Search results for "Coherence time"
showing 10 items of 16 documents
Optical d-level frequency-time-based cluster states
2019
Cluster states, a specific class of multi-partite entangled states, are of particular importance for quantum science, as such systems are equivalent to the realization of one-way (or measurement-based) quantum computers [1]. In this scheme, algorithms are implemented through high-fidelity measurements on the parties of the state [2]. While two-level (i.e. qubit) cluster states have been realized so far, increasing the number of particles to boost the computational resource comes at the price of significantly reduced coherence time and detection rates, as well as increased sensitivity to noise, restricting the realization of discrete cluster states to a record of eight qubits. In contrast, t…
Magnetometry with Nitrogen-Vacancy Centers in Diamond
2016
This chapter covers magnetic sensing with nitrogen-vacancy (NV) defect centers in diamond. The NV center fundamentals are introduced and NV optically detected magnetic resonance techniques for dc and ac magnetic sensing are summarized. After reviewing some successful sensing applications, the advantages for using NV magnetometry, as well as some ongoing challenges, are enumerated.
Spatial information transmission using orthogonal mutual coherence coding.
2005
We use the coherence of a light beam to encode spatial information. We apply this principle to obtain spatial superresolution in a limited aperture system. The method is based on shaping the mutual intensity function of the illumination beam in a set of orthogonal distributions, each one carrying the information for a different frequency bandpass or spatial region of the input object. The coherence coding is analogous to time multiplexing but with multiplexing time slots that are given by the coherence time of the illumination beam. Most images are static during times much longer than this coherence time, and thus the increase of resolution in our system is obtained without any noticeable c…
Ultrafast dynamics of halogens in rare gas solids
2007
We perform time resolved pump-probe spectroscopy on small halogen molecules ClF, Cl2, Br2, and I2 embedded in rare gas solids (RGS). We find that dissociation, angular depolarization, and the decoherence of the molecule is strongly influenced by the cage structure. The well ordered crystalline environment facilitates the modelling of the experimental angular distribution of the molecular axis after the collision with the rare gas cage. The observation of many subsequent vibrational wave packet oscillations allows the construction of anharmonic potentials and indicate a long vibrational coherence time. We control the vibrational wave packet revivals, thereby gaining information about the vib…
Emergence of long-range phase coherence in nonlocal nonlinear media
2017
The emergence of long range phase coherence among random nonlinear waves is a fascinating effect that characterizes many fundamental phenomena. For instance, the condensation of classical waves [1,2] is an important example of self-organization process that generates lot of interest as a classical analogue of quantum Bose-Einstein condensation. Wave condensation is known to be characterized by the emergence of long-range order and phase-coherence, in the sense that the correlation function of the wave amplitude does not decay at infinity. This property of long range phase coherence is fundamental, for instance for the manifestation of superfluid behaviors, or the generation of Bogoliubov so…
Optical control of vibrational coherence triggered by an ultrafast phase transition
2019
Femtosecond time-resolved x-ray diffraction is employed to study the dynamics of the periodic lattice distortion (PLD) associated with the charge-density-wave (CDW) in K0.3MoO3. Using a multi-pulse scheme we show the ability to extend the lifetime of coherent oscillations of the PLD about the undistorted structure through re-excitation of the electronic states. This suggests that it is possible to enter a regime where the symmetry of the potential energy landscape corresponds to the high symmetry phase but the scattering pathways that lead to the damping of coherent dynamics are still controllable by altering the electronic state population. The demonstrated control over the coherence time …
Improving the coherence properties of solid-state spin ensembles via optimized dynamical decoupling
2016
In this work, we optimize a dynamical decoupling (DD) protocol to improve the spin coherence properties of a dense ensemble of nitrogen-vacancy (NV) centers in diamond. Using liquid nitrogen-based cooling and DD microwave pulses, we increase the transverse coherence time T2 from ∼ 0.7 ms up to ∼ 30 ms. We extend previous work of single-axis (Carr-Purcell-Meiboom-Gill) DD towards the preservation of arbitrary spin states. After performing a detailed analysis of pulse and detuning errors, we compare the performance of various DD protocols. We identify that the concatenated XY8 pulse sequences serves as the optimal control scheme for preserving an arbitrary spin state. Finally, we use the conc…
Influence of dispersion on the resonant interaction between three incoherent waves
2005
We study the influence of group-velocity dispersion (or diffraction) on the coherence properties of the parametric three-wave interaction driven from an incoherent pump wave. We show that, under certain conditions, the incoherent pump may efficiently amplify a signal wave with a high degree of coherence, in contrast with the usual kinetic description of the incoherent three-wave interaction. The group-velocity dispersion is shown to be responsible for a spectral filtering process, in which the coherence of the generated signal increases, as the coherence of the pump wave decreases. As a result, the coherence acquired by the signal in the presence of an incoherent pump, is higher than that a…
Experimental evidence of X-shaped spatiotemporal coherence of superfluorescence radiation
2006
Considering the parametric generation process in a quadratic nonlinear crystal, we report the experimental observation of optical waves characterized by a X-shaped spatiotemporal coherence, i.e. a coherence skewed along spatiotemporal trajectories.
Optimizing a Dynamical Decoupling Protocol for Solid-State Electronic Spin Ensembles in Diamond
2015
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 ${T}_{1}$ effects and DD microwave pulses are used to increase the transverse coherence time ${T}_{2}$ from $\ensuremath{\sim}0.7\phantom{\rule{0.28em}{0ex}}\mathrm{ms}$ up to $\ensuremath{\sim}30\phantom{\rule{0.28em}{0ex}}\mathrm{ms}$. 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 c…