yb$^+$ ions by 1- and 2-color photoionization is demonstrated. State preparation and state selective detection of hyperfine states in \ybodd is investigated in order to optimize the purity of the prepared state and to time-optimize the detection process. Linear laser cooled Yb$^+$ ion crystals ions confined in a Paul trap are demonstrated. Advantageous features of different previous ion trap experiments are combined while at the same time the number of possible error sources is reduced by using a comparatively simple experimental apparatus. This opens a new path towards quantum state manipulation of individual trapped ions, and in particular, to scalable quantum computing.

quant-ph↗

arXiv2005

Robust state preparation of a single trapped ion by adiabatic passage

We report adiabatic passage experiments with a single trapped $^{40}$Ca$^+$ ion. By applying a frequency chirped laser pulse with a Gaussian amplitude envelope we reach a transfer efficiency of 0.990(10) on an optical transition from the electronic ground state S$_{1/2}$ to the metastable state D$_{5/2}$. This transfer method is shown to be insensitive to the accurate setting of laser parameters, and therefore is suitable as a robust tool for ion based quantum computing.

quant-ph↗

arXiv2004

A relaxationless demonstration of the Quantum Zeno Paradox on an individual atom

The driven evolution of the spin of an individual atomic ion on the ground-state hyperfine resonance is impeded by the observation of the ion in one of the pertaining eigenstates. Detection of resonantly scattered light identifies the ion in its upper ``bright'' state. The lower ``dark'' ion state is free of relaxation and correlated with the detector by a null signal. Null events represent the straightforward demonstration of the quantum Zeno paradox. Also, high probability of survival was demonstrated when the ion, driven by a fractionated $π$ pulse, was probed {\em and monitored} during the intermissions of the drive, such that the ion's evolution is completely documented.

quant-ph↗

arXiv2001

From Spectral Relaxation to Quantified Decoherence

Quantum information processing (QIP) requires thorough assessment of decoherence. Atoms or ions prepared for QIP often become addressed by radiation within schemes of alternating microwave-optical double resonance. A well-defined amount of decoherence may be applied to the system when spurious resonance light is admitted simultaneously with the driving radiation. This decoherence is quantified in terms of longitudinal and transversal relaxation. It may serve for calibrating observed decoherence as well as for testing error-correcting quantum codes.

quant-ph↗

arXiv2001

Evolution of an Atom Impeded by Measurement: The Quantum Zeno Effect

A quantum system being observed evolves more slowly. This `'quantum Zeno effect'' is reviewed with respect to a previous attempt of demonstration, and to subsequent criticism of the significance of the findings. A recent experiment on an {\it individual} cold trapped ion has been capable of revealing the micro-state of this quantum system, such that the effect of measurement is indeed discriminated from dephasing of the quantum state by either the meter or the environment.

quant-ph↗