Ultrafast quantum nondemolition measurements based on a diamond-shaped artificial atom

Igor Diniz (1) , Etienne Dumur (2) , Olivier Buisson (2) , Alexia Auffèves (1)

1 NEEL - NPSC - Nanophysique et Semiconducteurs
2 NEEL - QuantECA - Circuits électroniques quantiques Alpes

We propose a quantum nondemolition (QND) readout scheme for a superconducting artificial atom coupled to a resonator in a circuit QED architecture, for which we estimate a very high measurement fidelity without Purcell effect limitations. The device consists of two transmons coupled by a large inductance, giving rise to a diamond-shaped artificial atom with a logical qubit and an ancilla qubit interacting through a cross-Kerr-like term. The ancilla is strongly coupled to a transmission line resonator. Depending on the qubit state, the ancilla is resonantly or dispersively coupled to the resonator, leading to a large contrast in the transmitted microwave signal amplitude. This original method can be implemented with a state-of-the-art Josephson parametric amplifier, leading to QND measurements in a few tens of nanoseconds with fidelity as large as 99.9%.

Mots clés: superconducting qubit; quantum measurements; quantum non demolition

Domaines: Systèmes mésoscopiques et effet Hall quantique [cond-mat.mes-hall]

Igor Diniz, Etienne Dumur, Olivier Buisson, Alexia Auffèves. Ultrafast quantum nondemolition measurements based on a diamond-shaped artificial atom. Physical Review A : Atomic, molecular, and optical physics [1990-2015], 2013, 87, pp.033837. ⟨10.1103/PhysRevA.87.033837⟩. ⟨hal-00949053⟩