Continuous weak measurement of quantum coherent oscillations

Continuous weak measurement of quantum coherent oscillations

We consider the problem of continuous quantum measurement of coherent oscillations between two quantum states of an individual two-state system. It is shown that the interplay between the information acquisition and the backaction dephasing of the oscillations by the detector imposes a fundamental limit, equal to four, on the signal-to-noise ratio of the measurement. The limit is universal, e.g...

Comment on ‘‘Continuous Quantum Measurement: Inelastic Tunneling and Lack of Current Oscillations’’ A recent Letter [1] revisits the problem of continuous weak measurement of quantum coherent oscillations of a qubit

A recent Letter [1] revisits the problem of continuous weak measurement of quantum coherent oscillations of a qubit with a linear detector, the role of which is played by the quantum point contact (QPC) in the low-transparency regime. Previous studies of this problem [2–5] demonstrated that the qubit oscillations with the frequency should be reflected in the spectral density S ! of the detector...

Quantum Zeno stabilization in weak continuous measurement of two qubits

We have studied quantum coherent oscillations of two qubits under continuous measurement by a symmetrically coupled mesoscopic detector. The analysis is based on a Bayesian formalism that is applicable to individual quantum systems. Measurement continuously collapses the two-qubit system to one of the subspaces of the Bell basis. For a detector with linear response this corresponds to measureme...

Quantum coherent oscillations in the early universe

Blind quantum computing with weak coherent pulses.

The universal blind quantum computation (UBQC) protocol [A. Broadbent, J. Fitzsimons, and E. Kashefi, in Proceedings of the 50th Annual IEEE Symposiumon Foundations of Computer Science (IEEE Computer Society, Los Alamitos, CA, USA, 2009), pp. 517-526.] allows a client to perform quantum computation on a remote server. In an ideal setting, perfect privacy is guaranteed if the client is capable o...