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The Geonium Chip: engineering a scalable planar Penningtrap

Jonathan Pinder

Published Feb 21, 2017• 4 citations
OpenAlex

Abstract

In this thesis is presented the realisation of `The Geonium Chip', a novel planar Penning trap. The chip is designed with the goal of building a truly scalable planar Penning trap, while retaining the accuracy of 3D traps. Manufactured with conventional metalon- silicon microfabrication techniques, the chip takes the 5 electrodes of the compensated cylindrical trap and projects them onto a ground-plane surface, thus forming the basis for its layout by reducing the electrode shape to an array of at rectangular surfaces. In this thesis I describe the conception, design and construction of a full cryogenic set-up, including the magnetics, for trapping and observing a single electron in the Geonium Chip Penning trap. The cyclotron mode of the trapped electron lies in the microwave regime, and thus the Geonium Chip has the potential to become a powerful building block for quantum microwave circuits, with coherent coupling to the cyclotron degree of freedom. This will also allow non-destructive measurement and interaction with the spin state of the electron. The development of the experimental process is detailed from scratch including the design, fabrication, and testing of the Geonium Chip, as well as the design, fabrication and testing of the experimental apparatus. The original solutions and space saving designs developed as part of the construction process are detailed, such as the custom on-chip cryogenic vacuum chamber, planar magnetic field source, and the LED-based electron loading system. The vacuum chamber and control systems are also described, and the in-house manufacturing capabilities of the Geonium group are detailed at length, with an emphasis on rapid prototyping high-accuracy components suitable for experimental use. The apparatus built within this PhD is within a few weeks of performing the first loading of electrons into the chip trap.

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Development of a planar penning trap for quantum applications with electrons

April Louise Cridland

This thesis presents the development of the Geonium Chip, a planar Penning trap. The Geonium Chip consists of the five electrodes of a cylindrical Penning trap projected onto the surface of a microfabricated chip. Beneath the chip is a planar magnetic field source currently made from coils of niobium titanium wire. Traditionally the magnetic field source is a large superconducting solenoid, replacing this with a planar source makes the setup scalable, portable and economical. The Geonium Chip, with its magnetic field source and detection electronics, need to be placed in a cryostat. In this thesis, I describe the development of the cryogenic setup with particular emphasis on the design and optimisation of the non-destructive detection system. I detail the cryogenic wiring of the cryostat including the thermalisation of high current wires and the noise reduction techniques employed on the detection signal. In addition, I explore the parasitic capacitances of the Geonium Chip using microwave network analysis and describe the testing of the magnetic field source at 4 K. Finally, I discuss the generation of electrons within the trap and the results of our first attempts at trapping a cloud of electrons. Together, the chip and the magnetic field source can be used to trap ions for ultraaccurate mass spectrometry or an electron for single microwave photon detection. A single microwave photon detector is a tool that is currently still missing in quantum technology and is needed for determining the quantum state of microwave radiation fields. This is vital for quantum communication and cryptography. Additionally, using the Geonium Chip as a mass spectrometer has the potential to lead to very accurate mass spectrums without the need for frequent calibration. Finally, eliminating the expensive superconducting solenoid will make accurate mass spectrometry available to a wider market.

•Nov 20, 2018•2 citations

Development of a planar magnetic field source for the Geonium Chip Penning Trap

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This thesis presents the theoretical foundation and design of a planar magnetic field source for the Geonium Chip Penning trap. Conventional Penning traps are limited in their scalability by the size of their magnetic field sources, which often take the shape of large and expensive superconducting solenoids. For many practical applications, such as portable mass spectrometry and quantum radar, these conventional Penning trap systems would be unsuitable, due to their large size and need for very high currents (of the order of a few hundred amperes). The Geonium Chip Penning trap aims to overcome this problem by proposing a novel planar magnetic field source comprising several superconducting coils confined to a plane. The electrode surfaces of the trap sit less than a millimetre above the magnetic field source such that the trapping magnetic field is oriented parallel to the electrode surfaces. In this thesis, I explore many of the fundamental design issues concerned with developing such a planar magnetic field source. In particular, I devise an entirely new scheme of remotely magnetising a plurality of closed superconducting loops to carry currents in persistent mode, and show how persistent supercurrents of hundreds of amperes can be remotely induced with input currents of the order of a few (one to two) amperes. I introduce, and experimentally verify, a theoretical framework that allows for a high degree of control over the magnetic field distribution. From this framework, I present an optimised design of a planar persistent current-mode magnetic field source theoretically capable of achieving a 0.1 T field homogeneous up to fourth order in the Taylor expansion about the trapping position. This magnetic field source is due to be constructed and tested in the coming months.

