International Business Machines Corporation
Detection of leakage of a qubit without directly measuring the qubit

Abstract:

A method of detecting leakage of a data qubit includes applying a first cross-resonance pulse to the data qubit, the data qubit including a first state and a second state; applying a first echo pulse to the data qubit temporally following the applied first cross-resonance pulse; applying a second cross-resonance pulse to the data qubit temporally following the applied first echo pulse, the second cross-resonance pulse being an inverted form of the first cross-resonance pulse; applying a second echo pulse to the data qubit temporally following the second cross-resonance pulse; and detecting a leakage associated with the data qubit using an ancilla qubit coupled to the data qubit based on application of the first and second cross-resonance pulses, and the first and second echo pulses.