Transient effect of weak electromagnetic fields on calcium ion concentration in Arabidopsis thaliana

Background: Weak magnetic and electromagnetic fields can influence physiological processes in animals, plants and microorganisms, but the underlying way of perception is poorly understood. The ion cyclotron resonance is one of the discussed mechanisms, predicting biological effects for definite frequencies and intensities of electromagnetic fields possibly by affecting the physiological availability of small ions. Above all an influence on Calcium, which is crucial for many life processes, is in the focus of interest. We show that in Arabidopsis thaliana, changes in Ca(2+)-concentrations can be induced by combinations of magnetic and electromagnetic fields that match Ca(2+)-ion cyclotron resonance conditions. Results: An aequorin expressing Arabidopsis thaliana mutant (Col0-1 Aeq Cy+) was subjected to a magnetic field around 65 microtesla (0.65 Gauss) and an electromagnetic field with the corresponding Ca(2+) cyclotron frequency of 50 Hz. The resulting changes in free Ca(2+) were monitored by aequorin bioluminescence, using a high sensitive photomultiplier unit. The experiments were referenced by the additional use of wild type plants. Transient increases of cytosolic Ca(2+) were observed both after switching the electromagnetic field on and off, with the latter effect decreasing with increasing duration of the electromagnetic impact. Compared with this the uninfluenced long-term loss of bioluminescence activity without any exogenic impact was negligible. The magnetic field effect rapidly decreased if ion cyclotron resonance conditions were mismatched by varying the magnetic fieldstrength, also a dependence on the amplitude of the electromagnetic component was seen. Conclusion: Considering the various functions of Ca(2+) as a second messenger in plants, this mechanism may be relevant for perception of these combined fields. The applicability of recently hypothesized mechanisms for the ion cyclotron resonance effect in biological systems is discussed considering it's operating at magnetic field strengths weak enough, to occur occasionally in our all day environment

Handheld magnetic probe with permanent magnet and Hall sensor for identifying sentinel lymph nodes in breast cancer patients

Abstract The newly developed radioisotope-free technique based on magnetic nanoparticle detection using a magnetic probe is a promising method for sentinel lymph node biopsy. In this study, a novel handheld magnetic probe with a permanent magnet and magnetic sensor is developed to detect the sentinel lymph nodes in breast cancer patients. An outstanding feature of the probe is the precise positioning of the sensor at the magnetic null point of the magnet, leading to highly sensitive measurements unaffected by the strong ambient magnetic fields of the magnet. Numerical and experimental results show that the longitudinal detection length is approximately 10 mm, for 140 μg of iron. Clinical tests were performed, for the first time, using magnetic and blue dye tracers—without radioisotopes—in breast cancer patients to demonstrate the performance of the probe. The nodes were identified through transcutaneous and ex-vivo measurements, and the iron accumulation in the nodes was quantitatively revealed. These results show that the handheld magnetic probe is useful in sentinel lymph node biopsy and that magnetic techniques are widely being accepted as future standard methods in medical institutions lacking nuclear medicine facilities

Comparison of hyperpolarization techniques for ultralow-field magnetic resonance

Magnetic resonance (MR) studies are well established in numerous industrial, medical and scientific applications. Examples include MR spectroscopy (MRS), which is utilized for non-destructive chemical analysis, and MR imaging (MRI), which is a common noninvasive, medical imaging technique with great contrast in soft tissue. Conventional systems are bulky and expensive, because large magnet coils are utilized to generate high magnetic fields and signal amplitudes. The project presented in this thesis seeks to address these issues by combining the use of ultralow magnetic fields (ULF), with two signal enhancing hyperpolarization techniques. First, the experimental ULF-MR setup was established. It employs an open magnet coil assembly in combination with a superconducting quantum interference device (SQUID) as sensor, allowing for the quantitative measurement of the MR signal. Spectroscopic signal amplification by reversible exchange (SABRE) experiments and Overhauser dynamic nuclear polarization (ODNP) enhanced MRI showcased the successful implementation of these hyperpolarization techniques, and the imaging capabilities of the system. The results outline future applications and emphasize how the ultralowfield approach benefits from enhanced signal amplitude by hyperpolarization methods, while in turn facilitating the investigation and refinement of these techniques. Next, the simultaneous SABRE enhanced measurement of fluor and proton spins was performed. After investigating the influence of some measurement parameters on signal enhancement, correlation spectroscopy was utilized for a more detailed examination of the polarization transfer mechanisms. The studies demonstrated the capability of the system to perform multinuclear correlation spectroscopy experiments and the results are proof for the hyperpolarization of multiple-spin states by SABRE. The last part of this thesis focused on ODNP. With this technique, free radicals can facilitate an increase in nuclear spin polarization, enhancing the MR signal. Here, the polarization transfer efficacy of a broad range of nitroxide radicals was characterized. The comprehensive study allowed for a correlation of chemico-physical features with hyperpolarization-related properties. The results provide a catalog of polarizing agents and give direction for predicting and optimizing free radical performance in the future, especially for the development of functionalized polarizing agents. Reviewing the results allowed for a discussion of future utilization and direction of research for both hyperpolarization techniques. While possible applications differ greatly, they both share the prospect of profoundly enhancing MR signal and contrast in not only ultralow-fields but also in higher field regimes

