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Biomedical subjects

A Buchleitner

Publications and source records attributed to A Buchleitner.

14 recordsLinked to original sources
PubMed2006

Quantum accelerator modes from the Farey tree.

We show that mode locking finds a purely quantum nondissipative counterpart in atom-optical quantum accelerator modes. These modes are formed by exposing cold atoms to periodic kicks in the direction of the gravitational field. They are anchored to generalized Arnol'd tongues, parameter regions where driven nonlinear classical systems exhibit mode locking. A hierarchy for the rational numbers known as the Farey tree provides an ordering of the Arnol'd tongues and hence of experimentally observed accelerator modes.

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PubMed2006

Experimental determination of entanglement with a single measurement.

Nearly all protocols requiring shared quantum information--such as quantum teleportation or key distribution--rely on entanglement between distant parties. However, entanglement is difficult to characterize experimentally. All existing techniques for doing so, including entanglement witnesses or Bell inequalities, disclose the entanglement of some quantum states but fail for other states; therefore, they cannot provide satisfactory results in general. Such methods are fundamentally different from entanglement measures that, by definition, quantify the amount of entanglement in any state. However, these measures suffer from the severe disadvantage that they typically are not directly accessible in laboratory experiments. Here we report a linear optics experiment in which we directly observe a pure-state entanglement measure, namely concurrence. Our measurement set-up includes two copies of a quantum state: these 'twin' states are prepared in the polarization and momentum degrees of freedom of two photons, and concurrence is measured with a single, local measurement on just one of the photons.

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PubMed2001

Chaotic ionization of nonhydrogenic alkali Rydberg states.

We report the first ab initio quantum treatment of microwave driven alkali Rydberg states. We find that nonhydrogenic atomic initial states exhibit fingerprints of classically chaotic excitation, and identify the cause of their experimentally observed enhanced ionization, as compared to Rydberg states of atomic hydrogen.

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PubMed2000

Quantum state preparation via asymptotic completeness

We demonstrate that any quantum state |chi> of a single mode radiation field can be prepared with arbitrarily high fidelity by interaction with a sequence of two-level atoms, prepared in a suitable initial state. No final state measurement of the atoms is needed.

Journal Article↗
PubMed2000

Stochastic resonance in the coherence of a quantum system

We demonstrate the noise-induced amplification of a weak periodic signal inscribed in the coherence of a two-level atom, interacting with a single mode of the quantized radiation field coupled to a dissipative environment.

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