18 research outputs found
Vector DC magnetic-field sensing with reference microwave field using perfectly aligned nitrogen-vacancy centers in diamond
The measurement of vector magnetic fields with high sensitivity and spatial
resolution is important for both fundamental science and engineering
applications. In particular, magnetic-field sensing with nitrogen-vacancy (NV)
centers in diamond is a promising approach that can outperform existing
methods. Recent studies have demonstrated vector DC magnetic-field sensing with
perfectly aligned NV centers, which showed a higher readout contrast than NV
centers having four equally distributed orientations. However, to estimate the
azimuthal angle of the target magnetic field with respect to the NV axis in
these previous approaches, it is necessary to apply a strong reference DC
magnetic field, which can perturb the system to be measured. This is a crucial
problem, especially when attempting to measure vector magnetic fields from
materials that are sensitive to applied DC magnetic fields. Here, we propose a
method to measure vector DC magnetic fields using perfectly aligned NV centers
without reference DC magnetic fields. More specifically, we used the direction
of linearly polarized microwave fields to induce Rabi oscillation as a
reference and estimated the azimuthal angle of the target fields from the Rabi
frequency. We further demonstrate the potential of our method to improve
sensitivity by using entangled states to overcome the standard quantum limit.
Our method of using a reference microwave field is a novel technique for
sensitive vector DC magnetic-field sensing.Comment: 10 pages, 8 figure
Electron-spin double resonance of nitrogen-vacancy centers in diamond under strong driving field
The nitrogen-vacancy (NV) center in diamond has been the focus of research
efforts because of its suitability for use in applications such as quantum
sensing and quantum simulations. Recently, the electron-spin double resonance
(ESDR) of NV centers has been exploited for detecting radio-frequency (RF)
fields with continuous-wave optically detected magnetic resonance. However, the
characteristic phenomenon of ESDR under a strong RF field remains to be fully
elucidated. In this study, we theoretically and experimentally analyzed the
ESDR spectra under strong RF fields by adopting the Floquet theory. Our
analytical and numerical calculations could reproduce the ESDR spectra obtained
by measuring the spin-dependent photoluminescence under the continuous
application of microwaves and an RF field for a DC bias magnetic field
perpendicular to the NV axis. We found that anticrossing structures that appear
under a strong RF field are induced by the generation of RF-dressed states
owing to the two-RF-photon resonances. Moreover, we found that -RF-photon
resonances were allowed by an unintentional DC bias magnetic field parallel to
the NV axis. These results should help in the realization of precise MHz-range
AC magnetometry with a wide dynamic range beyond the rotating wave
approximation regime as well as Floquet engineering in open quantum systems.Comment: 11 pages, 4 figure
Theory of multiwave mixing and decoherence control in qubit array system
We develop a theory to analyze the decoherence effect in a charged qubit
array system with photon echo signals in the multiwave mixing configuration. We
present how the decoherence suppression effect by the {\it bang-bang} control
with the pulses can be demonstrated in laboratory by using a bulk
ensemble of exciton qubits and optical pulses whose pulse area is even smaller
than . Analysis is made on the time-integated multiwave mixing signals
diffracted into certain phase matching directions from a bulk ensemble.
Depending on the pulse interval conditions, the cross over from the decoherence
acceleration regime to the decoherence suppression regime, which is a peculiar
feature of the coherent interaction between a qubit and the reservoir bosons,
may be observed in the time-integated multiwave mixing signals in the realistic
case including inhomogeneous broadening effect. Our analysis will successfully
be applied to precise estimation of the reservoir parameters from experimental
data of the direction resolved signal intensities obtained in the multiwave
mixing technique.Comment: 19 pages, 11 figure
Control of all the transitions between ground state manifolds of nitrogen vacancy centers in diamonds by applying external magnetic driving fields
We demonstrate control of all the three transitions among the ground state sublevels of NV centers by applying magnetic driving fields. To address the states of a specific NV axis among the four axes, we apply a magnetic field orthogonal to the NV axis. We control two transitions by microwave pulses and the remaining transition by radio frequency (RF) pulses. In particular, we investigate the dependence of Rabi oscillations on the frequency and intensity of the RF pulses. In addition, we perform a π pulse by the RF pulses and measured the coherence time between the ground state sublevels. Our results pave the way for control of NV centers for the realization of quantum information processing and quantum sensing
Coalitional Extreme Desirability in Finitely Additive Economies with Asymmetric Information
We prove a coalitional core-Walras equivalence theorem for an asymmetric information exchange economy with a finitely additive measure space of agents, finitely many states of nature, and an infinite dimensional commodity space having the Radon-Nikodym property and whose positive cone has possibly empty interior. The result is based on a new cone condition, firstly developed in Centrone and Martellotti (2015), called coalitional extreme desirability. As a consequence, we also derive a new individualistic core-Walras equivalence result
AC Magnetic Field Sensing Using Continuous-Wave Optically Detected Magnetic Resonance of Nitrogen Vacancy Centers in Diamond
Nitrogen-vacancy (NV) centers in diamond are considered sensors for detecting
magnetic fields. Pulsed optically detected magnetic resonance (ODMR) is
typically used to detect AC magnetic fields; however, this technique can only
be implemented after careful calibration that involves aligning an external
static magnetic field, measuring continuous-wave (CW) ODMR, determining the
Rabi frequency, and setting the microwave phase. In contrast, CW-ODMR can be
simply implemented by continuous application of green CW laser and a microwave
filed. In this letter, we report a method that uses NV centers and CW-ODMR to
detect AC magnetic fields. Unlike conventional methods that use NV centers to
detect AC magnetic fields, the proposed method requires neither a pulse
sequence nor an externally applied DC magnetic field; this greatly simplifies
the procedure and apparatus needed to implement this method. This method
provides a sensitivity of 2.5 {\mu}T/Hz at room temperature. Thus, this
simple alternative to existing AC magnetic field sensors paves the way for a
practical and feasible quantum sensor.Comment: 5 pages, 4 figure