The Office of Dean-Research is organising the 6th Eminent Guest Lecture on October 27, 2025. Prof. Somnath Bhattacharyya, Founder and Head of Nano-Scale Transport Physics Laboratory, University of the Witwatersrand, Johannesburg, South Africa, will deliver a distinguished lecture on “Diamond-Based Hybrid Qubit System for Quantum Computation Technology”.
Abstract
There is a surge in exploring the best qubit platform for building efficient quantum computers suitable for complex operations. A qubit is analogous to the binary bit seen in a conventional computer. We show the potential for a diamond-based hybrid quantum system combining electrical (superconducting) and optical (nitrogen-vacancy centers) techniques. Superconducting qubit technology typically involves the fabrication of various logic elements based on Josephson junctions using standard superconducting materials such as Al or Nb. Boron-doped superconducting diamonds are, however, attractive due to better resistance to external perturbations. Considering a recent discovery of triplet-spin-based superconductivity in nanocrystalline diamond films and that diamond presents well-established quantum states in the form of nitrogen-vacancy centers (NV-centers), diamond demonstrates a potential platform for the realization of all diamond-based quantum circuitry. We advance the understanding of superconducting order parameters in boron-doped nanodiamond films and as a new type of qubit system through the design of the resonator and superconducting quantum interference devices. Quantum information can be exchanged between a superconducting diamond loop (with a phase-slip qubit junction) and an ensemble of spins (NV-centers) attached to a microwave line of the diamond nanowire, which would allow us to initialize, control through microwave circuitry, and perform measurements via an optical interface. Moreover, the diamond NV-centers offer ‘holonomic’ control of qubits for the acquisition of geometric phase, which can be added to the hybrid qubit system. The holonomic control of qubits implemented in a ‘nine-level’ NV center is demonstrated by using IBM QP. This modeling shows a long coherence time of a system of multiple NV centersand also uses the multiple ‘dark’ states present in the NV centers. Such a hybrid quantum system will be useful for studying complex quantum many-body problems and quantum artificial intelligence or vision.
About the Speaker
Prof. Somnath Bhattacharyya, a Professor in Physics at Wits University, Johannesburg, since 2012, founded the Nano-Scale Transport Physics Laboratory, which pioneered quantum-nanotechnology in South Africa. His expertise includes superconducting carbon-based quantum technology, qubit-circuit designing & testing, quantum simulations, and theoretical models. He demonstrated diamond-based quantum tunnel devices, spin-triplet superconductivity, diamond qubits, and NV-center-based quantum technology.He published two books [“Evolution: Classical Philosophy meets Quantum Science” and “Carbon Superstructures: From Quantum Transport to Quantum Computation”], five book chapters, and over 100 journal papers. He supervised 8 PhD, 8MSc students, 8postdocs, established many international collaborations, and founded a start-up company, Quantumquest Technologies Pty. Ltd.