The probe readout and quantum limited measurements

Abstract

Assuming that the parameter dependent evolution, as well as the measurements that are done for readout, of a quantum system that acts as the probe in a quantum limited measurement scheme are both fixed, we find the optimal initial states of the probe that will saturate the quantum Cramer-Rao bound. When the probe system is itself made of identical, elementary, two-level subsystems or qubits, we connect the optimal state of the N qubit probe to that of the one qubit probe. This is done for two different classes of dynamics for the probe qubits, one of which is entangling while the other is not. We study the limitations placed on the optimal initial state of the probe and the achievable measurement uncertainty by restrictions on the readout procedure that is applied on the probe qubits at the end of the measurement protocol.

10 Pages

References in corpus (6)

• LIGO: The Laser Interferometer Gravitational-Wave Observatory
• Quantum Optical Metrology -- The Lowdown on High-N00N States
• Optimal Quantum Phase Estimation
• Generalized Limits for Single-Parameter Quantum Estimation
• Quantum Metrology: Dynamics vs. Entanglement
• Quantum-limited metrology with product states

Cited by in corpus (2)

• Optimal condition for measurement observable via error-propagation
• Nonclassical states of light in a nonlinear Michelson interferometer