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Scalable quantum computation promises to revolutionise computing by leveraging quantum
mechanical properties like superposition and entanglement to achieve a parallelism far
exceeding that of classical systems. Realising versatile, large-scale quantum systems demands
a modular architecture with systematic control over quantum information, requiring long-lived
storage units, high-coherence ancillary qubits, and efficient remote links.
This talk presents mainly two recent experimental advancements that address these critical
hardware challenges, employing superconducting qubits operating at microwave frequencies.
First, we demonstrate high-fidelity two-qubit entanglement between remote transmon modules
connected by a detachable superconducting coaxial cable. To overcome significant channel and
interconnect loss and maintain high coherence, we combine a Raman detuned driving scheme
with degenerate pump-based SWAP gates. This architecture successfully prepares high-fidelity
remote entangled states, representing a crucial step toward building robust, distributed quantum
processors.
Second, we explore the capabilities of the fluxonium qubit, which is of recent interest for its
high coherence, large anharmonicity, and highly tunable interaction matrix elements. We show
how a fluxonium can function as an efficient ancillary qubit for bosonic quantum computing
with a high-quality storage cavity. By operating in a regime that maximizes the dispersive shift
while minimizing the imparted non-linearity on the cavity mode, the fluxonium acts as a
powerful control element. In conclusion, I shall also talk about our currently ongoing research
to leverage the unique properties of these qubits to implement fast, high-fidelity multi-qubit
entangling gates.
Collectively, these demonstrations introduce hardware-efficient protocols and architectures
necessary for realizing fast, robust, and distributed quantum computation across spatially
separated modular units. |