Stuttgart 2012 – scientific programme

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A: Fachverband Atomphysik

A 17: Precision spectroscopy of atoms and ions I

A 17.2: Talk

Tuesday, March 13, 2012, 14:30–14:45, V55.01

A Novel, Robust Quantum Detection Scheme for Ions — •Florian Gebert¹, Boerge Hemmerling², Yong Wan¹, and Piet O. Schmidt¹ — ¹QUEST Inst. for Exp. Quantum Metrology, PTB Braunschweig and Leibniz Univ. of Hannover — ²Department of Physics, Harvard University, Cambridge, MA02138, USA

Protocols used in quantum information and precision spectroscopy rely on efficient detection of the internal quantum state of the system under investigation. The basic principle of state discrimination in ions relies on electron-shelving, where two different energy states (qubit) are distinguished by their state-dependent fluorescence via coupling to a third level. In its simplest form, the number of collected photons during a single detection cycle determines whether the ion is assigned to a so called bright (dark) state depending on this number being higher (lower) than a chosen threshold. Detection fidelities can be further improved if photon arrival times are taken into account. Despite their high fidelities this Bayesian inference or maximum likelihood detection methods are affected by fluctuations of the power of the detection laser. We demonstrate a novel detection technique which combines two detection outcome with an intermediate well-controlled state inversion [1]. Observation of anti-correlated detection events acts as a post-selective statistical filter, which effectively improves the detection fidelity. It is therefore extremely robust against fluctuations of detection parameters and particularly well-suited for systems in which only very few photons are detected and a method for efficient state inversion exists. [1] B. Hemmerling et al., arXiv:1109.4981v2