May 13 2019
I will highlight recent progress in the application and optimization of ensemble NV-diamond magnetic sensing and imaging. Promising applications include NMR spectroscopy at the scale of individual biological cells, magnetic imaging of electrically active cells such as neurons, mapping magnetic signatures in ancient meteorites and rocks, and improved biomedical diagnostics. Challenges include simultaneously increasing the NV- density, ODMR contrast, and T2, T2*; minimizing diamond heterogeneity and its effects; and interfacing with target samples and their operational constraints.
Ensemble NV-Diamond Magnetometry
A broad effort is underway to improve the sensitivity of nuclear magnetic resonance through the use of dynamic nuclear polarization (DNP). Nitrogen-vacancy (NV) centers in diamond offer an appealing platform because these paramagnetic defects show efficient optical pumping at room temperature. This presentation focuses on the spin dynamics of NVs coupled to substitutional nitrogen (the so called P1 center) as a platform for DNP, with emphasis on recent schemes designed for powder geometries. I will also discuss new phenomenology at ~51 mT suggesting nuclear spins strongly coupled to paramagnetic impurities can efficiently transfer polarization to bulk nuclei. Finally, I will lay out theoretical work on the interplay between NV–P1 cross relaxation and mechanical degrees of freedom, to show how optical spin pumping should convert into rigid rotation of the crystal as a whole.
Carlos A. Meriles-
Spin dynamics of coupled NV–P1 pairs under optical excitation in its multiple facets: Dynamic nuclear polarization, spin diffusion, and conversion into crystal rotation
I will show that ab initio theory can determine coupling parameters between nuclear and electron spins, strain and electron spin as well as electric fields and zero-phonon-line transition. The results with combining with corresponding effective Hamiltonians can be used to identify features in the PL spectrum at constant magnetic fields at ground state level anticrossing regime in realistic NV diamond samples, fine tuning of hyperpolarization of nuclear spins in silicon carbide, prediction of efficient strain sensors and stable quantum emitters from diamond and silicon carbide defect quantum bits.
Ab initio study of defect qubits for hyperpolarization, quantum sensing and communication
Microfludic channels are now a well established platform for many purposes, including bio-medical research
and Lab on a Chip applications. Yet, the nature of flow within these channels is still uncertain. There have been
prior evidence that the mean drift velocity in these channels deviates from the regular Navier-Stokes soluion
with ‘no slip’ boundary conditions. On top of the fundamental fluid mechanics interest, understanding these
effects, is also of practical importance for the future development of microfluidic and nanofludic infrastructure.
In this talk I will introduce a theoretical proposal which is based on a nano-NMR setup for measuring the mean drift velocity near the surface of a microfludic channel in a non intrusive fashion. I will discuss different possible protocols, and provide a detailed analysis of the measurement’s sensitivity in each case. This scheme out-preforms current fluorescence based techniques.
Nano-NMR based flow meter
The explosion of interest in exploiting fundamental quantum mechanical principles for new technologies is driving a significant worldwide effort to address problems difficult or impossible to solve with classical technologies. We aim to investigate the foundations of large scale integration of single photon sources, passive optical circuits (waveguides, splitters, cavities, resonators) and single photon detectors all on a monolithic single crystal diamond substrate. Such devices will be essential building blocks for scalable quantum information processing and communication.
Diamond is well known to host over 500 optical centres, many of which display highly desirable quantum properties and indeed many essential foundations have already been developed independently with single photon sources and passive optical components already integrated into diamond photonic chips. But the translation to practical devices has been slow, and this is partly because for a practical, scalable platform for a monolithic quantum optics chip requires integration of three essential components. These are: (i) single photon sources, (ii) photonic routing (ie waveguides, cavities, splitters and (iii) single photon detectors.
In previous work, our group has demonstrated the fabrication, characterization and optimization of many single photon emitters in diamond. In the present work, we first report on a scalable method for the production of thin free standing, strain free, ultrapure and ultrahigh quality single crystal diamond membranes of thickness of less than 50nm. These membranes are fully compatible with the fabrication of multiple, complex, optical structures on the same single crystal membrane. We report on the fabrication methods, processing, (including nanopillars to collect and channel NV emission), surface functionalization and the range of potential applications of these membranes. We discuss evidence for primal sp2 defects at the diamond surface which may contribute to electron trapping and be the source of electronic noise which may be particularly important in the optimization of properties of the membranes which display two free surfaces.
Finally, we also report on progress towards the fabrication of integrated single photon detectors on diamond based on Boron doped superconducting nanowire detectors. By growing the nanowires epitaxially on the single crystal substrates, the detectors are expected to display superior properties in terms of increased bandwidth, higher quantum efficiency, and higher sensitivity to IR photons (1550nm in particular). When integrated with waveguides on the membranes, the prospects for a fully integrated platform for quantum optics appears to be most promising.
