Trapped ion quantum computing with global microwave fields
Abstract
Practical quantum computers have been described as one of the holy grails of science due to their disruptive capabilities across a wide range of sectors such as finance (optimisation problems), drug discovery and chemical reactions, intelligence and defense (breaking encryptions) to name a few. Machine learning and artificial intelligence have been flagged as an highly disruptive application. Trapped ions form one of the most promising hardware platforms to build practical quantum computers. Many practical realizations of trapped ion quantum computing make use of laser beams to execute quantum gates where the number of laser beams required scales with the number of ions used in the quantum computer. While this is fine with machines featuring tens or hundreds of quantum bits, it may be more challenging building a quantum computers with millions of quantum bits where millions of pairs of laser beams may need to be generated and aligned with an accuracy of 10µm. In 2016, the Ion Quantum Technology group at the University of Sussex invented a new approach where quantum gates are implemented by the application of voltages to a microchip making use of proven microwave technology and the presence of local magnetic field gradients (instead of pairs of laser beams). First proof-of-principle experiments were carried out making use of a macroscopic ion trap featuring permanent magnets to generate the B-field gradient. Using ion microchips incorporating current-carrying wires instead gives rise to an architecture that can scale to millions of qubits. As part of ARO project Development of microwave ion chip entanglement architectures for quantum technologies (W911NF-14-2-0106), key demonstrations for this new approach were realized including the successful fabrication of ion microchips incorporating current-carrying wires, along with numerous relevant physics demonstrations such as the realization of two qubit quantum gates with fidelity close to the fault-tolerant threshold and two-qubit quantum gates that are resilient to the presence of noise. The work also included drawing up a blueprint on how to build a practical quantum computer with millions of qubits based on this approach. This new project directly capitalizes on the achievements of W911NF-14-2-0106, in particular, on the demonstration of first ion microchips with current carrying wires. While key microchip specifications were already verified towards the end of that project (including magnitude of current that can be applied to the microchip and electrical testing of ion trap electrodes), the next logical step as part of this new project must be the demonstration of high-fidelity two qubit quantum gates making use of these newly developed ion microchips. Indeed, this new generation of chips allows for the generation of much larger magnetic field gradients. This in turn should enable significantly larger two-qubit gate fidelities along with much increased gate speeds. Furthermore, key improvements in the fabrication process will allow to fabricate more reliable devices with further improved specifications such as magnitude of voltages and currents that can be applied to the chip, further aiding the overall performance of these microchips. This project also includes the development of additional features for these microchips such centrally segmented electrodes which will enable fast diabatic ion transport and the development of on-chip atomic ovens which will simplify scaling to much larger qubit numbers. The team will execute fast high-fidelity quantum gates and demonstrate diabatic shuttling primitives on the newly developed ion microchips. The project will conclude with the demonstration of quantum algorithms formed from a sequence of fast ion transport and the execution of quantum gates in order to showcase the full potential of this new quantum computing architecture.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 25, 2021
- Source ID
- W911NF2110240
Entities
People
- Winfried K. Hensinger
Organizations
- Army Contracting Command
- United States Army
- University of Sussex