Quantum Error Mitigation by Pauli Check Sandwiching

Understand

We describe and analyze an error mitigation technique that uses multiple pairs of parity checks to detect the presence of errors.

• Each pair of checks uses one ancilla qubit to detect a component of the error operator and represents one layer of the technique.
• We build on the results on extended flag gadgets and put it on a firm theoretical foundation.
• We prove that this technique can recover the noiseless state under the assumption of noise not affecting the checks.