Document Type
Article
Publication Date
7-15-2014
Abstract
Large weak values have been used to amplify the sensitivity of a linear response signal for detecting changes in a small parameter, which has also enabled a simple method for precise parameter estimation. However, producing a large weak value requires a low postselection probability for an ancilla degree of freedom, which limits the utility of the technique. We propose an improvement to this method that uses entanglement to increase the efficiency. We show that by entangling and postselecting n ancillas, the postselection probability can be increased by a factor of n while keeping the weak value fixed (compared to n uncorrelated attempts with one ancilla), which is the optimal scaling with n that is expected from quantum metrology. Furthermore, we show the surprising result that the quantum Fisher information about the detected parameter can be almost entirely preserved in the postselected state, which allows the sensitive estimation to approximately saturate the relevant quantum Cramér-Rao bound. To illustrate this protocol we provide simple quantum circuits that can be implemented using current experimental realizations of three entangled qubits.
Recommended Citation
Pang, S., Dressel, J., Brun, T.A., 2014. Entanglement-Assisted Weak Value Amplification. Physical Review Letters 113, 030401. doi:10.1103/PhysRevLett.113.030401
Supplemental Material
Peer Reviewed
1
Copyright
American Physical Society
Comments
This article was originally published in Physical Review Letters, volume 113, in 2014. DOI: 10.1103/PhysRevLett.113.030401