QUROPE Quantum Information Processing and Communication in Europe

We report on the state of the art of quantum walk experiments with neutral atoms in state-dependent optical lattices. We demonstrate a novel state-dependent transport technique enabling the control of two spin-selective sublattices in a fully independent fashion. This transport technique allowed us to carry out a test of single-particle quantum interference based on the violation of the Leggett-Garg inequality and, more recently, to probe two-particle quantum interference effects with neutral atoms cooled into the motional ground state.

Z.-Y. Wang, May 2016, Shanghai (China), “Noise-resilient Control of Nuclear Spins in Interacting Clusters for Diamond-based Quantum Computing and Bio-imaging”

Methods for achieving quantum control and detection of individual nuclear spins by single electrons of solid-state defects play a central role for quantum information processing and nano-scale nuclear magnetic resonance (NMR). However, with standard techniques, no more than 8 nuclear spins have been resolved.

Selective control of qubits in a quantum register for the purposes of quantum information processing represents a critical challenge for dense spin ensembles in solid state systems. Here we present a protocol that achieves a complete set of selective single and two-qubit gates on nuclear spins in such an ensemble in diamond facilitated by a nearby NV center.

We propose the use of non-equally-spaced decoupling pulses for high-resolution selective addressing of nuclear spins by a quantum sensor. The analytical model of the basic operating principle is supplemented by detailed numerical studies that demonstrate the high degree of selectivity and the robustness against static and dynamic control-field errors of this scheme.

We propose a method to measure the hyperfine vectors between a nitrogen-vacancy (NV) center and an environment of interacting nuclear spins. Our protocol enables the generation of tunable electron-nuclear coupling Hamiltonians while suppressing unwanted internuclear interactions.

Nitrogen-vacancy (NV) centers in diamond have emerged as valuable tools for sensing and polarizing spins. Motivated by potential applications in chemistry, biology, and medicine, we show that NV-based sensors are capable of detecting single spin targets even if they undergo diffusive motion in an ambient thermal environment.

We introduce a detector that selectively probes the phononic excitations of a cold Bose gas.

Myung-Joong Hwang, 14-15 September 2015, Barcelona, Spain.

Myung-Joong Hwang, 25-29 May, 2015 Cartagena, Spain