The information about the state of a charge qubit gained by a weakly coupled quantum point contact

Abstract

We analyze the information that one can learn about the state of a quantum two-level system, i.e. a qubit, when probed weakly by a nearby detector. We consider the general case where the qubit Hamiltonian and the qubit's operator probed by the detector do not commute. Because the qubit's state keeps evolving while being probed and the measurement data is mixed with a detector-related background noise, one might expect the detector to fail in this case. We show, however, that under suitable conditions and by proper analysis of the measurement data useful information about the initial state of the qubit can be extracted. Our approach complements the usual master-equation and quantum-trajectory approaches, which describe the evolution of the qubit's quantum state during the measurement process but do not keep track of the acquired measurement information.

5 pages, 3 figures; Published in the proceedings of the Nobel Symposium 141: Qubits for Future Quantum Information

References in corpus (6)

• Superconducting Circuits and Quantum Information
• Interqubit coupling mediated by a high-excitation-energy quantum object
• Readout methods and devices for Josephson-junction-based solid-state qubits
• The information about the state of a qubit gained by a weakly coupled detector
• Weak and strong measurement of a qubit using a switching-based detector
• Time-Resolved Measurement of a Charge Qubit

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