Southwest Quantum Information and Technology

Quantum illumination, illuminated

Presenting Author: Rafael Alexander, University of New Mexico CQuIC
Contributing Author(s): Carlton M. Caves

Abstract: Technology based on the use of single-mode squeezed light is now being used to enhance detection of gravitational waves in the LIGO/VIRGO interferometers. A recent key idea in quantum metrology is quantum illumination [S. Lloyd, “Enhanced sensitivity of photodetection via quantum illumination,” Science 321, 1463 (2008)], in which the use of two-mode squeezed (quantum-entangled) light is used to detect the presence of a target with fundamentally better precision than any strategy using unentangled light. Though this fundamental improvement was shown theoretically over a decade ago, its translation into a practical real-world scenario is still an unsolved challenge due to a combination of both the fundamental difficulty of performing a first-principles analysis and the technical limitations set by the requirements of existing technology. We address the first of these issues and shed light on the second. We do this by investigating the role of interferometric symmetries. By framing the problem in terms of the natural SU(1,1) symmetry of two-mode squeezed light, we identify previously unstudied ``symmetry sectors'' for this problem. Within each sector, the output state is entangled and can be modelled as a single (nonlocal) qubit; the entanglement (coherence) within these qubit sectors is responsible for the detection enhancement in quantum illumination.

(Session 9b : Sunday from 5:45pm - 6:15pm)