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Q: Fachverband Quantenoptik und Photonik

Q 21: Quantum Computing and Simulation III

Q 21.3: Vortrag

Dienstag, 3. März 2026, 11:45–12:00, P 10

Can parity measurements be implemented for continuous quantum error correction? — •Anton Halaski and Christiane P. Koch — Freie Universität Berlin, Berlin, Germany

In time-continuous quantum error correction, required in computations with time-varying Hamiltonians, the commonly employed strong projective measurements for syndrome extraction are replaced by weak continuous measurements. These protocols rely on sufficiently strong and continuous multi-qubit parity measurements to extract the error syndromes. The implementation of such measurements is challenging since they require a perpetual three-body interaction between two qubits and a meter. Here we show that, for the circuit QED architecture, known parity measurement protocols destroy the information encoded in the qubits when used in continuous operation since it is impossible to protect both the logical subspace and the error subspace from measurement backaction at the same time. We find the failure to be rooted in the approximation of the three-body interaction by a sum over two-body interactions between meter and qubits. Our findings suggest that continuous quantum error correction is possible only for architectures based on erasure qubits, such as dual-rail encodings, where there is no need to protect the error subspace from measurement backaction.

Keywords: quantum error correction; continuous quantum measurements; circuit QED