Southwest Quantum Information and Technology

Measurement of correlations in a symmetric many-body quantum state via continuous measurement

Presenting Author: Ezad Shojaee, Center for Quantum Information and Control (CQuIC), University of New Mexico
Contributing Author(s): Amir Kalev and Ivan Deutsch

Continuous measurement on an ensemble of quantum systems in the presence of dynamical control is a fast and robust way to reconstruct the one-body reduced density matrix of a many-body quantum state [1-4]. We expand this protocol in order to reconstruct the correlations in a symmetric many-body state of multiple qubits.  In this continuous weak measurement, the many-body system is probed collectively, weakly enough not to erase the initial conditions over the duration of the measurement, but strongly enough to map the information about the initial state in the measurement outcome. This can be achieved by subjecting the system to an external control which differentiate states with different initial correlations. The problem of extracting the correlation from this record is an inverse problem which is tricky in the strong back-action regime because the measurement back-action on the state disturbs it in a way which depends on the correlations. The conditions and requirements for reconstruction of correlations and the information-gain/disturbance tradeoff are the subject of the present work. [1] Andrew Silberfarb, Poul S. Jessen, and Ivan H. Deutsch, Phys. Rev. Lett. 95, 030402 (2005) [2] Greg A. Smith, Andrew Silberfarb, Ivan H. Deutsch, and Poul S. Jessen Phys. Rev. Lett. 97, 180403 (2006) [3] Carlos A Riofrío, Poul S Jessen and Ivan H Deutsch, Journal of Physics B: Atomic, Molecular and Optical Physics, 44, 15 (2011) [4] A. Smith, C. A. Riofrío, B. E. Anderson, H. Sosa-Martinez, I. H. Deutsch, and P. S. Jessen, Phys. Rev. A 87, 030102(R) (2013)

(Session 5 : Thursday from 5:00pm - 7:00pm)