Quantum Control of Vanadium Nuclear Spin Registers Surrounding a Single Ytterbium Ion in a Crystal

Understanding and controlling solid state quantum systems at the level of single atoms, or atom-like systems, interacting with their environment is at the forefront of scientific research as it provides a window into the most fundamental quantum interactions in solid state. In recent years, multiple types of atoms embedded in solids have been studied, including elements in the lanthanide series of the periodic table, also known as rare earths.

In this work, the group will study the interaction between single ytterbium atoms and the nearby vanadium nuclei in an yttrium orthovanadate crystal. The nuclei can act as a local memory element for quantum information. They could be utilized to create future optical quantum networks that could lead to transmitting information with high security.

The techniques developed in the project may also be utilized for future protocols relevant for quantum sensing and quantum computing. Quantum technologies are expected to help the society at large as they may lead to substantial improvements in communication security, computing and sensing. This project will provide the opportunity to train graduate students that will constitute the workforce in a future quantum industry.

The interaction between the ytterbium and the nearby nuclei will be studied by measuring the ytterbium atom that is coupled to nano-photonic resonators. The group has already characterized the Hamiltonian of this interaction, developed techniques to polarize the nuclei and stored/retrieved the quantum state of the ytterbium qubit into/from the vanadium ensemble.

The localized spin ensemble surrounds every ytterbium qubit in an identical manner, thus providing a highly versatile resource for quantum technologies. In this work the group will employ dynamic Hamiltonian engineering to explore augmented quantum control of the vanadium spins including the creation of nuclear Greenberger–Horne–Zeilinger (GHZ) states, number-resolving measurements of the vanadium nuclear spin excitations and storing multiple quantum excitations in the register.

Direct driving of the nuclear spins via radio frequency fields will be realized, leading to increased memory storage time, which is necessary for future implementations of quantum repeater networks. This is the first exploration of a quantum system of this type, which provides new insights into the quantum many body physics of dense nuclear spins in a crystal.

The impact of this research is multi-faceted. On one side, it has pure scientific value as it allows for studying and controlling the new regime of quantum interaction between a single qubit and a dense but discrete nuclear spin ensemble. On another side, controlling this quantum interaction enables local quantum memory registers that are very important for implementing quantum machines like quantum repeaters for long distance quantum networks that will be utilized in interconnecting future quantum computers and establishing secure quantum communications.

Quantum technologies are seen as an area of strategic scientific growth for the United States and are aggressively pursued under the context of the National Quantum Initiative. It is expected that quantum technologies will impact computing and communications in a profound way that will lead to the next technological revolution. The techniques developed in this research specifically for ytterbium in yttrium orthovanadate can be extended to other quantum systems.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.