Insights from the Quantum Era - March 2024

Here are some scientific papers that caught our eye this month:

Concatenate codes, save qubits

The era of early fault-tolerance continues to advance. In this work, researchers from Tokyo U highlight a new technique for error correction that simultaneously tries to address the weaknesses of conventional protocols (such as the Steane code) and more modern ones. They highlight that conventional codes require too many qubits to be practical, while modern – LDPC – alternatives may achieve considerable savings in number of qubits, but only sacrificing on error threshold and modularity features. The authors put forward that recent advances in combining optimization and concatenation of codes offer a promising alternative venue. They exemplify it by combining C4/C6 and quantum Hamming codes to achieve constant overhead on numbers of physical qubits . Surprising advances in error correction are still abound and, from a hardware perspective, this work showcases the importance of having the flexibility to encode different strategies, empirically test them, and co-design processor and compilation

Read here on ArXiv.

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Quantum dimer models with Rydberg gadgets

A known limitation of analog quantum hardware is the flexibility for encoding different problems. A known strength of analog quantum hardware is, however, the capacity to simulate large complex quantum systems. In the context of optimization, the former problem has been previously addressed by creating “gadgets”, clusters of atoms whose joint dynamics leads to a richer class of behavior possibilities. In this paper, a German-Austrian collaboration uses the same strategy to diversify the capacity of neutral-atom quantum hardware to simulate broader classes of quantum many-body problems. This helps leverage the strengths of analog quantum hardware while mitigating their weaknesses.

Read here on ArXiv.

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Universal quantum operations and ancilla-based readout for tweezer clocks

Neutral-atom platforms can be operated by rich variety of different atomic species. Traditionally, Rb and Cs were considered the workhorses, while, more recently, Yb and Sr have been picking up interest of the community due to the opportunities offered by the richer, but harder to manipulate, energy level structure. While the focus of this work is metrology applications, the authors also demonstrate record performance of entangling operations with Sr atoms. They showcase a 99.35% fidelity CZ gate, with single-photon transitions. This represents an advance for Sr as a candidate species for neutral-atom quantum computation.

Read here on ArXiv.