Quantum non-demolition measurement of a superconducting two-level system

By A. Lupascu, S. Saito, T. Picot, P. D. Groot, C. Harmans, J. Mooij. 2006

230 citations recorded by the source corpus.

In quantum mechanics, the process of measurement is a subtle interplay between extraction of information and disturbance of the state of the quantum system. A quantum non-demolition (QND) measurement minimizes this disturbance by using a particular system—detector interaction that preserves the eigenstates of a suitable operator of the quantum system. This leads to an ideal projective measurement. We present experiments in which we carry out two consecutive measurements on a quantum two-level system, a superconducting flux qubit, by probing the hysteretic behaviour of a coupled nonlinear resonator. The large correlation between the results of the two measurements demonstrates the QND nature of the readout method. The fact that a QND measurement is possible for superconducting qubits strengthens the notion that these fabricated mesoscopic systems are to be regarded as fundamental quantum objects. Our results are also relevant for quantum-information processing for protocols such as state preparation and error correction.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/e6b6932f90844244a23e0f1f081e8cccd7e2caa1

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In Atomic and Molecular Physics, and Optics

Citations in the corpus

Atomic physics and quantum optics using superconducting circuits (2011, methodology): “Recent experiments [77, 78] show that QND measurements can also be implemented for a single superconducting qubit by using a nonlinear resonator as the detector.”
Introduction to quantum noise, measurement, and amplification (2008, background): “…(Haroche and Raimond, 2006; Nogues et al., 1999), and (iii) the “dispersive” measurement of a qubit state by its effect on the frequency of a driven microwave resonator (Blais et al., 2004; Lupaşcu et al., 2007; Wallraff et al., 2004), which is the first canonical example we will describe below.”
Quantum computers (2010, unknown): “Another promising development is thedemon-stration of QND measurements in which a qubit provides a state-dependent phase shift for an electromagnetic wave in a transmission line 82 .”
Analog information processing at the quantum limit with a Josephson ring modulator (2008, background): “Moreover, we would like to stress that the present level of control in the dynamics of tunnel junctions in resonant circuits, as demonstrated by recent several successful operations [12, 13, 14, 29, 30], ensures that its realization is entirely within reach.”
Quantum non-demolition detection of single microwave photons in a circuit (2010, unknown): “Recording the second interrogation results for different delays allows us to subtract the effect of photon T 1 and calculate the transition probabilities for the I 0 and I 1 processe”
Engineered dissipation for quantum information science (2022, background): “The measurement can be quantum non-demolition 146,147 : The system Hamiltonian commutes with the measurement jump operators which cause back-action dynamics.”