Quantum non-demolition measurement of a superconducting two-level system
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 eige...
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Veröffentlicht in: | Nature physics 2007-02, Vol.3 (2), p.119-125 |
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Sprache: | eng |
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Zusammenfassung: | 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. |
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ISSN: | 1745-2473 1745-2481 |
DOI: | 10.1038/nphys509 |