 For samples, please contact Alastair Stacey,
 See A. Stacey et al, Adv. Mater. Interfaces 2019, 6, 1801449.
Critical Components for Integrated Diamond Quantum Photonic Devices
In this talk I will discuss two recent results from my group. In the first experiment, we developed a new type of electron-nuclear quantum gate that enabled us to realize control over up to 10 qubits with a single NV center . This result opens the door towards advanced error correction codes and quantum algorithms based on solid-state spins. In the second experiment, we developed the atomic-scale imaging of complex nuclear-spin structures based on multi-dimensional spectroscopy with a single NV center, and applied it to retrieve the structure of a model system of 27 coupled nuclear spins in a diamond. Combined with progress with near-surface NVs, this result provides a path to imaging molecules and other complex spin structures with atomic resolution.
 Bradley et al., arXiv:1905.02094
 Abobeih et al., arXiv:1905.02095
Tim Hugo Taminiau-
Atomic-scale imaging and multi-qubit quantum registers with the NV center
May 14 2019
an overview of the recent activities of our group and collaborators [1,2] on magnetic sensing, including near-zero-field magnetometry with ensembles and single NV centers, microwave-free scalar and vector magnetometry, infrared-absorption based magnetometry, eddy-current imaging, and wide-field imaging of vortices in high-temperature superconductors.
Some recent results on sensing with color centers in diamond
I will discuss a set of recent experiments aimed at mapping individual 13C nuclei within diamond with sub-angstrom spatial resolution [1-3].
 J. Zopes, K. Herb et al., Physical Review Letters 121, 170801 (2018).
 J. Zopes et al., Nature Communications 9, 4678 (2018).
 K. S. Cujia et al., arXiv:1806.08243 (2018)
Christian Degen -
3D mapping of nuclear spins by NV-NMR
Quantum technologies is attracting significant investment due to the range of potential applications, yet behind any new technology are enabling materials. Diamond is one such material, which has been used in demonstrations ranging from magnetic sensing to quantum computing. In order for these diamond quantum technologies to move from laboratory-based demonstrations to commercial products requires material with repeatable properties that can be produced with scale.
This paper will focus on two diamond materials developed for magnetic sensing and quantum information processing. Specifically we will show the characterisation of high NV materials demonstrating repeatable properties such as T2* and intrinsic strain. Secondly, we will discuss the synthesis of uniform boron doped diamond for charge stabilisation of SiV0 qubits.
Matthew Markham -
Optimising Diamond for Quantum Technologies
Based on the previous work [1,2] we present our results on coherent single NV detection and discuss optimal conditions of NV qubit operation. Specifically, we examine the rate for the charge transfer from NV- to NV0 and its influence on the NV spin contrast limit at RT. We provide detail modeling of the optical rates including defects in the diamond gap, in particular substitutional nitrogen (P1) and an another arbitrary impurity level. Finally we discuss progress on the search of novel defect centers as SnV.
 Bourgeois, et al. Nat. Comm. 6, 8577 (2015)
 Siyushev, Nesladek et al. Science 363, 728 (2019
Coherent Photoelectric Readout of Single NV Spins: Update and Considerations
May 15 2019
The magnetic fields generated by spins and currents provide a unique window into the physics
of correlated-electron materials and devices. Proposed only a decade ago, magnetometry
based on the electron spin of nitrogen-vacancy (NV) defects in diamond is emerging as a
platform that is exceptionally suited for probing condensed matter systems: it can be operated
from cryogenic temperatures to above room temperature, has a dynamic range spanning from
DC to GHz, and allows sensor-sample distances as small as a few nanometers. As such, NV
magnetometry provides access to static and dynamic magnetic and electronic phenomena with
nanoscale spatial resolution. While pioneering work focused on proof-of-principle
demonstrations of its nanoscale imaging resolution and magnetic field sensitivity, now
experiments are starting to probe the correlated-electron physics of magnets and
superconductors and to explore the current distributions in low-dimensional materials. In this
talk, I will review some of our recent work which uses NV center magnetometry to explore magnon dispersion, dynamic properties of superconductors and hydrodynamic electron flow in graphene.
Probing condensed matter physics with magnetometry based on nitrogen-vacancy centers in diamond
The Nitrogen Vacancy center in diamond has emerged as a promising candidate for the nanoscale sensing of temperature, strain, electric and magnetic fields. The integration of NV-based sensing into diamond anvil cells (DAC), a workhorse of high pressure science, offers a means not only for making spatially resolved measurements of relevant sample properties but also for monitoring the stress distribution in the diamond anvil itself. Compared to conventional high pressure probes, key advantages of NV sensing include spatial resolution and versatility, thus enabling explorations of novel phases of matter and the transitions between them, with pressure as a tuning parameter. Additionally, imaging the stress distribution inside DACs can provide insight into the mechanical failure of anvils and inform improvements in anvil design. In this talk, I will describe two results that make use of a shallow layer of NVs near the tip of the diamond anvil: 1) DC magnetometry and T1 relaxometry to study pressure-driven magnetic phase transitions and 2) stress tensor mapping within the DAC itself.
