Periodic Reporting for period 3 - IONPEN (Trapped-ion quantum information in 2-dimensional Penning trap arrays)
Période du rapport: 2022-04-01 au 2023-09-30
This project aims to realize a new platform for quantum computing based on trapped ions. Quantum computing is attracting vast attention due to its potential to solve problems which are intractable on devices which only use classical physics. However expected scales for useful devices require many thousands of qubits. While trapped ions are a promising approach towards this goal, systems today use up to 50 qubits, trapped in systems where radio-freqeency fields are used to confine ions. This creates a number of problems for scaling, including heat dissipation, a lack of natural paths to 2-dimensional arrays, and a constant calibration challenge due to drifts in electric fields. This project aims to make a new path for trapped-ion quantum computing by replacing the radio-frequency field with a large static magnetic field (Penning trap), and thus avoiding the aforementioned problems. While Penning traps are used for precision spectroscopy and quantum simulation, these are all devices with centimetre scale electrodes, not suited for quantum computing. This project pursues microfabricated electrode structures, allowing arrays of Penning traps to be developed. This constitutes a new Quantum CCD architecture for ion trap quantum computing, which should open a clear path to useful quantum computers.
The primary tasks in the first phase of the project are to build an experimental apparatus to trap small numbers of ions in micro-fabricated Penning traps. To this end, a suitable superconducting magnet was identified and purchased, and a complete cryogenic UHV system was designed and built up to house the chips used for ion trapping. Optical systems, including 6 home-built UV laser systems, were set up, characterized and optimized in performance to be suited for trapping and performing quantum manipulations of trapped ions. Tests were performed on various of the elements which should go into the cryogenic vacuum, including optical layouts, sources of neutral beryllium atoms, and imaging systems. This included cooling down the system (and magnet) multiple times to characterize various aspects of the apparatus which change as materials change in size during the thermal cycle from 300 Kelvin to 4 Kelvin.
On the theoretical side, we have developed further the concept for using microfabricated Penning traps in quantum computing, and performed extensive simulations of ions in Penning traps to design the characteristics required from the laser light for cooling the ions as they are loaded into the trap. This led to new ideas regarding laser cooling, as well as novel aspects of harmonic oscillator physics related to the Penning trap setting.
On the theoretical side, we have developed further the concept for using microfabricated Penning traps in quantum computing, and performed extensive simulations of ions in Penning traps to design the characteristics required from the laser light for cooling the ions as they are loaded into the trap. This led to new ideas regarding laser cooling, as well as novel aspects of harmonic oscillator physics related to the Penning trap setting.
Since no system of this type has ever been built, building the setup constitutes work beyond the state of the art. New results have also been produced in the theoretical domain related to the behaviour of Penning traps at certain choices of trap curvature, where extended quantum wavepackets can be expected. Studies of laser cooling in Penning traps revealed that under certain conditions frequency modulation of the laser could produce cooling where a non frequency-modulated laser would not. Further results of the project will be expected once we have loaded ions (already a new step when it happens). We look forward to characterizing single ion performance in this novel system, as well as to performing gates and transport on 2-dimensional arrays.