Laboratoire de Physique de la Matière Condensée

Groupe Electrons Photons Surfaces

dinh-tien.nguyen-AT-polytechnique.edu

I am a PhD student in the QCMX group at the Condensed Matter Physics Laboratory, École Polytechnique.

Under the supervision of Joël Griesmar, I study the implementation of protected qubits using nearly transparent Josephson junctions. Currently, quantum information can be encoded in the number of Cooper pairs that have tunneled through a Josephson junction, a process similar to noisy tunneling events that typically limit qubit coherence.

These two processes can be distinguished if the information is instead encoded in the Cooper-pair number parity, providing topological protection at the hardware level. Achieving this requires a Josephson element that allows only two Cooper pairs to tunnel together, which does not occur naturally. However, such an element can be engineered from a superconducting circuit composed of several nearly transparent Josephson junctions, whose transport is mediated by Andreev bound states confined at the insulating layer. Embedding this circuit in a circuit-QED architecture enables coherent control of the protected qubit and provides a platform for studying mesoscopic phenomena in superconducting devices.