Stabilization of Gottesman-Kitaev-Preskill bosonic codes in fully 2D architectures | Lev-Arcady Sellem (University of Sherbrooke)

Gottesman-Kitaev-Preskill qubits represent a promising avenue for bosonic quantum error correction, with break-even performance demonstrated in a microwave 3D cavity coupled to an ancilla transmon qubit for bosonic control. Fault-tolerant quantum computation could be achieved through the concatenation of such stabilized GKP qubits with a quantum error-correcting code once the logical error rate of GKP qubits could be maintained below the threshold of these codes. We envision that at least two key modifications to existing stabilization protocols will be required to unlock that goal. On the one hand, replacing ancilla transmons by protected qubits to mitigate ancilla error backpropagation would lift the current primary limitation on observed logical lifetime. On the other hand, developing fully-2D architectures would enhance the scalability of multi-qubit devices.

In this talk, we present a recent proposal for stabilizing a GKP qubit in the high-quality mode of a planar resonator coupled to a protected heavy fluxonium ancilla qubit. We go over the adaptation of existing stabilization protocol to this 2D architecture as well as proposals of further potential improvements using microwave-activated couplers for stabilization and gates.