Magnetometry and Stress Tomography in Diamond Anvil Cells using Nitrogen Vacancy Centers
A question fundamental in quantum physics and useful in quantum technology is: Can the interaction between a quantum bath and a central spin can be fully simulated by the effects of classical noises, with certain given correlations regardless of the control applied to the central spin? A recent study finds that the answer is yes if the classical noises can be complex numbers . Thus, if the correlations of quantum fluctuations can be determined, the protection and control of the central spin dynamics can be optimized by designing the control. The correlations are also key information to understanding many-body physics, especially in mesoscopic systems (such as cold atom systems and nanoscale spin systems). However, there has been no systematic method to extract the bath correlations to arbitrary order. Based on the weak measurement , we propose a scheme that can systematically measure the correlations in a quantum bath of a central spin to arbitrary orders, including both the classical and the quantum components . The possibility to obtain the high-order correlations in a quantum bath provides new opportunities in quantum sensing (such as for the detection of correlated nuclear spin clusters or nuclear spins in a molecule) and in quantum many-body physics (such as for the demonstration of Leggett-Garg inequality.
References:  G. Gasbarri and L. Ferialdi, Phys. Rev. A 98, 042111 (2018).  M. Pfender, P. Wang, H. Sumiya, S. Onoda, W. Yang, D. B. Rao Dasari, P. Neumann, X.-Y. Pan, J. Isoya, R.-B. Liu, and J. Wrachtrup, Nature Communications 10, 594 (2019).  P. Wang, C. Chen, X. Peng, J. Wrachtrup, and R.-B. Liu, arXiv:1902.03606 (2019).
Extracting correlations in a quantum bath of a central spin by weak measurement
an overview on Boschs activity in the field of quantum technologies. Within this activity, Boschs focus lies on quantum sensors and especially on the magnetometry with Nitrogen vacancy centers in diamond. It has been shown that NV magnetometers could allow for sensitivities below 1 pT/ÖHz and measurement ranges from pT to T under ambient conditions. The talk will cover the basic science as well as possible future applications. A special focus will be laid on the current progress in the development of miniaturized diamond magnetometers, especially on the engineering of the photonic excitation and readout path.
Diamond Magnetometers – From Concepts to Products
Spin waves are the elementary spin excitations of magnetic materials. They provide fundamental insight into magnetic order and may play a key role in future information processing. I will present the use of nitrogen-vacancy sensor spins in diamond to explore spin-wave physics in ferromagnets. I will describe the characterization of spin-wave resonances, thermally excited spin waves, and spin-wave chemical potentials. These techniques open up new possibilities for nanoscale imaging and control of spin transport in mesoscopic spin systems.
Toeno van der Sar-
Probing spin waves using NV magnetometry
May 16 2019
Following the rise in big-data availability, computational power, and algorithmic know-how, artificial neural networks have re-emerged as a leading machine-learning tool. More recently ANNs have also found several applications within physics. In this talk, I'll provide a high-level introduction to ANNs and their computational abilities.
I'll then turn to a specific application of ANNs in the growing field of nano-NMR. Strong indications would be presented, that deep learning algorithms based on ANNs can efficiently mitigate the adversarial effects of noise inherent to nano-NMR settings. Over a wide range of scenarios, we find that the deep learning approach outperforms Bayesian methods even when the latter have full pre-knowledge of the noise model and the former has none. Our approach is also more efficient in terms of computational resources and run times.
Applications of machine-learning in NV center based nano-NMR
Here we report the fabrication of up to 30 % 13C enriched nanodiamonds via HPHT growth, which in contrast to the milling methods leads to less damaged surface and lower strain in the diamond. The NVs electron spin coherence and relaxation times of T2 ≈ 2 µs and T1 ≈ 1 ms make these novel NDs good candidates for the implementation of NV based DNP methods. Investigation of the substitutional nitrogen (electron spin S = 1/2, P1 centres) shows similar T2 values, suggesting that P1 concentration is limiting factor for the NV’s coherence time. The main decoherence mechanism is found to be instantaneous diffusion. Nuclear Magnetic Resonance (NMR) measurements reveal 13C T1 times up to a minute, probably also limited by the P1 concentration. The results presented here are important steps towards the implementation of NDs as high sensitive MRI markers, where the sensitivity can be enhanced by DNP.