Fault-tolerant quantum computing with bosonic qubits

A popular approach for realizing a fault-tolerant quantum computer is to construct logical qubits encoded in a surface code (or its variants) with bare two-level qubits (e.g., superconducting qubits or trapped-ion qubits) as underlying physical qubits. Recently, various alternative approaches have been proposed, such as using bosonic qubits (e.g., GKP qubits and cat qubits) as underlying qubits instead of bare two-level qubits. Bosonic qubits are distinguished from bare two-level qubits as they are themselves protected via bosonic quantum error correction (bosonic QEC). Moreover, bosonic QEC provides bosonic qubits with special structures that are absent in bare two-level qubits. In this talk, I will provide an overview of various proposals for bosonic-qubit architectures and explain how the unique properties of underlying bosonic qubits (e.g., extra analog information for GKP qubits and noise bias for some cat qubits) may be utilized to reduce the hardware resource overhead for building a fault-tolerant quantum computer.