At the University of Sussex we are building a coplanar-waveguide (CPW) Penning trap. This is a novel planar Penning trap, which results form the projection of the well-known cylindrical trap onto the surface of a chip [1]. The trap allows for the compensation of electrical anharmonicities up to the sixth order and permits the observation of a single trapped electron, a primary goal not yet achieved with planar Penning trap technology. The electron can be coupled to a distant superconducting coplanar-waveguide resonator, such as those used in circuit-QED with artificial two level systems. The cyclotron motion interacts coherently with the microwave resonator, implementing a system of two coupled quantum harmonic oscillators and with applications in quantum metrology and quantum computation. In the poster, we report on recent experimental progress in the construction of a cryogenic CPW- Penning trap.
At the University of Sussex we are building a coplanar-waveguide (CPW) Penning trap. This is a novel planar Penning trap, which results form the projection of the well-known cylindrical trap onto the surface of a chip [1]. The trap allows for the compensation of electrical anharmonicities up to the sixth order and permits the observation of a single trapped electron, a primary goal not yet achieved with planar Penning trap technology. The electron can be coupled to a distant superconducting coplanar-waveguide resonator, such as those used in circuit-QED with artificial two level systems. The cyclotron motion interacts coherently with the microwave resonator, implementing a system of two coupled quantum harmonic oscillators and with applications in quantum metrology and quantum computation. In the poster, we report on recent experimental progress in the construction of a cryogenic CPW- Penning trap.
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.
We investigate theoretically the use of an electron in a Penning trap as a detector of single microwave photons. At the University of Sussex we are developing a chip Penning trap technology, designed to be integrated within quantum circuits. Microwave photons are guided into the trap and interact with the electron’s quantum cyclotron motion. This is an electric dipole transition, where the near field of the microwave radiation induces quantum jumps of the cyclotron harmonic oscillator. The quantum jumps can be monitored using the continuous Stern-Gerlach effect, providing the quantum non demolition signal of the microwave quanta. We calculate the quantum efficiency of photon detection and discuss the main features and technical challenges for the trapped electron as a quantum microwave sensor.
We theoretically investigate the coupling of a single electron in a planar Penning trap with a remote superconducting microwave (MW) cavity. Coupling frequencies around Ω=2π·1 MHz can be reached with resonators with a loaded quality factor of Q=105, allowing for the strong coupling regime. The electron and the cavity form a system of two coupled quantum harmonic oscillators. This is a hybrid and linear microwave quantum network. We show that the coherent interaction can be sustained over distances of a few mm up to several cm. Similar to classical linear MW circuits, the coherent quantum exchange of photons is ruled by the impedances of the electron and the cavity. As one concrete application, we discuss the entanglement of the cyclotron motions of two electrons located in two separate traps.
A one-electron qubit would offer a new option for quantum information science, including the possibility of extremely long coherence times. One-quantum cyclotron transitions and spin flips have been observed for a single electron in a cylindrical Penning trap. However, an electron suspended in a planar Penning trap is a more promising building block for the array of coupled qubits needed for quantum information studies. The optimized design configurations identified here promise to make it possible to realize the elusive goal of one trapped electron in a planar Penning trap---a substantial step toward a one-electron qubit.
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.
Quantum computers have the potential to solve problems far beyond the reach of classical computers by using the principles of superposition and entanglement. However, existing platforms face challenges such as short coherence times, interference from the environment, and difficulties in scaling up.Trapped electrons in a planar Penning trap offer a promising alternative. Unlike other qubits, electrons do not interact with nuclear spins, which helps maintain quantum states for much longer. Additionally, their strong confinement allows for fast and precise quantum operations. In our approach, electron spins serve as logical qubits, while their motional states are used for entanglement. Our setup consists of 2-dimensional array of micro-sized Penning traps fabricated on a ceramic chip, placed inside a 1T superconducting magnet and cooled in a dilution refrigerator to reach millikelvin temperatures. This extreme cooling reduces unwanted motion and makes it possible to entangle electron spins and perform quantum gates with high accuracy. At Inter-University Accelerator Centre (IUAC), New Delhi, India, we are developing a prototype planar Penning trap. This new system offers a stable, scalable, and high-coherence platform for quantum computing.