Fast room temperature very low field-magnetic resonance imaging system compatible with MagnetoEncephaloGraphy environment

In recent years, ultra-low field (ULF)-MRI is being given more and more attention, due to the possibility of integrating ULF-MRI and Magnetoencephalography (MEG) in the same device. Despite the signal-to-noise ratio (SNR) reduction, there are several advantages to operating at ULF, including increased tissue contrast, reduced cost and weight of the scanners, the potential to image patients that are not compatible with clinical scanners, and the opportunity to integrate different imaging modalities. The majority of ULF-MRI systems are based, until now, on magnetic field pulsed techniques for increasing SNR, using SQUID based detectors with Larmor frequencies in the kHz range. Although promising results were recently obtained with such systems, it is an open question whether similar SNR and reduced acquisition time can be achieved with simpler devices. In this work a room-temperature, MEG-compatible very-low field (VLF)-MRI device working in the range of several hundred kHz without sample pre-polarization is presented. This preserves many advantages of ULF-MRI, but for equivalent imaging conditions and SNR we achieve reduced imaging time based on preliminary results using phantoms and ex-vivo rabbits heads

Spin Manipulation of the Nitrogen Vacancy Center and its Applications

Das Stickstoff-Fehlstellen-Zentrum (NV-Zentrum) in Diamant ist eines der vielver- sprechendsten Spinsysteme für Anwendungen im Bereich Quanten-Computing, -Information und -Sensorik. Die Abhängigkeit der Fluoreszenzintensität vom Spinzu- stand ermöglicht dabei das rein optische Auslesen des Spinzustandes. Für alle Anwendungen, die auf aktive Spinmanipulation angewiesen sind, ist Mikrowellen- strahlung unverzichtbar. Die Fähigkeit, den Spinzustand von NV-Zentren vollständig zu kontrollieren, wird durch die Richtung, Intensität und Polarisation der Mikrow- ellenstrahlung definiert. Es gibt verschiedene Ansätze, um geeignete Mikrowellen- strahlung zu erzeugen, aber oft ist die Feldintensität zu gering oder es gibt andere Einschränkungen, z.B. eine geringe Frequenzbandbreite. Im ersten Teil meiner Arbeit untersuche ich transparente Leiter auf Basis von Indium- Zinn-Oxid (ITO), um die Mikrowellenansteuerung von NV-Zentren zu optimieren. Dabei wird eine detaillierte Analyse von ITO auf Diamant bezüglich einzelner NV-Zentren vorgestellt. Ein mathematisches Modell wurde entwickelt, um die Feldverteilung vorherzusagen. Zusätzlich wird eine Methode zur Kontrolle der Mikrowellenpolarisation mit einer transparenten ITO-Struktur vorgestellt, die zu einer vollständigen Kontrolle des Spinzustands des NV-Zentrums führt. Weiterhin werden Simulationen in Kombination mit einem analytischen Modell verwendet, um optimale Mikrowellenparameter für die Spinkontrolle vorherzusagen. Für eine kommerzielle Anwendung von NV-Zentren als Magnetfeldsensor sind Pro- duktionskosten und Bauteilkomplexität wichtige Faktoren, die in der Forschung oft vernachlässigt werden. Der zweite Teil meiner Arbeit konzentriert sich da- her auf einen mikrowellenfreien Ansatz zur Magnetometrie mit NV-Zentren. Der Einfluss der Laseranregung auf den magnetischen Kontrast wird an einzelnen NV- Zentren, Ensembles von NV-Zentren und Nano-Diamantpulver mit einer hohen NV- Zentrenkonzentration dargestellt und nachfolgend zur Demonstration von isotropen Magnetfeldmessung verwendet. Abschließend wird die Anwendbarkeit durch die Konstruktion eines Magnetfeldsensors aus Komponenten der Automobilbranche gezeigt.The nitrogen vacancy center (NV center) in diamond is one of the most promising spin systems for applications in quantum computing, information and sensing. The dependency of the fluorescence intensity on the spin state allows a purely optical readout of the spin state. A green laser can be used to pump the NV center in the spin ground state while microwave radiation can manipulate the spin state of the NV center. For all applications depending on active spin manipulation, microwave radiation is indispensable. The ability to fully control the spin state of NV centers is defined by direction, strength and polarization of the microwave radiation. Different approaches exist to deliver the microwave radiation, but they often lack in strength or have other restrictions, e.g. a small frequency band width. In the first part of my thesis, I investigate transparent conductors based on indium tin oxide (ITO) to optimize microwave delivery. In this process a detailed analysis of ITO on diamond concerning confocal microscopy through this transparent film is presented. A mathematical model was developed and tested to predict the field distribution in possible applications. Additionally a method to control microwave polarization with a transparent ITO structure is shown which results in full spin state control of the NV center. Furthermore simulations combined with a analytical model are used to predict optimal microwave parameters for spin control. For a commercial application of NV centers as a magnetic field sensor, important factors are production cost and device complexity which are often neglected in research. The second part of my thesis therefore focuses on a microwave free approach of NV center magnetometry for industry applications. The influence of laser excitation on magnetic contrast was studied on single NV centers, ensembles of NV centers and nano diamond powder with a high NV center concentration. The findings were used to demonstrate isotropic magnetic field sensing. Finally, the applicability was shown by constructing a magnetic field sensor from automotive grade components

