arXiv subjects

Christian O. Bretschneider

Publications and source records attributed to Christian O. Bretschneider.

3 recordsLinked to original sources

arXiv2014

Local and bulk 13C hyperpolarization in NV-centered diamonds at variable fields and orientations

Polarizing nuclear spins is of fundamental importance in biology, chemistry and physics. Methods for hyperpolarizing 13C nuclei from free electrons in bulk, usually demand operation at cryogenic temperatures. Room-temperature approaches targeting diamonds with nitrogen-vacancy (NV) centers could alleviate this need, but hitherto proposed strategies lack generality as they demand stringent conditions on the strength and/or alignment of the magnetic field. We report here an approach for achieving efficient electron->13C spin alignment transfers, compatible with a broad range of magnetic field strengths and field orientations with respect to the diamond crystal. This versatility results from combining coherent microwave- and incoherent laser-induced transitions between selected energy states of the coupled electron-nuclear spin manifold. 13C-detected Nuclear Magnetic Resonance (NMR) experiments demonstrate that this hyperpolarization can be transferred via first-shell or via distant 13Cs, throughout the nuclear bulk ensemble. This method opens new perspectives for applications of diamond NV centers in NMR, and in quantum information processing.

quant-ph↗

arXiv2013

Bulk Nuclear Polarization Enhanced at Room-Temperature by Optical Pumping

Bulk 13C polarization can be strongly enhanced in diamond at room-temperature based on the optical pumping of nitrogen-vacancy color centers. This effect was confirmed by irradiating suitably aligned single-crystals at a ~50 mT field promoting anti-crossings between electronic excited-state levels, followed by shuttling of the sample into a custom-built NMR setup and by subsequent 13C detection. A nuclear polarization of ~0.5% - equivalent to the 13C polarization achievable by thermal polarization at room temperature at fields of ~2000 T - was measured, and its bulk nature determined based on line shape and relaxation measurements. Positive and negative enhanced polarizations were obtained, with a generally complex but predictable dependence on the magnetic field during optical pumping. Owing to its simplicity, this 13C room-temperature polarizing strategy provides a promising new addition to existing nuclear hyperpolarization techniques.

quant-ph↗

arXiv2011

Establishing spin-network topologies by repeated projective measurements

It has been recently shown that in quantum systems, the complex time evolution typical of many-bodied coupled networks can be transformed into a simple, relaxation-like dynamics, by relying on periodic dephasings of the off-diagonal density matrix elements. This represents a case of "quantum Zeno effects", where unitary evolutions are inhibited by projective measurements. We present here a novel exploitation of these effects, by showing that a relaxation-like behaviour is endowed to the polarization transfers occurring within a N-spin coupled network. Experimental implementations and coupling constant determinations for complex spin-coupling topologies, are thus demonstrated within the field of liquid-state nuclear magnetic resonance (NMR).

quant-ph↗