Hyunseong (Linus) Kim is currently a 5th year Ph.D. student in the Department of Physics, where he is advised by Professor Irfan Siddiqi. Linus received his B.S. in Physics from the California Institute of Technology (Caltech), where he worked on reducing dark counts in superconducting nanowire single photon detectors (SNSPDs) for quantum communication applications.
Linus’ doctoral research focuses on developing novel, protected superconducting qubits for fault-tolerant quantum computation. Suppressing the errors in qubits is critical towards achieving high-fidelity quantum operations. Encoding quantum information into a superconducting circuit with disjoint and delocalized eigenstates is a promising avenue for constructing a protected qubit.
As a Kavli ENSI fellow, Linus will work on realizing a superconducting qubit with grid-like eigenstates that is resilient against errors. This is inspired by the Gottesman-Kitaev-Preskill protocol, which encodes disjoint and delocalized grid states into a harmonic oscillator with tailored microwave drives. Alternatively, by combining two novel superconducting elements—a Cooper quartet tunneling (CQT) junction and a phase slip junction— the grid states can be hardware encoded into a circuit without microwave drives. Already, Linus has realized these components using Josephson junctions and superinductors. Furthermore, he has observed spectroscopic signatures of a grid-state qubit by constructing the proposed circuit. Now, he plans to develop the necessary control sequences to demonstrate error protection. This work will lower the overhead required for fault-tolerance and pave the way for real-world applications of quantum computers.