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A novel planar Penning trap is presented, which results from the projection of the well-known three-dimensional cylindrical trap onto the surface of a chip. The introduced trap is also a coplanar-waveguide cavity, similar to those used in circuit quantum electrodynamics experiments with superconducting two-level systems. It opens up the possibility of integrating a single trapped electron, or geonium atom, into quantum circuits. The trap is an elliptical Penning trap, with the magnetic field parallel to the chip's surface. A design procedure is described, which permits the compensation of electric anharmonicities up to sixth order. This should render possible the observation of a single trapped electron and the accurate measurement of its eigenfrequencies, a sine qua non requirement for a useful planar geonium technology.

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Cold atoms in your pocket : enabling technologies

Andrei-Aurel Dragomir

This thesis details the work carried out in the development towards a fully miniaturised integrated atom chip. The main focus of the project so far has been on the construction of miniaturised vacuum chambers, the study of the eutectic bond and the manufacturing of integrated electric feedthroughs, together with the development of new cold atom trap geometries. Current cold atom technologies rely on the use of bulky optical systems and large vacuum chambers. We propose the miniaturisation of the entire system into a device comparable in size with a match box. Afirst step towards this goal is the miniaturisation of the vacuum system and atomic source. In the first part of this thesis we present planar microfabrication techniques, such as anodic bonding and eutectic bonding, as a solution for providing hermetic seals. Several partially working devices i.e miniaturised vacuum chambers with rubidium atom sources are presented and compared to commercial rubidium cells. As ultimately our integrated atom chips will be used in metrology and sensing devices, they require current-carrying wires within the vacuum. Towards this purpose we propose a method of building hermetically sealed electrical feedthroughs through the process of glass reflow in thick silicon substrates. The second part of this thesis outlines a brief theory towards cooling atoms, together with new geometries designed for use with miniaturised devices and the attempts of achieving a functional integrated atom chip. Finally, we present the development of a new method for achieving a cold atom source without the use of magnetic fields.

