215 research outputs found
Control methods for improved Fisher information with quantum sensing
Recently new approaches for sensing the frequency of time dependent
Hamiltonians have been presented, and it was shown that the optimal Fisher
information scales as We present here our interpretation of this new
scaling, where the relative phase is accumulated quadratically with time, and
show that this can be produced by a variety of simple pulse sequences.
Interestingly, this scaling has a limited duration, and we show that certain
pulse sequences prolong the effect. The performance of these schemes is
analyzed and we examine their relevance to state-of-the-art experiments. We
analyze the scaling of the Fisher information which appears when
multiple synchronized measurements are performed, and is the optimal scaling in
the case of a finite coherence time
Protecting a nuclear spin from a noisy electron spin in diamond
Although a nuclear spin is weakly coupled to its environment, due to its
small gyromagnetic ratio, its coherence time is limited by the hyperfine
coupling to a nearby noisy electron. Here, we propose to utilize continuous
dynamical decoupling to refocus the coupling to the electron. If the random
phase accumulated by the nuclear spin through the reduced coupling terms is
sufficient small, we can increase the nuclear coherence time. Initially, we
demonstrate this on a simple case with a two-level electron spin, while taking
all relevant hyperfine coupling terms and noise terms into account. We then
extend the analysis to a nitrogen-vacancy center in diamond having a three
level structure
Revealing the emergence of classicality in nitrogen-vacancy centers
The origin of classical reality in our quantum world is a long-standing
mystery. Here, we examine a nitrogen vacancy center evolving naturally in the
presence of its environment to study quantum Darwinism - the proliferation of
information about preferred quantum states throughout the world via the
environment. This redundantly imprinted information accounts for the perception
of objective reality, as it is independently accessible by many without
perturbing the system of interest. To observe the emergence of redundant
information, we implement a novel dynamical decoupling scheme that enables the
measurement/control of several nuclear spins (the environment E) interacting
with a nitrogen vacancy (the system S). In addition to showing how to create
entangled SE states relevant to quantum metrology, we demonstrate that under
the decoherence of S, redundant information is imprinted onto E, giving rise to
classical objectivity - a consensus of the nuclear spins about the state of S.
This provides the first laboratory verification of the objective classical
world emerging from the underlying quantum substrate.Comment: accepted for publication in Physical Review Letter
Resonance-inclined optical nuclear spin polarization of liquids in diamond structures
Dynamic nuclear polarization (DNP) of molecules in a solution at room
temperature has potential to revolutionize nuclear magnetic resonance
spectroscopy and imaging. The prevalent methods for achieving DNP in solutions
are typically most effective in the regime of small interaction correlation
times between the electron and nuclear spins, limiting the size of accessible
molecules. To solve this limitation, we design a mechanism for DNP in the
liquid phase that is applicable for large interaction correlation times.
Importantly, while this mechanism makes use of a resonance condition similar to
solid-state DNP, the polarization transfer is robust to a relatively large
detuning from the resonance due to molecular motion. We combine this scheme
with optically polarized nitrogen vacancy (NV) center spins in nanodiamonds to
design a setup that employs optical pumping and is therefore not limited by
room temperature electron thermal polarisation. We illustrate numerically the
effectiveness of the model in a flow cell containing nanodiamonds immobilized
in a hydrogel, polarising flowing water molecules 4700-fold above thermal
polarisation in a magnetic field of 0.35 T, in volumes detectable by current
NMR scanners
Towards chemical structure resolution with nanoscale nuclear magnetic resonance spectroscopy
Nuclear magnetic resonance (NMR) spectroscopy has approached the limit of
single molecule sensitivity, however the spectral resolution is currently
insufficient to obtain detailed information on chemical structure and molecular
interactions. Here we demonstrate more than two orders of magnitude improvement
in spectral resolution by performing correlation spectroscopy with shallow
nitrogen-vacancy (NV) magnetic sensors in diamond. In principle, the resolution
is sufficient to observe chemical shifts in 1 T magnetic fields, and is
currently limited by molecular diffusion at the surface. We measure oil
diffusion rates of \,nms within (5 nm)
volumes at the diamond surface
Influence of a static magnetic field on the photoluminescence of an ensemble of Nitrogen-Vacancy color centers in a diamond single-crystal
We investigate the electron spin resonance of an ensemble of Nitrogen-Vacancy
(NV) color centers in a bulk diamond crystal. The four possible orientations of
the NV-center in the lattice lead to different dependences on the magnitude and
the orientation of an external static magnetic field. Experimental results
obtained with a continuous microwave excitation are in good agreement with
simulations. In addition, we observe that the average radiative lifetime of the
NV color center is also modified when the external magnetic field is applied.