Robust high fidelity microwave near-field entangling quantum logic gate

Trapped ions, together with superconducting qubits, are one of the two leading hardware platforms for scalable quantum information processing. The development of quantum computers represents a major technological breakthrough comparable to the introduction of classical computing. The benefits of this technology are currently limited by the technical capability to perform high fidelity entangling operations on the qubits. When gate fidelities surpass the fault-tolerance threshold it becomes possible, through error correction, to increase the system size to an arbitrary number of qubits. In this cumulative thesis we address some of the issues in the scalability of the trapped-ion quantum computer based on microwave near-fields. In this approach, gate operations on one or multiple ions are driven by an oscillating magnetic field generated by a current flowing through a conductor. In the first part of this work we discuss the design of traps toward the implementation of large scale systems. We introduce the basic design of a surface-electrode ion trap with embedded microwave conductors. The oscillating magnetic field required to perform the operations is generated by a single optimized conductor. We discuss the simulation and characterization of the magnetic field pattern, which is fixed by the microwave conductor design. In addition, we demonstrate the capability to simulate, fabricate and characterize a multilayer surface ion trap. Multilayer traps are a key aspect for scalability since they are necessary to achieve large system sizes, with many `ion registers', where the registers are interconnected by physically transporting ions between them. In the second part of this thesis we demonstrate the implementation of a two-qubit entangling gate and we explore the possibilities offered by quantum control methods to improve its fidelity. We perform an entangling gate on two 9Be+ ions and measure a Bell state fidelity of 98.2(1.2)%. Error characterization shows that the gate result is limited by technical issues connected to the ions' motional states. To reduce these errors we apply amplitude modulation of the gate microwave drive. After stabilization of the ions' radial modes, we obtain an amplitude modulated gate with infidelity in the 10^-3 range. The result is confirmed by analyzing the data using three different methods. Using additional dynamic decoupling techniques, these results could bring microwave near-field gates past the fault-tolerance threshold

Towards single spin magnetometry at mK temperatures

The liquefaction of helium and the dilution refrigerator have enabled cooling down objects to 4K and even mK temperatures. Fascinating effects, such as superconductivity and strongly correlated electron systems (SCES) emerge at these temperatures and can be studied in appropriate cryogenics experiments. A powerful tool to study magnetic phenomena in such systems is a point lattice defect in diamond, the nitrogen-vacancy (NV) center. The NV center contains an electron spin that offers exceptional properties in terms of coherence time and optical addressability, and can thereby be employed for high-performance magnetic field sensing. Due to its atom-like size, the NV center can be used for nanoscale magnetometry, particularly in a scanning probe configuration where a single NV is located in a tip. This allows for nanometric spatial resolution combined with sensitivities of approximately 1 µT/Hz^0.5. In this work, we pave the way towards NV magnetometry at mK temperature by implementing NV magnetometry in a dilution refrigerator, so far at 4 K, and by conducting transport experiments on a SCES at mK temperature. At first, two phenomena in the type-II superconductor YBCO are examined at 4K in a liquid helium bath cryostat. On the one hand, the Meissner effect is measured over a thin YBCO disk by directly imaging the penetration of magnetic fields into the superconductor. On the other hand, stray magnetic fields emerging from vortices in the same superconductor are imaged with approximately 30nm resolution. In both cases, we benchmark our findings against existing theoretical models and use this analysis to extract quantitative values for the London penetration depth. Additionally, we examine out-of-plane (OOP)-oriented NV centers with respect to the scanning plane, which offer benefits such as improved sensitivity and data interpretability. OOP-oriented NV centers in our fabricated scanning probes are uniquely identified and used for nanoscale magnetic imaging for the first time. The oxide interface LAO/STO, which hosts a two-dimensional electron gas that exhibits SCES physics, is examined in the dilution refrigerator. Transport measurements show signs of superconductivity and laser illumination is found to significantly increase the conductance. In terms of NV magnetometry in a dilution refrigerator at 4 K, current imaging reveals an inhomogeneous current ow through the interface. In contrast to previous findings, no magnetic signatures are found. Lastly, longitudinal T1 relaxation is studied in a high-density NV ensemble. Relaxation rates at mK are found to be lower than at 4 K, on the order of 1 Hz. However, they are still much higher than in previous findings, possibly explainable by spin diffusion out of the laser focus. At mK temperature, a shift of the thermal spin population is observed, corresponding to the Boltzmann distribution. Overall, in this thesis we can present meaningful results in several areas, some of which have already been published. In the future, we will use the increased sensitivity of OOP-oriented NV magnetometers and explore magnetism and superconductivity in various exotic materials at mK temperatures

