State tomography via weak measurements

Abstract

Recent work has revealed that the wave function of a pure state can be measured directly and that complementary knowledge of a quantum system can be obtained simultaneously by weak measurements. However, the original scheme applies only to pure states, and it is not efficient because most of the data are discarded by post-selection. Here, we propose tomography schemes for pure states and for mixed states via weak measurements, and our schemes are more efficient because we do not discard any data. Furthermore, we demonstrate that any matrix element of a general state can be directly read from an appropriate weak measurement. The density matrix (with all of its elements) represents all that is directly accessible from a general measurement.

7 pages, 2 figure

References in corpus (9)

• Ultrasensitive Beam Deflection Measurement via Interferometric Weak Value Amplification
• Complex weak values in quantum measurement
• Weak values and the Leggett-Garg inequality in solid-state qubits
• Optimizing the Signal to Noise Ratio of a Beam Deflection Measurement with Interferometric Weak Values
• Grounding Bohmian Mechanics in Weak Values and Bayesianism
• A double-slit `which-way' experiment on the complementarity--uncertainty debate
• Quantum theory of successive projective measurements
• Modular values and weak values of quantum observables
• Realization of quantum mechanical weak values of observables using entangled photons