Continuous-variable quantum process tomography with squeezed-state probes

TL;DR

This paper introduces a method for characterizing continuous-variable quantum processes using squeezed-state probes and homodyne detection, enabling efficient and feasible quantum process tomography with current technology.

Contribution

It presents a novel tomography procedure employing squeezed states and homodyne detection, extending to measurement device characterization, suitable for practical implementation.

Findings

Density matrix elements can be estimated via pattern functions.

The method is extendable to quantum measurement device characterization.

Probes can be mixed states, enhancing practicality.

Abstract

We propose a procedure for tomographic characterization of continuous variable quantum operations which employs homodyne detection and single-mode squeezed probe states with a fixed degree of squeezing and anti-squeezing and a variable displacement and orientation of squeezing ellipse. Density matrix elements of a quantum process matrix in Fock basis can be estimated by averaging well behaved pattern functions over the homodyne data. We show that this approach can be straightforwardly extended to characterization of quantum measurement devices. The probe states can be mixed, which makes the proposed procedure feasible with current technology.