Quantum Metrology: Detection of Weak Forces Using Schrödinger Cat Resources

Schrödinger cats and their power for quantum information processing

We outline a toolbox comprised of passive optical elements, single photon detection and superpositions of coherent states (Schrödinger cat states). Such a toolbox is a powerful collection of primitives for quantum information processing tasks. We illustrate its use by outlining a proposal for universal quantum computation. We utilize this toolbox for quantum metrology applications, for instance...

Weak Force Measurement in Bistable Optomechanical System

One of the main milestones in the study of opto-mechanical system is to increase the sensitivity of weak forces measurement up to the standard quantum limit. We have studied the detection of weak force under a bistable condition in red detuned regime. In this case, dynamics of the system behaves asymptotically similar to stationary state and applying external force affects phase and fluctuation...

Quantum Feedback for Protection of Schrödinger Cat States

We review the use of quantum feedback for combatting the decoherence of Schrödinger-cat-like states in electromagnetic cavities, with special emphasys on our recent proposal of an automatic mechanism based on the injection of appropriately prepared “probe” and “feedback” Rydberg atoms. In the latter scheme, the information transmission from the probe to the feedback atom is directly mediated by...

Quantum Fisher information as a predictor of decoherence in the preparation of spin-cat states for quantum metrology

Practical quantum metrology with large precision gains in the low photon number regime

Quantum metrology exploits quantum correlations to make precise measurements with limited particle numbers. By utilizing interand intramode correlations in an optical interferometer, we find a state that combines entanglement and squeezing to give a 7-fold enhancement in the quantum Fisher information (QFI) – a metric related to the precision – over the shot noise limit, for low photon numbers....