18 research outputs found
Low Temperature Spectroscopy of Solid State Quantum Systems
Control and coupling of individual quantum systems remains an important research area in experimental quantum information. Single quantum systems in the solid state offer many attractive properties in terms of isolation and control: strong interaction due to close proximity, and scalability using mature fabrication techniques. Similar to atoms, many solid state quantum systems can couple to photons, offering potential for long-range interaction. Two such candidate systems are the nitrogen vacancy center in diamond, and the nanowire semiconductor quantum dot. These systems can act like isolated atoms in a solid state system, and can serve as sources of indistinguishable photons. This report discusses low temperature excitation of these systems, a regime in which the spectral properties are desirable for applications in quantum information, such as long-distance entanglement
Towards Quantum Sensing of Chiral-Induced Spin Selectivity: Probing Donor-Bridge-Acceptor Molecules with NV Centers in Diamond
Photoexcitable donor-bridge-acceptor (D-B-A) molecules that support
intramolecular charge transfer are ideal platforms to probe the influence of
chiral-induced spin selectivity (CISS) in electron transfer and resulting
radical pairs. In particular, the extent to which CISS influences spin
polarization or spin coherence in the initial state of spin-correlated radical
pairs following charge transfer through a chiral bridge remains an open
question. Here, we introduce a quantum sensing scheme to measure directly the
hypothesized spin polarization in radical pairs using shallow nitrogen-vacancy
(NV) centers in diamond at the single- to few-molecule level. Importantly, we
highlight the perturbative nature of the electron spin-spin dipolar coupling
within the radical pair, and demonstrate how Lee-Goldburg decoupling can
preserve spin polarization in D-B-A molecules for enantioselective detection by
a single NV center. The proposed measurements will provide fresh insight into
spin selectivity in electron transfer reactions.Comment: 7 pages and 4 pages appendix including an extensive description of
the initial spin state of photo-generated radical pair
Multicone Diamond Waveguides for Nanoscale Quantum Sensing
The long-lived electronic spin of the nitrogen-vacancy (NV) center in diamond
is a promising quantum sensor for detecting nanoscopic magnetic and electric
fields in a variety of experimental conditions. Nevertheless, an outstanding
challenge in improving measurement sensitivity is the poor signal-to-noise
ratio (SNR) of prevalent optical spin-readout techniques. Here, we address this
limitation by coupling individual NV centers to optimized diamond nanopillar
structures, thereby improving optical collection efficiency of fluorescence.
First, we optimize the structure in simulation, observing an increase in
collection efficiency for tall ( 5 m) pillars with tapered
sidewalls. We subsequently verify these predictions by fabricating and
characterizing a representative set of structures using a reliable and
reproducible nanofabrication process. An optimized device yields increased SNR,
owing to improvements in collimation and directionality of emission.
Promisingly, these devices are compatible with low-numerical-aperture,
long-working-distance collection optics, as well as reduced tip radius,
facilitating improved spatial resolution for scanning applications.Comment: 22 pages, five figure
Single Nitrogen-Vacancy-NMR of Amine-Functionalized Diamond Surfaces
Nuclear magnetic resonance (NMR) imaging with shallow nitrogen-vacancy (NV)
centers in diamond offers an exciting route toward sensitive and localized
chemical characterization at the nanoscale. Remarkable progress has been made
to combat the degradation in coherence time and stability suffered by
near-surface NV centers using suitable chemical surface termination. However,
approaches that also enable robust control over adsorbed molecule density,
orientation, and binding configuration are needed. We demonstrate a diamond
surface preparation for mixed nitrogen- and oxygen-termination that
simultaneously improves NV center coherence times for emitters <10-nm-deep and
enables direct and recyclable chemical functionalization via amine-reactive
crosslinking. Using this approach, we probe single NV centers embedded in
nanopillar waveguides to perform NMR sensing of covalently
bound trifluoromethyl tags in the ca. 50-100 molecule regime. This work
signifies an important step toward nuclear spin localization and structure
interrogation at the single-molecule level.Comment: 21 pages and 16 pages supporting informatio
Diamond surface engineering for molecular sensing with nitrogen-vacancy centers
Quantum sensing using optically addressable atomic-scale defects, such as the
nitrogen--vacancy (NV) center in diamond, provides new opportunities for
sensitive and highly localized characterization of chemical functionality.
Notably, near-surface defects facilitate detection of the minute magnetic
fields generated by nuclear or electron spins outside of the diamond crystal,
such as those in chemisorbed and physisorbed molecules. However, the promise of
NV centers is hindered by a severe degradation of critical sensor properties,
namely charge stability and spin coherence, near surfaces (< ca. 10 nm deep).
Moreover, applications in the chemical sciences require methods for covalent
bonding of target molecules to diamond with robust control over density,
orientation, and binding configuration. This forward-looking Review provides a
survey of the rapidly converging fields of diamond surface science and
NV-center physics, highlighting their combined potential for quantum sensing of
molecules. We outline the diamond surface properties that are advantageous for
NV-sensing applications, and discuss strategies to mitigate deleterious effects
while simultaneously providing avenues for chemical attachment. Finally, we
present an outlook on emerging applications in which the unprecedented
sensitivity and spatial resolution of NV-based sensing could provide unique
insight into chemically functionalized surfaces at the single-molecule level.Comment: Review paper, 36 page
Cavity-Enhanced Photon Emission from a Single Germanium-Vacancy Center in a Diamond Membrane
The nitrogen-vacancy center in diamond has been explored extensively as a
light-matter interface for quantum information applications, however it is
limited by low coherent photon emission and spectral instability. Here, we
present a promising interface based on an alternate defect with superior
optical properties (the germanium-vacancy) coupled to a finesse
fiber cavity, resulting in a -fold increase
in the spectral density of emission. This work sets the stage for cryogenic
experiments, where we predict a measurable increase in the spontaneous emission
rate.Comment: 7 pages, 6 figure