16 research outputs found
Reply to a Commentary "Asking photons where they have been without telling them what to say"
Interesting objections to conclusions of our experiment with nested
interferometers raised by Salih in a recent Commentary are analysed and
refuted.Comment: Published version (Frontiers in Physics) to revised version of the
Commentar
Universality of local weak interactions and its application for interferometric alignment
The modification of the effect of interactions of a particle as a function of
its pre- and postselected states is analyzed theoretically and experimentally.
The universality property of this modification in the case of local
interactions of a spatially pre- and postselected particle has been found. It
allowed to define an operational approach for characterization of the presence
of a quantum particle in a particular place: the way it modifies the effect of
local interactions. The experiment demonstrating this universality property
provides an efficient interferometric alignment method, in which the beam on a
single detector throughout one phase scan yields all misalignment parameters.Comment: 12 pages, 7 figure
Optimizing a dynamical decoupling protocol for solid-state electronic spin ensembles in diamond
We demonstrate significant improvements of the spin coherence time of a dense ensemble of nitrogen-vacancy (NV) centers in diamond through optimized dynamical decoupling (DD). Cooling the sample down to 77 K suppresses longitudinal spin relaxation T1 effects and DD microwave pulses are used to increase the transverse coherence time T2 from ∼0.7ms up to ∼30ms. We extend previous work of single-axis (Carr-Purcell-Meiboom-Gill) DD towards the preservation of arbitrary spin states. Following a theoretical and experimental characterization of pulse and detuning errors, we compare the performance of various DD protocols. We identify that the optimal control scheme for preserving an arbitrary spin state is a recursive protocol, the concatenated version of the XY8 pulse sequence. The improved spin coherence might have an immediate impact on improvements of the sensitivities of ac magnetometry. Moreover, the protocol can be used on denser diamond samples to increase coherence times up to NV-NV interaction time scales, a major step towards the creation of quantum collective NV spin states.Physic
Spin ensemble-based AC magnetometry using concatenated dynamical decoupling at low temperatures
Ensembles of nitrogen-vacancy (NV) centers in diamond are widely used as AC
magnetometers. While such measurements are usually performed using standard
(XY) dynamical decoupling (DD) protocols at room temperature, we study the
sensitivities achieved by utilizing various DD protocols, for measuring
magnetic AC fields at frequencies in the 10-250 kHz range, at room temperature
and 77 K. By performing measurements on an isotopically pure C sample,
we find that the Carr-Purcell-Meiboom-Gill (CPMG) protocol, which is not robust
against pulse imperfections, is less efficient for magnetometry than robust
XY-based sequences. The concatenation of a standard XY-based protocol may
enhance the sensitivities only for measuring high-frequency fields, for which
many () DD pulses are necessary and the robustness against pulse
imperfections is critical. Moreover, we show that cooling is effective only for
measuring low-frequency fields (~10 kHz), for which the experiment time
apporaches at a small number of applied DD pulses