### Rev. Mod. Phys.:Protecting quantum information against environmental noise

**Colloquium: Protecting quantum information against environmental noise**

Dieter Suter and Gonzalo A. Álvarez

Rev. Mod. Phys. 88, 041001 (2016)

Published 10 October 2016

Quantum-mechanical systems retain their properties so long as the phase of quantum superpositions evolve stably over time. Contact with an environment can disrupt this phase evolution. But for environments that do not exchange energy with the quantum system, strategies exist where the controlled driving of the system can recover or maintain the quantum phase. This Colloquium surveys the host of techniques that are available to “refocus” the phase when disturbed by various forms of classical or quantum environment. While the first such techniques were developed long ago, ideas from quantum information theory have introduced new strategies for accomplishing this goal.

### Phys. Rev. Applied: Maximizing Information on the Environment by Dynamically Controlled Qubit Probes

Maximizing Information on the Environment by Dynamically Controlled Qubit Probes

Analia Zwick, Gonzalo A. Álvarez, and Gershon Kurizki

Phys. Rev. Applied 5, 014007 (2016)

Published 25 January 2016

From computers to medicine, miniaturization approaches the atomic scale, where device operation can be dominated by quantum effects that are strongly coupled to the local environment. These influences may be seen not as a nuisance, but rather a nearly untapped source of information about physical or biochemical processes playing out nearby. How can one extract maximum information from such fluctuations with an atomic probe, under typical experimental constraints? The authors use quantum estimation theory to outline a general strategy for dynamical measurement of a broad class of environmental processes.

Source: Physical Review Applied – Volume 5 Issue 1

### Nat. Commun.: Local and bulk 13C hyperpolarization in nitrogen-vacancy-centred diamonds at variable fields and orientations

Gonzalo A. Álvarez, Christian O. Bretschneider, Ran Fischer, Paz London, Hisao Kanda, Shinobu Onoda, Junichi Isoya, David Gershoni & Lucio Frydman

Nature Communications **6**, 8456 (2015). doi:10.1038/ncomms9456

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 centres could alleviate this need; however, 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 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 nitrogen-vacancy centres in nuclear magnetic resonance, and in quantum information processing.

### Quanten-Computer löst Quanten-Problem :: pro-physik.de

**Quanten-Computer löst Quanten-Problem**

Einfluss von Störungen auf das Ausbreiten eines Quantensystems untersucht.

Source: :: Quanten-Computer löst Quanten-Problem :: pro-physik.de

### Physiker lösen Problem mit Hilfe von Quanten-Computer der TU Dortmund

See the article about our work “Localization-delocalization transition in the dynamics of dipolar-coupled nuclear spins” in the idw – Informationsdienst Wissenschaft online magazine: Physiker lösen Problem mit Hilfe von Quanten-Computer der TU Dortmund

### Physiker lösen Problem mit Hilfe von Quanten-Computer der TU Dortmund

See the article about our work “Localization-delocalization transition in the dynamics of dipolar-coupled nuclear spins” in the Innovation Report magazine: Physiker lösen Problem mit Hilfe von Quanten-Computer der TU Dortmund

### Science: Localization-delocalization transition in the dynamics of dipolar-coupled nuclear spins

**Nonequilibrium dynamics of many-body systems are important in many scientific fields. Here, we report the experimental observation of a phase transition of the quantum coherent dynamics of a three-dimensional many-spin system with dipolar interactions. Using nuclear magnetic resonance (NMR) on a solid-state system of spins at room-temperature, we quench the interaction Hamiltonian to drive the evolution of the system. Depending on the quench strength, we then observe either localized or extended dynamics of the system coherence. We extract the critical exponents for the localized cluster size of correlated spins and diffusion coefficient around the phase transition separating the localized from the delocalized dynamical regime. These results show that NMR techniques are well suited to studying the nonequilibrium dynamics of complex many-body systems.**

Gonzalo A. Álvarez (1), Dieter Suter (2), Robin Kaiser (3)

(1) Department of Chemical Physics, Weizmann Institute of Science, 76100, Rehovot, Israel.

(2) Fakultät Physik, Technische Universität Dortmund, D-44221, Dortmund, Germany.

(3) Institut Non-Linéaire de Nice, CNRS, Université de Nice Sophia Antipolis, 06560, Valbonne, France.

via Localization-delocalization transition in the dynamics of dipolar-coupled nuclear spins.