arXiv subjects

J. A. Sidles

Publications and source records attributed to J. A. Sidles.

3 recordsLinked to original sources

arXiv2002

Path Integrals over Measurement Amplitudes: Practical Quantum Foundations for Signal Processing and Control

It is shown that classical control diagrams can be mapped one-to-one onto quantum path integrals over measurement amplitudes. To show the practical utility of this method, exact closed-form expressions are derived for the control dynamics and quantum noise levels of a test mass observed by a Fabry-Perot interferometer. This formalism provides an efficient yet rigorous method for analyzing complex systems such as interferometric gravity wave detectors and magnetic resonance force microscopy (MRFM) experiments. Quantum limits are conjectured for the sensitivity of interferometric observation of test mass trajectories.

quant-ph↗

arXiv2000

Fluctuation, Dissipation, and Entanglement: the Classical and Quantum Theory of Thermal Magnetic Noise

A general theory of thermal magnetic fluctuations near conductive materials is developed; such fluctuations are the magnetic analog of Johnson noise. For realistic experiments in quantum computing and magnetic resonance force microscopy, the predicted relaxation can be rapid enough that substantial experimental care should be taken to minimize it. The same Hamiltonian matrix elements that govern fluctuation and dissipation are shown to also govern entanglement and renormalization, and a specific example of a fluctuation-dissipation-entanglement theorem is constructed.

quant-ph↗

arXiv1996

The AC Stark, Stern-Gerlach, and Quantum Zeno Effects in Interferometric Qubit Readout

This article describes the AC Stark, Stern-Gerlach, and Quantum Zeno effects as they are manifested during continuous interferometric measurement of a two-state quantum system (qubit). A simple yet realistic model of the interferometric measurement process is presented, and solved to all orders of perturbation theory in the absence of thermal noise. The statistical properties of the interferometric Stern-Gerlach effect are described in terms of a Fokker-Plank equation, and a closed-form expression for the Green's function of this equation is obtained. Thermal noise is added in the form of a externally-applied Langevin force, and the combined effects of thermal noise and measurement are considered. Optical Bloch equations are obtained which describe the AC Stark and Quantum Zeno effects. Spontaneous qubit transitions are shown to be observationally equivalent to transitions induced by external Langevin forces. The effects of delayed choice are discussed. Practical experiments involving trapped ions are suggested. The results are relevant to the design of qubit readout systems in quantum computing, and to single-spin detection in magnetic resonance force microscopy.

quant-ph↗