Quantum non-demolition measurement of a superconducting qubit
Adrian Lupaşcu, Shiro Saito, Thomas Picot, P. C. de Groot, C. J. P. M. Harmans, Johan E. Mooij, Hsi‐Sheng Goan, Yueh-Nan Chen · AIP conference proceedings · 2008
We present experiments that address the issue of measurement of superconducting qubits. A quantum non‐demolition (QND) type of readout is used to implement a projective measurement, which is an important component of many protocols in quantum information. The state of a persistent current qubit is measured using a driven non‐linear resonator, based on DC‐SQUID whose Josephson inductance is qubit‐state dependent. When properly optimized, the readout is efficient and projective. We discuss the relation between the concept of QND detection and the observed projective character of the measurement.