Fault-tolerant detection of a quantum error

Understand

A critical component of any quantum error-correcting scheme is detection of errors by using an ancilla system.

• However, errors occurring in the ancilla can propagate onto the logical qubit, irreversibly corrupting the encoded information.
• We demonstrate a fault-tolerant error-detection scheme that suppresses spreading of ancilla errors by a factor of 5, while maintaining the assignment fidelity.
• The same method is used to prevent propagation of ancilla excitations, increasing the logical qubit dephasing time by an order of magnitude.