2,181 research outputs found
Near-Field Scanning Microwave Microscopy in the Single Photon Regime
The microwave properties of nano-scale structures are important in a wide
variety of applications in quantum technology. Here we describe a low-power
cryogenic near-field scanning microwave microscope (NSMM) which maintains
nano-scale dielectric contrast down to the single microwave photon regime, up
to times lower power than in typical NSMMs. We discuss the remaining
challenges towards developing nano-scale NSMM for quantum coherent interaction
with two-level systems as an enabling tool for the development of quantum
technologies in the microwave regime
Multiport Vector Network Analyzer Configured in RF Interferometric Mode for Reference Impedance Renormalization
International audienceA novel active microwave interferometric technique is implemented on a multiport vector network analyzer for renormalizing the reference impedance 50 Ohms into any desired complex impedance. The resulting measured reflection coefficient around the new reference impedance is around zero, resulting in high measurement sensitivity. The method proposed avoids any external component commonly found in interferometric setups. In addition, a zeroing process including vector calibration is developed for broad frequency range and requires only a software procedure to be implemented in the system framework
Near-field microwave techniques for micro – and nano - scale characterization in materials science
In this paper, the basic principles of Near-Field Microscopy will be reviewed with focus on the micro-
and nano-scale resolution configurations for material science measurements. Results on doping profile, dielectric
and magnetic properties will be presented, with details on the calibration protocols needed for quantitative estimation
of the dielectric constant and of the permeability
Deterministic coupling of a single nitrogen vacancy center to a photonic crystal cavity
We describe and experimentally demonstrate a technique for deterministic
coupling between a photonic crystal (PC) nanocavity and single emitters. The
technique is based on in-situ scanning of a PC cavity over a sample and allows
the positioning of the cavity over a desired emitter with nanoscale resolution.
The power of the technique, which we term a Scanning Cavity Microscope (SCM),
is demonstrated by coupling the PC nanocavity to a single nitrogen vacancy (NV)
center in diamond, an emitter system that provides optically accessible
electron and nuclear spin qubits
Magnetic Resonance Lithography with Nanometer Resolution
We propose an approach for super-resolution optical lithography which is
based on the inverse of magnetic resonance imaging (MRI). The technique uses
atomic coherence in an ensemble of spin systems whose final state population
can be optically detected. In principle, our method is capable of producing
arbitrary one and two dimensional high-resolution patterns with high contrast
Reconstruction of the Antenna Near-Field
Cílem disertační práce je navrhnout efektivně pracující algoritmus, který na základě bezfázového měření v blízkém poli antény bude schopen zrekonstruovat komplexní blízké pole antény resp. vyzařovací diagram antény ve vzdáleném poli. Na základě těchto úvah byly zkoumány vlastnosti minimalizačního algoritmu. Zejména byl analyzován a vhodně zvolen minimalizační přistup, optimalizační metoda a v neposlední řadě i optimalizační funkce tzv. funkcionál. Dále pro urychlení celého minimalizačního procesu byly uvažovány prvotní odhady. A na závěr byla do minimalizačního algoritmu zahrnuta myšlenka nahrazující hledané elektrické pole několika koeficienty. Na základě předchozích analýz byla navržená bezfázová metoda pro charakterizaci vyzařovacích vlastností antén. Tato metoda kombinuje globální optimalizaci s obrazovou kompresní metodou a s lokální metodou ve spojení s konvečním amplitudovým měřením na dvou površích. V našem případě je globální optimalizace použita k nalezení globálního minima minimalizovaného funkcionálu, kompresní metoda k redukci neznámých proměnných na apertuře antény a lokální metoda zajišťuje přesnější nalezení minima. Navržená metoda je velmi robustní a mnohem rychlejší než jiné dostupné minimalizační algoritmy. Další výzkum byl zaměřen na možnosti využití měřených amplitud pouze z jednoho měřícího povrchu pro rekonstrukci vyzařovacích charakteristik antén a využití nového algoritmu pro rekonstrukci fáze na válcové geometrii.The aim of this dissertation thesis is to design a very effective algorithm, which is able to reconstruct the antenna near-field and radiation patterns, respectively, from amplitude-only measurements. Under these circumstances, the properties of minimization algorithm were researched. The selection of the minimization approach, optimization technique and the appropriate functional were investigated and appropriately chosen. To reveal the global minimum area faster, the possibilities in the form of initial estimates for accelerating minimization algorithm were also considered. And finally, the idea to represent the unknown electric field distribution by a few coefficients was implicated into the minimization algorithm. The designed near-field phaseless approach for the antenna far-field characterization combines a global optimization, an image compression method and a local optimization in conjunction with conventional two-surface amplitude measurements. The global optimization method is used to minimize the functional, the image compression method is used to reduce the number of unknown variables, and the local optimization method is used to improve the estimate achieved by the previous method. The proposed algorithm is very robust and faster than comparable algorithms available. Other investigations were focused on possibilities of using amplitude from only single scanning surface for reconstruction of radiation patterns and the application of the novel phase retrieval algorithm for cylindrical geometry.
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