• Publications
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Violation of local uncertainty relations as a signature of entanglement
Entangled states represent correlations between two separate systems that are too precise to be represented by products of local quantum states. We show that this limit of precision for the localExpand
Directional control of light by a nano-optical Yagi–Uda antenna
A Yagi–Uda directional antenna — the work horse of radiofrequency communications for more than 60 years — has now been demonstrated at visible wavelengths. An array of appropriately tunedExpand
High-photon-number path entanglement in the interference of spontaneously down-converted photon pairs with coherent laser light
We show that the quantum interference between down-converted photon pairs and photons from coherent laser light can produce a maximally path entangled N-photon output component with a fidelityExpand
All path-symmetric pure states achieve their maximal phase sensitivity in conventional two-path interferometry
It is shown that the condition for achieving the quantum Cramer-Rao bound of phase estimation in conventional two-path interferometers is that the state is symmetric with regard to an (unphysical)Expand
Design parameters for a nano-optical Yagi–Uda antenna
We investigate the possibility of directing optical emissions using a Yagi–Uda antenna composed of a finite linear array of nanoparticles. The relevant parameters characterizing the plasma resonancesExpand
Complementary classical fidelities as an efficient criterion for the evaluation of experimentally realized quantum operations.
  • H. Hofmann
  • Computer Science, Medicine
  • Physical review letters
  • 15 September 2004
It is shown that a good estimate of the fidelity of an experimentally realized quantum process can be obtained by measuring the outputs for only two complementary sets of input states. The number ofExpand
Violation of Leggett–Garg inequalities in quantum measurements with variable resolution and back-action
Quantum mechanics violates Leggett–Garg inequalities because the operator formalism predicts correlations between different spin components that would correspond to negative joint probabilities forExpand
How weak values emerge in joint measurements on cloned quantum systems.
  • H. Hofmann
  • Physics, Medicine
  • Physical review letters
  • 25 November 2011
A statistical analysis of optimal universal cloning shows that it is possible to identify an ideal (but nonpositive) copying process that faithfully maps all properties of the original Hilbert spaceExpand
Demonstration of an optical quantum controlled-NOT gate without path interference.
We report the first experimental demonstration of an optical quantum controlled-NOT gate without any path interference, where the two interacting path interferometers of the original proposals haveExpand
Quantum phase gate for photonic qubits using only beam splitters and postselection
We show that a beam splitter of reflectivity one-third can be used to realize a quantum phase gate operation if only the outputs conserving the number of photons on each side are postselected.