This variation is explained by the mixing between mS = 0 and mS = 1 spin
states of the NV-center with different radiative lifetimes, due to magnetic
coupling. These results are of interest for a broad range of applications, such
as spin-resonance-based magnetometry with a high-density ensemble of NV-centersComment: 14 pages, published on Applied Physics Letters journa
Accelerated 2D magnetic resonance spectroscopy of single spins using matrix completion
Two dimensional nuclear magnetic resonance (NMR) spectroscopy is one of the
major tools for analysing the chemical structure of organic molecules and
proteins. Despite its power, this technique requires long measurement times,
which, particularly in the recently emerging diamond based single molecule NMR,
limits its application to stable samples. Here we demonstrate a method which
allows to obtain the spectrum by collecting only a small fraction of the
experimental data. Our method is based on matrix completion which can recover
the full spectral information from randomly sampled data points. We confirm
experimentally the applicability of this technique by performing two
dimensional electron spin echo envelope modulation (ESEEM) experiments on a two
spin system consisting of a single nitrogen vacancy (NV) centre in diamond
coupled to a single 13C nuclear spin. We show that the main peaks in the
spectrum can be obtained with only 10 % of the total number of the data points.
We believe that our results reported here can find an application in all types
of two dimensional spectroscopy, as long as the measured matrices have a low
rank
Camera-limits for wide-field magnetic resonance imaging of a nitrogen-vacancy spin sensor
Sensitive, real-time optical magnetometry with nitrogen-vacancy centers in
diamond relies on accurate imaging of small () fractional
fluorescence changes across the diamond sample. We discuss the limitations on
magnetic-field sensitivity resulting from the limited number of photoelectrons
that a camera can record in a given time. Several types of camera sensors are
analyzed and the smallest measurable magnetic-field change is estimated for
each type. We show that most common sensors are of a limited use in such
applications, while certain highly specific cameras allow to achieve
nanotesla-level sensitivity in ~s of a combined exposure. Finally, we
demonstrate the results obtained with a lock-in camera that pave the way for
real-time, wide-field magnetometry at the nanotesla level and with micrometer
resolution.Comment: 7 pages, 4 figure
Tin-Vacancy Quantum Emitters in Diamond
Tin-vacancy (SnV) color centers were created in diamond by ion implantation
and subsequent high temperature annealing up to 2100 {\deg}C at 7.7 GPa. The
first-principles calculation suggests that the large atom of tin can be
incorporated into the diamond lattice with a split-vacancy configuration, in
which a tin atom sits on an interstitial site with two neighboring vacancies.
The SnV center shows a sharp zero phonon line at 619 nm at room temperature.
This line splits into four peaks at cryogenic temperatures with a larger ground
state splitting of ~850 GHz than those of color centers based on other IV group
elements, silicon-vacancy (SiV) and germanium vacancy (GeV) centers. The
excited state lifetime was estimated to be ~5 ns by Hanbury Brown-Twiss
interferometry measurements on single SnV quantum emitters. The order of the
experimentally obtained optical transition energies comparing with the SiV and
GeV centers is good agreement with the theoretical calculations.Comment: 10 pages, 4 figures and Supplementary 3 pages, 2 figure
Coupling of nitrogen vacancy centers in nanodiamonds by means of phonons
Realising controlled quantum dynamics via the magnetic interactions between
colour centers in diamond remains a challenge despite recent demonstrations for
nanometer separated pairs. Here we propose to use the intrinsic acoustical
phonons in diamond as a data bus for accomplishing this task. We show that for
nanodiamonds the electron-phonon coupling can take significant values that
together with mode frequencies in the THz range, can serve as a resource for
conditional gate operations. Based on these results we analyze how to use this
phonon-induced interaction for constructing quantum gates among the
electron-spin triplet ground states, introducing the phonon dependence via
Raman transitions. Combined with decoupling pulses this offers the possibility
for creating entangled states within nanodiamonds on the scale of several tens
of nanometers, a promising prerequisite for quantum sensing applications.Comment: 28 pages (incl. appendices), 6 figure
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