Pranev Mundada

The pursuit of fault-tolerant quantum computation is often hindered by the substantial resource overhead required for full quantum error correction (QEC), especially given the limited size of current quantum systems. In this presentation, we introduce an innovative approach that leverages QEC primitives without necessitating full logical encoding, thereby achieving significant computational advantages on superconducting processors with minimal overhead.

We propose a novel protocol for executing long-range CNOT gates that utilizes a unitarily-prepared Greenberger-Horne-Zeilinger (GHZ) state, complemented by a unitary disentangling step. This method inherently incorporates an error-detection mechanism, employing the disentangled qubits as flags to identify errors. Our experimental implementation of this protocol demonstrates state-of-the-art gate fidelities exceeding 85% across distances of up to 40 lattice sites. We also successfully produce a 75-qubit GHZ state exhibiting genuine multipartite entanglement—the largest reported to date. Notably, this performance markedly surpasses that of the best existing measurement-based protocols and does so without the need for additional ancilla qubits. Our solution directly addresses QEC challenges due to the limited connectivity available in solid-state quantum devices.

Our findings provide compelling evidence that the strategic application of QEC primitives on current-generation quantum devices can yield substantial computational benefits.

For a comprehensive exploration of our methodologies and experimental results, please refer to our full paper : PRXQuantum.6.020331.