•Dec 1, 2018•0 citations
In this thesis is presented the realisation of `The Geonium Chip', a novel planar Penning trap. The chip is designed with the goal of building a truly scalable planar Penning trap, while retaining the accuracy of 3D traps. Manufactured with conventional metalon- silicon microfabrication techniques, the chip takes the 5 electrodes of the compensated cylindrical trap and projects them onto a ground-plane surface, thus forming the basis for its layout by reducing the electrode shape to an array of at rectangular surfaces. In this thesis I describe the conception, design and construction of a full cryogenic set-up, including the magnetics, for trapping and observing a single electron in the Geonium Chip Penning trap. The cyclotron mode of the trapped electron lies in the microwave regime, and thus the Geonium Chip has the potential to become a powerful building block for quantum microwave circuits, with coherent coupling to the cyclotron degree of freedom. This will also allow non-destructive measurement and interaction with the spin state of the electron. The development of the experimental process is detailed from scratch including the design, fabrication, and testing of the Geonium Chip, as well as the design, fabrication and testing of the experimental apparatus. The original solutions and space saving designs developed as part of the construction process are detailed, such as the custom on-chip cryogenic vacuum chamber, planar magnetic field source, and the LED-based electron loading system. The vacuum chamber and control systems are also described, and the in-house manufacturing capabilities of the Geonium group are detailed at length, with an emphasis on rapid prototyping high-accuracy components suitable for experimental use. The apparatus built within this PhD is within a few weeks of performing the first loading of electrons into the chip trap.
This thesis presents the development of the Geonium Chip, a planar Penning trap. The Geonium Chip consists of the five electrodes of a cylindrical Penning trap projected onto the surface of a microfabricated chip. Beneath the chip is a planar magnetic field source currently made from coils of niobium titanium wire. Traditionally the magnetic field source is a large superconducting solenoid, replacing this with a planar source makes the setup scalable, portable and economical. The Geonium Chip, with its magnetic field source and detection electronics, need to be placed in a cryostat. In this thesis, I describe the development of the cryogenic setup with particular emphasis on the design and optimisation of the non-destructive detection system. I detail the cryogenic wiring of the cryostat including the thermalisation of high current wires and the noise reduction techniques employed on the detection signal. In addition, I explore the parasitic capacitances of the Geonium Chip using microwave network analysis and describe the testing of the magnetic field source at 4 K. Finally, I discuss the generation of electrons within the trap and the results of our first attempts at trapping a cloud of electrons. Together, the chip and the magnetic field source can be used to trap ions for ultraaccurate mass spectrometry or an electron for single microwave photon detection. A single microwave photon detector is a tool that is currently still missing in quantum technology and is needed for determining the quantum state of microwave radiation fields. This is vital for quantum communication and cryptography. Additionally, using the Geonium Chip as a mass spectrometer has the potential to lead to very accurate mass spectrums without the need for frequent calibration. Finally, eliminating the expensive superconducting solenoid will make accurate mass spectrometry available to a wider market.
This thesis presents the theoretical foundation and design of a planar magnetic field source for the Geonium Chip Penning trap. Conventional Penning traps are limited in their scalability by the size of their magnetic field sources, which often take the shape of large and expensive superconducting solenoids. For many practical applications, such as portable mass spectrometry and quantum radar, these conventional Penning trap systems would be unsuitable, due to their large size and need for very high currents (of the order of a few hundred amperes). The Geonium Chip Penning trap aims to overcome this problem by proposing a novel planar magnetic field source comprising several superconducting coils confined to a plane. The electrode surfaces of the trap sit less than a millimetre above the magnetic field source such that the trapping magnetic field is oriented parallel to the electrode surfaces. In this thesis, I explore many of the fundamental design issues concerned with developing such a planar magnetic field source. In particular, I devise an entirely new scheme of remotely magnetising a plurality of closed superconducting loops to carry currents in persistent mode, and show how persistent supercurrents of hundreds of amperes can be remotely induced with input currents of the order of a few (one to two) amperes. I introduce, and experimentally verify, a theoretical framework that allows for a high degree of control over the magnetic field distribution. From this framework, I present an optimised design of a planar persistent current-mode magnetic field source theoretically capable of achieving a 0.1 T field homogeneous up to fourth order in the Taylor expansion about the trapping position. This magnetic field source is due to be constructed and tested in the coming months.
The Geonium Chip Penning trap is a planar trap that aims to reduce both the size and the cost of other conventional systems while maintaining the same level of accuracy, making it an ideal candidate for practical quantum technology applications, such as the implementation of the Microwave Quantum Illumination Protocol. This is possible thanks to the possibility of using a single electron trapped in the Geonium Chip as the emitter and receiver of single microwave photons, as well as to facilitate the creation and detection of quantum correlations. The results presented in this thesis consist on the first steps towards the engineering of a scalable and deployable system, adapted to the requirements of the Quantum Illumination Protocol. This thesis has tackled all the aspects associated to this task, such as studies on how to enhance the quantum efficiency of single microwave photons using a trapped electron, the engineering and characterisation of a novel LED-based electron source which will help to reduce the overall size of the experiment and the first steps towards the development of a novel planar magnetic field source made of GdBCO, a high temperature superconductor.
This thesis presents the development of a novel type of planar Penning Trap known as the Geonium Chip. The thesis describes a wide array of experimental work done in the laboratory in different topics in order to build the trap. The main focus is a detailed research of the high frequency properties of the trap and the design of new methods of detection of the trapped particles. The Geonium Chip aims at developing a practical planar, scalable Penning Trap making it suitable for new uses and technologies, such as mass spectrometry and single microwave photon detection. This thesis is mainly focussed on the high frequency properties of the trap, essential to the design of experiment and specially of the chip itself. A new trapped particle detection system is investigated, which replaces the narrow band superconducting resonator normally used in Penning trap experiments by a common SMD resistor. This represents a considerable reduction of the size of the set-up. Moreover, it is an important progress with respect to previous resonator systems, since it is able to work in a broad range of frequencies - a severe limitation of current Penning traps in applications such as mass spectrometry
A novel planar Penning trap is presented, which results from the projection of the well-known three-dimensional cylindrical trap onto the surface of a chip. The introduced trap is also a coplanar-waveguide cavity, similar to those used in circuit quantum electrodynamics experiments with superconducting two-level systems. It opens up the possibility of integrating a single trapped electron, or geonium atom, into quantum circuits. The trap is an elliptical Penning trap, with the magnetic field parallel to the chip's surface. A design procedure is described, which permits the compensation of electric anharmonicities up to sixth order. This should render possible the observation of a single trapped electron and the accurate measurement of its eigenfrequencies, a sine qua non requirement for a useful planar geonium technology.
This thesis details the work carried out in the development towards a fully miniaturised integrated atom chip. The main focus of the project so far has been on the construction of miniaturised vacuum chambers, the study of the eutectic bond and the manufacturing of integrated electric feedthroughs, together with the development of new cold atom trap geometries. Current cold atom technologies rely on the use of bulky optical systems and large vacuum chambers. We propose the miniaturisation of the entire system into a device comparable in size with a match box. Afirst step towards this goal is the miniaturisation of the vacuum system and atomic source. In the first part of this thesis we present planar microfabrication techniques, such as anodic bonding and eutectic bonding, as a solution for providing hermetic seals. Several partially working devices i.e miniaturised vacuum chambers with rubidium atom sources are presented and compared to commercial rubidium cells. As ultimately our integrated atom chips will be used in metrology and sensing devices, they require current-carrying wires within the vacuum. Towards this purpose we propose a method of building hermetically sealed electrical feedthroughs through the process of glass reflow in thick silicon substrates. The second part of this thesis outlines a brief theory towards cooling atoms, together with new geometries designed for use with miniaturised devices and the attempts of achieving a functional integrated atom chip. Finally, we present the development of a new method for achieving a cold atom source without the use of magnetic fields.