Single-shot qubit readout in circuit Quantum Electrodynamics

François Mallet (1) , Florian R. Ong (1) , Agustin Palacios-Laloy (1) , François Nguyen (1) , Patrice Bertet (1) , Denis Vion (1) , Daniel Estève (1)

1 QUANTRONICS - Quantronics Group

The future development of quantum information using superconducting circuits requires Josephson qubits with long coherence times combined to a high-delity readout. Major progress in the control of coherence has recently been achieved using circuit quantum electrodynamics (cQED) architectures, where the qubit is embedded in a coplanar waveguide resonator (CPWR) which both provides a well controlled electromagnetic environment and serves as qubit readout. In particular a new qubit design, the transmon, yields reproducibly long coherence times. However, a high-delity single-shot readout of the transmon, highly desirable for running simple quantum algorithms or measuring quantum correlations in multi-qubit experiments, is still lacking. In this work, we demonstrate a new transmon circuit where the CPWR is turned into a sample-and-hold detector, namely a Josephson Bifurcation Amplifer (JBA), which allows both fast measurement and single-shot discrimination of the qubit states. We report Rabi oscillations with a high visibility of 94% together with dephasing and relaxation times longer than 0.5 µs. By performing two subsequent measurements, we also demonstrate that this new readout does not induce extra qubit relaxation.

Domaines: Physique Quantique [quant-ph]; Supraconductivité [cond-mat.supr-con]

François Mallet, Florian R. Ong, Agustin Palacios-Laloy, François Nguyen, Patrice Bertet, et al.. Single-shot qubit readout in circuit Quantum Electrodynamics. Nature Physics, 2009, 5, pp.791. ⟨10.1038/nphys1400⟩. ⟨hal-00440277v1⟩