Prototyping the next generation of versatile paleomagnetic laboratory

Investigating the Earth’s magnetic field provides a unique window into the history of Earth’s outer core, where the field is generated. Rocks gain a magnetization that is in the direction of and proportional to the Earth’s magnetic field at the time of their formation, such as when magma erupts from a volcano and cools below its Curie temperature. The gained magnetization has a relaxation time that is frequently longer than the age of the universe, but unfortunately, rocks are subject to the whims of the Earth over geologic time. Given the ages of rocks commonly studied (millions to billions of years old), some paleomagnetic data is noisy and complex. Paleomagnetic intensity data in particular have long been plagued by large and poorly quantified uncertainties. Extracting accurate magnetic measurements relies on having the most advanced equipment and best experimental techniques. This thesis approaches these goals from two directions: prototyping new equipment, which also introduces novel methodology, and fine-tuning existing methods. Contained herein is the development of the world’s first automated high-temperature SQUID (Superconducting Quantum Interference Device) thermomagnetometer. This system can automatically measure the remanent magnetic field of a specimen at an elevated temperature without needing to cool the specimen to ambient temperature. Without repeated heating/cooling cycles, thermochemical alteration is minimized, and the rate of data collection is greatly increased. SQUID sensors improve the sensitivity of the magnetometer system, avoid low blocking temperature components, and provide precise temperature control and minimal alteration. While the original design called for an instrument that could provide continuous magnetization measurements, this proved to be untenable due to technical constraints with the SQUID sensors. Thus, a stepwise version was produced that measures each specimen in (up to) 10 °C increments, instead of continuously. Introducing new equipment by itself is futile if the experiments performed on them are not well calibrated and optimized. To address this problem, this thesis investigates differences in paleomagnetic intensity results produced by different variants of Thellier-style paleointensity protocols using established instruments. The most modern protocol, the IZZI protocol, was found to be broadly accurate but sometimes imprecise. This thesis further attempts to ascertain the cause of differences observed in paleointensity data when the demagnetization mechanism or paleointensity protocol is changed, as nearly a dozen methods are in use throughout the world. Finally, a series of tests evaluates whether the addition of alternating field or liquid nitrogen demagnetization cleansing steps can improve data fidelity. The additional cleansing steps can, in some cases, improve the linearity of paleointensity data sufficiently to pass selection criteria, but cannot affect, for example, other complications like thermochemical alteration. With the ever-growing pressure to provide tangible impacts to the broader scientific community, expanding the versatility of magnetic techniques to new applications is paramount. This thesis broadly applies magnetic techniques to the energy sector, through Magnetic Flux Leakage experiments on Coiled Tubing, in conjunction with Schlumberger as an industrial partner. The future paleomagnetic laboratory is a versatile one, capable of running large batches of specimens (both paleomagnetic and metallic) quickly and accurately, through a combination of improved methods and equipment. This thesis has successfully introduced a new prototype magnetometer design and found that for non-ideal (i.e. real) rocks, the interactions between the rocks and methods are complex. Going forward, the new magnetometer brings high temperature remanence measurements to more rock types and potentially further partnerships with external, industrial partners, like Schlumberger

Measuring the stability of fundamental constants with a network of clocks

The detection of variations of fundamental constants of the Standard Model would provide us with compelling evidence of new physics, and could lift the veil on the nature of dark matter and dark energy. In this work, we discuss how a network of atomic and molecular clocks can be used to look for such variations with unprecedented sensitivity over a wide range of time scales. This is precisely the goal of the recently launched QSNET project: A network of clocks for measuring the stability of fundamental constants. QSNET will include state-of-the-art atomic clocks, but will also develop next-generation molecular and highly charged ion clocks with enhanced sensitivity to variations of fundamental constants. We describe the technological and scientific aims of QSNET and evaluate its expected performance. We show that in the range of parameters probed by QSNET, either we will discover new physics, or we will impose new constraints on violations of fundamental symmetries and a range of theories beyond the Standard Model, including dark matter and dark energy models